CONTROL OF CIRCULATORY ASSIST SYSTEMS

1 . A controller for a heart assist system, comprising:

a processing unit configured to

generate a pulsatility index for a right blood pump,

set a speed of the right blood pump based on the pulsatility index for the right blood pump,

generate a pulsatility index for a left blood pump, and

set a speed of the left blood pump based on the pulsatility index for the left blood pump.

2 . A method of controlling a heart assist system, comprising:

calculating a pulsatility index for a right blood pump, the right blood pump supporting a right ventricle;

controlling the speed of the right blood pump based on the pulsatility index for the right blood pump;

calculating a pulsatility index for a left blood pump, the left blood pump supporting a left ventricle; and

controlling the speed of the left blood pump based on the pulsatility index for the left blood pump.

3 . The method of claim 2 , wherein the right blood pump is a rotary pump, and wherein the left blood pump is a rotary pump.

4 . The method of claim 2 , wherein the pulsatility index for the right blood pump indicates a load on the right ventricle experienced during contraction of the right ventricle, and wherein the pulsatility index for the left blood pump indicates a load on the left ventricle experienced during contraction of the left ventricle.

5 . The method of claim 2 , wherein each pulsatility index (PI) is calculated over a control interval according to the following equation: PI=(Q max −Q min )/Q ave , where Q max is a maximum flow rate through the pump in the control interval, Q min is a minimum flow rate through the pump in the control interval, and Q ave is an average flow rate through the pump over the control interval.

6 . The method of claim 2 , further comprising:

measuring blood flow through the right blood pump;

measuring blood flow through the left blood pump; and

controlling a speed of one of the rotary blood pumps based on the measured blood flow through the other blood pump.

7 . The method of claim 6 , further comprising determining whether the blood flow through one of the blood pumps exceeds a flow threshold,

wherein controlling the speed of the right blood pump and controlling the speed of the left blood pump comprise, when the pulsatility index for the right blood pump is below a first target level and the pulsatility index for the left blood pump is below a second target level:

when the blood flow through the one of the blood pumps does not exceed the flow threshold, decreasing the speed of the right blood pump and decreasing the speed of the left blood pump, and

when the blood flow through the one of the blood pumps exceeds the flow threshold, maintaining the speed of the right blood pump and maintaining the speed of the left blood pump.

8 . The method of claim 7 , wherein controlling the speed of one of the rotary blood pumps based on the measured blood flow through the other blood pump comprises:

determining that a relationship between the measured blood flow through the right blood pump and the measured blood flow through the left blood pump is not satisfied; and

in response to determining that the relationship is not satisfied, adjusting the speed of the one of the blood pumps such that the relationship is achieved.

9 . The method of claim 2 , wherein controlling the speed of the right blood pump is further based on the pulsatility index for the left blood pump.

10 . The method of claim 2 , wherein controlling the speed of the left blood pump is further based on the pulsatility index for the right blood pump.

11 . The method of claim 2 , further comprising detecting a heart rate,

wherein controlling the speed of the right blood pump is further based on the heart rate, and wherein controlling the speed of the left blood pump is further based on the heart rate.

12 . The method of claim 11 , further comprising determining whether the heart rate exceeds a threshold heart rate,

wherein controlling the speed of the right blood pump and controlling the speed of the left blood pump comprise, when the pulsatility index for the right blood pump is below a first target level and the pulsatility index for the left blood pump is below a second target level:

when the heart rate does not exceed the threshold heart rate, decreasing the speed of the right blood pump and decreasing the speed of the left blood pump, and

when the heart rate exceeds the threshold heart rate, maintaining the speed of the right blood pump and maintaining the speed of the left blood pump.

13 . The method of claim 2 , further comprising operating the left blood pump to produce an artificially induced pulsatile blood flow; and

calculating the left pulsatility index such that data influenced by artificial blood flow variations of the artificially induced pulsatile blood flow are excluded from calculating the left pulsatility index.