The cardiac cycle encompasses one full heartbeat, from the beginning of one contraction to the beginning of the next. It consists of two main phases: systole, when the heart muscle contracts and pumps blood out to the body, and diastole, when the heart muscle relaxes and fills with blood. Understanding the cardiac cycle is essential for sonographers performing echocardiography because virtually every measurement and assessment depends on knowing which phase of the cycle is being observed. Valve movements, chamber dimensions, blood flow velocities, and wall motion are all evaluated in relation to specific phases of the cardiac cycle.
Sonography Term