Ventricular assist device method and apparatus

1. Apparatus for use with a ventricular assist device that is assisting cardiac function of a biological subject, the apparatus including an electronic processing device that:

a) determines a flow rate of blood through the ventricular assist device;

b) analyses the flow rate to determine a flow parameter value, wherein the flow parameter value is indicative of a flow rate gradient during diastole and is determined by:

i) determining the flow rate over at least one cardiac cycle;

ii) analysing the flow rate to identify a period of the cardiac cycle corresponding to diastole;

iii) determining the flow rate gradient during the diastole period; and,

iv) determining the flow rate parameter value using the flow rate gradient; and,

c) uses the flow parameter value to control the ventricular assist device.

2. Apparatus according to claim 1 , wherein the electronic processing device:

a) compares a parameter value to at least one threshold, the parameter value being at least one of the flow parameter value and a blood pressure parameter value; and,

b) in response to results of the comparison, at least one of:

i) selectively adjusts blood flow through the ventricular assist device; and

ii) selectively generates a notification.

3. Apparatus according to claim 2 , wherein the threshold is at least one of:

a) indicative of a nominal range;

b) determined based on a parameter value determined from a sample population; and,

c) at least in part based on a parameter value previously determined for the subject.

4. Apparatus according to claim 1 , wherein the ventricular assist device includes a rotating impeller, and wherein the electronic processing device controls blood flow through the ventricular assist device by causing a rate of rotation of the impeller to be adjusted.

5. Apparatus according to claim 1 , wherein the electronic processing device:

a) analyses the flow rate over a plurality of cardiac cycles;

b) determines a mean flow rate gradient during diastole; and,

c) determines the flow rate parameter value using a mean flow rate gradient.

6. Apparatus according to claim 5 , wherein the electronic processing device:

a) calculates flow rate maxima and minima for each of the plurality of cardiac cycles; and,

b) selectively excludes a cardiac cycle based on at least one of the respective flow rate maxima and minima of the cardiac cycle.

7. Apparatus according to claim 6 , wherein the electronic processing device selectively excludes cardiac cycles corresponding to suction events.

8. Apparatus according to claim 5 , wherein the electronic processing device:

a) calculates flow rate maxima and minima for each of the plurality of cardiac cycles; and,

b) determines a period of the cardiac cycle corresponding to diastole using the flow rate maxima and minima.

9. Apparatus according to claim 8 , wherein the electronic processing device determines diastole as a period of the cardiac cycle from the flow rate minima to proportion of the flow rate maxima.

10. Apparatus according to claim 9 , wherein the proportion of the flow rate maxima is at least one of:

a) half of the flow rate maxima; and,

b) quarter of the flow rate maxima.

11. Apparatus according to claim 1 , wherein the electronic processing device analyses the flow rate using waveform analysis.

12. Apparatus according to claim 1 , wherein the electronic processing device at least one of:

a) records the flow parameter value;

b) displays a representation of the flow parameter value;

c) records a blood pressure parameter value; and,

d) displays a representation of the blood pressure parameter value.

13. Apparatus according to claim 1 , wherein the at least one blood pressure parameter value is at least partially indicative of at least one of:

a) an intra-cardiac pressure;

b) an atrial pressure;

c) a ventricular filling pressure;

d) a pulmonary capillary wedge pressure;

e) a ventricular end diastole pressure; and,

f) a mean arterial pressure.

14. Apparatus according to claim 1 , wherein the electronic processing device:

a) calculates a ventricular filling pressure using the flow parameter value;

b) determines a ventricular assist device power usage; and,

c) calculates a mean arterial pressure using the ventricular filling pressure and the ventricular assist device power usage.

15. Apparatus according to claim 1 , wherein the electronic processing device is at least one of:

a) at least part of a ventricular assist device controller; and,

b) coupled to a ventricular assist device controller.

16. Apparatus according to claim 1 , wherein the electronic processing device determines the blood flow rate at least one of:

a) in accordance with signals received from a sensor;

b) by receiving flow rate data from a ventricular assist device controller; and,

c) by calculating a flow rate based on rotation of a ventricular assist device impeller.

17. A method for use with a ventricular assist device that is assisting cardiac function of a biological subject, the method including:

a) determining a flow rate of blood through the ventricular assist device;

b) analysing the flow rate to determine a flow parameter value, wherein the flow parameter value is indicative of a flow rate gradient during diastole and is determined by:

i) determining the flow rate over at least one cardiac cycle;

ii) analysing the flow rate to identify a period of the cardiac cycle corresponding to diastole;

iii) determining the flow rate gradient during the diastole period; and,

iv) determining the flow rate parameter value using the flow rate gradient; and,

c) using the flow parameter value to control the ventricular assist device.

18. Apparatus for use when assisting cardiac function of a biological subject, the apparatus including:

a) a ventricular assist device: and,

b) an electronic processing device that:

i) measures a flow rate of blood by the ventricular assist device;

c) analyses the flow rate to determine a flow parameter value, wherein the flow parameter value is indicative of a flow rate gradient during diastole and is determined by:

i) determining the flow rate over at least one cardiac cycle;

ii) analysing the flow rate to identify a period of the cardiac cycle corresponding to diastole;

iii) determining the flow rate gradient during the diastole period; and,

iv) determining the flow rate parameter value using the flow rate gradient; and,

d) uses the flow parameter value to derive at least one blood pressure parameter value at least partially indicative of a blood pressure in the biological subject.

19. A method for use when assisting cardiac function of a biological subject, the method including:

a) using a ventricular assist device to assist cardiac function of the biological subject;

b) using an electronic processing device to:

i) measure a flow rate of blood by the ventricular assist device;

c) analyse the flow rate to determine a flow parameter value, wherein the flow parameter value is indicative of a flow rate gradient during diastole and is determined by:

i) determining the flow rate over at least one cardiac cycle;

ii) analysing the flow rate to identify a period of the cardiac cycle corresponding to diastole;

iii) determining the flow rate gradient during the diastole period; and,

iv) determining the flow rate parameter value using the flow rate gradient; and,

d) use the flow parameter value to control the ventricular assist device.

20. Apparatus including:

a) a ventricular assist device that is assisting cardiac function of a biological subject; and,

b) an electronic processing device that:

i) determines a flow rate of blood through the ventricular assist device;

ii) analyses the flow rate to determine a flow parameter value, wherein the flow parameter value is indicative of a flow rate gradient during diastole and is determined by:

1) determining the flow rate over at least one cardiac cycle;

2) analysing the flow rate to identify a period of the cardiac cycle corresponding to diastole;

3) determining the flow rate gradient during the diastole period; and,

4) determining the flow rate parameter value using the flow rate gradient;

and,

iii) uses the flow parameter value to control the ventricular assist device.