“Bionic Women and Men”: The Unique Physiology of Left Ventricular Assist Device Patients – Keep your finger on the pulse!

Abstract

Across many countries in the world, advanced heart failure patients who are eligible for a heart transplant face the same dilemma: there are not enough donor hearts available for all. The current next-best alternative to a heart transplant is the surgical implantation of a left ventricular assist device (LVAD). Although the purpose of the LVAD is to relieve the overloaded left ventricle of heart failure patients and restore a normal cardiac output, patients have presented with high levels of stroke gastrointestinal bleeding and right-heart failure. One potential reason for this increased risk is the continuous flow of the implanted LVAD. As a result, the majority of LVAD patients do not have a palpable pulse (Purohit et al., 2018), creating a unique arterial biology in these humans (Castagna et al., 2017). Perhaps surprising is the superior health outcome of patients supported with continuous-flow (CF) compared with pulsatile-flow LVADs. In addition, the reduced/absent pulsatility in these CF-LVAD patients (see figure 1.) enables the investigation of unique arterial physiology and cardiovascular regulation, which has already revealed some unexpected observations. For example, continuous-flow patients appear to have a higher sympathetic activity (Cornwell et al., 2015), and suffer complications above a low systolic blood pressure of ~100 mmHg, atypical of non-LVAD populations in whom hypertension (>140 mmHg) is a predictor of stroke (Pinsino et al., 2019). Thus, the medical debate whether continuous flow is truly better for the health of advanced heart failure patients also necessitates a more generic, fundamental discussion into ‘normal’ arterial physiology & health. The comprehensive study investigating the detailed cardiovascular response and adaptations to drastically altered haemodynamics in heart failure, with and without LVAD support, at rest, during physical activity and in combination with cardiovascular acting medication, is essential. This unique area of research presents an opportunity to significantly increase our fundamental physiological understanding of the interaction between cardiac dynamics (volume, force, ejection pattern) and arterial regulation (flow, blood pressure, sympathetic activity, endothelial function, pulsatility). Therefore, the symposium entitled “Bionic women and men – Physiology lessons from implantable cardiac devices” held at the 2019 Annual Meeting of The Physiological Society in Aberdeen, UK, brought together clinicians and scientists from a previous CrossTalk debate (Cornwell et al., 2019; Stöhr et al., 2019) to review the current knowledge of LVAD patients and identify outstanding questions in the field. In total, four presentations were given and each of them have been published as symposium reports in this edition of Experimental Physiology.