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Description
There are 5.8 million cases of heart failure (HF) in the United States. Dilated cardiomyopathy (DCM) is the weakening and enlargement of the left ventricle (LV) and is associated with HF. Those with severe HF can have Left Ventricular Assist Devices (LVADs) implanted into the heart to pump blood and increase end-organ perfusion. LVADs are attached by inflow and outflow cannulas at the heart apex and aorta, respectively. Some risks associated with LVADs include thrombosis and aortic insufficiency. Inflow cannula (IC) diameters vary between different LVAD models but are not patient specific. Our experiment assesses the interaction of IC diameter, LVAD support (rotary pump speed), and left ventricular volume (LVV) using the SDSU Cardiac Simulator (CS). Some clinically relevant indices measured include ejection fraction (EF), pulsatility index (PI), and aortic valve opening time (AVOT) which will help determine the optimal IC diameter for a patient. The CS is a mock circulatory loop that can be manually adjusted to match patient conditions with repeatability. The LVV models are made of silicone with an elasticity similar to the heart. The large LVV represents a patient with DCM while the small LVV represents a patient that has a normal LVV. The LVAD support levels are varied based on the most common speeds used clinically. Particle Image Velocimetry (PIV) is used to capture the 2-D velocity fields within the mid-plane of the left ventricle. Further analysis is done within regions of interest (ROI) such as the apical region, inside the inflow cannula, and the aortic outflow region. An increase in LVAD support increases the EF with the effects being greater in patients with smaller LVVs. As LVAD speed increases, AVOT decreases which can lead to aortic insufficiency from the absence of intermittent aortic valve opening. The smallest IC diameter tested allowed for the longest AVOT when paired with the large LVV. PI is the measurement of flow pulse and decreases with an increase in LVAD support. The large IC had the lowest PI which increases the stroke risk.
