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Updated June 10, 2015.

Definition:

The cardiac cycle is the name doctors often use to describe a single heart beat. The cardiac cycle is generally divided into two phases: diastole and systole. Diastole is the part of the cardiac cycle in which the heart's ventricles are being filled with blood. Systole is the part of the cardiac cycle in which the heart actually squeezes or "beats," ejecting blood out into the arteries.

• Read about the cardiac chambers.