Catecholaminergic polymorphic ventricular tachycardia (CPVT): symptoms, testing and treatment

The heart's rhythm depends on tightly controlled electrical signals. In CPVT the heart muscle cells are prone to abnormal rhythms when adrenaline levels rise. The British Heart Foundation explains that within heart cells, proteins regulate the release of calcium ions, and in CPVT these proteins function abnormally, causing calcium to rise inside cells and leading to abnormal rhythms. In particular, CPVT causes a very fast heart rhythm called ventricular tachycardia.

The heart usually looks structurally normal. NHS England's Genomics Education Programme (GeNotes) describes CPVT as episodes of ventricular tachycardia, bidirectional or polymorphic, triggered by exercise or intense emotion. The rhythm may subside spontaneously or progress to ventricular fibrillation and cardiac arrest, which is why it is an important diagnosis to make.

The British Heart Foundation lists the most common symptoms and says they can be brought on by too much physical activity and stressful times, which raise the amount of adrenaline in the blood. GeNotes adds that affected people may be asymptomatic, or present with palpitations, syncope or sudden death, usually in the first decade of life or during adolescence, often with fainting, though for some the first event may be sudden death.

• Blackouts or fainting, especially during exercise or emotional stress.

• Palpitations, an awareness of a fast or irregular heartbeat.

• Dizziness.

• No symptoms at all in some people, which is why family screening matters.

The British Heart Foundation advises speaking to your doctor if symptoms start to worsen. If you are with someone who collapses suddenly and is not breathing normally, call 999 immediately and perform CPR until an ambulance arrives; if you are untrained, the 999 operator can talk you through it. The BHF describes ventricular tachycardia as a medical emergency that needs treatment right away, usually with an electrical shock (cardioversion or defibrillation).

A fainting episode during exercise or strong emotion, particularly in a child or young person, should always be assessed by a doctor.

The BHF says CPVT is known to be caused by a genetic change passed down from one of your parents. GeNotes says CPVT is associated with pathogenic variants in the cardiac ryanodine receptor gene (RYR2) and the cardiac calsequestrin gene (CASQ2), which are largely responsible for handling calcium inside cells. Variants in other genes, such as CALM1, CALM2, CALM3, TRDN and TECR, have been found in people with similar features.

Inheritance depends on the gene: RYR2 and CALM variants are inherited in an autosomal dominant pattern, TECRL and TRDN variants in an autosomal recessive pattern, and CASQ2 variants are typically recessive, with rare dominant cases. GeNotes also says CPVT may present de novo, with no clear family history.

If you have symptoms, the BHF says your doctor will refer you to a specialist who will do an exercise test. This is an ECG that records the heart's electrical activity while you exercise, to try to induce the abnormal rhythm in a controlled, safe way. You may also have a resting ECG and a 24-hour monitor. The BHF stresses that families affected by CPVT should receive assessment, diagnosis, treatment and support from specialists in a clinic for inherited heart conditions.

Genetic testing can be done if someone in the family has already been diagnosed, even if you do not have symptoms. GeNotes says that where the pathogenic variant is known, other relatives should be offered predictive screening as part of cascade genomic testing, and that people with CPVT should be considered for genomic counselling.

For long-term management, the BHF says doctors may advise avoiding intense exercise and competitive sports, taking a daily medicine such as a beta-blocker or calcium channel blocker, and having an implantable cardioverter defibrillator (ICD) to monitor the heart rhythm and treat dangerous rhythms. Beta-blockers slow the heart rate and help prevent life-threatening arrhythmias.

GeNotes sets out a stepped approach. The first-line medical therapy is a nonselective beta blocker such as nadolol or propranolol. Flecainide can be added if arrhythmia persists during exercise testing on high-dose beta blocker. Left cardiac sympathetic denervation should be considered for people who cannot tolerate beta blockers or who have recurrent fainting or arrhythmias despite maximal medical therapy. An ICD, in addition to beta blockers, should be considered for people with a history of cardiac arrest or recurrent syncope or arrhythmias despite maximal therapy.

The BHF says about 1 in 3 people need an ICD if medicine is not enough to reduce risk. With an ICD, you will have to avoid contact sports and it could affect the type of work you do, especially work with magnetic or power tools.

GeNotes advises that, where possible, affected individuals avoid competitive sport, strenuous exercise and stressful environments. The BHF recommends discussing the level of activity that is safe for you with your doctor.

The BHF runs a heart helpline and a genetic information service staffed by specialist nurses, and has online communities for people with heart conditions. Cardiac Risk in the Young is also signposted in NHS genomics material.

Diagnosis and long-term management are usually led by NHS inherited cardiac conditions services, which combine cardiology, genetics and specialist nursing, and which see families rather than individuals alone. Genomic testing for eligible people is provided through the NHS National Genomic Test Directory, according to GeNotes. Private cardiology assessment exists, but family screening and genetic counselling are best coordinated with the NHS clinic.