By Dr Ananya Mandal, MD
Diastolic dysfunction refers to an abnormality in how the heart fills with blood during diastole. The heart muscles do not relax in a normal manner and the heart may fill too slowly, asynchronously or with an elevation in filling pressure only.
Phases of the cardiac cycle
There are two phases in a heartbeat or a cardiac cycle. Systole refers to when the heart muscles squeeze to compress the heart and pump blood into the arteries and diastole is the phase where the heart expands in order to allow blood in to fill the ventricles.
Blood from the lungs is carried into the left ventricle by the pulmonary vein and blood from other parts of the body is carried into the right ventricle. When the heart is functioning normally, blood from the lungs passes into the left atrium via the pulmonary vein and into the left ventricle. However, if the ventricle wall does not relax properly or is thick and stiff, the ventricle does not fill in the usual manner and blood is drawn back into the atrium and eventually into the lungs.
The abnormal stiffening of the ventricular wall and subsequent inadequate ventricular filling is referred to as diastolic dysfunction and when this leads to blood building up in other organs such as the lungs, diastolic heart failure is diagnosed.
This diastolic dysfunction raises the pressure gradient of blood in the pulmonary vessels, which causes fluid or transudate to leak from these vessels into the lung alveoli, causing pulmonary edema. This condition impairs oxygenation of blood in the lungs, causing shortness of breath and even death if the condition is not detected and treated promptly.
Diagnosis and treatment
The diagnosis and treatment of isolated diastolic failure is often a challenge, since the symptoms are so similar to systolic heart failure. It is important to distinguish between these conditions because the treatment for one condition can aggravate the other condition.
Patient outcomes in cases of diastolic dysfunction are more favorable compared with those of systolic dysfunction, where the pumping mechanism of the heart fails rather than the filling function. Although diastolic heart failure is characterized by typical symptoms of heart failure, a normal ejection fraction accompanied by abnormal diastolic function confirm a diagnosis of diastolic heart failure.
The ejection fraction refers to the percentage of blood that is pumped out of the heart with each heartbeat or cardiac cycle. Treatment of diastolic dysfunction is aimed at increasing cardiac filling and examples of the drugs prescribed include angiotensin-converting enzyme, diuretics and beta blockers.
Reviewed by Sally Robertson, BSc