Rotary Blood Pump Flow Spontaneously Increases During Exercise Under Constant Pump Speed: Results of a Chronic Study

Abstract

Many types of rotary blood pumps and pump control methods have recently been developed with the goal of clinical use. From experiments, we know that pump flow spontaneously increases during exercise without changing pump control parameters. The purpose of this study was to determine the hemodynamics associated with the long-term observation of calves implanted with centrifugal blood pumps (EVAHEART, Sun Medical Technology Research Corporation, Nagano, Japan). Two healthy female Jersey calves were implanted with devices in the left thoracic cavity. A total of 22 treadmill exercise tests were performed after the 50th postoperative day. During exercise, the following parameters were compared with conditions at rest: heart rate, blood pressure, central venous oxygen saturation (SvO2), pump speed, and pump flow. The pump flow in a cardiac cycle was analyzed by separating the systole and diastole. Compared to the base data, statistically significant differences were found in the following interrelated parameters: the heart rate (66.8 +/- 5.2 vs. 106 +/- 9.7 bpm), mean pump flow (4.8 +/- 0.2 vs. 7.0 +/- 0.3 L/min), and volume of pump flow in diastole (26.0 +/- 1.8 vs. 13.5 +/- 2.5 ml). During exercise, the volume of pump flow in systole was 3 times larger than that measured in diastole. Blood pressure, SvO2, and pump speed did not change significantly from rest to exercise. These results suggested that the mean pump flow depends on the systolic pump flow. Therefore, the increase in the mean pump flow during exercise under constant pump speed was caused by an increase in the heart rate.

Changes in the Functional Status Measures of Heart Failure Patients With Mechanical Assist Devices

“…During exercise with a cfLVAD operating at a fixed speed, a modest increase in pump flow may occur that can be attributable to increased preload from the left ventricle and increased ratio of systole to diastole as HR increases. 16,17 However, the cfLVAD response is limited when compared with the Frank-Starling response of a healthy ventricle. 18 In patients with a moderate amount of intrinsic heart function, the native left ventricle may contribute significantly to the cardiac output, both by increasing cfLVAD inlet pressure through the pump and by direct ejection through the aortic valve.…”

First Clinical Experience with an Automatic Control System for Rotary Blood Pumps During Ergometry and Right-Heart Catheterization

“…[1][2][3][4][5] Even at constant speed, changes in the remaining cardiac activity cause a minor adaptation of pump flow to physiologic demand. 1,6 However, this increase remains below the natural response owing to the Frank-Starling mechanism. 7,8 Therefore, to avoid overpumping with subsequent collapse of the left ventricle and impairment of right heart function owing to septal shift, 9 a speed-control system capable of adapting to the patient's physiologic requirements would provide additional clinical benefit.…”

Completely pulsatile high flow circulatory support with a constant-speed centrifugal blood pump: mechanisms and early clinical observations

“…Because the total blood fl ow is supplied mainly as systolic fl ow, as the heart rate increases when exercising the fl ow rate naturally increases without needing to change the pump speed because the relative duration of the systolic phase increases. 5 Therefore, it is anticipated that there would not be a need to know the pump fl ow for patient management. Simply monitoring the peak blood pressure (systolic) may be enough to ensure good circulatory support.…”