In silico analysis of pressure distribution and flow profiles across an experimental left ventricular assist device accessory.

OBJECTIVES

Implantation of left ventricular assist devices conventionally requires a sternotomy and cardiopulmonary bypass. An experimental accessory was designed to redirect the device's outflow graft through the left ventricle into the ascending aorta. This design allows for implantation via left thoracotomy only but resulted in significant pressure loss both in vitro and in vivo. We evaluated the reasons for the pressure loss of the experimental accessory by quantifying pressure distribution and flow profiles using computational fluid dynamics simulation tools.

METHODS

A computational fluid dynamics model based on the accessory's geometry was used to simulate nominal blood flow through the model. Quantities of interest included pressure and flow velocity. Pressure differences between the pump inlet and outlet were calculated at different rotational speeds (4000, 5200, 6400 rpm) and pump flow rates (1, 5, 8.4 L/min). Results were compared with simulations of a generic left ventricular assist device to determine the accessory's impact.

RESULTS

Natural pump characteristics were observed, as increased rotational speed caused an increase in pressure head with a constant flow rate. For all cases, a greater decrease in pressure head was seen between 5 and 8.4 L/min than between 1 and 5 L/min. Curvature intensity and channel bifurcation in the outflow were the main contributors to downstream pressure loss.

CONCLUSIONS

The next iteration of the left ventricular assist device accessory should focus on minimizing curvatures and avoiding bifurcations in the outflow. Further development may allow for less invasive left ventricular assist device implantation with negligible alterations in pump performance.