Controllable Flexibility Catheter With Eccentric Stiffener

FIG. 1 is a schematic representation of a guiding catheter of the prior art engaged within the left main coronary artery illustrating the configuration of the guiding catheter prior to manipulation of the angioplasty dilitation balloon catheter across a region of the stenosis within the left anterior descending coronary artery;

FIG. 2 is a schematic representation similar to FIG. 1 illustrating one disadvantage of prior art guiding catheters, namely disengagement during manipulation of the dilation balloon catheter across the region of coronary stenosis;

FIG. 3 illustrates the forces which develop within the guiding catheter as the angioplasty dilation balloon catheter is advanced within (in this case) the left coronary artery, as well as the impact of these forces on the configuration of the guiding catheter;

FIG. 4 is a cross section of one embodiment of the catheter of my invention, together with a schematic sagittal section included for the purpose of orientation;

FIG. 5A, 5B, and 5C illustrates the means by which the catheter of my design functions to oppose the forces generated during manipulation of the dilitation balloon catheter;

FIGS. 6A-6D illustrate various alternate structures of the preferred embodiment;

FIG. 7 is a cross-sectional and longitudinal illustration of the preferred embddiment that depicts the venting system of the catheter; and

FIG. 8 depicts several cross sections and longitudinal sections of the distal aspect of the catheter illustrating a means of deflecting the tip of the catheter to optimize coronary ostial engagement.

FIG. 1 illustrates the typical configuration of a conventional left coronary guiding catheter in the aorta when engaged within the left main coronary artery during the performance of a left coronary artery 18 PTCA. (The guiding catheter has been drawn with a relatively large caliber for the purpose of clarity.) The aorta 10 includes an ascending portion 12 and a descending portion 14. The angioplasty dilation balloon 28 and intra-coronary guidewire 25 have been included in FIG. 1. Although a left Judkin's configuration guiding catheter is shown in this and subsequent illustrations, the invention is not confined to this configuration. My variably compliant guiding catheter can be applied to all configurations of guiding catheters including left and right Judkin's , Sone's , Stertzer and Amplatz configurations.

As described above, the performance of an angioplasty initially requires the introduction of a guiding catheter within a peripheral artery. By virtue of a guidewire (not shown) and the preshaped nature of guiding catheter 20 at its distal end 32, the catheter is manipulated up the descending aorta 14 and down the ascending aorta 12 to place the end 32 of the guiding catheter 20 within the coronar ostium, thus permitting subsequent advancement of the angioplasty guidewire 25 and balloon catheter 28 within the diseased vessel 18.

FIG. 2 illustrates a disadvantage of a guiding catheter of the prior art. The components depicted in FIG. 2 have been labeled with reference numerals corresponding to the components in FIG. 1. In FIG. 2 the dilation balloon 28 has been advanced to the region of stenosis 19. Because the resistance imparted by the lesion exceeds the compliance characteristics of the guiding catheter, however, further attempts to advance the balloon catheter result in disengagement of the guiding catheter 20 and prolapse of the balloon catheter.

In this circumstance, further attempts to advance the dilitation balloon catheter 28 across the region of stenosis 19 results in progressive destabilization of the system. This instability precludes the manipulation of the dilation balloon catheter 28 across the region of stenosis and thus, the successful completion of the angioplasty procedure. The instability of the guiding catheter is believed to result from several causes. The catheter itself has intrinsic flexibility to accommodate introduction. Also the material from which the catheter is manufactured (multiple layers of Dacron webbing coated with a plastic polymer) becomes more flexible as it warms to body temperature. Additionally, the configuration of the catheter provides little or no resistance to the forces which cause it to back out. For example, as shown in FIG. 3, the application of force 30 on the dilation balloon 28 to advance the dilation balloon across the region of stenosis increases the torque 31 on bend 35 in guiding catheter 20, causing the angioplasty balloon catheter 28 to prolapse in the ascending aorta precluding further progress.

FIGS. 4A and 4B illustrate one embodiment of the guiding catheter 20 of my invention. In contrast to prior art devices, the guiding catheter includes a means for varying the flexibility of the catheter as well as varying the torque generated within the distal aspect of the catheter at the option of the operator. For the embodiment shown in FIG. 4, these features are provided by a closed chamber 50 eccentrically disposed along almost the entire length of the housing 42 such that it virtually encompasses the housing. Chamber 50 may be filled with fluid. The channel preferably contains a relatively elastic segment 44 disposed preferentially along the outer circumference of the curvature 46 in the catheter. The hydrostatic pressure within channel 50 is adjusted as desired by the operator, for example, by use of a syringe 47 connected to channel 50 at the distal extracorporeal aspect of the catheter.

As shown by FIG. 5, the application of force to syringe 47 (not shown) results in the even distribution of hydrostatic pressure 41 within channel 50. Typically, the chamber will be designed to tolerate pressures on the order of 10 atmospheres. Because in one embodiment this channel contains a series of relatively flexible elastic segments 44 disposed along the circumferential surface 51 of the catheter in the region of curvature 46, surface 51 tends to elongate relative to the corresponding contra-lateral catheter surface 52 in response to the application of pressure in chamber 50, resulting in the development of torque 48 within the distal aspect of the catheter in the direction of the coronary ostium. In this circumstance the region 13 of the ascending aorta 12 (see FIGS. 1 and 2) functions as a fulcrum to support the catheter within the coronary ostium. The combination of the support afforded by the ascending aorta and the torque generated within the catheter by the pressure induced by syringe 47 oppose the force 49 generated during advancement of the dilitation balloon catheter and thus prevents disengagement of the guiding catheter. This enables the use of additional force to advance the dilation balloon 28 through the region of stenosis. Once the dilation balloon 28 has been advanced through the region of stenosis, the hydrostatic pressure within channel 50 is relieved, rendering the guiding catheter 20 substantially more flexible, and hence less likely to induce any intimal vascular damage. A pressure source is then applied to inflate tee balloon 28 of the dilation catheter (see FIG. 1) and thereby ablate the stenosis.

My invention offers several advantage over conventional guiding catheters used in the performance of an angioplasty procedure. Present catheters, in an effort to reach a compromise between flexibility and rigidity, are generally stiff, and therefore more difficult to advance within the aorta and engage within the ostium. My guiding catheter in its most flexible condition, permits easier engagement within the coronary ostium. Once engaged, the relative inflexibility of my catheter enables it to remain engaged within the ostium in a more stable manner than conventional catheters. This stability frequently precludes the need for multiple angioplasty catheters and exchange wires, with their associated disadvantages described above. By virtue of the controllable flexibility, the use of this catheter substantially eliminates the need to apply force to the coronary ostium and hence minimizes the trauma sustained by the patient during the course of the angioplasty. Disruption of the intima of the coronary ostium by conventional guiding catheters represents a well known complication of angioplasty procedures. This complication can result in a coronary occlusion, and hence, myocardial infarction. Finally, the compliance characteristics of my catheter are not affected by "warming up" to body temperature.

Because the catheter itself need not be as rigid as conventional catheters, the walls of the housing 42 need not be as thick. Accordingly, the caliber of the catheter may be less than the caliber of conventional guiding catheters. This feature permits insertion of the catheter within a smaller arteriotomy. Because the cross-sectional area of channel 50 is relatively large throughout nearly the entire length of the catheter, changes in hydrostatic pressure may be accomplished rapidly.

A further advantage of my catheter is that its use may preclude the normal requirement for two physicians. Two physicians typically are necessary, one to monitor the engagement of the guiding catheter, and one to advance the guidewire and balloon catheter. With my catheter, a physician may advance the catheter with one hand while adjusting the hydrostatic pressure within channel 50 with a syringe in the other hand, thus increasing and decreasing the rigidity of the, catheter as necessary to advance the dilitation catheter contained therein.

FIGS. 6A-6D illustrate alternative embodiments of my catheter. The various embodiments depicted in FIGS. 6A-6D differ with respect to the design and construction of the elastic segment 44 discussed above.

In FIG. 6A, a segment of the outer housing has been replaced by an elastic membrane 71. In FIG. 6B, the elastic membrane has been divided into a series of wedge-shaped elements 72. The relatively inflexible, inelastic segments 74 interposed between the elastic elements provide structural support and prevent axial expansion during pressurization of channel 50. In FIG. 6C, the wedge-shaped elements have been replaced by a series of kerfs 76, each composed of a par of planar elements 77. In this embodiment the catheter is constructed such that the angle 78 described by the junction of the pair of planar surfaces is controlled by the perator by adjusting the pressure within channel 50. Pressurization of channel 50 will cause the kerfs to unfold, and the planar surfaces of each kerf will contribute more to the outer surface of catheter 20 along the circumferential aspect of the preshaped curve 46 relative to the previous depressurized circumstance. Unfolding of the kerfs thus enhances the disparity in length between the inner 52 and outer 51 (see FIG. 5) of catheter 20 in the region of curve 46.

FIG. 6D illustrates another embodiment of the catheter wherein the kerfs have been replaced by a thin film 80 of a flexible inelastic material capable of withstanding very high pressures, such as mylar. Each wedge is constructed using excess film to permit elongation of surface 51 relative to surface 52 (see Fig.5) during pressurization of channel 50.

FIGS. 7A and 7B illustrate the means by which air is vented from the catheter during infusion of fluid within channel 50. If air were contained within this channel, it could escape in the event of a rupture and embolize within the bloodstream. Furthermore, the presence of air compromises the function of the stiffening element. Hence for both safety and performance, air is vented from channel 50 during infusion of the fluid. This is accomplished by two venting ports 82 which extend along nearly the entire length of the catheter. These venting ports communicate with the lumen of channel 50 at the very distal aspect of the catheter by means of channel 84. During the infusion of fluid in channel 50, these veining ports 82 allow air to be displaced until the entire channel 50 is fluid filled. Fluid leaking out of the vent ports notifies the operator that the channel is entirely vented. Valve 64 then is closed to prevent further loss of fluid (as well as loss of hydrostatic pressure) during subsequent use of the catheter through the venting ports.

FIGS. 8A-8F illustrate other embodiments of my catheter. In this embodiment a second eccentrically disposed channel 54 is provided which is coupled to syringe 55 by communicating channel 56. In the same manner as channel 550, channel 54 contains an elastic segment 61 and may be pressurized from outside the patient. Secondary channel 54 enables selective deflection of the distal end 32 of the catheter 20 to assist in positioning the catheter within the coronary artery. It should be understood that any one of the various embodiments of the flexible, elastic segment of channel 50 (depicted in FIGS. 6A-6D) may be employed in segment 61 of channel 54. By placing the secondary channel on catheter 20 at about 0.degree. or 90.degree. rotation from the preshaped curve 46 (and from the orientation of channel 50), as illustrated i FIGS. 8B and 8C respectively, the distal end of the catheter may be deflected inferior or posteriorly (see FIG. 8C) to aid subselective cannulization of the LAD and circumflex branches of the left coronary system, respectively. Channel 83 functions as the vent port for channel 54.

The foregoing has been a description of the preferred embodiments of the invention. Although many specific details have been described, it should be understood that the description is only for the purposes of explaining the invention, and not limiting it. It should be further understood that the configuration of the catheter proposed herein is not limited to the left Judkin's configuration alone. This configuration was selected for the purpose of illustration only. The scope of the invention may be ascertained from the appended claims.