Blood flow regulates the remodeling of our cardiovascular system from initial heart beats until our death. As the first developing organ, the heart provides critical feedback to cardiovascular cells through the flow-derived stress environment corresponding to its pumping mechanism. Although this feedback is critical to proper development, the mechanism that drives flow remains ill-defined as the heart transforms from a semi-straight primitive tube to the multi-chambered adult heart. Here, we describe changes in pumping by analyzing high speed planar videos. Spatiotemporal plots and particle imaging velocimetry are used to quantify flow and to derive relative pressure fields. We show that through coordinated motion between cardiac layers, the valveless heart is able to maximize forward flow despite a series of changes in heart morphology.