There are two parts to the pumping action of the heart. The first part is called diastole, when blood collects in the lower heart chambers (right and left ventricles) as it is pushed through the tricuspid and mitral valves.

Once the ventricles are filled with blood, the second part of the pumping action begins. The ventricles contract and blood is pushed from the right ventricle into the pulmonary artery and from the left ventricle into the aortic valves. This part is called systole.

The pathophysiology of diastolic dysfunction

Diastolic dysfunction refers to when the diastole part of this action is abnormal. The ventricles do not properly relax and become stiff meaning they cannot fill with blood properly. This causes blood to “dam up” in other parts of the body.

Pressure in the ventricles then increases as blood from the next heartbeat tries to enter. This leads to extra pressure and fluid building up in the vessels of the lungs (referred to as pulmonary congestion) or in the vessels that lead back to the heart (referred to as systemic congestion).

Pulmonary congestion causes fluid or transudate to leak from these vessels into the lung alveoli, causing pulmonary edema. This condition hampers oxygenation of blood in the lungs, resulting in shortness of breath and (in some instances) even death if the condition is not discovered and treated swiftly.

The systemic congestion has detrimental effects on other organs in the body such as the kidney and liver, as a result of poor organ perfusion. Swelling and congestion may also occur in the legs and within the abdomen.

Diastolic dysfunction is a common problem, with many people aged older than 70 years having the condition. In the majority of cases, the condition is not severe enough to lead to diastolic heart failure.

Symptoms and causes of diastolic dysfunction

Diastolic dysfunction itself often does not cause any symptoms. However, if the problem progresses to the point that it starts to affect other organs and body parts, diastolic heart failure is diagnosed. In those situations common symptoms include:

• Difficulty breathing and shortness of breath. Initially, this may only occur when exercising, but as the illness progresses, breathing can become problematic during any activity, including resting or lying down.
• Unusual weight gain or swelling (edema) in the ankles, legs and abdomen.
• Irregular or rapid heartbeat.

The main causes of diastolic dysfunction are:

• Chronic hypertension
• Coronary heart disease
• Aging
• Aortic stenosis – the narrowing of a heart valve
• Hypertrophic cardiomyopathy – thickened and stiffness in walls of the heart
• Restrictive cardiomyopathy – where scars or deposits have led to stiff heart muscles

Diagnosis and treatment

Both the diagnosis and treatment of isolated diastolic failure often represent a challenge, since the symptoms can be very similar to systolic heart failure. It is essential to distinguish between these two conditions as the treatment for one condition can worsen the other.

When diastolic dysfunction is diagnosed, it is by echocardiography (ECG), which enables assessment of diastolic relaxation and ventricular stiffness and thickening. It may also provide clues as to the cause of the problem.

Diastolic dysfunction is treated by aggressive management of the underlying cause. Approaches may include:

• Strict control of hypertension
• Aggressive treatment of coronary artery disease
• Careful management or arrhythmia
• The use of diuretics to control pulmonary congestion

If the underlying cause cannot be identified, a doctor will consider the possibility of undiagnosed hypertension, in which case careful monitoring is initiated. Undiagnosed coronary artery disease is also considered, in which case exercising testing can be used as a diagnostic tool.