Pulsatility in ventricular assistance devices: A translational review focused on applied haemodynamics

Heart failure affects more than 30 million people worldwide and its prevalence is constantly rising. In 2020, heart transplantation is the only curative treatment, but left ventricular assistance devices (LVADs) are fully integrated into the decision algorithm for management of patients with advanced heart failure, with more than 20,000 devices implanted worldwide in the last decade. Intended to support cardiac output, LVADs remove the blood from the left ventricle and eject it into the proximal aorta. Whereas first-generation LVADs were pulsatile, second- and third-generation LVADs are more reliable, but create a laminar flow, with reduced (or absent) blood flow pulsatility. Concomitantly, several new adverse events, some of them lethal, appeared when continuous-flow LVADs started to be implanted, including acquired von Willebrand disease, gastrointestinal bleeding and aortic valve fusion or regurgitation. This review aims to apply models describing pulsatility (such as the Windkessel effect applied by Frank, Guyton's continuity model of venous return and Sunagawa's left ventricular-arterial coupling) to LVADs, to better understand the physiopathology in patients using continuous-flow devices. This review also covers the means of exploring pulsatility and adverse events associated with a reduction in pulsatility, as well as the possible ways for restoring pulsatility in patients implanted with an LVAD.