Biomechanics of the Aortic Valve in the Continuous Flow VAD-Assisted Heart

The biomechanics of the aortic valve are altered in patients with ventricular assist devices (VADs). During high VAD flow and low cardiac function, transvalvular pressure is high, and the aortic valve remains closed throughout the cardiac cycle. This condition has been linked to the development of aortic valve fusion and incompetence during VAD use. Thus, physicians try to maintain pulsatile flow to assure periodic valve opening. The aim of this study was to determine the extent of aortic valve opening and alterations in valve leaflet strain before and during VAD support using a specially designed mock loop. The results showed that diastole is prolonged during VAD use. In addition, there is a reduction in valve opening area, producing a VAD-related functional stenosis. The average leaflet strain increased during VAD support, primarily due to an increase in the minimum strain, during systole, rather than the maximum strain during diastole. The findings support our hypothesis that altered biomechanics in the VAD-assisted heart results in increased strain in the aortic valve leaflets, which can stimulate soft tissue remodeling. The implication for clinical use is that valve opening during parallel VAD flow is reduced compared with normal flow conditions. Consequently, current clinical practice for VAD patients may not be achieving sufficient valve opening to prevent changes such as fusion and incompetence. ASAIO Journal 2010; 56:301-308.