Effect of inflow cannula tip design on potential parameters of blood compatibility and thrombosis

During ventricular assist device support, a cannula acts as a bridge between the native cardiovascular system and a foreign mechanical device. Cannula tip design strongly affects the function of the cannula and its potential for blood trauma. In this study, the flow fields of five different tip geometries within the ventricle were evaluated using stereo particle image velocimetry. Inflow cannulae with conventional tip geometries (blunt, blunt with four side ports, beveled with three side ports, and cage) and a custom-designed crown tip were interposed between a mixed-flow rotary blood pump and a compressible, translucent silicone left ventricle. The contractile function of the failing ventricle and hemodynamics were reproduced in a mock circulation loop. The rotary blood pump was interfaced with the ventricle and aorta and used to fully support the failing ventricle. Among these five tip geometries, high-shear volume (γ ˙ ≥ 2778 / s , potential parameter of platelet activation) was found to be the greatest in the blunt tip. The cage tip was observed to have the highest low-shear volume and recirculation volume (γ ˙ ≤ 100 / s and V>0, respectively; potential parameters of thrombus formation). The crown tip, together with conventional tip geometries with side ports (blunt with four side ports and beveled with three side ports) showed no significant difference in either high-shear volume or low-shear volume. However, recirculation volume was reduced significantly in the crown tip. Despite limited generalizability to clinical situations, these transient-state measurements supported the potential mitigation of complications by changing the design of conventional cannula tip geometries.