Sensors for transcutaneous pneumatic cardiac assist systems.

Abstract

The cardiac assist system includes a pneumatic effector and an external drive unit. The pneumatic effector is implanted proximal to a patient's heart to enhance left ventricular contraction. The external drive unit includes a gas pump connectable to the pneumatic effector and is configured to actuate the pneumatic effector assembly in response to a sensed cardiac rhythm of the patient. The system may include an isolation valve positioned between the gas pump assembly and an inlet to the pneumatic effector, and a pressure sensor positioned between the isolation valve and the inlet to the pneumatic effector, where the control circuit is configured to receive a change in pressure sensed by the pressure sensor when the isolation valve closes to isolate the pneumatic effector. The system may also include a liquid accumulator and a liquid sensor adjacent to the liquid accumulator sensor for detecting liquid in the pneumatic effector.

Description

[Technical Field]

[0001] cross reference This application claims the benefit of U.S. Provisional Application No. 63 / 407,100, filed September 15, 2022, which is incorporated herein by reference in its entirety. [Background technology]

[0002] 1. Field of the Invention. The present invention relates generally to medical devices, systems, and methods. More particularly, the present invention relates to a system for providing cardiac assistance to patients suffering from late-stage heart failure.

[0003] 2. Description of the Background Art. WO 2020 / 176670, commonly assigned to the present application, describes a "ventricular assist" balloon cannula configured to be inserted into a patient's pericardium and positioned anterior to the patient's left ventricle. The balloon is inflated during systole and deflated during diastole to increase cardiac output in patients with congestive heart failure and other conditions.

[0004] The ventricular assist balloon cannula is typically inserted through the pericardium on the underside of the heart near the apex, typically via a percutaneous subxiphoid incision or needle puncture. The distal tip of the ventricular assist balloon cannula is advanced to the left lateral surface of the heart just inferior to the left atrial appendage, positioning the balloon anterior to the left ventricle.

[0005] A fluid-tight reservoir is then attached to the proximal end of the ventricular assist balloon cannula, and the reservoir is implanted subcutaneously in the subxiphoid region. The balloon is inflated with air or other gas via an external pump using a large-bore needle that penetrates through the patient's skin into the subcutaneous reservoir. A gaseous inflation medium is used because it allows for the rapid inflation and deflation necessary to maintain cardiac rhythm. Leaks from or into the air pump circuit, including either pressure loss or liquid intrusion, can be problematic.

[0006] Pressure loss can be monitored directly, but small leaks can be difficult to detect because system pressure measurements are noisy. Liquid intrusion can be difficult to detect because liquids tend to pool in locations where their presence can be difficult to sense.

[0007] It would therefore be desirable to provide improved devices, systems, and methods for detecting or sensing both pressure loss and fluid intrusion in the air pump system of a ventricular assist balloon cannula system of the type described in WO 2020 / 176670. It would be further desirable if such devices, systems, and methods could be used in other percutaneous systems having pump systems, such as left atrial assist devices (LVADs), intra-aortic balloon pumps (IABPs), etc. At least some of these objectives will be achieved by the present invention, as described below. Summary of the Invention

[0008] In accordance with the principles of the present invention, a cardiac assist system includes a pneumatic effector assembly and an external drive unit. The pneumatic effector system's balloon or other pneumatic effector is implanted proximal to a patient's heart to enhance cardiac contractions, such as left ventricular contractions, and pumping action, and the external drive unit includes a gas pump connectable to the pneumatic effector assembly and configured to actuate the pneumatic effector in response to a sensed cardiac rhythm of the patient. In some embodiments, the cardiac assist system may include an isolation valve positioned between the gas pump assembly and an inlet to the pneumatic effector, and a pressure sensor positioned between the isolation valve and the inlet to the pneumatic effector, with the control circuit configured to receive a pressure change sensed by the pressure sensor when the isolation valve closes to isolate the pneumatic effector. In some embodiments, the cardiac assist system may include a fluid accumulator and a fluid sensor adjacent to the fluid accumulator sensor for detecting fluid in the pneumatic effector. In some embodiments, the cardiac assist system may include both pressure sensing and fluid accumulation detection capabilities.

[0009] In a first aspect, the present invention provides a cardiac assist system comprising a pneumatic effector assembly, an external drive unit, and a sensor assembly or subsystem for monitoring system performance during use. The pneumatic effector assembly is typically configured to be implanted proximal to a patient's heart to enhance left ventricular contraction. The external drive unit typically comprises (a) a gas pump assembly connectable to the pneumatic effector assembly, and (b) a control circuit configured to operate the gas pump assembly to actuate the pneumatic effector assembly in response to a sensed cardiac rhythm of the patient.

[0010] In a first embodiment, the sensor assembly or subsystem is configured to measure pressure within the pneumatic effector, typically specifically for leak detection. For example, the pressure sensing subsystem may include an isolation valve positioned between the gas pump assembly and an inlet to the pneumatic effector. A pressure transducer or other sensor is positioned between the isolation valve and the inlet to the pneumatic effector, and the control circuit is configured to receive a change in pressure sensed by the pressure sensor when the isolation valve is closed to isolate the pneumatic effector. Because closing the isolation valve isolates the pneumatic effector assembly, any loss of pressure indicates a break or other failure of the pneumatic effector assembly.

[0011] In a particular example, the isolation valve may be located within the external drive unit housing along with the gas pump assembly and control circuitry, hi another example, the isolation valve may be located between the external drive unit housing and the pneumatic effector assembly.

[0012] In a second embodiment, the sensor assembly or subsystem includes (1) a liquid accumulator positioned between the gas pump assembly outlet and the pneumatic effector assembly inlet, and (2) a liquid sensor adjacent to the liquid accumulator sensor. The liquid accumulator is configured to collect liquid that has infiltrated the pneumatic effector assembly or otherwise entered the air pump circuit. Such liquid intrusion may result from a breach in the pneumatic effector assembly, in which case there is likely to be a pressure loss, or there may be intrusion from another source with significant pressure loss. In this manner, the pressure sensor and liquid intrusion sensor subsystems are independent yet complementary, and either may indicate a system failure.

[0013] In a specific example, the pneumatic effector assembly of a pressure-sensing embodiment may include a catheter body having a proximal end, a distal end, and at least one gas exchange lumen therebetween. The pneumatic effector is typically positioned at the distal end of the catheter body, which is configured to (1) be implanted proximal to a patient's heart to enhance left ventricular contraction and (2) receive and expel inflation gas through the gas exchange lumen. A hub may be positioned at the proximal end of the catheter body and may be configured to be removably connected to a gas pump assembly of an external drive unit. A pressure sensor may be positioned in or on the hub and configured to sense pressure within the at least one gas exchange lumen. The hub may be attached directly to the proximal end of the catheter body (if the catheter body is intended for percutaneous introduction) but often includes a cannula for percutaneous access to an implantable port subcutaneously (directly) attached to the proximal end of the catheter body, where the implantable port is configured to percutaneously receive the cannula.

[0014] In a specific example, the control circuitry may be configured to calculate a pressure change gradient of any pressure change received from the pressure sensor during a predetermined pressure measurement period. For example, a calculated pressure change gradient (rate of change measured over a short time interval, typically 50 ms to 250 ms, usually 100 ms to 150 ms) greater than a predetermined threshold value would typically indicate the presence of a pressure leak within the pneumatic effector assembly. The pressure change gradient is considered a more sensitive indicator of pressure loss than the pressure loss value itself.

[0015] In a specific example, the pneumatic effector assembly of a liquid intrusion sensing embodiment may include a catheter body having a proximal end, a distal end, and at least one gas exchange lumen therebetween. The pneumatic effector at the distal end of the catheter body is configured to (1) be implanted proximal to a patient's heart to enhance left ventricular contraction and (2) receive and expel inflation gas through the gas exchange lumen. A hub at the proximal end of the catheter body is configured to be removably connected to a gas pump assembly of an external drive unit, with a liquid accumulator located in or on the hub and configured to accumulate liquid from the at least one gas exchange lumen, and a liquid sensor configured to detect liquid accumulated in the liquid accumulator. The hub may be attached directly to the proximal end of the catheter body (if the catheter body is intended for percutaneous introduction), but often includes a cannula for percutaneously accessing an implantable port attached directly to the proximal end of the catheter body, the implantable port configured to percutaneously receive the cannula.

[0016] In a particular example, the liquid accumulator may include a flow path between the gas pump assembly and the pneumatic effector, where the flow path may have a baffle and / or a reduced cross-sectional area for collecting liquid entrained in the gas flowing through the flow path. In such an example, the liquid sensor is typically located in the hub adjacent the baffle and / or reduced cross-sectional area of ​​the flow path.

[0017] Regardless of the type of sensor, the cardiac assist system may further include a connecting tube having a pump end attachable to the gas pump assembly and a hub end attachable to the hub, the connecting tube connecting the gas pump assembly to the pneumatic effector assembly. The pneumatic effector assembly may be configured to be implanted beneath the patient's pericardium and over the surface of the myocardium covering the patient's left ventricle. The pneumatic effector assembly may be configured to be implanted in a heart chamber. The cardiac assist system may further include at least one ECG electrode, wherein the at least one ECG electrode is positioned on the pneumatic effector assembly and configured to provide the patient's cardiac rhythm to the control circuitry. Alternatively, the at least one ECG electrode may be configured to be attached external to the patient and connected to the ECG circuitry by an external lead.

[0018] In a second aspect, the present invention provides a method for assisting cardiac function, the method comprising: detecting a patient's ECG to determine the cardiac rhythm; and delivering a drive gas from an external gas pump assembly to a pneumatic effector assembly implanted proximal to the patient's heart to enhance left ventricular contraction. The delivery of the drive gas is synchronized with the determined cardiac rhythm, causing the pneumatic effector assembly to compress and / or expand within the left ventricle of the heart at a rate consistent with the cardiac rhythm. The external pump assembly is isolated from the pneumatic effector assembly to prevent any exchange of drive gas, and pressure within the pneumatic effector assembly is measured while the pneumatic effector assembly is isolated from the external pump assembly. Potential leaks within the pneumatic effector assembly can be detected by detecting changes in the measured pressure.

[0019] In a specific example, isolating the external pump assembly from the pneumatic effector assembly may include closing an isolation valve disposed between the external gas pump assembly and the pneumatic effector assembly. Typically, the isolation valve is closed at the end of contraction during systole and opened at the beginning of expansion during diastole. Typically, pressure within the pneumatic effector assembly is measured by a pressure sensor positioned between the isolation valve and an inlet to the pneumatic effector assembly.

[0020] In a specific example, the control circuit receives pressure readings or values ​​from the pressure sensor and determines whether the pressure change exceeds a threshold value indicative of a gas leak in the pneumatic effector assembly. In a preferred example, the control circuit calculates the slope of the pressure change, with a slope value that exceeds a threshold value indicative of a gas leak in the pneumatic effector assembly.

[0021] In a specific example, the pneumatic effector assembly is implanted beneath the patient's pericardium and over the myocardial surface.

[0022] In a specific example, the patient's cardiac rhythm is determined by sensing an ECG using one or more electrodes positioned on the pneumatic effector, or alternatively, the ECG is sensed using external electrodes.

[0023] In a third aspect, the present invention provides a method for assisting cardiac function, the method comprising the steps of: detecting a patient's ECG to determine the cardiac rhythm; and delivering a drive gas from an external gas pump assembly to a pneumatic effector assembly implanted proximal to the patient's heart to enhance left ventricular contraction, the delivery of the drive gas being synchronized with the determined cardiac rhythm to cause the pneumatic effector assembly to compress or expand the heart within the left ventricle of the heart at a rate consistent with the cardiac rhythm. Liquid in the air pump circuit, if present, is accumulated at a location between the outlet of the gas pump assembly and the inlet of the pneumatic effector, typically using a liquid sensor adjacent to the liquid accumulator sensor.

[0024] In some examples, the accumulator includes a flow path between the gas pump assembly and the pneumatic effector, where the flow path may have a baffle and / or a reduced cross-sectional area for collecting liquid entrained in the gas flowing through the flow path. In such examples, the liquid sensor is typically located in the hub adjacent the baffle and / or reduced cross-sectional area of ​​the flow path.

[0025] In some examples, the pneumatic effector assembly is implanted beneath the patient's pericardium and over the myocardial surface. In some examples, the patient's cardiac rhythm is detected using ECG electrodes, which may be positioned on the pneumatic effector or on external electrodes.

[0026] In a fourth aspect, the present invention provides an implantable cardiac assist catheter for use with an external drive unit. The implantable cardiac assist catheter includes a catheter body having a proximal end, a distal end, and at least one gas exchange lumen therebetween. A pneumatic effector is disposed at the distal end of the catheter body and configured to (1) be implanted proximal to a patient's heart to enhance left ventricular contraction and (2) receive and expel inflation gas through the gas exchange lumen. A hub is positioned at the proximal end of the catheter body and configured to be removably connected to a gas pump assembly of the external drive unit. A pressure sensor is configured to be removably connected to control circuitry in the external drive unit to measure pressure within the pneumatic effector assembly.

[0027] In a specific example, a hub is attached directly to the proximal end of the catheter body, where the hub may further include a cannula, and the pneumatic effector assembly may include an implantable port attached directly to the proximal end of the catheter body, where the implantable port is configured to percutaneously receive the cannula. A connecting tube having a pump end attachable to the gas pump assembly and a hub end attachable to the hub is typically provided to connect the gas pump assembly to the pneumatic effector assembly. The pneumatic effector assembly is typically configured to be implanted beneath the patient's pericardium and over the surface of the myocardium covering the patient's left ventricle. The pneumatic effector assembly is typically configured to be implanted in a heart chamber, and the catheter may further include at least one ECG electrode. For example, at least one ECG electrode may be positioned on the pneumatic effector assembly and configured to provide the patient's cardiac rhythm to the control circuit.

[0028] In a fifth aspect, the present invention provides an implantable cardiac assist catheter for use with an external drive unit. The implantable cardiac assist catheter includes a catheter body having a proximal end, a distal end, and at least one gas exchange lumen therebetween. A pneumatic effector at the distal end of the catheter body is configured (1) to be implanted proximal to the patient's heart to enhance left ventricular contraction, and (2) to receive and expel inflation gas through the gas exchange lumen. A hub at the proximal end of the catheter body is configured to be removably connected to a gas pump assembly of the external drive unit, and a liquid accumulator is positioned between an outlet of the gas pump assembly and an inlet of the pneumatic effector. A liquid sensor is adjacent to a sensor of the liquid accumulator.

[0029] In some embodiments, the hub may be attached directly to the proximal end of the catheter body, allowing for direct percutaneous implantation of the catheter, but in many cases the hub will further comprise a cannula and the pneumatic effector assembly will comprise an implantable port attached directly to the proximal end of the catheter body, such that the implantable port can receive the cannula percutaneously.

[0030] In a specific example, the implantable cardiac assist catheter further comprises a connecting tube having a pump end attachable to the gas pump assembly and a hub end attachable to the hub, the connecting tube connecting the gas pump assembly to the pneumatic effector assembly.

[0031] The pneumatic effector assembly is typically configured to be implanted beneath the patient's pericardium and across the surface of the myocardium overlying the patient's left ventricle. Alternatively, the pneumatic effector assembly may be configured to be implanted within a heart chamber. The implantable cardiac assist catheter will typically further include at least one ECG electrode, for example, positioned on the pneumatic effector assembly and configured to provide the patient's cardiac rhythm to the control circuitry.

[0032] In a sixth aspect, the present invention provides an external drive unit (EDU) for use with an implantable cardiac assist catheter having a pneumatic effector assembly and a pressure sensor. The EDU includes a gas pump assembly having a port connectable to the pneumatic effector assembly, a control circuit configured to operate the gas pump assembly to actuate the pneumatic effector assembly in response to a sensed cardiac rhythm of the patient, and an isolation valve positioned between the outlet of the gas pump assembly and the port. The control circuit is typically configured to receive a pressure change sensed by the pressure sensor when the isolation valve closes to isolate the pneumatic effector.

[0033] In a seventh aspect, the present invention provides an external drive unit (EDU) for use with an implantable cardiac assist catheter having a pneumatic effector assembly and a fluid accumulation sensor. The EDU includes a gas pump assembly having a port connectable to the pneumatic effector assembly, and control circuitry configured to operate the gas pump assembly to actuate the pneumatic effector assembly in response to a sensed cardiac rhythm of the patient. The control circuitry is configured to receive an output of the fluid accumulation sensor to detect when fluid is accumulating within the implantable cardiac assist catheter. [Brief explanation of the drawings]

[0034] The novel features of the invention are set forth with particularity in the appended claims. The features and advantages of the present invention will be better understood by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings.

[0035] [Figure 1] FIG. 1 illustrates the prior art cardiac assist system described in WO 2020 / 176670 implanted in a patient. [Figure 2] 1 is a schematic diagram of a cardiac assist system constructed in accordance with the principles of the present invention; [Figure 3] 1 is a cross-sectional view of a hub of a cardiac assist system of the present invention including both pressure sensing and fluid accumulation sensing components. [Figure 3A] FIG. 10 is a detailed view of an alternative structure of the storage sensing component of the present invention. [Figure 4] FIG. 4 is an isometric view of the hub of FIG. [Figure 4A] FIG. 4 is an end view of the hub of FIG. 3. [Figure 5] FIG. 10 is an isometric view of an alternative embodiment of a hub having a cannula configured to access an implanted port. [Figure 6]10A-10C illustrate the relationship between ECG monitoring and pressure sensing in accordance with the principles of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0036] In this patent application, the term "distal" refers to the end of the device that is furthest from the operator and closest to the heart. This is also the "upstream" direction of blood flow. The term "proximal" refers to the end of the device that is closer to the operator, toward the access site where the device is introduced into the body, and farthest from the heart. This is also the "downstream" direction of blood flow.

[0037] The devices, systems, and methods of the present invention are intended to provide complementary features and improvements to the "ventricular assist" balloon described in commonly assigned PCT Publication WO 2020 / 176670, the entire disclosure of which is incorporated herein by reference. As described in that PCT publication, a cardiac assist system (10), such as that shown in FIG. 1, may be implanted in a patient, as illustrated. A balloon or other pneumatic effector (20) is introduced into the pericardium between the inner surface of the pericardial sac P and the outer surface of the myocardium M. The pneumatic effector (20) would preferably be positioned generally over the left ventricle, as shown by the dashed line in FIG. 10, so that inflation or other actuation of the effector compresses the left ventricle. An implanted port (24) is connected to the balloon by a catheter body (18) and is percutaneously accessed by a cannula (14). An external drive unit (48) typically delivers actuation gas through connecting tube (46) and cannula (14) to port (24) to actuate the pneumatic effector by inflating and deflating it. ECG is measured by ECG pads (56), which are connected to the external drive unit by cable (58). Optionally, other ECG signals may be measured by electrodes on the implantable port (24) or elsewhere in the system.

[0038] Referring now to Figure 2, a cardiac assist system (100) constructed in accordance with the principles of the present invention will be described. The cardiac assist system includes a pneumatic effector assembly (102), a gas pump assembly (104), and a control circuit (106). The gas pump assembly (104) and the control circuit (106) are typically housed in an external drive unit housing (110), which typically further includes an isolation valve (108). The isolation valve is typically a solenoid valve, but may be any electrically actuated valve capable of controlling gas flow on and off.

[0039] The pneumatic effector assembly (102) is connected directly or indirectly to a hub (112). As shown in FIG. 2, the hub (112) is connected directly to the catheter shaft of the pneumatic effector assembly (102), which in turn is connected to a pneumatic effector 128, typically an inflatable balloon. Alternatively, the hub (112) may be configured for indirect connection to a pneumatic effector or assembly of the type shown in the prior art cardiac assist system (10) of FIG. 1. In such a case, the hub would include a cannula (162) configured to percutaneously penetrate the patient's skin, typically in the chest, to access the implanted port (24), as described above.

[0040] The external drive unit (110) is connected to the hub (112) by connecting lines and cables so that the external drive unit can be maintained at a location remote from the patient during operation of the cardiac assist system (100). The isolation valve (108) is connected to the inlet port (150) by an inflation line (114), which in turn is connected to the gas pump assembly (104) so ​​that inflation gas can be reciprocally delivered to the pneumatic effector (128) to compress the heart, as described in WO 2020 / 176670. The gas pump assembly (104) typically comprises a reciprocating pump, a peristaltic pump, or any other pump capable of pumping and removing gas from the pneumatic effector at rates desired for cardiac assistance. Isolation valve (108) would normally be open while gas pump assembly (104) is driving pneumatic effector (128), but would be closed to isolate the entire pneumatic effector assembly (102) (including pneumatic effector (128), shaft (126), and hub (112)) while pressure is being measured, as described in more detail below.

[0041] Pressure sensor (116) in hub 110 is connected to control circuitry (106) in external drive unit (110) by pressure sensor cable (118). Liquid sensor (120) is connected to control circuitry (106) by liquid sensor cable (122). In this manner, the external drive unit can inspect pneumatic effector assembly (102) for damage or malfunctions that could result in either a loss of gas pressure or liquid accumulation in the gas lines, as described in further detail below.

[0042] Referring now to FIG. 3, the internal structure of an exemplary hub 112 will be described. Typically, the hub (112) comprises a solid polymeric or other body with a passageway or cavity formed therein. A liquid accumulation structure (132) is formed in the gas flow path (133) between the gas inlet port (150) and the gas outlet port (152). As shown in FIG. 3, the liquid accumulator structure (132) may include a baffle (134) that forms a restricted flow path (136) therebetween. By restricting expansion flow into this flow path (136), any liquid entrained in the gas will collect and accumulate in the "upper" region of the path, as shown in FIG. 3. By further positioning the liquid accumulation sensor (120) in a liquid sensor port (152) positioned adjacent to the restricted flow path (136), the ability to detect fluid is greatly improved.

[0043] The liquid accumulator structure may have a variety of different designs. For example, as shown in Figure 3A, the liquid accumulator structure (140) may include a plurality of baffles (142) arranged in a chevron pattern to collect liquid from the expanding gas as it flows through the gas flow path (133).

[0044] Referring again to Figure 3, the pressure sensor 116 may be positioned within a pressure sensor port 156 formed within the body of the hub 112. A pressure transducer element 157 on the pressure sensor 116 may be positioned adjacent to a pressure passage 158 that exposes the transducer to pressure present in the gas flow line between the gas inlet port 150 and the gas outlet port 152.

[0045] An external isometric view of the hub (112) is shown in Figure 4. The gas inlet port (150) is configured to removably or fixedly receive the proximal end of the catheter shaft (126), and a cable clip (160) is typically provided to hold the pressure sensor cable (118) in place as it is routed back and connected to the external drive unit (110), as seen in Figure 2. The gas outlet port (152) and pressure sensor port (156) are located on the underside (164) of the hub (112), as seen in Figure 4A.

[0046] In a preferred example, as shown in Figure 5, the hub (112a) will include a cannula (162) configured for percutaneous connection to an implanted port, such as the implanted port (24) shown in Figure 1. In such a case, the hub (112a) will not require a gas inlet port (50), and the internal passageway of the hub will be reconfigured so that gas enters the gas flow path through the cannula (162).

[0047] Referring now to FIG. 6, the operation of the isolation valve (108) and pressure sensor (116) for detecting pressure loss from the cardiac assist system (100) will be described. The patient's ECG and heart rate will typically be monitored using an external ECG sensor, such as that shown in FIG. 1. When an "R-peak" is detected in the patient's ECG, the isolation valve (108) will open and the gas pump assembly (104) will be started. The gas pump assembly (104) will inflate the pneumatic effector (128) during systole and then reverse to deflate the pneumatic effector during diastole. The isolation valve (108) will close at or near the end of diastole, and pressure will be measured from the end of diastole to the beginning of systole, shown in FIG. 6 as the "measurement period." Because the pneumatic effector assembly (102) is fully isolated by the isolation valve (108), any loss of pressure detected by the pressure sensor (116) is due to damage or failure of the pneumatic effector assembly (102).

[0048] In some examples, the control circuit (106) may be programmed to detect the "total" pressure loss over all or part of the measurement period between the end of diastole and the beginning of systole while the pneumatic effector assembly (102) is isolated. However, in many cases, it will be desirable to additionally calculate the slope or derivative of the pressure change at one or more times during the measurement period. Even if the overall pressure loss is small, the slope or rate of change of pressure may be relatively large and easy to detect.

[0049] While preferred embodiments of the present invention have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be utilized in practicing the invention. The following claims define the scope of the invention, and it is intended that methods and structures within the scope of these claims and their equivalents be covered thereby.

Claims

1. 1. A cardiac assist system comprising: a pneumatic effector assembly configured to be implanted proximal to a patient's heart to enhance cardiac contractility; an external drive unit, (a) a gas pump assembly connectable to the pneumatic effector assembly; and (b) an external drive unit including a control circuit configured to operate the gas pump assembly to actuate the pneumatic effector assembly in response to a sensed cardiac rhythm of the patient; an isolation valve positioned between the gas pump assembly and an inlet to a pneumatic effector; a pressure sensor positioned between the isolation valve and the inlet of the pneumatic effector; Equipped with The cardiac assist system, wherein the control circuit is configured to receive a pressure change sensed by the pressure sensor when the isolation valve closes to isolate the pneumatic effector.

2. The cardiac assist system of claim 1 , wherein the isolation valve is located within an external drive unit housing.

3. The cardiac assist system of claim 1 , wherein the isolation valve is positioned between an external drive unit housing and the pneumatic effector assembly.

4. the pneumatic effector assembly: a catheter body having a proximal end, a distal end, and at least one gas exchange lumen therebetween; a pneumatic effector at the distal end of the catheter body, the pneumatic effector (1) being implanted proximal to the patient's heart to enhance left ventricular contraction, and (2) being configured to receive and exhaust inflation gas through the gas exchange lumen; a hub at the proximal end of the catheter body configured to be removably connected to the gas pump assembly of the external drive unit; Equipped with 4. The cardiac assist system of claim 1, wherein the pressure sensor is positioned in or on the hub and configured to sense pressure within the at least one gas exchange lumen.

5. The cardiac assist system of claim 4 , wherein the hub is attached directly to the proximal end of the catheter body.

6. 5. The cardiac assist system of claim 4, wherein the hub further comprises a cannula, and the pneumatic effector assembly comprises an implantable port mounted directly to the proximal end of the catheter body, the implantable port configured to percutaneously receive the cannula.

7. The cardiac assist system of any one of claims 1 to 6, wherein the control circuit is configured to calculate a pressure change gradient of any pressure change received from the pressure sensor.

8. 8. The cardiac assist system of claim 7, wherein a calculated pressure change gradient greater than a predetermined threshold indicates a pressure leak in the pneumatic effector assembly.

9. 9. The cardiac assist system of claim 4, further comprising a connecting tube having a pump end attachable to the gas pump assembly and a hub end attachable to the hub, the connecting tube connecting the gas pump assembly to the pneumatic effector assembly.

10. 10. The cardiac assist system of claim 1, wherein the pneumatic effector assembly is configured to be implanted beneath the patient's pericardium and over the myocardial surface overlying the patient's left ventricle.

11. The cardiac assist system of any one of claims 1 to 9, wherein the pneumatic effector assembly is configured to be implanted in a heart chamber.

12. A cardiac assist system according to any one of claims 1 to 11, further comprising at least one ECG electrode.

13. 13. The cardiac assist system of claim 12, wherein the at least one ECG electrode is positioned on the pneumatic effector assembly and configured to provide the patient's cardiac rhythm to the control circuitry.

14. 13. The cardiac assist system of claim 12, wherein the at least one ECG electrode is configured to be attached externally to the patient and connected to an ECG circuit by an external lead.

15. 1. A method for assisting cardiac function, comprising: detecting an ECG of the patient to determine a cardiac rhythm; delivering a drive gas from an external gas pump assembly to a pneumatic effector assembly implanted proximal to the patient's heart to enhance left ventricular contraction, wherein delivery of the drive gas is synchronized with the determined cardiac rhythm to cause the pneumatic effector assembly to compress or expand the heart within the left ventricle of the heart at a rate consistent with the cardiac rhythm; isolating the external gas pump assembly from the pneumatic effector assembly to prevent any exchange of the drive gas; measuring pressure within the pneumatic effector assembly while the pneumatic effector assembly is isolated from the external gas pump assembly; detecting a change in the measured pressure indicative of a leak in the pneumatic effector assembly; A method comprising:

16. 16. The method of claim 15, wherein isolating the external gas pump assembly from the pneumatic effector assembly includes closing an isolation valve disposed between the external gas pump assembly and the pneumatic effector assembly.

17. 17. The method of claim 15 or 16, wherein the isolation valve is closed at the end of contraction during systole and opened at the beginning of expansion during diastole.

18. The method of any one of claims 15 to 17, wherein the pressure within the pneumatic effector assembly is measured by a pressure sensor positioned between the isolation valve and an inlet to the pneumatic effector.

19. 19. The method of any one of claims 15 to 18, wherein a control circuit receives pressure from the pressure sensor and determines whether a change in pressure exceeds a threshold indicative of a gas leak in the pneumatic effector assembly.

20. 20. The method of claim 19, wherein the control circuit calculates a slope of the pressure change, and a slope value exceeding a threshold value indicates a gas leak in the pneumatic effector assembly.

21. The method of any one of claims 15 to 20, wherein the pneumatic effector assembly is implanted beneath the patient's pericardium and over the myocardial surface.

22. The method of any one of claims 15 to 21, further comprising detecting an ECG to provide the patient's cardiac rhythm.

23. 23. The method of claim 22, wherein the ECG is detected using one or more electrodes positioned on a pneumatic effector.

24. 23. The method of claim 22, wherein the ECG is detected using external electrodes.

25. 1. A cardiac assist system comprising: a pneumatic effector assembly configured to be implanted proximal to a patient's heart to enhance left ventricular contraction; an external drive unit, (a) a gas pump assembly connectable to the pneumatic effector assembly; and (b) an external drive unit including control circuitry configured to operate the gas pump assembly to actuate the pneumatic effector assembly in response to a sensed cardiac rhythm of the patient; a liquid accumulator disposed in series between the outlet of the gas pump assembly and the inlet of a pneumatic effector; a liquid sensor adjacent to the liquid accumulator sensor; A cardiac assist system comprising:

26. 1. A method for assisting cardiac function, comprising: detecting an ECG of the patient to determine a cardiac rhythm; delivering a drive gas from an external gas pump assembly to a pneumatic effector assembly implanted proximal to the patient's heart to enhance left ventricular contraction, wherein delivery of the drive gas is synchronized with the determined cardiac rhythm to cause the pneumatic effector assembly to compress or expand the heart within the left ventricle of the heart at a rate consistent with the cardiac rhythm; allowing a liquid to accumulate at a location between the outlet of the external gas pump assembly and the inlet of a pneumatic effector; a liquid sensor adjacent to the liquid accumulator sensor; A method comprising:

27. 27. The method of claim 26, wherein the liquid accumulator comprises a flow path between the external gas pump assembly and the pneumatic effector, the flow path having baffles and / or a narrow cross-sectional area for collecting liquid entrained in gas flowing through the flow path.

28. 28. The method of claim 26 or 27, wherein the liquid sensor is positioned within a hub adjacent a baffle and / or a narrowed cross-sectional area of ​​the flow path.

29. The method of any one of claims 26 to 28, wherein the pneumatic effector assembly is implanted beneath the patient's pericardium and over the myocardial surface.

30. 30. The method of any one of claims 26 to 29, further comprising detecting an ECG to provide the patient's cardiac rhythm.

31. 31. The method of claim 30, wherein the ECG is detected using one or more electrodes positioned on the pneumatic effector.

32. 31. The method of claim 30, wherein the ECG is detected using external electrodes.

33. 1. An implantable cardiac assist catheter for use with an external drive unit, comprising: a catheter body having a proximal end, a distal end, and at least one gas exchange lumen therebetween; a pneumatic effector at the distal end of the catheter body, the pneumatic effector (1) being implanted proximal to the patient's heart to enhance left ventricular contraction, and (2) being configured to receive and exhaust inflation gas through the gas exchange lumen; a hub at the proximal end of the catheter body configured to be removably connected to a gas pump assembly of the external drive unit; a pressure sensor configured to be removably connected to control circuitry within the external drive unit to measure pressure within the pneumatic effector; An implantable cardiac assist catheter comprising:

34. 34. The implantable cardiac assist catheter of claim 33, wherein the hub is attached directly to the proximal end of the catheter body.

35. 35. The implantable cardiac assist catheter of claim 33 or 34, wherein the hub further comprises a cannula, and the pneumatic effector assembly comprises an implantable port mounted directly on the proximal end of the catheter body, the implantable port configured to percutaneously receive the cannula.

36. 36. The implantable cardiac assist catheter of claim 33, further comprising a connecting tube having a pump end attachable to the gas pump assembly and a hub end attachable to the hub, the connecting tube connecting the gas pump assembly to a pneumatic effector assembly.

37. 37. The implantable cardiac assist catheter of any one of claims 33 to 36, wherein the pneumatic effector assembly is configured to be implanted beneath the patient's pericardium and across the myocardial surface overlying the patient's left ventricle.

38. The implantable cardiac assist catheter of any one of claims 33 to 36, wherein the pneumatic effector assembly is configured to be implanted in a chamber of the heart.

39. The implantable cardiac assist catheter of any one of claims 33 to 38, further comprising at least one ECG electrode.

40. 40. The implantable cardiac assist catheter of claim 39, wherein the at least one ECG electrode is positioned on a pneumatic effector assembly and configured to provide the patient's cardiac rhythm to the control circuitry.

41. 1. An implantable cardiac assist catheter for use with an external drive unit, comprising: a catheter body having a proximal end, a distal end, and at least one gas exchange lumen therebetween; a pneumatic effector at the distal end of the catheter body, the pneumatic effector (1) being implanted proximal to the patient's heart to enhance left ventricular contraction, and (2) being configured to receive and exhaust inflation gas through the gas exchange lumen; a hub at the proximal end of the catheter body configured to be removably connected to a gas pump assembly of the external drive unit; a liquid accumulator disposed in series between the outlet of the gas pump assembly and the inlet of the pneumatic effector; a liquid sensor adjacent to the liquid accumulator sensor; An implantable cardiac assist catheter comprising:

42. 42. The implantable cardiac assist catheter of claim 41, wherein the hub is attached directly to the proximal end of the catheter body.

43. 43. The implantable cardiac assist catheter of claim 41 or 42, wherein the hub further comprises a cannula, and the pneumatic effector assembly comprises an implantable port mounted directly on the proximal end of the catheter body, the implantable port configured to percutaneously receive the cannula.

44. 44. The implantable cardiac assist catheter of claim 41, further comprising a connecting tube having a pump end attachable to the gas pump assembly and a hub end attachable to the hub, the connecting tube connecting the gas pump assembly to the pneumatic effector assembly.

45. 45. The implantable cardiac assist catheter of any one of claims 41 to 44, wherein the pneumatic effector assembly is configured to be implanted beneath the patient's pericardium and across the myocardial surface overlying the patient's left ventricle.

46. 45. The implantable cardiac assist catheter of any one of claims 41 to 44, wherein the pneumatic effector assembly is configured to be implanted in a chamber of the heart.

47. The implantable cardiac assist catheter of any one of claims 41 to 46, further comprising at least one ECG electrode.

48. 48. The implantable cardiac assist catheter of claim 47, wherein the at least one ECG electrode is positioned on a pneumatic effector assembly and configured to provide the patient's cardiac rhythm to a control circuit.

49. 1. An external drive unit for use with an implantable cardiac assist catheter having a pneumatic effector assembly and a pressure sensor, comprising: a gas pump assembly having a port connectable to said pneumatic effector assembly; a control circuit configured to operate the gas pump assembly to actuate the pneumatic effector assembly in response to a sensed cardiac rhythm of a patient; an isolation valve positioned between the outlet of the gas pump assembly and the port; Equipped with The external drive unit, wherein the control circuit is configured to receive a pressure change sensed by the pressure sensor when the isolation valve is closed to isolate the pneumatic effector.

50. 1. An external drive unit for use with an implantable cardiac assist catheter having a pneumatic effector assembly and a fluid accumulation sensor, comprising: a gas pump assembly having a port connectable to said pneumatic effector assembly; a control circuit configured to operate the gas pump assembly to actuate the pneumatic effector assembly in response to a sensed cardiac rhythm of the patient; Equipped with An external drive unit, wherein the control circuitry is configured to receive the output of the fluid accumulation sensor and detect when fluid is accumulating within the implantable cardiac assist catheter.

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