Diastole - Inside The Heart

Inside The Heart

During ventricular diastole, the pressure in the (left and right) ventricles drops from the peak that it reaches in systole. When the pressure in the left ventricle drops to below the pressure in the left atrium, the mitral valve opens, causing accumulated blood from the atrium to flow into the ventricle.

This is not a suction mechanism. Instead, the heart is refilled by the momentum of the blood still flowing from the previous systolic cycle. As the left and right atria contract during systole, the blood pressure in each atrium increases, forcing additional blood into the ventricles. This is known as atrial kick and it "hoists" the ventricular myocardium over the mass of blood contained within the chamber. 80% of the blood flows passively down to the ventricles, so the atria do not have to contract a great amount.

The ventricular filling velocity or flow into the ventricles have two main components; First an early (E) diastolic one caused by accumulation of blood in the atria during previous systole, and second, a late one created by atrial contraction (A). The E/A ratio can be used as a diagnostic measure, since it is reduced in diastolic dysfunction.

Atria and ventricles undergo diastole at the same time.