CPVT (catecholaminergic polymorphic ventricular tachycardia): symptoms, tests and treatment

CPVT is an inherited heart rhythm disorder. The Arrhythmia Alliance leaflet explains that it is sometimes known as a channelopathy because it is caused by an abnormality of ion channels which allows calcium to accumulate in the heart muscle cell, leading to abnormal heartbeats, usually during exercise or when adrenaline is released in stressful situations. In CPVT the heart usually has a normal structure.

The extra beats may come from the upper chambers (atrial) or, more often, from the lower pumping chambers (ventricular). Runs of fast beats are called tachycardia. The British Heart Foundation says that ventricular tachycardia is a rhythm that can cause cardiac arrest, which is why it is a medical emergency if it happens.

The BHF lists blackouts, palpitations, dizziness and fainting as the most common symptoms, which can be brought on by too much physical activity and stressful times, increasing the amount of adrenaline in the blood. Some people with CPVT have no symptoms. Symptoms usually start in childhood but can appear in young adults for the first time, according to Arrhythmia Alliance.

The leaflet says most fainting episodes in childhood are benign, but those that occur during exercise or in response to an adrenaline surge should be investigated further. It says these episodes can be mistaken for a fit or epilepsy as they can look very similar, and that in a child not responding to anti-epileptic drugs, CPVT should be considered. Sometimes the first presentation is sudden cardiac arrest.

The BHF says CPVT is caused by a genetic change passed down from one of your parents. Arrhythmia Alliance explains that the most common cause is a variant in the cardiac ryanodine receptor gene (RYR2), with less common variants in genes such as calsequestrin, calmodulin and triadin, and that familial inheritance is seen in about a third of cases. RYR2 variants cause autosomal dominant inheritance, so you can get the disease if you inherit the abnormal gene from only one parent.

First-degree relatives (parents, brothers, sisters and children) should be evaluated with ECG, Holter monitoring and exercise stress testing, and genetic testing can sometimes help. Identifying a definite disease-causing variant can allow other family members to be tested, and may identify silent carriers who may be recommended to take medicine such as beta-blockers even without symptoms. A variant of unknown significance cannot be used for family screening. The BHF stresses that families should be assessed in a clinic for inherited heart conditions.

The BHF says that if you have symptoms your doctor will refer you to a specialist who will carry out an exercise test, an ECG recorded while you exercise, to try to induce the abnormal rhythm in a controlled and safe way. You may also have a resting ECG and 24-hour monitor. Arrhythmia Alliance notes that resting ECG and echocardiogram are usually normal, and that clinical diagnosis is based on family history, symptoms induced by exercise or emotional stress and the response to exercise or adrenaline infusion, although not all episodes are triggered by adrenaline.

CPVT should be considered in anyone with sudden cardiac arrest in the absence of structural heart disease. Genetic testing can confirm the cause, and also be offered to family members of someone diagnosed even if they have no symptoms.

Arrhythmia Alliance says treatment is usually with a beta-blocker, which blocks the effect of adrenaline and reduces the number of episodes of ventricular tachycardia. A high dose is often required and missing even a single dose can be potentially dangerous. The BHF lists avoiding intense exercise and competitive sports, daily medicine such as beta-blockers or calcium channel blockers, and an implantable cardioverter defibrillator (ICD) as options.

The BHF says that if you are with someone who collapses suddenly and is not breathing normally, you should call 999 immediately and perform CPR until an ambulance or medical help arrives; if you are untrained, the 999 operator will talk you through it. The BHF says ventricular tachycardia is a medical emergency and is usually treated with an electrical shock to return the rhythm to normal.

Anyone with CPVT who faints during exercise or with strong emotion, or has palpitations that do not settle, should get medical attention and tell their specialist team, as symptoms may mean treatment needs reviewing.

Living with an inherited arrhythmia involves taking medicine reliably, understanding which activities are safe, and planning around work and school. The BHF notes that someone with an ICD will have to avoid contact sports and that it could affect the type of work, especially work with magnetic or power tools. The BHF has a heart helpline and a genetic information service, and support groups are available.

Parents of a child with CPVT often worry about school and sport. The BHF stresses that families should be seen in a clinic for inherited heart conditions, which can advise on what is safe, and Arrhythmia Alliance also publishes information.