Synchronization control system

Abstract

The various embodiments herein relate to systems and methods for controlling the operation of a pulsatile heart assist device in a patient. The systems and methods include utilizing sounds and electrical signals produced by the heart to control the operation of the heart assist device.

Claims

1. A heart assist system, comprising: (a) a heart assist device comprising an inflatable cuff configured to apply pressure to blood in a blood vessel; (b) a pump configured to generate fluid pressure; (c) a fluid disposed within the inflatable cuff and the pump, the fluid configured to transfer the fluid pressure between the pump and the inflatable cuff; (d) a controller operably coupled to the pump; and (e) a phonocardiographic (PCG) lead operably coupled to the controller, the PCG lead comprising a sound sensor configured to detect heart sounds, wherein at least a portion of the sound sensor is positioned in contact with the fluid, wherein the controller is configured to use the heart sounds to control the operation of the heart assist device.

2. The heart assist system of claim 1, wherein the blood vessel is an aorta, and further wherein the inflatable cuff is configured to apply the pressure to an exterior of the aorta.

3. The heart assist system of claim 1, wherein the inflatable cuff comprises a flexible membrane, wherein the flexible membrane is configured to apply the pressure to the blood in the blood vessel.

4. The heart assist system of claim 1, wherein the fluid is a liquid or a gas.

5. The heart assist system of claim 1, wherein the heart sounds comprise S1 and S2 sounds.

6. The heart assist system of claim 1, wherein the heart sounds comprise sounds created when an aortic valve of the heart closes.

7. The heart assist system of claim 1, wherein the sound sensor comprises a microphone.

8. A heart assist system, comprising: (a) a pump configured to generate fluid pressure; (b) an inflatable cuff operably coupled to the pump, the inflatable cuff configured to receive fluid pressure from the pump and apply pressure to blood in a blood vessel; (c) a fluid disposed within the inflatable cuff and the pump, the fluid configured to transfer the fluid pressure between the pump and the inflatable cuff; (d) a controller operably coupled to the pump; (e) a digital signal processor and transmitter (DSPT) operably coupled to the controller, the DSPT comprising a PCG channel; and (f) a PCG lead operably coupled to the PCG channel of the DSPT, the PCG lead comprising a sound sensor configured to detect heart sounds, wherein at least a portion of the sound sensor is positioned in contact with the fluid, wherein the DSPT is configured to transmit signals relating to the heart sounds to the controller, and further wherein the controller is configured to transmit actuation instructions to the pump based on the signals relating to the heart sounds from the DSPT.

9. The heart assist system of claim 8, wherein the sound sensor comprises a microphone.

10. The heart assist system of claim 8, wherein the DSPT is wirelessly coupled to the controller.

11. The heart assist system of claim 8, wherein the inflatable cuff comprises a flexible membrane, wherein the flexible membrane is configured to apply the pressure to the blood in the blood vessel.

12. The heart assist system of claim 8, wherein the fluid is a liquid or a gas.

13. A method of controlling a heart assist system, the method comprising: positioning a PCG lead such that at least a portion of the PCG lead is positioned in contact with a fluid configured to transfer fluid pressure between a pump and an inflatable cuff; detecting a heart sound with the PCG lead; transmitting a signal relating to the heart sound to the controller; and applying pressure to blood in a blood vessel with an inflatable cuff based on the heart sound.

14. The method of claim 13, further comprising transmitting an actuation signal from the controller to the pump based on at least one of the signals relating to the heart sound.

15. The method of claim 14, further comprising actuating the pump to generate fluid pressure based on the actuation signal.

16. The method of claim 15, further comprising transferring the fluid from the pump to the inflatable cuff as a result of the fluid pressure, whereby the inflatable cuff is inflated.

17. The method of claim 13, further comprising receiving the signals relating to the heart sound at a digital signal processor and transmitter (DSPT) and transmitting signals relating to the heart sound to the controller.

18. The method of claim 17, further comprising transmitting an actuation signal from the controller to the pump based on at least one of the signals relating to the heart sound from the DSPT.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Preferred forms of the present invention will now be described, by way of examples only, with reference to the accompanying drawings, wherein:

(2) FIG. 1 is a cut away view of a patient with a heart assist device controlled in accordance with a first embodiment of the invention;

(3) FIG. 2 is a cut away view of a patient with a heart assist device controlled in accordance with a second embodiment of the invention

(4) FIG. 3 is a cut away view of a patient with a heart assist device controlled in accordance with a third embodiment of the invention; and

(5) FIG. 4 is a cut away view of a patient with a heart assist device controlled in accordance with a fourth embodiment of the invention, in which an externally mounted housing containing the DSPT and the pump and controller is shown partially cut-away.

DETAILED DESCRIPTION

(6) By way of further background, the DSPT has the basic modalities of sensing, transmitting, and programmability.

(7) Sensing is the capability to detect and interpret a patient's native heart electro- and phonocardiograms (ECG's and PCG's respectively). An implanted sensing lead detects the patient's native heart electrical activity and transmits it to the DSPT circuitry. The firmware and/or software within the DSPT unit interprets the patient's R-wave and transmits a signal indicating R-wave detection. An implanted microphone lead detects the patient's native heart sounds and transmits it to the DSPT circuitry. The firmware and/or software within the DSPT unit interprets the patient's heart sounds and transmits a signal indicating S1 and S2 detection.

(8) Programmability is the capability to allow a physician to adjust the DSPT's sensing and transmitting functions to the patient's individual needs. This is achieved by using a laptop-like device, typically called a programmer, that has an input device that is placed over the patient's skin in the vicinity of an implanted DSPT. The programmer transdermally communicates with the patient's DSPT, using either auditory (tonal) or electromagnetic pulses, and allows the physician to manipulate the DSPTs settings as needed.

(9) The ECG sensing system is expected to be able to work in the presence of a dual-chambered pacemaker providing pacing control over the patient's rhythm because their native rhythm would be deficient or absent.

(10) Combination pacemakers and internal cardioverter/defibrillators (ICDs) can, when ventricular tachycardia or VF is sensed, either attempt to overdrive pace a patient out of the rhythm (i.e. pace with a strong impulse that will override the patient's native rhythm and slowly decrease rate to control the patient's rhythm) or shock the heart out of the rhythm and then pace it.

(11) A first embodiment of the invention will now be described with reference to FIG. 1, which shows a patient 10 with a heart 12. The output of the heart 12 is assisted by a pulsatile, fully implantable, heart assist device, indicated generally by the reference numeral 14. The heart assist device 14 has an aortic cuff 16 around the patient's ascending aorta. The cuff 16 is essentially the same as those disclosed in the Applicant's previously referred to International PCT Patent application no. PCT/AU00/00654. The cuff 16 is driven by a pump 18, which essentially the same as those disclosed in the Applicant's International PCT Patent application no. PCT/AU02/00974 entitled A fluid pressure generating means. Also shown is an implanted DSPT 20. The pump 18 is powered/controlled by an external battery/controller 22 via a percutaneous electrical cable 24. The DSPT 20 transmits RF signals to the controller 22 of the heart assist device 14.

(12) The DSPT 20 has an ECG channel connected to sensing lead 26 and an PCG channel connected to the microphone lead 28.

(13) The DSPT ECG channel is connected, via the sensing lead 26, to the epicardial surface of the ventricle of the patient's heart 12 and the DSPT PCG channel is connected, via the microphone lead 28, to a microphone 30 implanted in close proximity to the aortic valve, exterior to the aortic root

(14) In operation, the DSPT 20 detects an R-wave (i.e. the R wave of the ventricle) through the ECG channel, then waits for a predetermined time (for example from 0-30 msec) before transmitting a signal to the controller 22 which in turn controls the pulsation of the heart assist device 14. It will be understood that, in the above configuration, the DSPT 20 will always issue the signal to the controller 22 and the controller may be programmable as to what action is taken when this signal is received. If desired, the DSPT 20 may issue the signal from the ECG channel immediately upon receiving the sensed signal in the ECG channel. In this case there would be a variable delay programmable into the controller 22 to ensure that the time at which the heart assist device 14 is actuated is correctly timed for that individual patient.

(15) Further, the DSPT 20 is designed to allow correct sensing of cardiac activity even in the presence of electrical or pressure or other noise interference. It is also designed to withstand defibrillation pulses without damage.

(16) In the preferred form shown, the heart assist device 14 is a counter pulsation device in which the pulsations are out of phase with the heart's native rhythm.

(17) The controller 22 is configured to turn the heart assist device off in the event that the pacing signal received from the ventricular circuit falls below a rate below the minimum rate, say 40 beats per minute. If the controller 22 indicates that it is not receiving any pacing signal this will be typically indicative of the DSPT 20 not transmitting to the controller 22 or a gross malfunction of the DSPT 20 or its leads 26 or 28.

(18) A second embodiment of the invention will now be described with reference to FIG. 2, in which like features to the first embodiment will be indicated with like reference numerals. FIG. 2 shows a patient 10 with a heart 12. The output of the heart 12 is assisted by a pulsatile, partially implantable, heart assist device, indicated generally by the reference numeral 14. The heart assist device 14 has an aortic cuff 16 around the patient's ascending aorta. The cuff 16 is essentially the same as those disclosed in the Applicant's previously mentioned PCT Patent application. The cuff 16 is driven by an external pump and controller 22 via a percutaneous gas line 23. These types of pumps and controllers are well known to persons skilled in the art and will not be described in further detail herein. A battery (not shown) is also mounted within the casing of the pump and controller 22.

(19) Also shown is the DSPT 20, which has an ECG channel connected to the sensing lead 26 and a PCG channel connected to the microphone lead 28. The DSPT transmits signals to the controller 22 of the heart assist device 14.

(20) The DSPT ECG channel is connected, via the sensing lead 26, to the endocardial surface of the ventricle of the patient's heart 12 and the DSPT PCG channel is connected, via the microphone lead 28, to a microphone 30 implanted in close proximity to the aortic valve, also via the endocardium. These leads may be placed via the subclavian or jugular vein, and positioned in the right heart chamber, either the right atrium, right ventricle, or in the coronary sinus.

(21) In operation, the DSPT 20 detects an R-wave (i.e. the R wave of the ventricle) through the ECG channel, then waits for a predetermined time (for example from 0-30 msec) before transmitting a signal to the controller 22 which in turn controls the pulsation of the heart assist device 14. It will be understood that, in the above configuration, the DSPT 20 will always issue the signal to the controller 22 and the controller may be programmable as to what action is taken when this signal is received. If desired, the DSPT 20 may issue the signal from the ECG channel immediately upon receiving the sensed signal in the ECG channel. In this case there would be a variable delay programmable into the controller 22 to ensure that the time at which the heart assist device 14 is actuated is correctly timed for that individual patient.

(22) The DSPT 20 is implanted under the skin, preferably in the front of the shoulder, over the delto-pectoral region, or under the skin over the abdomen. This location makes it easy to locate a battery recharging coil or a programmer wand (not shown).

(23) A third embodiment of the invention will now be described with reference to FIG. 3, in which like features to the second embodiment will be indicated with like reference numerals. The third embodiment is, and operates, very similar to the second embodiment except the microphone 30 detects heart sounds in the gas line 23 and the external controller 22 transmits corresponding signals to the PCG channel of the implanted DSPT 20.

(24) A fourth embodiment of the invention will now be described with reference to FIG. 4, in which like features to the third embodiment will be indicated with like reference numerals. The fourth embodiment is very similar to the third embodiment except the heart assist device 14 is controlled using only heart sounds in the gas line 23 detected by the microphone 30. (i.e. no ECG signals are monitored). In this embodiment, the microphone 30 is positioned within an externally positioned housing 32 which also contains the pump and controller 22 and the DSPT 20. The microphone 30 is in direct communication with the gas line 23 which acts as a stethoscope transmitting sound from the heart 12 to the externally mounted microphone 30. In operation, the microphone 30 receives the S1 sound as the aortic valve opens and the DSPT transmits a signal indicative of that reception to the controller and pump 22. The heart assist device 14 is deflated on receipt of the DSPT signal. When the microphone 30 receives the S2 sound indicative of the aortic valve closing the DSPT signals the controller and pump 22 to reinflate the heart assist device 14. In this embodiment of the invention the DSPT may contain software to filter out sounds other than the S1 and S2 sounds or the system may be such that the pump is periodically stopped for a single heart beat to allow detection of the S1 and S2 sounds and the controller and pump 22 then operates for a predetermined time on the basis of the timing detected during the period that the pump was inoperative.

(25) The arrangement shown in FIG. 4 may be altered by providing an ECG lead which extends from the heart 12 to the housing 32. In this case the DSPT will operate on the basis of the ECG detection of the R wave and on reception of the S2 sound. The ECG lead will preferably be disposed within the lumen of the gas line at the point of exit from the patient's body or be attached to the gas line. This means that there is only one point of percutaneous access into the patient. The ECG lead may also be brought out adjacent the gas line.

(26) The detection of both R-wave and heart sounds dramatically improves the accuracy of timing the heart assist device accurately, from beat-to-beat, to events in the cardiac cycle such as the beginning of systole and diastole. Further, the signal transmission arrangement provides a cost effective and robust wireless telemetry system with minimal patient discomfort. Also, as the percutaneous gas line does not have to carry any internal leads, it can be made relatively smaller and more flexible to improve patient comfort.

(27) It will be appreciated by the person skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiment without departing from the spirit or scope of the invention as broadly described. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive.

(28) For example, although epicardial leads are shown in FIG. 2, one lead could be endocardial and the other epicardial or visa versa.