Diastole is the period of ventricular filling after contraction. It is defined clinically from aortic valve (AV) closure to mitral valve (MV) closure or, physiologically, as the duration of myocardial relaxation (although this actually begins in late systole).
Diastole involves energy-dependent interrelated cellular and mechanical processes that allow the heart to relax and fill. Adequate diastolic filling is essential for normal systolic ventricular function. Diastole forms 2/3 of the cardiac cycle at resting heart rates (HR), but shortens at faster rates.
Diastole is divided into 4 phases.