LVAD speed increase during exercise, which patients would benefit the most? A simulation study

Abstract

Patients supported with a left ventricular assist device (LVAD) have impaired cardiovascular adaptations during exercise, resulting in reduced total cardiac output and exercise intolerance. The aim of this study is to report associations among these impaired cardiovascular parameters and exercise hemodynamics, and to identify in which conditions an LVAD speed increase can provide substantial benefits to exercise. A cardiorespiratory simulator was used to reproduce the average hemodynamics of LVAD patients at exercise. Then, a sensitivity study was conducted where cardiovascular parameters were changed individually ±20% of their baseline value at exercise (heart rate, left/right ventricular contractility, total peripheral resistance, and valve pathologies). Simulations were performed at a baseline LVAD speed of 2700 rpm and repeated at 3500 rpm to evaluate the benefits of a higher LVAD support on hemodynamics. Total cardiac output (TCO) was mostly impaired by a poor left ventricular contractility or vasodilation at exercise (−0.6 L/min), followed by a poor chronotropic response (−0.3 L/min) and by a poor right ventricular contractility (−0.2 L/min). LVAD speed increase better unloads the left ventricle and improves total cardiac output in all the simulated conditions. The most substantial benefits from LVAD speed increase were observed in case of poor left ventricular contractility (TCO + 1.6 L/min) and vascular dysfunction (TCO + 1.4 L/min) followed by lower heart rate (TCO + 1.3 L/min) and impaired right ventricular contractility (TCO + 1.1 L/min). Despite the presence of the LVAD, exercise hemodynamic is strongly depending on the ability of the cardiovascular system to adapt to exercise. A poor left ventricular inotropic response and a poor vascular function can strongly impair cardiac output at exercise. In these conditions, LVAD speed increase can be an effective strategy to augment total cardiac output and unload the left ventricle. These results evidence the need to design a physiological LVAD speed controller, tailored on specific patient’s needs.

Hemodynamic exercise responses with a continuous-flow left ventricular assist device: Comparison of patients’ response and cardiorespiratory simulations

“…AV open at peak exercise (Response type 3): These patients may experience minor benefits of a speed increase during exercise due to a remaining LV contractility and its ability to increase total cardiac output. LVAD speed increase during exercise in this category could result in the redistribution of cardiac output between the LVAD and what it is ejected towards the aortic valve without the degree of increase of overall flow as it might be observed in others [37].…”

“…Constant speed LVAD devices lack adequate adaption of pump output to exercise levels resulting in the hypoperfusion of patients during stress [3,34]. The observed differences in Q MEAN responses from rest to exercise in patients and simulations underline that the support of the device in sustaining cardiac output is different among patients and can be influenced by several cardiovascular parameters [37]. Clinical observations in LVAD patients during exercise with increased as well as decreased LVAD speeds have demonstrated effects on exercise hemodynamics in patient subgroups, but not in the whole study cohorts [38,39].…”

“…These hemodynamic differences mainly affect the diastolic part of the LVAD flow waveform (see Fig 5). (Additional information on cardiac output for the simulations are published in Gross et al [37]).…”

Exercise capacity following ventricular assist device implantation via thoracotomy with outflow cannula anastomosis to the descending aorta

“…Meanwhile, there is evidence to suggest that LVAD speed may influence exercise capacity in LVAD patients. [34][35][36] Unfortunately, our data set did not include RPM values at the time of exercise precluding us from making quantitative comparisons of pump speed. Another interesting aspect of the relationship between descending aorta anastomosis and exercise is the change in peripheral vascular resistance during exercise.…”

Changes in Resting and Exercise Hemodynamics Early After Heart Transplantation: A Simulation Perspective

“…In recent years, numerical simulations have gained increasing popularity in cardiovascular research, especially to gain a better understanding of the human hemodynamics and its changes associated with various diseases ( Jung et al, 2006 ; Banerjee et al, 2008 ; Qian et al, 2010 ; Politi et al, 2016 ). Moreover, mathematical modeling was successfully proven to be an effective technique for the design and evaluation of potential treatment modalities for heart failure patients, such as mechanical circulatory assist devices ( Moscato et al, 2010 , 2013 ; Gross et al, 2020 ).…”