Factors influencing vortex development in a model of a skeletal muscle ventricle

A video technique was used to visualize flow patterns in a pulsatile model of a skeletal muscle ventricle (SMV). The shape and duration of SMV filling/emptying curves were determined by the stroke action of a computer-controlled piston pump. In this way we examined the effect of filling duration and injection volume on the flow structures. To simulate the interaction between the left ventricle and the SMV in the proposed clinical application, two filling/emptying regimes were employed with the period of each SMV cycle being either equal to or twice that of a typical cardiac cycle. Vortex formation at the inlet to the ventricle was a feature of both flow cycles during filling for all the combinations of injection volume and filling duration considered. When a pacing ratio of 1:1 was simulated, SMV filling was immediately followed by ejection, and the formed vortex was expelled. Under this flow regime, fluid in the apical end of the ventricle remained undisturbed. When the pacing ratio was 2:1, however, the quiescent period that followed filling allowed time for the formed vortex to travel a significant distance toward the apical end of the ventricle. Under certain conditions of injection volume and flow rate, the vortex reached the apex by the end of the quiescent period. We suggest that a ventricle connected to the aorta by a single, valveless conduit would require a flow regime that included a significant period of quiescence after filling. This would allow the vortex to reach and displace blood that would otherwise stagnate in the apex, thereby reducing the risk of thrombus formation.