The cardiac cycle is divided into two parts - systole and diastole.

Systole is the heart's major pumping chambers. It contracts and ejects blood out of the heart and into the arteries.

When ventricles have finished contracting, then relax, they re-fill with blood to prepare for the next contraction. This relaxation phase is called diastole.

Due to certain medical conditions, the ventricles become relatively "stiff." Stiff ventricles cannot fully relax during diastole, and the ventricles may not fill completely, the blood can "dam up" in the body's organs mostly in the lungs. An abnormal "stiffening" of the ventricles, and the abnormal ventricular filling during diastole, is referred to as diastolic dysfunction.

Diastolic dysfunction is very common in women who didn’t know that they had heart disease. Diastolic dysfunction is a fairly new find in heart disease.

When a person has a diastolic dysfunction, they had a blood buildup in the lungs. Diastolic Heart Failure is said to be the known case.

The major causes of diastolic heart failure are: coronary artery disease, Hypertrophic Cardiomyopathy, chronic high blood pressure, aging and restrictive Cardiomyopathy.