What primarily occurs during early diastole?

During early diastole, the heart transitions from systole (contraction) to diastole (relaxation), allowing the ventricles to fill with blood. Coronary perfusion predominantly occurs during this phase because the myocardium receives blood supply through the coronary arteries when the heart relaxes.

As the ventricles relax, the pressure within them decreases, leading to the closure of the aortic and pulmonary valves. This relaxation phase allows for increased blood flow into the coronary arteries, which are perfused primarily when the heart muscle is not actively contracting. The flow of blood through these arteries is essential for providing oxygen and nutrients to the cardiac tissue.

In early diastole, while it is important to know the roles of other phases such as atrial contraction, isovolumetric phases, and systolic actions, these do not primarily characterize the early diastolic period when coronary perfusion is crucial.