Cardiac stimulating device

[0001] 1. Field of the Invention

[0002] The present invention relates to an implantable cardiac stimulating device of the type having the capability to sense and stimulate the right atrium, to sense the left atrium, and to sense and stimulate the right and left ventricles, respectively.

[0003] 2. Description of the Prior Art

[0004] Most pacers are arranged to stimulate the right ventricle of the heart, but it is also known to stimulate the left ventricle. In particular for the treatment of congestive heart failure or other severe cardiac failures it is known to stimulate the left ventricle, or both ventricles, in order to optimize the hemodynamic performance of the heart.

[0005] U.S. Pat. No. 5,720,768 describes different possible electrode positions in order to stimulate or sense the different chambers of the heart. It is also disclosed that the conduction time from right atrium to left atrium may be observed and the left atrium may be paced if the conduction time is too long.

[0006] It is well known in the art that it is difficult to position an electrode to pace and sense the left atrium. There is a need to provide a device alleviating these difficulties.

[0007] An object of the present invention is to provide a cardiac pacemaker which provides an AV-interval which is optimized for the left side of the heart. This object is achieved in accordance with the invention in a cardiac stimulating device of the type initially described, wherein a first AV-interval is started at paced or sensed events occurring in the right atrium. When the atrial depolarization has conducted to the left atrium this is sensed through an electrode located in the coronary sinus, preferably the proximal portion thereof. At the detection of the left atrial depolarization a second AV-interval optimized for the left heart is started. When this AV-interval has elapsed the left ventricle is stimulated with the left heart AV-interval. If no atrial event is detected on the coronary sinus electrode the initially started first AV-interval, AV1, will be used. Thus the AV-interval for the left side of the heart is optimized without any need for stimulating the left atrium.

[0010] FIG. 1 shows an implantable cardiac stimulating device, hereinafter also called a pacemaker system 1, according to the invention. The pacemaker system 1 has a housing 2 and leads 17, 18, 19, 20. A pacing circuit 3 is enclosed in the housing 2. The pacing circuit 3 is adapted to be connected to lead 19 with electrode 23. FIG. 1 shows such an electrode 23 which is connected to the pacemaker via lead 19. The first electrode 23 is adapted to be positioned to stimulate the left ventricle 9 of the heart 5. The pacing circuit 13 is also adapted to be connected to a second electrode 22. FIG. 1 shows such a second electrode 22 connected to the pacing circuit 3 via a lead 18. The second electrode 22 is positioned to sense depolarizations of the left atrium of the heart 5. The pacing circuit 3 is further adapted to be connected to a third electrode 21. FIG. 1 shows such a third electrode 21 connected to the pacing circuit 13 via a lead 17. The third electrode 21 is positioned to sense depolarizations the right atrium of the heart 5.

[0011] The leads 17, 19 and 20 are appropriately connected to respective output amplifiers 12, 13 and 15 (which emit stimulation pulses) and the leads 17, 18 19 and 20 are connected to respective sense amplifiers 11, 12, 14, and 16. The amplifiers 10–16 are connected to a control unit 4. A sensed or paced event originating from the right atrial electrode 21 causes the control unit 4 to start a first AV-interval AV1. The first AV-interval AV1 may be set to optimize the PA-RV contraction, the RA-LV contraction or the RA-both RV,LV contraction in the absence of a LA sense. In the normal case this right atrial depolarization will be conducted to the left atrium and be sensed by sense amplifier 12 via lead 18 and electrode 22. When the depolarization is detected at the left atrium the first ongoing AV-interval AV1 is superseded by the control unit 4 with a second AV delay AV2, specifically optimized for the left side of the heart 5. This will provide a correct left side AV interval also if there is slow conduction from right atrium 6 to left atrium 7. If no P-wave is detected from left atrial electrode 22 then the initially started first AV-interval AV1 will be used. At the end of the first AV-interval AV1 a stimulation pulse is delivered to the left ventricle via lead the 19 and electrode 23.

[0012] The leads 17, 18, 19 and 20 may include more than one electrical conductor in order to allow for bipolar pacing and sensing. In that case electrodes 21, 22, 23, and 24 will have two active surfaces each.

[0013] In a preferred embodiment the system also has a lead 20 with electrode 24 for stimulation of the right ventricle S and for detection of R-waves from the right ventricle. In that case the right ventricle may be paced with an AV-delay optimized for the right heart and the left ventricle may be paced with an AV-delay optimized for the left heart. Alternatively both ventricles are paced synchronously with an AV-interval optimized for the left ventricle.

[0014] According to an alternative embodiment as shown in FIG. 2 leads 18 and 19 are integrated into one lead 25 comprising electrodes 23 and 22 for placement in left ventricle and left atrium respectively.

[0015] In still another embodiment differential sensing is applied between electrodes 23 and 22 and discrimination between left ventricular P-waves and R-waves is accomplished through analysis of timing and morphology of the differential signal. This sensing concept is described in U.S. Pat. No. 5,571,143 and in U.S. Pat. No. 5,871,507, the teaching of which are hereby incorporated herein by reference.

[0016] In still another embodiment the left atrial contraction is detected as a Far-Field P-Wave, FFPW, by sensing amplifier 14 via lead 19 and electrode 23. Morphology discrimination may be applied to discriminate between left ventricular R-waves and FFPW as described above. Upon detection of a FFPW the ongoing AV-interval is superseded by the second AV-delay AV2, that is started to provide an AV-delay optimized for the left side of the heart.

[0017] In a further refinement individual timing is provided for 25 pacing the right and left ventricles. Right ventricle stimulation is delivered after the first AV-interval AV1 has elapsed. The second AV-interval AV2, which is started at the detection of a left atrial depolarization determines when the stimulation pulse shall be delivered to the left ventricle. If no left atrial depolarization is detected, the stimulation of the left ventricle is coordinated with the stimulation of the right ventricle.

[0018] Although modifications and changes may be suggested by those skilled in the art, it is the invention of the inventors to embody within the patent warranted heron all changes and modifications as reasonably and properly come within the scope of their contribution to the art.