UC San Diego

Healthy heart valves act as gateways to ensure unidirectional blood flow inside the normal heart. Dysfunctional valves compromise cardiac output and disrupt the normal intraventricular flow pattern, resulting in a degeneration of cardiac function if left untreated. In the presence of a left ventricular assist device (LVAD), valvular dysfunction can significantly affect patient outcomes. It is challenging to study the intraventricular flow pattern directly in LVAD patients since this is a very sick population suffering from many underlying diseases. Therefore in this study, we use a mock circulator, which mimics the cardiac hemodynamics of end-stage heart failure (HF) patient, to characterize the change in the left ventricle (LV) flow and hemodynamics in the presence of LVAD and prosthetic mitral valve (MV) or aortic insufficiency (AI).

MV diseases are common in advanced HF patients, who are often required surgical correction to replace MV with prosthetic valves. Upon LVAD implant, pre-existing prosthetic MV are often left in patients and subjected them to higher thromboembolic (TE) risks. Intraventricular flow field indices for six different MV prosthesis designs/orientations under matched HF conditions during low and high HeartMate II (HM2) LVAD support were measured in a cardiac simulator and assessed for TE risks. While the intraventricular vortex patterns were not substantially altered by the LVAD, the pump introduced instinct residual flow regions at different LVAD support levels and identified very high TE risk in the presence of a tilting-disk mechanical valve in septal orientation.

AI Is a serious complication in more than 20% of LVAD patients within one year of LVAD implant. Pre-existing mild-less AI is often left untreated at the time of LVAD implant and can progress to significant AI. Three models of AI severity were tested under three levels of HM2, and HM3 LVAD supports. The result shows that LVAD worsens AI indices by introducing LV turbulence, increasing energy loss, and prolong the diastolic phase.

By examining in detail the interaction of LVAD to intraventricular flow during the presence of MV prostheses or AI, the study provide new sights to aid in future LVAD design and patient management.