Diastolic dysfunction refers to a mechanical failure of the heart’s chambers to fill properly with blood during the diastole phase of the cardiac cycle. This is caused by inadequate relaxation of the ventricles during diastole.
There are two phases in a heartbeat or a cardiac cycle. During the systole phase, the heart muscles squeeze to compress the heart and pump blood out into the arteries. During diastole, the heart expands in order to allow blood to flow into and fill the ventricles.
Impairment of the diastolic phase can cause several problems. Inadequate filling of the left ventricle leads to a reduction in the amount of blood that is pumped out of the heart to oxygenate the various parts of the body. In addition, if the ventricle does not fill with blood adequately, blood is drawn back into the atrium and eventually into the lungs, raising the pressure gradient of blood in the pulmonary vessels. This mismatched pressure gradient causes fluid or transudate to leak from these vessels into the lung alveoli, causing pulmonary edema.
Histological analysis of cardiac samples from patients with diastolic dysfunction reveals hypertrophy of the muscle tissue as well as the increased deposition of interstitial collagen and infiltration of the myocardium, leading to decreased elasticity of the heart muscle.