Single cannula ventricular-assist method and apparatus

• US 20020173693A1
• Filed: 05/16/2001
• Published: 11/21/2002
• Est. Priority Date: 05/16/2001
• Status: Active Grant

• Current Assignee: Levram Medical Devices Limited
• Original Assignee: Levram Medical Devices Limited
• Inventors: Landesberg, Amir
• Granted Patent: US 6,511,413 B2
• Time in Patent Office: Days
• US Class Current: 600/16
• CPC Class Codes: A61M 2205/33 Controlling, regulating or measuring
• CPC Class Codes: A61M 2205/3303 Using a biosensor
• CPC Class Codes: A61M 2205/3334 Measuring or controlling the flow rate
• CPC Class Codes: A61M 2210/125 Heart
• CPC Class Codes: A61M 2230/005 Parameter used as control input for the apparatus
• CPC Class Codes: A61M 2230/04 Heartbeat characteristics, e.g. ECG, blood pressure modulation
• CPC Class Codes: A61M 2230/30 Blood pressure A61M2230/04 takes precedence
• 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 60/178 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 60/427 the force acting on the blood contacting member being hydraulic or pneumatic
• CPC Class Codes: A61M 60/441 generated by an electromotor
• CPC Class Codes: A61M 60/515 Regulation using real-time patient data
• CPC Class Codes: A61M 60/523 using blood flow data, e.g. from blood flow transducers
• CPC Class Codes: A61M 60/531 using blood pressure data, e.g. from blood pressure sensors
• CPC Class Codes: A61M 60/546 of blood flow, e.g. by adapting rotor speed
• CPC Class Codes: A61M 60/869 Compliance chambers containing a gas or liquid other than blood to compensate volume variations of a blood chamber

Abstract

A system for assisting the failing ventricle, which utilizes a single blood displacement chamber and a single cannula. The cannula is inserted into the failing ventricle cavity and is connected to a blood displacement actuator. The device produces blood displacement at a critical time for a critical duration and with blood flow time course such that it improves the systolic function of the heart: augments the cardiac output and increases the generated pressure. The device also improves the diastolic function by increasing the ventricle compliance and imposing rapid relaxation of the ventricle wall. The device provides additional external work without deteriorating the mechanical function of the failing ventricular, moreover it decreases the energy consumption of the failing heart and improves the coronary perfusion. Consequently, the device improves the balance between the energy supply (coronary perfusion) to the ventricle wall and the mechanical demands, and allows recovery of the failing heart.

Claims

1. A ventricular assist device comprising:

a single cannula inserted into a ventricle of a failing heart; and

a single blood displacement chamber connected to said cannula and under computer control for displacement of blood through said cannula into said ventricle of the failing heart during systole and for subsequent retraction of blood from said ventricle through said cannula into said displacement chamber.

2. A ventricular assist method that comprises the steps of:

(a) inserting into at least one failing ventricular cavity of a failing heart through a wall thereof a respective cannula connected to blood displacement chamber having a blood displacement actuator;

(b) in cadence with normal functioning of said failing heart, effecting blood inflow into the ventricle cavity from the displacement chamber, with each heart beat and commencing only after opening of the 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 generated by the blood displacement actuator, per systolic phase;

(c) controlling a time course of blood inward displacement through the said cannula in step (b) to reduce a shortening and thereby increasing the intraventricular pressure in said ventricular cavity, but at the same time to prevent stretching of a respective monitored ventricular wall region of the failing heart by comparison with ventricular wall shortening without an inflow from the displacement chamber; and

(d) retracting blood from said failing ventricular cavity, through the cannula immediately upon closing of a respective outlet valve of the failing ventricular cavity.

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

measuring parameters of ventricular wall motion during systole including possible parameters of regional wall motion, and parameters of global cardiac function; and

applying and controlling a profile of the blood inflow generated by the blood displacement actuator to decrease a measured ventricular wall motion, thereby obtaining an increase in pressure within the respective ventricular cavity and an increase in the cardiac output.

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

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

in response to measurement of said parameters of ventricle wall shortening and cardiac output and selectively either in real time or by beat-by-beat computation, determining a desired blood volume and inflow time profile; and

controlling a rate and profile of blood inflow of the respective blood displacement actuator during step (b).

5. The method defined in claim 3 wherein said parameters include ventricular diameter.

6. The method defined in claim 3 wherein said parameters include ventricular volume.

7. The method defined in claim 3 wherein said parameters include ventricular wall strain.

8. The method defined in claim 3 wherein said parameters include ventricular flow.

9. The method defined in claim 3 wherein a respective cannula is inserted into each failing ventricle of the failing heart and is connected to a respective blood displacement chamber and the blood flow in each said cannula are effected by respective actuators.

10. The method defined in claim 2 wherein a said cannula is inserted into a failing ventricular 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.

11. A ventricular assist apparatus comprising:

a hollow cannula inserted into the ventricular cavity of a failing ventricle through a cardiac wall thereof;

means including a computer-controlled blood displacement chamber connected to said cannula, said blood displacement chamber being actuated by a computer-controlled actuator for effecting blood inflow and outflow from the blood chamber into the ventricular cavity 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 the stroke volume generated by the blood displacement actuator, per systolic phase; and

at least one sensor of wall shortening of said failing ventricle connected to said computer-controlled actuator for controlling a time course of flow and profile blood flow of said blood displacement actuator.

12. The apparatus defined in claim 11 wherein said means including said computer-controlled actuator includes means for monitoring parameters of ventricle wall shortening and cardiac output, and means for correcting the profile and flow function of said blood displacement actuator, based upon a difference between desired and evaluated cardiac output using a feedback amplification factor.

13. The apparatus defined in claim 11, further comprising a computer receiving input from said sensor and 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 the blood displacement actuator, blood flow and profile will be corrected to achieve a desired cardiac output;

(c) multiplying the amplification factor (A_F) by a weighting function (W(t)) to enable an operator to determine the magnitude of feedback and to modulate it within the ejection phase;

(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 the blood displacement actuator inflow function;

EXP_n+1(t)=EXP_n(t)+A_F*W(t)*Err_n(t) ; and

(e) control blood flow and profile, generated by the blood displacement actuator, at a next beat (n+1) with said inflow function EXP_n+1(t)=EXP_n(t)+A_F*W(t)*Err_n(t).

14. The apparatus defined in claim 13 wherein said computer is a computer that controls said actuator, at the next beat (n+1) with an inflow/outflow function, by regulating onset time of inflow/outflow and a function of flow, the inflow and outflow functions being calculated between heartbeats before an onset of a next beat, the onset times being detected in real time, the computer being an implanted device, when the device is used for a prolonged time or a bedside device when the assist device is used as a bridge to recovery, for a short time period.

15. The apparatus defined in claim 13 wherein said weighting factor (W(t)) is a function of time determined by said operator where O≦

W(t)≦

−

1, when 0≦

t≦

T, and t=0 is the time onset of the inflow and t=T is the end of inflow or the end of systole.

16. The apparatus defined in claim 11, further comprising a computer receiving input from said sensor and 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 stretch in part of the wall based upon additional sensor 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;

(e) from the amplification factor and a desired profile of ventricle wall shortening, determine a time course of the inward blood flow as an inflow function in the cannula; and

(f) generate the inflow function, through the cannula, representing the time course of blood inflow at a next beat (n+1) with said inflow function.

17. The apparatus defined in claim 11 wherein said computer is programmed to initiate blood flow through the cannula upon detection of an outlet valve opening or significant shortening of a monitored region in the ventricular wall in real time.

18. The apparatus defined in claim 11 wherein said computer is programmed to initiate blood retraction through the said cannula upon detection of an outlet valve closure in real time.

19. The apparatus defined in claim 16 wherein said computer is programmed to control the actuator, which regulates the blood displacement chamber volume, the cannula being connected to the said compressible blood displacement chamber.

20. The apparatus defined in claim 11, further comprising sensors for detecting opening and closure of said outlet valve and including at least one of the following:

a pressure gauge for measuring intraventricular pressure,

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

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

ultrasound or electrical impedance means for measuring intraventricular volume;

a strain gauge means for measuring regional ventricle wall shortening; and

a sound detector.

21. The apparatus defined in claim 11 may further comprise means for monitoring timing and profile of blood flow through the cannula based on regional ventricle wall motion, to optimize the apparatus based on the function of the preserved region of the ventricle wall, said means for monitoring including at least one of the following:

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

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

22. The apparatus defined in claim 11 wherein said blood displacement chamber is selected from the group which consists of a syringe pump, a flexible membrane or diaphragm, a bellows or compressive flexible sack operated by an actuator motor.

23. The apparatus defined in claim 11 wherein said actuator motor is selected from the group which consists of an electric motor, pneumatic device, centrifuge or axial flow pump, a transplanted heart or a patient'"'"'s own skeletal muscle.

24. The apparatus defined in claim 13 wherein said sensor includes at least one ultrasonic crystal on said ventricle wall or inside the ventricle cavity that have been introduced into the ventricle through the cannula.

25. The apparatus defined in claim 11, further comprising at least one sensor on said cannula for measuring the ventricle volume thereof and an additional sensor on said cannula for measuring ventricle cavity pressure.

26. The apparatus defined in claim 11 for implantation in a patient, further comprising a compliance chamber connected to said displacement actuator.