Programmer System and Associated Methods for Rapidly Evaluating and Programming an Implanted Cardiac Device

This application claims the benefit of U.S. Provisional application Ser. No. 60/017,671, filed May 14, 1996.

The present invention relates generally to cardiac pacemakers, and other types of implantable medical devices, which can be programmed and/or analyzed following implantation using an external diagnostic/programmer system. More particularly, the invention relates to a diagnostic/programmer system, including software routines thereof, for enabling a physician to rapidly and accurately evaluate and modify the operation of an implanted pacemaker.

Implantable cardiac pacemakers commonly store a variety of different types of diagnostic data which assist the physician in evaluating both the operation of the patient's heart and the operation of the implanted device. Depending upon the particular pacemaker and its mode of operation, this information may include, for example, a heart rate histogram (which indicates the distribution of the patient's heart rate over a period of time, such as one month), an event histogram (which indicates the distribution of the various sensing and stimulation events), a sensor indicated rate histogram (which indicates the distribution over time of the recommended pacing rate indicated by an implanted sensor), a variety of event counters, one or more event-triggered intracardiac electrograms, and the status of the pacemaker's battery.

The various items of diagnostic data may be retrieved from the pacemaker for display and evaluation using a pacemaker programmer/diagnostic system ("programmer"), which uses RF telemetry to communicate with the implanted device. This is typically accomplished during routine follow-up visits of the patient to the clinic, during which time the patient is asked to hold a telemetry wand in the locality of the implanted pacemaker. To read out and view a particular item of information (e.g., a heart rate histogram), the physician employs a user interface of the programmer to designate the diagnostic item to be retrieved, and then initiates the retrieval. The programmer in-turn interrogates the pacemaker to cause the pacemaker to transmit the selected diagnostic item, and then receives and displays the selected item on the screen. The physician may also initiate various types of tests using the programmer, such as a ventricular or atrial capture test which determines the minimum pulse voltage needed to effectively stimulate the respective chamber of the heart. The physician may retrieve and adjust various programmable pacing parameters, such as sensor control parameters that are used to adjust the pacing rate according to the output of an event (or other) sensor which senses electrical activity generated within the cardiac tissue.

During the follow-up visit, it is common for the physician (or other clinician) to follow a predetermined sequence or "protocol" for the evaluation of the patient. The particular protocol will often vary from physician-to-physician and/or clinic-to-clinic, and may depend upon the medical condition of the patient. By way of example, a follow-up protocol may include the ordered steps of (1) retrieving, viewing and printing the atrial and ventricular rate histograms; (2) retrieving and viewing (and optionally printing) the event histogram; (3) conducting ventricular and atrial sense tests; (4) conducting ventricular and atrial capture tests; (5) contingent upon the results of steps 1-4, retrieving and viewing the R-wave and P-wave histograms (indicative of the contraction of the ventricles and the atria, respectively); (6) retrieving, viewing and printing the sensor indicated rate histogram; and (7) if appropriate, adjusting the sensor control parameters. During each step of the protocol, the physician typically interviews the patient and records the patient's comments. At the end of the examination, the physician normally prepares a written report, which typically includes various printouts of the retrieved diagnostic data.

One problem with current diagnostic methods used to evaluate the follow-up patient is that the physician is typically required to scroll through large volumes of data on the programmer screen, even though only selected portions of this data are significant for diagnostic purposes. This is true, for example, in the case of atrial and ventricular capture tests, in which the physician is typically presented with a snap-shot of real-time data (typically, several seconds long), and must scroll through the data to locate the point at which capture was lost. Because much of the data viewed by the physician is insignificant, the process tends to be inefficient.

Based upon the results of the pacemaker diagnostic, the physician sometimes alters the pacemaker parameters (i.e., the stored values that specify the therapy delivered by the pacemaker). These modifications to the pacemaker parameters are typically standard given a certain set of results. However, the steps of programming each parameter change tend to be time consuming, further adding to the overall time required to complete the follow-up examination.

Finally, many conventional pacemaker diagnostic systems merely provide historical data to the physician and are not capable of providing for real-time analysis of pacemaker parameters. Even those systems which do provide real-time analysis of some diagnostic items do not allow the clinician to modify pacemaker parameters "on the fly" so that the clinician can immediately observe the results of such parameter modification. This can significantly reduce the physician's ability to actively interact with the pacemaker to achieve an unambiguous result.

The present invention addresses these and other concerns by providing an improved programmer. According to one preferred embodiment, the improved programmer can automatically step through a pacemaker test sequence and automatically identify significant events or transitions (e.g., the loss of atrial or ventricular capture, substantial heart rate changes, etc.). This aspect of the invention greatly reduces the amount of time it takes a physician to evaluate pacemaker performance, since it reduces or eliminates the need for the physician to manually scroll through the test sequence.

According to another aspect of the invention, the programmer of the preferred embodiment automatically suggests pacemaker parameter modifications based upon (i) the results of the automatic analysis and (ii) patient history trends stored within the pacemaker. In order to effect a modification in a parameter, the suggested modification is presented to the physician for confirmation. This makes parameter modification essentially a "one step" process.

According to yet another aspect of the invention, the programmer evaluates the pacemaker operations in real time. The evaluation of pacemaker operation on a real-time basis allows the physician to interactively modify parameters "on the fly" and evaluate the results immediately. This in turn allows the physician to test and program the pacemaker more rapidly, and to achieve an unambiguous result. In addition, real-time analysis and interaction with the telemetry system minimizes pauses, and prevents unwanted rhythms (e.g., retrograde conduction and PMT).

These and other features and advantages of the invention will now be described with reference to the drawings of a preferred embodiment, which is intended to illustrate and not to limit the invention, and in which:

FIG. 1 illustrates a patient in the context of a follow-up session with a clinician using a programmer system in accordance with the invention.

FIG. 2 is an example data display screen of the programmer's user interface.

FIG. 3 is a programmer display screen which may be used to select between existing follow-up protocols.

FIG. 4 is a protocol definition display screen of the programmer's user interface.

FIG. 5 is an architectural diagram of the primary hardware components of the programmer.

FIG. 6 is a conceptual schematic block diagram which illustrates an overview of the software architecture used in the preferred embodiment of the invention.

FIG. 7 is a flowchart which illustrates the overall method employed by a preferred embodiment of the present invention for a pacemaker which is providing dual-chamber pacing with atrial tracking and which is pacing and sensing in both the atrium and the ventricle with an inhibited or triggered response to sensing.

FIG. 8 is a flowchart which illustrates in greater detail the method used to perform the pace and capture tests represented in the subroutine of FIG. 7.

FIG. 9 is a flowchart which illustrates the overall method used in the preferred embodiment to perform sensing tests within the subroutine block of FIG. 7.

FIG. 10 is a flowchart which illustrates, in greater detail, the method employed within the subroutine block of FIG. 9 to verify ventricular sense function.

FIG. 11 is a flowchart which illustrates, in greater detail, the method employed within the subroutine block of FIG. 9 to verify atrial sense function.

FIG. 12 is a flowchart which details the method used to assess the ventricular sensing function within the subroutine block of FIG. 10.

FIG. 13 is a flowchart which details the method used to assess the atrial sensing function within the subroutine block of FIG. 10.

FIG. 14 is a flowchart which details the method used within the subroutine block of FIG. 10 to test the ventricular sensing function at a slower test rate.

FIG. 15 is a flowchart which details the method employed within the subroutine block of FIG. 11 to test the atrial sensing function at a slow rate.

FIG. 16 is a flowchart which details the method employed within the subroutine block of FIG. 14 to program the pacemaker to perform ventricular inhibited pacing.

FIG. 17 is a flowchart which details the method used within the subroutine block of FIG. 7 to test the battery and leads.

FIG. 18 is a flowchart which details the method employed within the subroutine block of FIG. 8 to test the ventricular capture function.

FIG. 19 is a flowchart which details the method employed within the subroutine block of FIG. 8 to test the atrial capture function.

FIG. 20 is a flowchart which details the method employed within the subroutine block of FIG. 15 to test the atrial sensing function.

The preferred embodiment of the present invention is an interactive pacemaker programmer system that includes various software-based features which allow a physician to program and evaluate the operation of an implanted pacemaker with increased accuracy and efficiency. In accordance with one aspect of the invention, the programmer automatically and temporarily changes various program parameters while collecting diagnostic data indicative of the effectiveness of such parameter changes. The data collected includes, among other items, ECG data, IEGM data, and markers. As is well known in the art, an ECG is a graphic depiction of the electrical signal emitted by active cardiac tissue and recorded through electrodes placed on the surface of the body. Similarly, an IEGM is a graphic depiction of the electrical signal emitted by active cardiac tissue and recorded through electrodes placed on or within the heart. This graphical depiction is sometimes referred to as an electrogram. As used herein, an event marker, or a marker, is a real-time annotation of paced and sensed events for a pacemaker, usually displayed on a display screen in conjunction with the simultaneously recorded surface ECG.

In accordance with a further aspect of the invention, novel use of historical data is made in order to automatically perform trend analysis. That is, multiple events are recorded and stored within the pacemaker in the form of, for example, an event histogram, and a statistical analysis is performed on this historical data (preferably within the programmer) in order to make decisions for setting the pacemaker parameters. These decisions are based upon trends observed within the historical data.

The preferred embodiment of the present invention also allows analysis to be performed even in the presence of IEGM signal amplifier saturation after the pacing spike. As is well known in the art, the pacing spike typically drives the sensing amplifier for the intracardiac electrogram into saturation, since the pacing pulse has a relatively high amplitude compared to the natural electrical signals generated within the cardiac tissue. As a result, prior systems are not able to perform analysis in the presence of IEGM signal amplifier saturation. In accordance with the invention, however, this difficulty is avoided by using tests which use data surrounding the pacing spike. These tests use surface ECG waveforms and markers to determine results, in place of IEGM signal.

In accordance with a further aspect of the present invention, the removal of the repolarization artifact, which is often quite difficult, is not required. Repolarization is the recovery process of excitable tissue following depolarization. Thus, repolarization involves the voltage potential of the cardiac tissue returning to its resting value. For example, ventricular polarization is represented on the ECG by the T-wave, while atrial repolarization is usually not visible on the ECG, since it is obscured by the simultaneously occurring QRS complex. This repolarization process sometimes produces artifacts which inhibit an accurate sensing of the QRS complex so that it is desirable to remove the repolarization artifact. The preferred embodiment of the present invention analyzes the ECG waveform in relation to surrounding marker events, and therefore does not require the removal of repolarization artifact. The markers provide a "time tag" so criteria for detecting the corresponding event in the ECG waveform can be less stringent than in a morphological analysis.

Finally, automatic testing of pacing and sensing safety margins are incorporated into the preferred embodiment in order to provide, in addition to the qualitative assessments of conventional systems, a quantitative assessment of pacing and sensing function adequacy. Because the system of the present invention analyzes the data in real-time and interacts with the telemetry system, it is capable of minimizing pauses and preventing unwanted rhythms (e.g., retrograde conduction and PMT) which can result from either manual capture testing or automatic capture testing with a delayed analysis and/or a passive system. For example, because retrograde conduction is a backward conveyance of the electrical impulse originating in the junction or ventricles and traveling backward to the atria, causing an atrial depolarization, such an abnormal conduction is undesirable. Retrograde conduction can be seen on the ECG by P-waves of opposite polarity to sinus P-waves and usually follows an ectopic or ventricular paced event. Thus, when an analysis is performed in real-time, it is possible to mitigate the effects of retrograde conduction by one of two ways. If the retrograde conduction is being caused by ventricular paced events, the AV delay may be shortened so the ventricular pulse is delivered (and the retrograde impulse is conducted) while the atrial tissue is still refractory. In cases where the atrium does depolarize, the PVARP is increased so the pacemaker "ignores" the retrograde P-wave.

Similarly, pacemaker-mediated tachycardia (PMT) is a cardiac arrhythmia characterized by a rapid rate induced by competition between the paced and native rhythms and sustained by the continued participation of the pacemaker. Thus, if an analysis is performed in real-time, PMT can be avoided, since the monitoring physician is able to immediately discontinue the pacemaker-induced rhythm so that only the natural rhythm causes the heart to beat.

An overview of the programmer and the follow-up process will now be provided with reference to FIGS. 1-6. The above features of the programmer will then be described in greater detail with reference to FIGS. 7-20.

1. Overview (FIG. 1)

FIG. 1 is a diagram of a patient 100 in the context of a hypothetical follow-up session with a clinician 102, and will be used to provide an overview of the follow-up examination process. The patient has an implanted, battery-powered pacemaker 110, such as an AFFINITY.TM. pacemaker available from PACESETTER, Inc., 15900 Valley View Court, Sylmar, Calif. One or more pacing leads 112 extend from the pacemaker 110 into the patient's heart 115. The pacing leads 112 are used to apply electrical pulses to the inner tissue of the heart (typically within the right ventricle and/or the right atrium), and may also be used to sense intrinsic electrical activity within the heart. The pacemaker 110 and/or the leads 112 may also carry one or more sensors (not shown), such as an activity sensor for sensing changes in the patient's level of physical activity.

The pacemaker 110 includes conventional telemetry circuitry (not shown) which permits the exchange of information with an external "APS III" programmer 120 via a conventional telemetry wand 122. In the preferred embodiment, the programmer 120 includes a 486 (or Pentium.TM.) based computer system 124, and includes a monitor 126 having a touch-sensitive display screen 128. (In one implementation, the display screen 128 and computer system 124 are integrated within a common housing.) The computer system 124 may be provided with an internal printer, as depicted in FIG. 1, and/or may be connected to an external printer (not shown).

During the follow-up session, the patient 100 is asked to hold the telemetry wand 122 near the implanted pacemaker 110 to permit the interrogation of the pacemaker 110, which involves the transmission of RF commands to the pacemaker 110. Data transfers between the programmer 120 and the pacemaker 110 are accomplished using a standard interrogation protocol, in which the programmer 120 transmits commands (via the telemetry wand 122) to the pacemaker 110 to cause the pacemaker to take specific actions, such as transmit a particular record of diagnostic data.

In addition to the data collected from the pacemaker 110, the programmer receives surface electrocardiograph (ECG) signals from conventional surface electrodes 132, which attach to the skin of the patient 100. The ECG signals are displayed to the clinician 102 on a continuous, real-time basis via the monitor 126, and are used by the programmer 120 to perform tests relating to, for example, atrial and ventricular capture.

As is conventional in the art, the pacemaker 110 stores a variety of different diagnostic data records, including various types of histograms, real-time event records, event counters, and event-triggered snapshots of data. These diagnostic data records are collected by the pacemaker 110 over a period of time, such as between visits of the patient to the clinic, and can be retrieved and displayed to allow the clinician to evaluate the effectiveness of the pacing treatment. The stored diagnostic data records may also include information relating to the operation of the pacemaker itself, such as a history of the pacemaker's battery voltage. (Accordingly, as used herein, the term "diagnostic data record," or simply "diagnostic record," refers to a collection of data captured or generated by the implanted device over a period of time, which may be retrieved from the implanted device to obtain information about the patient and/or the operation of the implanted device.) The particular diagnostic data records stored by the pacemaker 110 depend upon both the model of the pacemaker and its programmed mode of operation.

As is also conventional, the pacemaker 110 stores a variety of parameters (referred to generally as "parametric data") which define the therapy administered by the pacemaker 110, and which can be modified during the follow-up session. These parameters typically include, for example the base rate (i.e., the rate at which pulses are applied to the heart in the absence of intrinsic activity), the AV delay (i.e., the delay between a sensed or paced atrial event and the delivery of a ventricular output pulse), the amplitude and width of pulses applied to the atrium and/or ventricle, and various sensor parameters for defining the control relationship between sensor output and pacing rate. As with the diagnostic data records, the specific program parameters which may be modified depend upon both the model of the pacemaker and its mode of operation. Typically, the parameters are retrieved from the pacemaker one set at-a-time (such as the set of all sensor parameters), as opposed to being retrieved on a parameter-specific basis.

In the course of a typical follow-up session (using either a prior art programmer or a programmer 120 in accordance with the invention), the clinician uses the programmer to retrieve, view and print various diagnostic data records, and to clear stored diagnostic data records from memory (to permit the subsequent capture of new diagnostic data). The clinician may also retrieve and view the various sets of parameters, as well as information about the pacemaker and the patient. In addition, the clinician may use the programmer to initiate various diagnostic tests, such as an atrial capture test or a retrograde conduction test. Based on the test results and the clinician's evaluation of retrieved diagnostic data, the clinician may choose to modify certain parameters or otherwise modify the treatment of the patient.

As described below, the programmer 120 of the preferred embodiment allows the clinician to perform these various follow-up steps either manually (i.e., by interactively selecting each individual item to be displayed and test to be performed), or by using an "automated follow-up" feature which allows the clinician to semi-automatically follow a predefined follow-up protocol.

2. User Interface (FIG. 2)

In the preferred embodiment, the clinician interacts with the programmer 120 and the pacemaker 110 via a graphical user interface of the programmer 120, a representative display screen 200 of which is shown in FIG. 2. The clinician may also use a keyboard (not shown in FIG. 1) to enter remarks and other data. With reference to the EVENT HISTOGRAM display screen 200 of FIG. 2, which is illustrative of the general format of the display screens used for displaying diagnostic and parametric data, the display screen 200 includes three primary sub-screens or "panels:" a real-time data display panel 202, a control panel 204, and a foreground panel 208. The real-time data display panel 202 displays the ECG and IEGM signals (including markers) transmitted, respectively, by the ECG electrodes 132 (FIG. 1) and the pacemaker 110. (In the FIG. 2 example, only an ECG signal is shown).

The control panel 204 includes various control buttons 220 for allowing the clinician to view other display screens and to initiate other follow-up related events. For example, the clinician can select the "PROGRAM PARAMETERS" button to view the program parameters (via corresponding display screens) stored by the implanted device, or can select a "CLEAR HISTOGRAM" button to clear the displayed histogram from the memory of the implanted device. The control buttons 220 can be selected by depressing corresponding portions of the touch-sensitive screen 128 (FIG. 1), or by clicking on the buttons using a mouse 136 (FIG. 1) or other pointing device. The functions performed by some of the buttons are specific to the particular display screen/data item being viewed. (The term "data item" is used herein to refer generally to the diagnostic records, parameters sets and other viewable data sets that can be retrieved from the implanted device and displayed by the programmer.)

The foreground display panel 208 is used to display the data associated with the foreground operation being performed by the clinician. This data may include, for example, a scrollable graph generated as part of an atrial capture test, a retrieved histogram, or a set of parameters. Diagnostic records are displayed within this panel 208 in a preformatted manner, along with associated explanatory text which is hard coded within the programmer's display routines. In the FIG. 2 example, the diagnostic record (i.e., the event histogram data) is displayed in both graphical and tabular form, along with hard coded explanatory text (e.g., the phrase "data last cleared:") of the display screen 200. In general, each diagnostic data record that can be retrieved from the pacemaker is displayed using its own respective display screen (such as the EVENT HISTOGRAM display screen shown in FIG. 2). However, some diagnostic records can be viewed in multiple different formats via different display screens of the programmer.

The clinician can access the various data display screens either manually (by selecting the corresponding control buttons 220) or semi-automatically (by using the automated follow-up features of the programmer, which can be accessed by selecting the AUTOMATED FOLLOW-UP button). Regardless of the method used, when a data display screen is selected (such as the EVENT HISTOGRAM display screen of FIG. 2), the programmer 120 initially checks to see if the corresponding (diagnostic or parametric) data item has already been read from the implanted device into programmer memory. If the data item has already been retrieved (e.g., by background interrogation), it is immediately displayed via the display screen. If the data item has not been retrieved, the programmer begins retrieving the data item (or finishes retrieving the data item if retrieval has already been initiated), and then displays the data item via the display screen.

In addition to the display screens used for the display of diagnostic and parametric data items, the user interface includes display screens and controls which correspond to other types of tasks, including protocol generation (FIG. 4), file management, and diagnostic tests.

3. Automated Follow-Up (FIGS. 2-4)

One of the automated follow-up features of the programmer 120 involves the use of a pre-specified examination protocol, which may be either a custom protocol (previously specified by the clinician or another user) or a standard (non-custom) protocol provided with the programmer 120. To access this feature, the clinician initially selects an AUTOMATED FOLLOW-UP button (shown in FIG. 2); the clinician is then presented with various controls and display screens which allow the clinician to, for example, define a new protocol, view a list of existing protocols of a particular clinician (FIG. 3), display and edit the steps of a protocol (FIG. 4), and start a selected protocol.

FIG. 3 illustrates a protocol display screen which displays the predefined protocols of a particular clinician. In this example, the clinician (Dr. Jones) has four predefined protocols, each of which is stored as a respective protocol definition file on the Programmer's hard disk. In general, each protocol corresponds to a particular family of implantable device, which may be specified by the clinician prior to defining the protocol. Of course, any suitable naming convention and grouping method can be used for organizing the protocol definition files for display via the user interface. Using either the touch screen 128 or the mouse 136, the clinician can select any one of the displayed protocols. (In the FIG. 3 example, the "Routine Follow-up" protocol is selected.) The clinician can then use the "START PROTOCOL" button to start the protocol (i.e., to begin the interrogation process), or use the "DISPLAY PROTOCOL" button to display the steps of the protocol (as shown in FIG. 4).

FIG. 4 illustrates a protocol definition screen, including an example follow-up protocol, in accordance with one embodiment of the system. From this display screen, the clinician can view the steps of the protocol, modify the protocol (using the MOVE STEP and OTHER EDIT OPTIONS BUTTONS, as described below), and/or start the protocol. The clinician can also generate new custom protocols by, for example, modifying the steps of the displayed protocol and then saving the modified protocol under a new filename.

As illustrated by the example protocol displayed in FIG. 4, each protocol consists generally of an ordered list of protocol steps, with each step consisting of an identifier of a display screen (e.g., "EVENT HISTOGRAM" and "VENTRICULAR RATE HISTOGRAM") along with an action to be performed (e.g., VIEW or PRINT) with respect to the display screen. ("SKIP" indicates that no action will be performed. In other embodiments, only the protocol steps which include an action other than SKIP are displayed in the protocol definition screen.) In this example, the first automated action to be performed will be the retrieval and display of the event histogram, and the second automated action will be the retrieval, display and printing of the ventricular rate histogram.

In another implementation, the programmer 120 allows the clinician to separately specify an ordered list of the display screens to be printed. The clinician can thereby specify a print order which differs from the protocol's viewing order. This feature allows the clinician to flexibly specify the order of the printed display screens within a custom follow-up report. For example, the clinician can designate the "final summary" display screen (which summarizes the follow-up session) as the first page of the printed report, even though the display screen was viewed at the end of the follow-up session.

Table 1, which is attached at the end of this disclosure, lists a master set of the protocol steps (each corresponding to a respective display screen) that can be included in a custom protocol for the AFFINITY.TM. family of pacemakers. (Earlier pacemakers from Pacesetter, Inc. generally support various subsets of these protocol steps.) Listed to the right of each protocol step are the options that can be specified by the clinician for each protocol step. Using edit buttons such as the MOVE STEP and SAVE PROTOCOL buttons of FIG. 4 (and other edit buttons that can be accessed by selecting the OTHER EDIT OPTIONS button), the clinician can create, modify and save follow-up protocols which include various combinations of these protocol steps. (Options designated with a star symbol are the default options which are used if no option is specified by the clinician.) During the protocol generation process, only. those steps that are supported by the pre-specified family of implanted device are displayed to the clinician. The protocol steps and options listed in Table 1 represent one preferred implementation of the automated follow-up software, and are not intended as a comprehensive list of the types of actions that can be performed using the custom protocol feature.

Once a follow-up protocol has been initiated (using the "START PROTOCOL" button 304), the programmer 120 begins to retrieve the diagnostic and parametric data items of the protocol (using background interrogation, as described below) from the implanted device. As the data items are retrieved, the clinician can semi-automatically sequence through the various display screens of the protocol (to view the corresponding diagnostic and parametric data items and to conduct the corresponding tests) by simply selecting the "CONTINUE PROTOCOL" button (FIG. 2), which causes the next display screen of the protocol to be displayed.

In addition, the clinician can depart from the protocol (to, for example, view a non-protocol diagnostic record, or temporarily jump ahead in the protocol) at any time, and then return to the protocol by selecting the "CONTINUE PROTOCOL" button. Advantageously, selection of the CONTINUE PROTOCOL button will not cause any display screen to be re-displayed. Thus, for example, if the clinician jumps ahead in the protocol to view the event histogram, the programmer will subsequently skip over the event histogram screen when the clinician continues the protocol. As the clinician views the protocol display screens, the designated print screens are automatically printed in the background, in the order specified within the protocol.

If, during a follow-up session, a protocol is used which includes steps that are not supported by the implanted device, the programmer 120 automatically skips over the unsupported steps.

As indicated above, whenever the clinician follows a predefined protocol, the programmer 120 uses a background interrogation process to automatically retrieve the diagnostic and parametric data items corresponding to the protocol. This feature advantageously enables the clinician to view some protocol items (e.g., a heart rate histogram, or a list of sensor parameters) while other protocol items are being retrieved by the programmer 120 in the background (transparently to the clinician). This in-turn reduces or eliminates the need for the clinician to wait for each data item to be retrieved--a process which typically takes a few seconds or more per retrievable data item. To maximize the benefit of this feature, the background interrogation is carried out in an order which corresponds to the viewing order specified within the protocol. Thus, for example, if the first display screen of the protocol is the event histogram screen, the programmer 120 retrieves the event histogram data first, and then automatically proceeds to retrieve the next protocol item.

Whenever, during the background interrogation process, the clinician initiates a operation (referred to as a "foreground operation") which requires the use of the telemetry channel, the background interrogation process is temporarily halted to allow the programmer (and clinician) to immediately perform the foreground operation. (The term "telemetry channel" refers generally to the hardware and software/firmware components used to transfer information between the programmer 120 and the implanted device by RF.) This situation arises, for example, when the clinician departs from (e.g., jumps ahead in) the protocol to view an item that has not yet been retrieved, or initiates a diagnostic test (which may or may not be part of the protocol) that makes use of the telemetry channel. This feature ensures that the step currently being performed by the clinician (i.e., the foreground step) is given the highest data transfer priority, so that the clinician need not wait unnecessarily for the retrieval of data items unrelated to the follow-up step being performed. As described below, this feature of the invention is implemented in-part using two device handler software tasks--one in charge of background interrogation and the other in charge of foreground telemetry operations--which contend with one another for control of the telemetry channel. Once the foreground telemetry operation has been completed, the programmer 120 automatically resumes the background interrogation process to retrieve the data items corresponding to the remaining protocol steps.

The programmer software can advantageously be configured by the user such that, once all protocol data items have been retrieved, the programmer 120 automatically retrieves all other diagnostic and parametric data items (in the background) stored by the implanted device; this advantageously allows the clinician to view non-protocol data items (e.g., at the end of the automated session) without having to wait for interrogation and data retrieval. When this option is selected, all of the retrievable data items stored by the implanted device reside within the programmer's memory at the end of the background interrogation process. (For an AFFINITYT.TM. pacemaker, the process of retrieving all of the pacemaker data by background interrogation typically takes about 45 seconds, assuming the background interrogation sequence is not interrupted.) The programmer automatically stores this data in a session log file (on the programmer's hard disk) for subsequent recall and use; thus, even if the clinician does not view all of the available diagnostic data during the follow-up session, the data can be viewed at a later time (e.g., during a subsequent patient visit).

While it is contemplated that the background interrogation feature will be most beneficial when used in conjunction with an automated follow-up protocol, it should be noted that the feature can also be used when no protocol is selected. For example, in one embodiment of the programmer 120, background interrogation is used to retrieve all of the pacemaker data (in a default order) whenever the clinician performs an initial interrogation of the implanted device.

Advantageously, the custom protocol and background interrogation features of the programmer 120 do not require any modification to the hardware or firmware of existing pacemakers. Thus, these automated follow-up features can be used in the examination of patients with a wide range of preexisting pacemakers, including, for example, pacemakers in the SYNCHRONY.TM., TRILOGY.TM., MICRONY.TM., SOLUS.TM., PARAGON.TM., PROGRAMALITH.TM., REGENCY.TM., PHOENIX.TM., SENSOLOG.TM., DIALOG.TM. and MULTILOG.TM. families of Pacesetter, Inc. These features can also be used to facilitate data retrieval and analysis with other types of implantable devices, such as defibrillators, drug pumps, and neural stimulators.

4. Benefits of Automated Follow-Up Features

As will be readily appreciated by those skilled in the art, the above-described automated follow-up features provide a number of significant advantages over existing programmers and methods of use thereof. One advantage is a significant reduction in the interaction required between the clinician 102 and the programmer 120 to follow a particular protocol. This allows the clinician to focus on interviewing the patient 100, rather than being concerned with the menu selections needed to initiate the various diagnostic tests and to retrieve, view and print the various diagnostic data records.

Another advantage is a significant reduction in the time required to conduct a follow-up session. This reduction in time is the result of both (1) the reduction in the number of menu selections required on the part of the clinician, and (2) the data retrieval efficiency which results from the background-interrogation-related features of the programmer. In initial tests, it has been found that a follow-up protocol which normally takes 20 minutes when performed manually can be performed in roughly three minutes when the automated follow-up option is used.

In addition to the foregoing efficiency-related advantages, the automated follow-up features help to ensure that all of the clinically significant information stored by the pacemaker will be considered during the follow-up session. For example, for a physician that normally follows a follow-up protocol (manually), the feature will help to ensure that no step of the protocol is accidentally skipped, even if the physician temporarily departs from the protocol. Furthermore, as a result of the time savings and added convenience provided by the automated follow-up feature, it is believed that many physicians will take the time to view more of the diagnostic data records stored by pacemakers.

Additional details of the protocol and background interrogation features of the programmer 120 are set forth in an application titled SYSTEM AND METHOD FOR FACILITATING RAPID RETRIEVAL AND EVALUATION OF DIAGNOSTIC DATA STORED BY AN IMPLANTABLE MEDICAL DEVICE, filed May 5, 1997, which is hereby incorporated by reference.

5. Hardware Architecture (FIG. 5)

The hardware architecture of the programmer 120 will now be described with reference to FIG. 5.

FIG. 5 is an overall system block diagram showing the main internal components of the pacemaker programmer 120. As shown in FIG. 5, the programmer 120 includes a central processing unit (CPU) board 500 which includes a 486 CPU 504, or the like. The CPU 504 communicates with a CPU chip set 510 which may, for example, include buffers, interface circuitry, random access memory (RAM), etc. In one embodiment, at least 16 megabytes of RAM are included in the CPU chip set 510 for use by the CPU 504.

The CPU board 500 communicates with an input/output (I/O) board 512 via an industry standard architecture (ISA) bus 514, with information being passed between the CPU 504 and the ISA bus 514 via the chip set 510. The ISA bus 514 communicates with UART (universal asynchronous receiver-transmitter) serial port interfaces 520 and 524, and a memory-mapped parallel interface 530. Each of the interfaces 520, 524, 530 acts as an interface between a peripheral unit and the CPU board 500. The serial port interface 520 communicates with a slave microprocessor 534 (e.g., an INTEL 87C451 microprocessor) within a telemetry hardware board 540.

The serial port interface 524 communicates with a touch controller 544 on the I/O board 512, which receives inputs from the touch screen 128. In one embodiment, the touch screen 128 is integrally formed with the main chassis 124 of the programmer 120 (not shown in FIG. 1). The memory-mapped parallel interface 530 acts as an interface between the CPU board 500 and a printer controller 548 within an internal printer 550. As illustrated in FIG. 1, the internal printer 550 is preferably integrally formed with the chassis of the programmer 120, although an external printer could alternatively be used.

The telemetry hardware board 540 includes the slave microprocessor 534, as well as a slave digital signal processor (DSP) 554 (e.g., a 2111 DSP) and telemetry analog circuitry 560. The microprocessor 534 communicates bidirectionally with the slave DSP 554, as well as with the telemetry analog circuitry 560. In addition, the slave DSP 554 communicates bidirectionally with the analog circuitry 560. The telemetry analog circuitry 560 transmits and receives RF signals via the telemetry wand 122.

In one preferred embodiment, the programmer 120 is provided with a PCMCIA or other modem (not shown) which communicates with a hospital network. Via this modem, the clinician can readily view and/or update patient status information (e.g., transcribed medical reports, images of chest X-rays and ultrasound scans, follow-up session files from previous follow-up visits, etc.) available on the network.

In operation, the CPU 504 serves as a main control processor within the programmer 120. All other processors (including the printer controller 547, the touch controller 544, the DSP 554 and the slave microprocessor 534) act as slaves to the CPU 504. Inputs are provided to the CPU 504 from the printer controller 548, the touch screen 128, the telemetry wand 122 (via the slave microprocessor 534), the mouse 136 and an external keyboard (not shown in FIG. 5). In addition, conventional hardware inputs, such as a system clock, are provided to the CPU 504. Furthermore, disk drive inputs from a CD-ROM, hard disk, floppy disk, etc. (not shown in FIG. 5) are provided to the CPU 504. Surface ECG information is also provided to the CPU 504.

The CPU 504 processes the information received via these inputs, and outputs instructions and data to each of the peripheral controllers 548, 544, 534 via the chip set 510, the ISA bus 514, and the I/O board 512. For example, the touchscreen controller 544 may transmit signals to the CPU 504 indicating that the clinician has touched the part of the touchscreen 128 which corresponds to a CLEAR HISTOGRAM button (FIG. 2) of the user interface. The CPU processes this input and in-turn instructs the slave microcontroller 534 to initiate transmission of a command from the telemetry wand 122 to clear a particular histogram from pacemaker memory.

The slave microprocessor 534 acts as a control processor of the telemetry hardware board 540. In a preferred embodiment, the slave microprocessor 534 controls the DSP 554 by sending the DSP 554 commands and data. The slave microprocessor 534 also can reset the DSP 554 to regain control of the DSP 554 in the event that the DSP 554 fails to respond properly. The program which is executed within the DSP 554 is preferably downloaded to the DSP 554 from the slave microprocessor 534. In like manner, the slave microprocessor 534 is monitored by the CPU 504, and the CPU 504 can reset the slave microprocessor 534 in the event that the code executing within the slave microprocessor 534 fails to operate properly. The code executed by the slave microprocessor 534 is downloaded to the microprocessor 534 from the CPU 504.

More specifically, the slave microprocessor 534 receives serial commands and data from the CPU 504, telemetry data output from the DSP 554, and signals from the analog circuitry 560. The slave microprocessor 534 processes commands from the CPU 504 and responds to these commands in accordance with requests issued by the CPU 504. In addition, a continuous stream of IEGM and surface ECG data is transmitted to the CPU 504 and to the analog outputs from the slave microprocessor 534. The slave microprocessor 534 also monitors the DSP 554 for correct operation, and reloads the DSP program upon a reset condition.

The DSP 554 manages a telemetry protocol at the telemetry frame level, and performs a variety of standard signal processing functions such as filtering IEGM received from the pacemaker 110 and ECG data received from the surface electrodes 132. The touch controller 544 (also referred to hereinafter as the "touch panel processor") serves as a decoder for the touch screen 128. When a user presses a point on the touch screen 128, this information is decoded by the touch panel processor 544 and sent to the CPU 504 via the serial interface 524. The printer controller 548 controls the operation of the internal printer hardware in response to instructions from the CPU 504. The telemetry wand 122 transmits and receives information to and from the pacemaker 110 via a conventional wireless communications link.

6. Software Architecture and Data Flow (FIGS. 6-16)

FIG. 6 is a conceptual schematic block diagram which illustrates an overview of the software architecture used in the preferred embodiment of the invention. The software system 310 includes a graphical user interface 315 which runs under the control of an operating system 320. In one embodiment, the operating system may be implemented as the VxWorks real time operating system available from Wind River Systems. Applications subsystem 330 passes parameters and other information to the user interface 315 and also runs under the control of the operating system 320. A device handler module 340 accesses processes included within the applications module 330 using operation system objects to transfer control of the processes to the device handler module 340. Finally, a telemetry module 350 accesses processes within the device handler module 340 using operating system objects to transfer control of the processes to the telemetry module 350.

In operation, the user interface module 315 includes routines and tasks which are used to control the display of data on the touch-screen monitor 128, as well as the input of data received via the touch-screen monitor 128, the mouse 136, an external keyboard, permanent buttons on the programmer 120, etc. For example, if the user touches a certain place on the touch screen 128, the user interface determines which operation is to be performed based upon the coordinates of the location touched by the user.

The user interface 315 calls application processes and subroutines within the applications module 330 to perform some of the input/output and display operations required by the user interface module 315. The operating system 320 is used to command the execution of routines and tasks, and also provides resource allocations amongst the various modules. Communication between tasks, with the exception of the output from the applications module 330 to the user interface 315, is through interprocess communication facilities provided by the operating system 320. In one preferred embodiment, the user interface module 315, the operation system 320, and the processes within the applications module 330, are all executed within the central processing unit 504.

The device handler module 340 includes processes and subroutines which are executed within the CPU 504 to manage control of the peripheral devices such as the printer 550, the touch screen 128, and the telemetry wand 122. A device handler module 340 may access applications, processes and subroutines stored within the applications library module 330 in order to manage each of the peripheral devices connected to the pacemaker programmer 120.

Finally, the telemetry module 350 includes processes and subroutines which are used to directly control the operation of the telemetry hardware board 240, as well as the telemetry wand 122. The processes and subroutines within the telemetry module 350 execute within the slave microcontroller 235 or the slave DSP 255. Different tasks, processes or subroutines within the device handler module 340 can be accessed from the telemetry module 350 via the operation system 320.

The various automated analysis and programming features of the invention will now be described with reference to the flowcharts of FIGS. 7-20.

PIG. 7 is a flowchart which illustrates an example sequence of tests that may be performed during a follow-up visit, and will be used to describe the automated analysis and programming features of the programmer 120. Typically, these tests will be part of a custom or standard protocol, and will be interleaved with protocol steps that involve the retrieval of histogram and other diagnostic data. For purposes of this illustration, however, it may be assumed that the tests listed in FIG. 7 are the only steps of the predefined protocol.

It may also be assumed that the follow-up examination is in connection with a pacemaker which is providing dual-chamber pacing with atrial tracking, and which is pacing and sensing in both the atrium and the ventricle with an inhibited or triggered response to sensing. In this pacing mode, in the absence of intrinsic activity, both chambers are paced at the program base rate. Intrinsic atrial activity (i.e., electrical stimuli provided to the cardiac tissue by the natural operation of the heart) during the atrial alert period inhibits the pacemaker atrial output. Furthermore, the interval used to measure the time between the last ventricular sensed or paced event and the delivery of the next atrial pulse (commonly referred to as the atrial escape interval) is terminated to initiate the AV delay (i.e., the interval used to measure the time between the last atrial sensed or paced event and the delivery of the next ventricular pulse). This pacing mode is typically referred to as DDD pacing.

As depicted in FIG. 7, in response to initiation of the protocol by the physician, the programmer 120 performs pace and capture tests, as represented within a subroutine block 410. A pace and capture test is a test which is used to determine when a pulse generated by the pacemaker 110 is at a sufficient amplitude to produce a ventricular or atrial beat within the patient's heart 115. The method employed within the subroutine block 410 will be described in greater detail below with reference to FIG. 8.

Once the programmer 120 completes the pace and capture tests, the programmer 120 proceeds to perform sensing tests, as represented within a subroutine block 420. The sensing tests are used to verify the sensitivity of the pacemaker 110 in accurately sensing and recording electrical activity in the heart. Thus, the method performed within the subroutine block 420 verifies the ability of the pacemaker to recognize and respond to the electrical activity of the patient's heart 115. The manner in which the pacemaker 110 responds to the sensed signals depends upon the program mode and parameters of the pacemaker 110. The method employed within the subroutine block 420 will be described in greater detail below with reference to FIG. 9.

Finally, the programmer 120 tests the hardware within the pacemaker 110 to ensure that, for example, the battery is charged and the leads of the pacemaker 110 are operational. This method is represented within a subroutine block 430 and will be described in greater detail below with reference to FIG. 17. Finally, the method terminates, as represented within an end block 440.

FIG. 8 is a flowchart which illustrates in greater detail the method used to perform the pace and capture tests represented in the subroutine 410 of FIG. 7. As depicted in FIG. 8, the submethod initiates, as represented by a begin block 445, and thereafter the programmer 120 automatically interrogates the pacemaker 110 to retrieve the parameters, as represented within an activity block 450. The programmer 120 retrieves each of the parameters and data history stored in the memory within the pacemaker 110 via the telemetry link 122.

Once the programmer 120 has interrogated the paced parameters, the programmer 120 defines a baseline data strip, as represented within an activity block 455. As is well known in the art, a baseline data strip constitutes the data taken for the ECG, IEGM, and corresponding markers while the patient is in the normal resting state, and is used as a reference against which unusual or abnormal states may be measured. This baseline may comprise paced and/or sensed data in the atrial channel, as well as paced and/or sensed data in the ventricular channel. Both the heart rate and the PR interval (i.e., the period of time measured from the onset of atrial depolarization to the onset of ventricular depolarization) are measured by the programmer 120. In accordance with the preferred embodiment of the invention, both sensed and paced beats can be analyzed when the sensing function is monitored. Likewise, paced beats can be analyzed for capture verification.

Once the baseline data strip has been defined within the activity block 455, the programmer 120 instructs the pacemaker 110 to increase the pulse rate and to decrease the AV interval as represented within an activity block 460. As is well known in the art, the AV interval is the length of time between an atrial paced event and the delivery of a ventricular output pulse. For sensing purposes, the AV interval is defined as the length of time measured between an atrial sensed event and the delivery of a ventricular output pulse. Since the method described in FIG. 8 is a method of performing pace and capture tests, however, the decrease of the AV interval means that the programmer 120 decreases the length of time between the atrial paced event and the delivery of a ventricular output pulse. The AV interval is also referred to herein as the AV delay. The purpose of increasing the pulse rate and decreasing the AV interval is to overdrive both chambers of the patient's heart 115 to obtain a data strip. This step allows capture to be verified in both chambers, even if the output pulses are masked by sinus rhythm and/or AV conduction. Furthermore, by increasing the pulse rate and decreasing the AV interval, the likelihood of fusion beats in both chambers of the patient's heart 115 is substantially reduced. When the data strip is obtained, only the surface ECG and markers are analyzed during this step, since it is likely that the IEGM output signals are saturated after the pacing spikes. The surface ECG is analyzed to verify that every pacer pulse on the marker data is followed by an evoked response at the appropriate time. A failure to capture in the ventricle in the presence of intact AV conduction, for example, will show up as a lengthening of the time between the ventricular stimulus to the evoked response. If the AV delay had not been shortened, this determination would be more difficult. Thus, the decrease in the AV interval and the increase in the pulse rate increases the ability of the programmer 120 to verify that every pacer pulse is followed by an evoked response at the appropriate time.

Once the pulse rate has been increased and the AV interval has been decreased, a determination is made if the atrial rate is above a pre-specified threshold value, as represented within a decision block 465. If the measured atrial rate is high enough that the overdrive rate would be above this predetermined limit, then the physician 102 is asked if he wishes to skip the determination of atrial capture. Thus, if the atrial rate is over the predefined threshold value, a further determination is made if the atrial rate is above a second, higher predefined threshold value, as represented within a decision block 470. However, if the atrial rate is not above the first threshold value, the method proceeds according to the normal fashion, and the ventricular capture test is performed, as represented within a subroutine block 477.

If it is determined within the decision block 470 that the atrial rate is above the second threshold value, then the atrial capture test would be automatically skipped, as represented within an activity block 475. In the event that the atrial capture test is automatically skipped, the physician 102 is informed by a message on the display screen 128. However, if the atrial rate is not over the second predefined threshold value, then the physician 102 is asked if the atrial capture test should be skipped, as represented within a decision block 472. If the physician decides that the atrial capture test should be skipped, then the method proceeds to the activity block 475, which causes the atrial capture test to be skipped and which confirms that the test has been skipped with a message to the physician on the display screen 125. However, if the physician 102 determines that the atrial capture test should not be skipped, then the method proceeds to the subroutine block 477, wherein the ventricular capture test is performed.

If the physician 102 has determined that the atrial capture test should be skipped, the ventricular capture test is still conducted, as represented within a subroutine block 480 which is entered from the activity block 475. However, if the ventricular capture test is performed as represented within the subroutine block 480, the atrial capture test will not be performed after the ventricular capture test, as is the case with the ventricular capture test performed within the subroutine block 477. Other than this difference, the method employed within the subroutine block 477 is substantially the same as the method employed within the subroutine block 480 and will be described in greater detail below with reference to FIG. 18. Because the AV delay has been decreased, loss of capture will result in an increase in the measured time between the ventricular stimulus to the evoked response. This measurement is performed in order to provide an automatic measurement of ventricular capture safety margin. According to one preferred embodiment of the invention, if the analysis program does not observe an evoked response within a predefined period (e.g., 100 milliseconds), then a command is sent by the programmer 120 to the pacer 110, which causes the pacer 110 to provide a back-up pulse to the ventricle at a higher voltage. This avoids an excessive prolongation of the ventricular contraction in the absence of intact conduction. In an alternative embodiment of the invention, if the programmer 120 does not observe an evoked response within the same predetermined time period, then the ventricular amplitude is restored, and the rate of the output pulses produced by the pacemaker 110 is increased to minimize the pause in the ventricular contraction rate.

Once the ventricular capture test has been performed, as represented within a subroutine block 477, the AV delay is increased, as is the post-ventricular atrial refractory period (PVARP), as represented in an activity block 482. The PVARP constitutes one of the timing cycles in dual-chamber pacemakers during which the atrial channel's sensing circuitry is rendered unresponsive. Initiated by a sensed or ventricular paced event, and ending with an atrial sensed or paced event, the PVARP is intended to prevent the atrial-sensed amplifier from sensing far afield ventricular signals. Thus, the PVARP may be considered as the atrial equivalent of the ventricular blanking (i.e., the period in which the ventricular sense amplifier is temporarily disabled during the delivery of an output pulse so that signals from the opposite chamber are not detected). If the PVARP is sufficiently long, it can prevent the atrial channel from responding to premature atrial contractions or retrograde atrial depolarization, and thus prevent pacemaker-mediated tachycardias. Once the AV interval and the PVARP have been increased, the atrial capture test is performed, as represented within a subroutine block 485. The method employed within the subroutine block 485 to perform the atrial capture test will be described in greater detail below with reference to FIG. 19. Because the pulse rate has been increased and the AV delay has been increased, a loss of atrial capture will result in a delay in the atrial evoked response and a delay in the conducted R-wave (assuming intact AV conduction is present).

It should be noted that the PVARP could be lengthened for the entire testing procedure, since the patient 100 is at rest. The lengthening of the P-VARP would therefore prevent tracking of retrograde P-waves. This concept is an improvement which can also be applied to semi-automatic or automatic pace and sensing tests without the automatic analysis described herein.

In one embodiment of the invention, when loss of atrial capture is detected, a command is sent to the pacemaker 110, which causes the pacemaker 110 to produce an atrial stimulation pulse at an increased amplitude after a predetermined time (e.g., 100 milliseconds). If the programmer 120 is relying on R-wave measurements to determine atrial capture, then the atrial stimulation pulse would be provided with the ventricular stimulus pulse. In an alternative embodiment, when the loss of atrial capture is detected, the atrial amplitude is restored and a PVC (premature ventricular contraction) response is initiated in the pacemaker 110 by external control signals from the programmer 120 following the ventricular stimulus (i.e., the R-wave) in order to prevent retrograde conduction from starting a pacemaker-mediated tachycardia. In yet another embodiment of the invention, when loss of atrial capture is detected, the atrial amplitude is restored and the AV delay is substantially shortened to prevent retrograde conduction.

Since a trade-off exists between the number of cycles at each pulse amplitude during capture threshold determination and the test time, one aspect of the present invention involves saving physician preferences within the programmer 120 and also within the pacemaker 110 so that the physician 102 can initiate a patient-specific override. Other physician preferences, such as the first and second predefined thresholds, are similarly saved in the programmer 120 and/or the pacemaker 110. The saving of physician preferences is represented within an activity block 487, which may be entered from the atrial capture test subroutine 485 or directly from the ventricular capture test subroutine 480. Once the physician preferences have been saved, the method for performing ventricular and atrial capture tests terminates, as represented within an end block 490.

FIG. 9 is a flowchart which illustrates the overall method used in the preferred embodiment to perform sensing tests within the subroutine block 420 of FIG. 7. As depicted in FIG. 9, the method initiates as represented by a begin block 600, and thereafter all pacing parameters are restored to their original values, as represented within an activity block 610. The restoration of all pacing parameters to their initial values allows the programmer 120 to reestablish the baseline data strip which was initially established at the commencement of the pacing capture tests described above. Thus, after a predetermined number of cycles, the baseline strip is again analyzed. Thereafter, as represented within a subroutine block 620, the ventricular sense function is verified. The method of verifying the ventricular sense function will be described in greater detail below with reference to FIG. 10. Finally, the atrial sense function is verified, as represented within a subroutine block 630. The method employed to verify the atrial sense function will be described in greater detail below with reference to FIG. 11. Once both the ventricular and atrial sense functions have been verified, the method terminates, as represented within an end block 640.

FIG. 10 is a flowchart which illustrates, in greater detail, the method employed within the subroutine block 620 of FIG. 9 to verify ventricular sense function. As depicted in FIG. 10, the method initiates as represented by a begin block 700, and a ventricular sensing function is assessed as represented within a subroutine block 710. The method by which the ventricular sensing function is assessed will be described in greater detail below with reference to FIG. 12.

Once the ventricular sensing function has been assessed, a determination is made, as represented within a decision block 720, if the test was successful. That is, if the ventricular sensing function was confirmed so that the pacemaker 110 accurately senses each of the significant electrical events within the patient's heart 115, then the method proceeds to increase the AV interval and PVARP, as represented within an activity block 730. However, if the test was determined to be unsuccessful, the testing is performed again at a slower rate, as represented within a subroutine block 740. The method employed within the subroutine block 740 to test the ventricular sensing function at a slower rate will be described in greater detail below with reference to FIG. 14.

If it is determined within the decision block 720 that the test is successful, and the AV interval and PVARP have been increased, then a further test is performed, as represented within a decision block 750, to determine if intact conduction is present. Intact conduction occurs when electrical stimulus initiated in the atrium is transmitted to the ventricle. If intact conduction is not present, then the method enters the subroutine block 740 to test the ventricular sensing function at a slower rate. However, if intact conduction is present, ventricular sensing must be confirmed under the planned test conditions before the test can be performed. Therefore, the method enters a subroutine block 760 wherein the ventricular sense function is reassessed as will be described below with reference to FIG. 12.

Once the ventricular sense function has been reassessed, a determination is made if this test is successful, as represented within a decision block 770. If the test is not successful, then the method enters the subroutine block 740 to test the ventricular sense function at a slower rate. However, if the test is determined to be successful within the decision block 770, then an automatic sense test is carried out, as represented within a subroutine block 780. Performing the automatic test at a base rate with a long AV delay and a long PVARP for patients with intact conduction has the advantage of not requiring that traditional testing at a rate of 30 pulses per minute and the concomitant bradycardia. The loss of sensing is recognized by the continued presence of an R wave on the surface ECG and ventricular IEGM, together with the loss of an R wave marker and the presence of a ventricular stimulation marker. Once the automatic sense test has been performed or testing has been conducted at a slower rate, the method for verifying ventricular sensing function terminates, as represented within an end of block 790.

FIG. 11 is a flowchart which illustrates, in greater detail, the method employed within the subroutine block 630 of FIG. 9 to verify atrial sense function. As depicted in FIG. 11, the method initiates as represented by a begin block 800, and an atrial sensing function is assessed as represented within a subroutine block 810. The method by which the atrial sensing function is assessed will be described in greater detail below with reference to FIG. 13.

Once the atrial sensing function has been assessed, a determination is made, as represented within a decision block 820, if the test was successful. That is, if the atrial sensing function was confirmed so that the pacemaker 110 accurately senses each of the significant electrical events within the patient's heart 115, then the method proceeds to increase the AV interval and PVARP, as represented within an activity block 830. However, if the test was determined to be unsuccessful, the testing is performed again at a slower rate, as represented within a subroutine block 840. The method employed within the subroutine block 840 to test the atrial sensing function at a slower rate will be described in greater detail below with reference to FIG. 15.

If it is determined within the decision block 820 that the test is successful, and the AV interval and PVARP have been increased, then a further test is performed, as represented within a decision block 850, to determine if intact conduction is present. As discussed above, intact conduction is when electrical stimulus initiated in the atrium is transmitted to the ventricle. If intact conduction is not present, then the method enters the subroutine block 840 to test the atrial sensing function at a slower rate. However, if intact conduction is present, then the method enters a subroutine block 860 wherein the atrial sense function is reassessed.

Once the atrial sense function has been reassessed, a determination is made if this test is successful, as represented within a decision block 870. If the test is not successful, then the method enters the subroutine block 840 to test the atrial sense function at a slower rate. However, if the test is determined to be successful within the decision block 870, then an automatic sense test is carried out, as represented within a subroutine block 880. Once the automatic sense test has been performed or testing has been conducted at a slower rate, the method for verifying atrial sensing function terminates, as represented within an end of block 890.

FIG. 12 is a flowchart which details the method used to assess the ventricular sensing function within the subroutine block 710 of FIG. 10. The method initiates as represented by a begin block 900, and thereafter a determination is made if R waves are present on the ventricular IEGM and on the surface ECG coincident with R wave markers, as represented by a decision block 910. Furthermore, a determination is made if no ventricular stimuli is applied by the pacemaker 110. If the programmer 120 determines that each of these conditions is satisfied, the programmer 120 confirms that accurate ventricular sensing has taken place, as represented within an activity block 920. If these conditions are not satisfied, the programmer 120 determines if no R wave markers and VIEGM precedes the ventricular stimulation, as represented by activity block 930. If this condition is not satisfied, the sensing cannot be confirmed and the test ends, as represented by an end block 960. However, if it is determined that a ventricular stimulation marker is present and no R wave marker is present while the ventricular IEGM precedes the ventricular stimulation marker by a predetermined amount, then a ventricular under-sensing failure is confirmed, as represented within an activity block 940. Once the ventricular under sensing failure has been confirmed within the activity block 940, the physician is queried to confirm the sensing failure, as represented within an activity block 950. The physician confirmation assures that no errors are made within the automatic analysis so that the monitoring physician 102 can make the final determination as to whether or not a sensing failure has taken place by observing the wave forms on the display screen 125. Finally, the method of assessing the ventricular sense function terminates, as represented by an end block 960, which is entered from either the activity block 920 or the activity block 950.

FIG. 13 is a flowchart which details the method used to assess the ventricular sensing function within the subroutine block 810 of FIG. 11. The method initiates as represented by a begin block 1000, and thereafter a determination is made if P waves are present on the atrial IEGM and on the surface ECG coincident with P wave markers, as represented by a decision block 1010. Furthermore, a determination is made if no atrial stimuli is applied by the pacemaker 110. If the programmer 120 determines that each of these conditions is satisfied, the programmer 120 confirms that accurate atrial sensing has taken place, as represented within an activity block 1020. If these conditions are not satisfied, the programmer 120 determines if no P wave markers and AIEGM precedes the atrial, as represented by activity block 1030. If this condition is not satisfied, the sensing cannot be confirmed and the test ends, as represented by an end block 1060. However, if it is determined that an atrial stimulation marker is present and no P wave marker is present while the atrial IEGM precedes the atrial stimulation marker by a predetermined amount, then an atrial under sensing failure is confirmed, as represented within an activity block 940. Once the atrial under sensing failure has been confirmed within the activity block 1040, the physician 102 is queried to confirm the sensing failure, as represented within an activity block 1050. The physician confirmation assures that no errors are made within the automatic analysis so that the monitoring physician 102 can make the final determination as to whether or not a sensing failure has taken place by observing the wave forms on the display screen 125. Finally, the method of assessing the atrial sense function terminates, as represented by an end block 1060, which is entered from either the activity block 1020 or the activity block 1050.

FIG. 14 is a flowchart which details the method used within the subroutine block 740 of FIG. 10 to test the ventricular sensing function at a slower test rate (e.g., 30 pulses per minute). The method initiates as represented by a begin block 1100, and thereafter the programmer 120 determines if the ventricular IEGM signals and surface ECG signals are correlated with the R wave markers, as represented within a decision block 1105. If it is determined that the ventricular IEGM signals and the surface ECG are correlated with the R wave markers, then the ventricular sensing function is confirmed, as represented within an activity block 1110, and an automatic ventricular sense test is carried out, as represented within an activity block 1115.

However, if it is determined within the decision block 1105 that the ventricular IEGM signals and the surface ECG signals are not correlated with the R wave markers, then a further determination is made, as represented within a decision block 1120, if R waves are present on the ventricular IEGM and the surface ECG, and furthermore, if ventricular stimulation is present while the R wave marker is absent. If it is determined that the test conditions determined within the decision block 1120 are fulfilled, then ventricular sensing is considered to be lost, as represented within an activity block 1125, and the physician is notified via the display screen 125. However, if it is determined that the test conditions within the decision block 1120 are not met, then a still further determination is made, as represented within a decision block 1135, if R wave markers are absent but ventricular stimulus markers are present. If R wave markers are absent while the ventricular stimulus markers are present, then the ventricular IEGM and surface ECG are analyzed for the presence of R wave signals, as represented within an activity block 1140. However, if it is determined that the ventricular stimulus markers are not present or that the R wave markers are not absent, then ventricular sensing is considered to be lost and a monitoring physician 102 is notified via the display screen 125, as represented within the activity block 1125. Once ventricular sensing has been confirmed lost, the method terminates as represented within an end block 1130.

If it was determined within the decision block 1135 that R wave markers were absent but ventricular stimulus markers were present, so that the ventricular IEGM and the surface ECG were analyzed for the presence of R wave signals, then a further determination is made, as represented within a decision block 1145, if R wave markers were found during the analysis performed within the activity block 1140. If it is determined that R wave markers were found, then a ventricular under sensing failure is confirmed, as represented within an activity block 1150. However, if no R wave markers are found, a further determination is made of atrial stimulation markers are present, as represented within a decision block 1155. If it is determined that atrial stimulation markers are present, then the programmer 120 reports that the ventricular sensing function cannot be verified as represented within activity block 1160. However, if it is determined within the decision block 1155 that atrial stimulation markers are not present, then the physician 102 is advised of this condition and the pacemaker 110 is programmed by the programmer 120 to initiate ventricular inhibited pacing at 30 pulses per minute, as represented within a subroutine block 1165. The method employed within the subroutine block 1165 is described in greater detail below with reference to FIG. 16. Finally, the method terminates, as represented within the end block 1130, which may be entered from the subroutine block 1165, the activity block 1150, the activity block 1160, or the activity block 1125 of FIG. 14.

FIG. 15 is a flowchart which details the method employed within the subroutine block 840 of FIG. 11 to test the atrial sensing function at a slow rate (e.g., 30 pulses per minute). The method initiates as represented by a begin block 1200, and a determination is made if the atrial IEGM signals are correlated with the P wave markers, as represented within a decision block 1205. If the atrial IEGM signals are correlated with the P wave markers, then the atrial sensing function is verified, as represented within an activity block 1210, and an automatic atrial sense test is performed, as represented within an activity block 1215. The automatic atrial sense test will be described below in reference to FIG. 20.

If it is determined within the decision block 1205 that the atrial IEGM signals are not correlated with the P wave markers, then a further determination is made if P waves are present on the atrial IEGM and atrial stimulus markers are present, while the P wave markers are absent. This determination is represented within a decision block 1220. If the conditions within the decision block 1220 are satisfied, then the programmer 120 confirms that atrial sensing is lost and sends a message to the monitoring physician 102 via the display screen 125, as represented within an activity block 1225. However, if the test conditions within the decision block 1220 are not satisfied, then a further determination is made, as represented within decision block 1235, if the P wave markers are absent, while the atrial stimulus or the R wave markers are present for at least a predetermined time delay. If the test conditions of the decision block 1235 are not satisfied, then atrial sense is lost, and a notification is provided to the monitoring physician 102 via the display screen 125, as represented within the activity block 1225. If it is determined that atrial sensing is lost, then the method for testing atrial sensing function terminates, as represented within an end block 1230.

However, if it is determined within the decision block 1235 that P wave markers are absent while the atrial stimulus or R wave markers were present, then the atrial IEGM is analyzed for the presence of P wave markers. If no P wave markers are found, as represented within a decision block 1245, then the programmer 120 reports that atrial sensing cannot be verified as represented within an activity block 1247. However, if it is determined that P wave markers are found within the decision block 1245, then an atrial under sensing failure is confirmed, as represented within an activity block 1250, and the monitoring physician 102 is notified of the atrial under sensing failure. The physician is then given the opportunity to confirm the atrial under sensing failures based upon the physician's observations of the displayed surface ECG and atrial IEGM. Thereafter, the method terminates within the end block 1230.

FIG. 16 is a flowchart which details the method employed within the subroutine block 1165 of FIG. 14 to program the pacemaker 110 to perform ventricular inhibited pacing. The method initiates as represented within a begin block 1300, and thereafter, a determination is made if ventricular stimulation markers are present, while R wave markers are absent, as represented within a decision block 1305. If ventricular stimulation markers are present while the R wave markers are absent, then the ventricular IEGM and surface ECG are analyzed for R wave signals, as represented within an activity block 1310. However, if ventricular stimulation markers are not present or the R wave markers are not absent, a further determination is made within a decision block 1315 if R wave markers are present while the ventricular stimulation markers are absent.

If during the analysis of the ventricular IEGM and surface ECG R wave markers are found, as represented within a decision block 1320, then a ventricular under sensing failure is reported to the monitoring physician 102 via the display screen 125, as represented within an activity block 1325. However, if no R wave markers are found upon the analysis, then the programmer 120 reports that the ventricular sense function cannot be verified, and the programmer 120 restores the parameters of the pacemaker 110 to their original settings, as represented within an activity block 1330. Thereafter, the method terminates from the activity blocks 1325 or 1330, as represented by an end block 1355.

Within the decision block 1350, if it is determined that R waves are present while ventricular stimulation markers are absent, then the R wave sensing is verified, as represented within an activity block 1335, and a ventricular sense test is performed automatically, as represented within an activity block 1340. It should be noted that the ventricular sense test performed within the activity block 1340 is performed at a slow rate of 30 pulses per minute. However, if it was determined within the decision block 1350 that either the R waves are absent or the ventricular stimulation markers were present, then the programmer 120 reports that ventricular sensing has been lost, as represented within an activity block 1345, and all pacing values are restored to their initial settings by the programmer 120, as represented within an activity block 1350. The activity block 1350 is entered from either the activity block 1340 or the activity block 1345. Finally, the method for testing ventricular sensing in the ventricular-inhibited pacing mode terminates within the end block 1355.

FIG. 17 is a flowchart which details the method employed within the subroutine block 430 of FIG. 7 to test the battery and leads. The test initiates as represented within a begin block 1700, and thereafter, the measured data is retrieved from the pacemaker (if not yet retrieved), as represented within an activity block 1710. From the measured data, the Daily Average Battery Voltage is analyzed to determine if the battery has reached the Recommended Replacement Time or End of Life levels, as represented within a decision block 1720. If either of these conditions is met, the programmer 120 notifies the physician of the need to replace the battery, as represented within an activity block 1730. If neither condition is met, the battery is determined to be operating within acceptable parameters. At this point, the battery test is complete and the lead tests begin.

To perform the lead tests, diagnostic data is retrieved from the pacemaker, as represented within an activity block 1740. From the diagnostic data, the status bits of the Lead Supervision algorithm are analyzed to determine if lead switching was performed in either the atrial or ventricular leads, as represented within a decision block 1750. If lead switching has occurred, the physician is notified of a lead fault, as represented within an activity block 1760. If no lead switching has occurred, the leads are determined to be operating normally. The battery and lead test then terminates within the end block 1770.

FIG. 18 is a flowchart which details the method employed within the subroutine blocks 477 and 480 of FIG. 8 to perform a ventricular capture test. The test initiates as represented by a begin block 1800 and then historical data is retrieved from the pacemaker as indicated within an activity block 1810. From the historical data, an initial ventricular pulse amplitude is determined and programmed into the pacemaker, as represented within activity block 1820. Typically, the initial pulse amplitudes is simply one increment below the currently programmed amplitude. However, the preferred embodiment of the present invention uses the historical data to estimate the amplitude at which capture will be lost. Then, the amplitude step immediately above that estimated value is used as the initial value. This reduces the number of amplitude steps which must be programmed during the test. The test then determines if a loss of capture occurs, as represented within decision block 1830. A loss of capture is declared when no ventricular event is detected in the ECG waveform during the 120 ms following a "V" marker. If a loss of capture is not detected, the ventricular pulse amplitude is decreased as represented within activity block 1840. The amplitude is decreased until a loss of capture is detected. After a loss of capture is detected, the programmer 120 records the capture threshold as represented within activity block 1850. The ventricular pulse amplitude is restored to the pre-test value, as represented within activity block 1860 and the test terminates in the end block 1870.

FIG. 19 is a flowchart which details the method employed within the subroutine block 485 of FIG. 8 to perform an atrial capture test. The test initiates as represented by a begin block 1900 and then historical data is retrieved from the pacemaker as indicated within an activity block 1910. From the historical data, an initial atrial pulse amplitude is determined and programmed into the pacemaker, as represented within activity block 1920. Typically, the initial pulse amplitude is simply one increment below the currently programmed amplitude. However, the preferred embodiment of the present invention uses the historical data to estimate the amplitude at which capture will be lost. Then, the amplitude step immediately above that estimated value is used as the initial value. This reduces the number of amplitude steps which must be programmed during the test. The test then determines if a loss of capture occurs, as represented within decision block 1930. A loss of capture is declared in one of two situations. If intact conduction is present and the pre-test rhythm was AR, then loss of capture is declared when the "A" marker is followed by a "V" marker instead of an "R" marker. Alternatively, loss of capture is declared if no atrial event is detected in the ECG waveform during the 120 ms following an "A" marker. If a loss of capture is not detected, the atrial pulse amplitude is decreased as represented within activity block 1940. The amplitude is decreased until a loss of capture is detected. After a loss of capture is detected, the programmer 120 records the capture threshold as represented within activity block 1950. The atrial pulse amplitude is then restored to the pre-test value, as represented within activity block 1960 and the test terminates in the end block 1970.

FIG. 20 is a flowchart which details the method employed within the subroutine block 1215 of FIG. 15 to perform an automatic atrial sense test. The test initiates as represented by a begin block 2000 and then historical data is retrieved (if not yet retrieved) from the pacemaker as indicated within an activity block 2010. From the historical data, an initial atrial sensitivity is determined and programmed into the pacemaker, as represented within activity block 2020. The sensitivity step immediately below the value in the historical data at which sensitivity is lost is used as the initial value. The test then determines if a loss of sensing occurs, as represented within decision block 2030. A loss of sensing is declared if a P-wave is detected in the IEGM waveform, followed by an "A" marker or "R" marker, and no "P" marker. If a loss of sensing is not detected, the atrial sensitivity is increased as represented within activity block 2040. The sensitivity is increased until a loss of sensing is detected. After a loss of sensing is detected, the programmer 120 records the sensing threshold as represented within activity block 2050. The atrial sensitivity is restored to the pre-test value, as represented within activity block 2060 and the test terminates in the end block 2070.

Automating the above tests as described above significantly shortens the time required to perform the follow-up examination. For example, the follow-up time for a complex DDD pacer could be shortened from more than 15 minutes to less than 2 minutes. Of course, while a DDD follow-up is detailed herein, similar analysis may be performed for other pacing systems.

While certain preferred embodiments of the invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the present invention. For example, while the various automated features have been described as being embodied within a programmer system that includes both diagnostic and device programming features, some of these features can be embodied within a purely diagnostic system. Thus, the breadth and scope of the present invention should be defined only in accordance with the following claims and their equivalents.