Diagram of the Cardiac Cycle, Showing Pressure Curves of the Cardiac Chambers, Heart Sounds, Jugular Pulse Wave, and the ECG
Diagram of the Cardiac Cycle, Showing Pressure Curves of the Cardiac Chambers, Heart Sounds, Jugular Pulse Wave, and the ECG
Diagram of the Cardiac Cycle, Showing Pressure Curves of the Cardiac Chambers, Heart Sounds, Jugular Pulse Wave, and the ECG

The phases of the cardiac cycle are atrial systole (a), isometric contraction (b), maximal ejection (c), reduced ejection (d), protodiastolic phase (e), isometric relaxation (f), rapid inflow (g), and diastasis, or slow LV filling (h). For illustrative purposes, time intervals between valvular events have been modified, and the z point has been prolonged.

In the jugular venous pulse tracing, the A wave represents atrial contraction at end-diastole, C wave is the carotid artery impulse or bulging of the tricuspid valve into the right atrium in early systole, V wave is the increase in pressure and volume of right atrial filling in late systole and early diastole, X and X' descents represent movement of the lower part of the right atrium toward the ventricle with X' at end-systole, and the Y descent is tricuspid valve opening and ventricular filling in diastole.

AO = aortic valve opening; AC = aortic valve closing; LV = left ventricle; LA = left atrium; RV = right ventricle; RA = right atrium; MO = mitral valve opening.