Structural performance and hydrodynamic resistance of a new silicone auricular cannula tip

Numerical investigation of the effect of cannula placement on thrombosis

Despite the rapid advancement of left ventricular assist devices (LVADs), adverse events leading to deaths have been frequently reported in patients implanted with LVADs, including bleeding, infection, thromboembolism, neurological dysfunction and hemolysis. Cannulation forms an important component with regards to thrombus formation in assisted patients by varying the intraventricular flow distribution in the left ventricle (LV). To investigate the correlation between LVAD cannula placement and potential for thrombus formation, detailed analysis of the intraventricular flow field was carried out in the present study using a two way fluid structure interaction (FSI), axisymmetric model of a passive LV incorporating an inflow cannula. Three different cannula placements were simulated, with device insertion near the LV apex, penetrating one-fourth and mid-way into the LV long axis. The risk of thrombus formation is assessed by analyzing the intraventricular vorticity distribution and its associated vortex intensity, amount of stagnation flow in the ventricle as well as the level of wall shear stress. Our results show that the one-fourth placement of the cannula into the LV achieves the best performance in reducing the risk of thrombus formation. Compared to cannula placement near the apex, higher vortex intensity is achieved at the one-fourth placement, thus increasing wash out of platelets at the ventricular wall. One-fourth LV penetration produced negligible stagnation flow region near the apical wall region, helping to reduce platelet deposition on the surface of the cannula and the ventricular wall.

Performance of extracorporeally adjustable ventricular assist device inflow cannula

PURPOSE

This study evaluated the feasibility and efficacy of a newly developed adjustable left ventricular assist device inflow cannula in a short-term calf model.

DESCRIPTION

In this inflow cannula, the angle between the cannula body and the inflow cannula tip can be altered extracorporeally by manipulating 2 externalized cables connected to the cannula. The cannula tip is adjustable in any plane to a maximum of ±15 degrees.

EVALUATION

After initial prototyping in 4 calf cadavers, a Cleveland Heart left ventricular assist device was implanted with the adjustable inflow cannula placed in the left ventricular apex and the outlet to the descending aorta. Under hypovolemic conditions, the angle of the cannula tip could be changed to induce varying degrees of ventricular suction and then eliminate it, as evidenced by recorded pump and native left ventricular flows. Epicardial echocardiography and fluoroscopy in the closed-chest condition documented extracorporeal adjustments of the inflow cannula position.

CONCLUSIONS

This extracorporeally adjustable inflow cannula was effective in preventing or controlling left ventricular suction.