Electrocardiogram‐Synchronized Rotational Speed Change Mode in Rotary Pumps Could Improve Pulsatility

Abstract

Continuous-flow left ventricular assist devices (LVADs) have greatly improved the prognosis of patients with end-stage heart failure, even if continuous flow is different from physiological flow in that it has less pulsatility. A novel pump controller of continuous-flow LVADs has been developed, which can change its rotational speed (RS) in synchronization with the native cardiac cycle, and we speculated that pulsatile mode, which increases RS just in the systolic phase, can create more pulsatility than the current system with constant RS does. The purpose of the present study is to evaluate the effect of this pulsatile mode of continuous-flow LVADs on pulsatility in in vivo settings. Experiments were performed on eight adult goats (61.7 ± 7.5 kg). A centrifugal pump, EVAHEART (Sun Medical Technology Research Corporation, Nagano, Japan), was installed by the apex drainage and the descending aortic perfusion. A pacing lead for the detection of ventricular electrocardiogram was sutured on the anterior wall of the right ventricle. In the present study, we compared pulse pressure or other parameters in the following three conditions, including Circuit-Clamp (i.e., no pump support), Continuous mode (constant RS), and Pulsatile mode (increase RS in systole). Assist rate was calculated by dividing pump flow (PF) by the sum of PF and ascending aortic flow (AoF). In continuous and pulsatile modes, these assist rates were adjusted around 80-90%. The following three parameters were used to evaluate pulsatility, including pulse pressure, dp/dt of aortic pressure (AoP), and energy equivalent pulse pressure (EEP = (∫PF*AoP dt)/(∫PF dt), mm Hg). The percent difference between EEP and mean AoP is used as an indicator of pulsatility, and normally it is around 10% of mean AoP in physiological pulse. Both pulse pressure and mean dp/dt max were decreased in continuous mode compared with clamp condition, while those were regained by pulsatile mode nearly to clamp condition (pulse pressure, clamp/continuous/pulsatile, 25.0 ± 7.6/11.7 ± 6.4/22.6 ± 9.8 mm Hg, mean dp/dt max, 481.9 ± 207.6/75.6 ± 36.2/351.1 ± 137.8 mm Hg/s, respectively). In clamp condition, %EEP was 10% higher than mean AoP (P = 0.0078), while in continuous mode, %EEP was nearly equivalent to mean AoP (N.S.). In pulsatile mode, %EEP was 9% higher than mean AoP (P = 0.038). Our newly developed pulsatile mode of continuous-flow LVADs can produce pulsatility comparable to physiological pulsatile flow. Further investigation on the effect of this novel drive mode on organ perfusion is currently ongoing.

High-frequency operation of a pulsatile VAD – a simulation study

“…The tVAD simulation was intended as a baseline experiment that represents the use of tVADs in clinical application today. There are numerous studies that have investigated augmented pulsatility in tVADs through speed modulation [1,3,4,16,26,27,33,34]. These studies have shown improved levels of pulsatility, left ventricular unloading and blood flow through the aortic valve, but were exceeded by the values of our pVAD simulation.…”

“…Previous studies have investigated synchronization ratios (1:2 and 1:4) lower than the HR under one given phase-shift setting [24] with the intention of establishing a weaning protocol. The importance of considering the pump timing and systolic fraction as an integral part of the investigation has been shown in vivo by [2] for pVADs and by [1,3,4,26,33,34] both in silico and in vivo for tVADs.…”

Alteration of LV end-diastolic volume by controlling the power of the continuous-flow LVAD, so it is synchronized with cardiac beat: development of a native heart load control system (NHLCS)

“…We have already reported details of our novel pump controller, which can change the RS of the EVAHEARTÒ so it is synchronized with the cardiac cycle [7,8,12,13]. We defined the systolic phase as 33% of the RR interval and the diastolic phase as 67% of the RR interval, and input the duration of each phase in accordance with the heart rate.…”

“…With this unit we define the distance and rotational speed (RS) of the systolic and diastolic phases to drive the EVAHEARTÒ so it is synchronized with the native heart rate. By using normal heart goat models [7] we have already shown that we can change the coronary flow (CoF) [8] by use of its remarkable pulsatility. In the work discussed in this report we wished to determine whether it was possible to change the native heart load by use of this system, by investigating the LV end-diastolic volume (EDV) with normal and acute heartfailure models.…”

Change of Coronary Flow by Continuous-Flow Left Ventricular Assist Device With Cardiac Beat Synchronizing System (Native Heart Load Control System) in Acute Ischemic Heart Failure Model

“…Such a pulsatile driving technique had not been tried or discussed before our group's recent report. [30][31][32][33][34][35][36] Using this system in normal goats' hearts, we found that coronary flow (CoF) could be altered according to the control mode. 30, 31 If we can achieve strong CoF by controlling the rotation of the cf-LVAD, in synchrony with the cardiac beat, we may have a atients with severe heart failure (HF) are treated with a multidisciplinary approach of medical management, including left ventricular assist device (LVAD) 1,2 and heart transplantation, and the prognosis has tremendously improved these days.…”