Diástole

Diástole refers to the relaxation phase of the heart cycle. During diastole, the heart muscle, specifically the ventricles, relaxes and expands. This relaxation allows the chambers to fill with blood returning from the body and lungs. It is the counterpart to systole, which is the contraction phase of the heart.

The cardiac cycle is divided into two main phases: systole and diastole. Diastole is crucial for effective cardiac function as it ensures the heart chambers are adequately filled with blood before the next contraction. This filling process is largely passive, driven by the pressure difference between the atria and the relaxed ventricles.

There are different stages within diastole, including isovolumetric relaxation, where the ventricles begin to relax, and ventricular filling, where blood flows into the ventricles. The duration of diastole can vary depending on factors such as heart rate and physiological demand. A longer diastole allows for more complete ventricular filling, which can increase stroke volume.

In clinical terms, diastolic blood pressure is the lowest blood pressure reading, measured during diastole when the heart is resting between beats. It reflects the pressure in the arteries when the ventricles are refilling. Abnormalities in diastole can be indicative of various heart conditions, such as diastolic dysfunction or heart failure.