The cardiac cycle consists of a series of phases that facilitate the effective pumping of blood through the heart and the circulatory system. Each phase is characterized by specific mechanical and electrical activities that ensure optimal function. Learn about the cardiac cycle, the performance of the human heart from one heartbeat to the next, with a diagram and detailed description. See how blood flows, valves open and close, and electrical impulses coordinate the cycle. The Wiggers diagram, named after its developer, Carl Wiggers, is a composite of several graphs related to the cardiac cycle. Physiologists use the information the Wiggers diagram provides to interpret and comprehend the changing events associated with each part of a heartbeat. The cardiac cycle diagram shown below depicts changes in aortic pressure (AP), left ventricular pressure (LVP), left atrial pressure (LAP), left ventricular volume (LV Vol), and heart sounds during a single cycle of cardiac contraction and relaxation. These changes are related in time to the electrocardiogram. A single cycle of cardiac activity can be divided into two basic stages. The first stage is diastole, which represents ventricular filling and a brief period just prior to filling at ...
