The Impact of Cannulas on the Heart-Blood Pump Interaction

Rotary Blood Pumps (RBPs) as ventricular assist devices (VADs) are connected to the heart by inflow and outflow cannulas; the cannulation is typically performed through the apex of the left ventricle (inflow) and the ascending aorta (outflow). In this study, we investigate the impact of cannulas on heart-pump interaction in vivo. RBPs are characterized by their pressure head and flow rate curves, which give information about what pressures and flow rates the pump can generate at a certain speed. To study how the cannulas (30 ± 5 cm) affect the pump performance, we implanted the CentriMagTM RBP in three sheep via left thoracotomy and cannulated from ventricular apex to descending aorta. Pressure head and flow rate relationship of the pump with and without cannulas at different continuous and pulsatile pump speeds were recorded and analyzed. The results demonstrate high impact of cannulas on the pressure head losses of the pump. For example, at 4 kRPM, while the average pump pressure head is 295 mmHg excluding the cannulas, it becomes 31 mmHg including the cannulas. In general, the higher pump speed, the more pressure loss inside cannulas.