Aortic regurgitation during continuous-flow left ventricular assist device support: An insufficient understanding of an insufficient lesion

Abstract

Aortic valve insufficiency (AI) was not an anticipated complication of left ventricular (LV) assist device (LVAD) support. The phenomena of continuous AI largely materialized after the evolution of devices from pulsatile-flow to continuous-flow (CF) technology. Most patients on CF-LVAD support have a closed aortic valve during ventricular systole because pressures in the LV never exceed that of the aorta during isovolumic contraction. Going against nature, the closed aortic valve becomes subjected to high shear stress and strain during systole, with blood flow from the LVAD outflow cannula repeatedly contacting the root side of the closed aortic valve. Inflammation, calcification, and commissural fusion of the aortic valve leaflets instigated by this high shear stress can lead to aortic valvular degeneration and resultant AI. AI of at least moderate severity can be seen in 30% of patient by 2 years of CF-LVAD support. As the regurgitant fraction of AI increases, patients can develop recurrent heart failure (HF) symptoms despite seemingly normal pump function. HF symptoms in this setting are due to a combination of reduced effective cardiac output (secondary to recycling of LVAD and native cardiac output via AI) and elevated LV filling pressures. On the basis of several recent studies, it has become very clear that AI is a challenge to quantify and qualify using traditional echocardiography measures and that the clinical effect of AI at present mean durations (3.7 years in Interagency Registry for Mechanically Assisted Circulatory Support) of CF-LVAD support remains debatable. The Columbia group monitored 232 patients on CF-LVAD support for a mean of 344 days. They observed moderate or worse AI in 21 patients (28%) at 2 years, and symptomatic HF developed in 8 of these patients (38%) that was attributed to AI. In contrast, the Michigan group monitored