Pump preload index/indicator
A method of estimating an amount of work available to be performed by a blood pump implanted in a patient includes calculating a first coordinate value characterizing a volume of blood impelled in the pump and a second coordinate value characterizing a differential pressure across the pump for each of a plurality of flow rate data points of a given cardiac cycle of the patient, each flow rate data point indicative of a flow rate of blood through the pump. An area enclosed by the first and second coordinate values of the plurality of flow rate data points is determined, the determined area being indicative of an amount of work available to be performed by the blood pump.
1. A method of estimating an amount of work available to be performed by a blood pump implanted in a patient, comprising:
calculating a first coordinate value characterizing a volume of blood impelled in the pump and a second coordinate value characterizing a differential pressure across the pump for each of a plurality of flow rate data points of a given cardiac cycle of the patient, each flow rate data point indicative of a flow rate of blood through the pump;
determining an area enclosed by the first and second coordinate values of the plurality of flow rate data points, the determined area being indicative of an amount of work available to be performed by the blood pump;
determining a starting time of the given cardiac cycle based on the determined flow rate data points crossing a running average flow rate; and
determining an ending time of the given cardiac cycle based on the determined flow rate data points crossing the running average flow rate;
the plurality of flow rate data points of the given cardiac cycle being indicative of a flow rate of blood between the starting time and the ending time.
2. The method of claim 1 , wherein determining the starting and ending times are further based on one of:
identifying consecutive instances of the determined flow rate data points crossing the running average flow rate with a negative slope;
identifying consecutive instances of the determined flow rate data points crossing the running average flow rate with a positive slope; and
identifying three consecutive instances of the determined flow rate data points crossing of the running average flow rate, the first of the three consecutive instances being the starting time and the third of the three consecutive instances being the ending time.
3. The method of claim 1 , wherein for each of the flow rate data points of the given cardiac cycle of the patient, the calculated first coordinate value is a derivative of the flow rate data point.
4. The method of claim 1 , wherein for each of the flow rate data points of the given cardiac cycle of the patient, the calculated second coordinate value is a differential pressure corresponding to the flow rate data point.
5. The method of claim 4 , further comprising determining a rotational speed of the blood pump, wherein the second coordinate value is determined at least in part using the determined rotational speed of the blood pump.
6. The method of claim 4 , wherein the calculated second coordinate value is interpolated from a reference curve correlating differential pressure across the pump and flow rate through the pump for a given rotational speed of the blood pump.
7. The method of claim 1 , wherein the flow rate data points are determined based on a non-invasive estimation of flow rate.
8. The method of claim 1 , further including comparing the determined area to a predetermined value indicative of a minimum allowable amount of ventricular loading, wherein the determined area being less than the predetermined value is indicative of the presence of adverse condition.