Topic overview

Start with the big picture

The cycle is organized into diastole, when the ventricles relax and fill, and systole, when they contract and eject blood. During isovolumetric phases, all valves are closed while ventricular pressure changes; valve opening begins the next flow phase. Rapid filling and atrial contraction contribute to ventricular volume, while end-diastolic and end-systolic volumes help define stroke volume and ejection fraction. A pressure-volume loop relates stroke volume to loop width and stroke work to enclosed area. Heart sounds mark valve closure or filling events, and atrial pressure waves correspond to specific mechanical events. The lesson also explains how tachycardia shortens diastole and reviews preload, afterload, contractility, and heart rate as determinants of cycle hemodynamics.