Ventricular-assist method and apparatus

• US 6,406,422 B1
• Filed: 03/02/2000
• Issued: 06/18/2002
• Est. Priority Date: 03/02/2000
• Status: Expired due to Fees

• Current Assignee: Levram Medical Devices Limited
• Original Assignee: Levram Medical Devices Limited
• Inventors: Landesberg, Amir
• Primary Examiner(s): EVANISKO, GEORGE ROBERT
• Application Number:
  US09/517,834
• Time in Patent Office: 838 Days
• Field of Search: 600/16-18, 623/2.1, 623/3-6-, 623/3.28
• US Class Current: 600/17
• CPC Class Codes: A61M 60/148 in line with a blood vessel using resection or like techniques, e.g. permanent endovascular heart assist devices
• CPC Class Codes: A61M 60/17 inside a ventricle, e.g. intraventricular balloon pumps
• CPC Class Codes: A61M 60/178 drawing blood from a ventricle and returning the blood to the arterial system via a cannula external to the ventricle, e.g. left or right ventricular assist devices
• CPC Class Codes: A61M 60/274 the inlet and outlet being the same, e.g. para-aortic counter-pulsation blood pumps
• CPC Class Codes: A61M 60/295 Balloon pumps for circulatory assistance
• CPC Class Codes: A61M 60/411 generated by an electromotor
• CPC Class Codes: A61M 60/432 with diastole or systole switching by stopping or reversing the blood pump operating at a much higher cyclical speed than the heart beat
• CPC Class Codes: A61M 60/497 for balloon pumps for circulatory assistance
• CPC Class Codes: A61M 60/515 Regulation using real-time patient data
• CPC Class Codes: A61M 60/538 Regulation using real-time blood pump operational parameter data, e.g. motor current

Abstract

A system for ventricular-assist of the normal heart action utilizes an intraventricular device with a limited volume which is expanded at a critical time, for a critical duration and with a volume change course such that it assists the pumping action of the heart without inducing stretching of the ventricular wall.

Claims

1. A ventricular assist method which comprises the steps of:

(a) inserting into at least one failing ventricular cavity of a failing heart through a wall thereof a respective expandable intraventricular chamber;

(b) in cadence with normal functioning of said failing heart, effecting expansion of said intraventricular chamber with each heart beat and commencing only after opening of an outlet valve of the respective ventricular cavity of the failing heart or only after a detected shortening of a monitored region of a wall of the respective ventricular cavity of the failing heart and continuing during an ejection phase of the respective ventricular cavity, thereby augmenting ejection volume from the respective ventricular cavity by up a maximum volume of the intraventricular chamber per systolic phase;

(c) monitoring ventricular ejection or a ventricular wall region for shortening and controlling a course of expansion of each said intraventricular chamber in step (b) to reduce a shortening and at the same time to prevent stretching of a respective monitored ventricular wall region of the failing heart by comparison with ventricular wall shortening prior to insertion of the respective intraventricular chamber; and

(d) depressurizing and contracting each said intraventricular chamber immediately upon closing of a respective said outlet valve of the failing heart.

2. The method defined in claim 1, further comprising the steps of:

measuring parameters of ventricular wall motion during systole and the expansion of a respective intraventricular chamber in step (b) and parameters of global cardiac function; and

applying and controlling a profile of the expanding intraventricular chamber in a course of expansion thereof to decrease the measured ventricular wall motion thereby obtaining an increase in pressure within the respective ventricular cavity and an increase in the cardiac output.

3. The method defined in claim 1, further comprising the steps of:

monitoring at least one parameter of ventricular wall shortening and at least one parameter of ventricular output during systole; and

in response to measurement of said parameters of ventricle wall shortening and ventricular output and selectively either in real time or by beat-by-beat computation, determining a desired shape of each said intraventricular chamber during expansion thereof; and

controlling the shape and a rate of expansion and a rate of contraction of the respective intraventricular chamber during step (b) to correspond to said desired shape.

4. The method defined in claim 3 wherein said ventricular diameter is measured as a measurement of ventricle wall shortening or as a measurement of ventricular volume change.

5. The method defined in claim 3 wherein ventricular volume is measured as a measurement of ventricle wall shortening or as a measurement of ventricular output.

6. The method defined in claim 3 wherein said parameter is ventricular wall strain and is measured as a measurement of ventricle wall shortening.

7. The method defined in claim 3 wherein said parameter is ventricular flow and is measured as a measurement of ventricle wall shortening.

8. The method defined in claim 3 wherein each said intraventricular chamber is a balloon and the expansion of each said intraventricular chamber is effected by fluid expansion of the respective balloon with a physiological solution.

9. The method defined in claim 8 wherein a said balloon is implanted into the failing ventricle cavity at the apex thereof or at another site of a respective wall affording access without interference with papillary muscle and ventricle valve apparatus or cardiac circulatory or conductive systems.

10. A ventricular assist apparatus comprising:

an expandable intraventricular chamber insertable into a ventricular cavity of a failing heart through a wall thereof;

means including a computer-controlled actuator connected to said intraventricular chamber for effecting expansion and contraction of said intraventricular chamber in cadence with normal functioning of said failing heart and commencing only after opening of an outlet valve of the respective ventricular cavity of the failing heart or only after a detected shortening of a monitored region of a wall of the respective ventricular cavity of the failing heart and continuing during an ejection phase of the respective ventricular cavity, thereby augmenting ejection volume from the respective ventricular cavity by up to a maximum volume of the intraventricular chamber per systolic phase; and

at least one sensor for monitoring wall shortening of said failing ventricle, said sensor being connected to said computer-controlled actuator and controlling a course of expansion of said intraventricular chamber.

11. The apparatus defined in claim 10 wherein said means including said computer-controlled actuator includes means for monitoring parameters of ventricle wall shortening and cardiac output, and means for correcting an expansion function of said intraventricular chamber based upon a difference between desired and monitored cardiac output using a predetermined feedback amplification factor.

12. The apparatus defined in claim 10, further comprising a computer receiving input from said sensor and connected to said actuator, said computer controlling said actuator with an output, said computer being programmed for each heartbeat (n) to:

(a) evaluate cardiac output and work at the n beat;

(b) compare the evaluated cardiac output and work at the n beat with a desired cardiac output to determine an amplification factor (A_F) constituting a gain of a feedback loop which determines a rate at which a function of intraventricular chamber expansion will be corrected to achieve a desired cardiac output;

(c) multiply the amplification factor (A_F) by a predetermined weighting function (W(t)) to enable an operator to determine a magnitude of feedback;

(d) evaluate ventricle wall shortening (S_n(t)) and compare the evaluated wall shortening with a desired wall shortening (Des(t)) to obtain an incremental correction profile Err_n(t)=Des(t)−

S_n(t);

(d) generate an expansion function EXP_n+1(t)=EXP_n(t)+A_F*W(t)*Err_n(t); and

(e) control expansion of the intraventricular chamber at a next beat (n+1) with said expansion function EXP_n+1(t)=EXP_n(t)+A_F*W(t)*Err_n(t).

13. The apparatus defined in claim 12 wherein said computer is an implantable computer which controls the intraventricular chamber at the next beat (n+1) with a predetermined expansion/contraction function by regulating onset time of expansion/contraction and a function of expansion, the expansion/contraction function being calculated between heartbeats before an onset of a next beat, the apparatus including means for detecting the onset time in real time.

14. The apparatus defined in claim 12 wherein said weighting factor (W(t)) is a function of time determined by said operator where 0≦

W (t)≦

1 when 0≦

t≦

T, and t=0 is the onset of expansion and t=T is the end of expansion.

15. The apparatus defined in claim 10, further comprising a computer receiving input from said sensor and connected to said actuator, said computer controlling said actuator with an output, said computer being programmed for each heartbeat (n) to:

(a) evaluate cardiac output and work at the n beat;

(b) compare the evaluated cardiac output and work at the n beat with a desired cardiac output and determine an amplification factor that will not cause wall stretch in part based upon additional inputs;

(c) evaluate ventricle wall shortening (S_n(t)) at said n beat and providing the ventricle wall shortening as one of said additional inputs;

(d) detect possible ventricle wall lengthening from the evaluation of the wall shortening in step (c) and providing therewith another of said additional inputs, and triggering an alarm upon ventricular wall lengthening

(f) from the amplification factor and a desired profile of expansion, determine a time course of expansion of the intraventricular chamber; and

(g) generate an expansion function representing the time course of expansion control expansion of the intraventricular chamber at a next beat (n+1) with said expansion function.

16. The apparatus defined in claim 10, further comprising a computer connected to said actuator and wherein said computer actuator is programmed to initiate expansion of said intraventricular chamber upon detection of an outlet valve opening or significant shortening of the monitored ventricle wall in real time.

17. The apparatus defined in claim 10 wherein said computer-controlled actuator is programmed to initiate contraction of said intraventricular chamber upon detection of an outlet valve closure in real time.

18. The apparatus defined in claim 17 wherein said computer-controlled actuator is programmed to connect said intraventricular chamber to intrathoracic pressure and said computer-controlled actuator includes a compressible extraventicular chamber and connection tubing between said extraventricular chamber and said intraventricular chamber.

19. The apparatus defined in claim 10, further comprising means for detecting opening and closure of said outlet valve and including at least one of the following:

means for measuring intraventricular and aortic pressure or a gradient between intraventricular and aortic pressure;

a Doppler or an ultrasonic or electromagnetic flowmeter measuring ventricle outlet flow;

ultrasound or electrical impedance means for measuring intraventricular volume;

strain gauge means for measuring ventricle wall shortening; and

means for detecting heart sounds.

20. The apparatus defined in claim 10, further comprising means for monitoring timing and profile of intraventricular chamber expansion based on a detection of regional ventricle wall motion, to optimize the apparatus based on a preserved measured functional region of the ventricle wall, said means for monitoring including at least one of the following:

means for measuring ventricle diameters or distances between anatomical points on the ventricle wall; and

means for measuring local changes in strain in the ventricle wall.

21. The apparatus defined in claim 10 wherein said actuator is selected from the group which consists of a syringe pump, a bellows or a flexible membrane, and an actuator motor operating said actuator.

22. The apparatus defined in claim 21 wherein said actuator motor is selected from the group which consists of an electric motor and a contractile motor.

23. The apparatus defined in claim 22, further comprising a computer connected to said actuator and said at least one sensor on said intraventricular chamber for measuring a volume thereof and an additional sensor on said intraventricular chamber for measuring ventricle pressure, said sensors being connected to said computer.

24. The apparatus defined in claim 10, wherein said sensor includes at least one sonomicrometer adopted to be attached to or implanted in said ventricle wall.