**1. Introduction**

Moderate-severe aortic insufficiency (AI) develops in more than 25% of left ventricular assist device (LVAD) recipients and reduces survival and freedom from other complications. Improvements in LVAD design have not addressed this problem, which continues to threaten the benefits of mechanical circulatory support. AI can develop de novo or progress from pre-existing AI conditions [1–7] and is associated primarily with rotary LVADs, also called continuous flow pumps. AI occurs when the mitral valve does not close completely during diastolic filling (**Figure 1**). The large pressure difference across the valve produces retrograde flow from the aorta to the LV. During LVAD support, the retrograde flow passes through the LVAD and into the ascending aorta, and a portion joins the regurgitant flow to repeat the cycle, exposing the blood to more shear. Significant AI diminishes cardiac output, negatively affects myocardial recovery and induces end-organ hypoperfusion [1]. Previous studies have linked a lack of aortic valve (AV) opening to the development of AI. Alterations in AV biomechanics during LVAD support can increase the activation of valvular interstitial cells, which transform into myofibroblasts that increase fibrosis preferentially at the ventricular face of the leaflets and fusion at the commissures. The subsequent contraction of fibrotic tissue and the fragmentation of elastin reduces coaptation, eventually resulting in AI. Assessment of AI in LVAD patients must be adapted from standard guidelines to determine when treatment is needed.

**Figure 1.** *Schematic of aortic insufficiency (AI), when the aortic valve leaks under high pressures, reducing forward flow.*
