On the dynamic suction pumping of blood cells in tubular hearts

TL;DR

This study uses numerical simulations to compare valveless pumping mechanisms in embryonic hearts, finding that dynamic suction pumping can generate net flow under certain conditions, while peristalsis is consistently effective.

Contribution

It introduces a numerical model analyzing the effects of hematocrit on blood flow in valveless embryonic hearts, comparing dynamic suction pumping and peristalsis.

Findings

Dynamic suction pumping can produce net flow at specific Womersley numbers.

Hematocrit has minimal impact on flow rates in dynamic suction pumping.

Peristalsis reliably drives blood flow across all tested conditions.

Abstract

Around the third week after gestation in embryonic development, the human heart consists only of a valvless tube, unlike a fully developed adult heart, which is multi-chambered. At this stage in development, the heart valves have not formed and so net flow of blood through the heart must be driven by a different mechanism. It is hypothesized that there are two possible mechanisms that drive blood flow at this stage - Liebau pumping (dynamic suction pumping or valveless pumping) and peristaltic pumping. We implement the immersed boundary method with adaptive mesh refinement (IBAMR) to numerically study the effect of hematocrit on the circulation around a valveless. Both peristalsis and dynamic suction pumping are considered. In the case of dynamic suction pumping, the heart and circulatory system is simplified as a flexible tube attached to a relatively rigid racetrack. For some Womersley number (Wo) regimes, there is significant net flow around the racetrack. We find that the addition of flexible blood cells does not significantly affect flow rates within the tube for Wo $\leq$ 10. On the other hand, peristalsis consistently drives blood around the racetrack for all Wo and for all hematocrit considered.