Ex Vivo Assessment of a Parabolic-Tip Inflow Cannula for Pediatric Continuous-Flow VADs

To address the challenge of unloading the left ventricle during pediatric mechanical circulatory support using next-generation rotary blood pumps, a novel inflow cannula was developed. This unique inflow cannula for pediatric, continuous-flow, left ventricular assist devices (VADs) with a parabolic-shaped inlet entrance was evaluated alongside a bevel-tip and fenestrated-tip cannula via an ex vivo, isolated-heart experimental setup. Performance was characterized using two clinical scenarios of over-pumping and hypovolemia, created by varying pump speed and filling preload pressure respectively, at ideal and off-axis cannula placement to assess ventricular unloading and positional sensitivity. Quantitative and qualitative assessments were performed on the resultant hemodynamics and intra-ventricular boroscopic images to classify conditions of non-suction, partial, gradual or severe entrainment, and ventricular collapse. The parabolic-tip cannula was found to be significantly less sensitive to placement position (p-values < 0.001) than the bevel-tip cannula under all conditions, while not statistically different from the fenestrated cannula. Visual analysis of the parabolic-tip cannula showed complete resistance to entrainment whereas the fenestrated-tip had partial entrainment in 90% and 87% of the over-pumping and hypovolemic studies, respectively. We conclude that future pediatric VAD designs may benefit from incorporating the parabolic-tip inflow cannula design in order to maximize unloading of the left ventricle in ideal and non-optimal conditions.