Catecholaminergic polymorphic ventricular tachycardia (CPVT)

Catecholaminergic polymorphic ventricular tachycardia is a rare condition mainly associated with two genes that make proteins found inside the cell – the human ryanodine receptor (a calcium ion channel) and calsequestrin (a protein that interacts with the calcium channel). These regulate the release of calcium ions into the rest of the cell. If these do not function normally, the level of calcium inside the cell becomes too high, resulting in arrhythmias.

Symptoms

Some people with CPVT have no symptoms at all. Others may have palpitations (a fast or irregular heart beat), or blackouts while exerting themselves or suffering emotional stress. The condition may be found in most age groups but appears to be most severe in children and adolescents and in males.

Signs

There are no physical signs.

Diagnosis

The diagnosis is usually made after the recording of arrhythmias that are characteristic of CPVT, while the person is exercising. The exercise ECG is therefore useful although some doctors use adrenaline testing (as in LQTS) as well. The resting ECG is usually normal. Blackouts during exercise or emotional stress should be assessed.

Genetic testing is of use as 1 in 2 people with the condition carry a ryanodine receptor mutation. When a member of a family has been found to carry a mutation, testing is then useful in detecting carriers who have not yet shown any signs of the condition.

Management

Your doctor will advise you to take beta-blockers (a type of drug), to restrict the amount of exercise you do and avoid medications that stimulate the heart. This combination can greatly improve the outlook for people with CPVT. Up to 1 in every 3 people with the condition, however, may also need to have an ICD fitted, particularly if they have blackouts while taking beta-blockers. Occasionally some patients will be given additional tablets (flecainide) to help reduce the amount of arrhythmia.

Surgery
Recently some groups have carried out sympathectomy (already used in Long QT Syndrome) to treat CPVT, with some success.