Arrhythmogenic right ventricular cardiomyopathy (ARVC; also known as arrhythmogenic right ventricular dysplasia – (ARVD)) is a heart muscle disease that can cause life-threatening heart rhythm abnormalities and, rarely, significant “weakening” of the right side of the heart.
ARVC is caused by a defect in the ‘glue’ that holds the muscle cells of the heart together. As the heart muscle is continuously stretching and contracting, the ‘glue’ breaks down, the muscle cells separate and some die. The body then tries to repair this by replacing the normal heart muscle cells with scar and fat tissue. This process creates small islands of heart tissue that do not conduct electrical signals in the normal way and are not able to contract in the normal way. This allows abnormal ‘short-circuits’ to develop, which cause the heart rhythm abnormalities that define the condition.
Initially, only small areas of the right ventricle may be affected but the condition may progress over time, becoming more widespread and even involving the left ventricle. In fact, some forms only affect the left ventricle.
ARVC is thought to affect between 1 in 1,000 and 1 in 5,000 people, depending on which area of the world has been studied and the definition of the condition used. The disease affects men and women equally and has been recognised in people from many ethnic backgrounds. It tends to first present in early adulthood but can occasionally affect children.
ARVC commonly runs in families and several genes have been identified as causing the condition in these families. These genes are needed to make the proteins that form the glue holding the cells together. Therefore, if these genes do not work correctly the glue does not hold the cells together as it should. The pattern of inheritance is known as ‘autosomal dominant with variable penetrance’ meaning the child of an affected parent will have 50% chance of inheriting the abnormal gene, but will not then necessarily go on to have the condition.
The other factors that contribute to the disease are not fully understood but may include viral infection, inflammation and endurance exercise.
Symptoms of ARVC
The most common symptom is palpitations. Palpitations can occur at rest but are often triggered by physical activity. They may be associated with chest pain, light-headedness or blackouts. ARVC is also a recognised cause of sudden cardiac death. If the right ventricle becomes significantly weakened it can cause breathlessness and swelling of the legs and abdomen (features sometimes referred to as ‘right heart failure’) although this is relatively uncommon and tends to affect those who have had the condition for several years or longer. Many people with ARVC do not have any symptoms, however.
How is ARVC diagnosed?
The diagnosis is based on finding the electrical and structural problems that define the disease. Diagnosis can be complicated and often requires several tests undertaken by a specialist. In the first instance a detailed record of symptoms, medical and family background and a physical examination are required. Following this, an ECG (including a signal average ECG) and an ultrasound scan of the heart (echocardiogram, or echo) will be used.
The ECG can often pick up an abnormality, but the signs on an echocardiogram can be very subtle in the early stages of the condition. Therefore, more detailed imaging with a magnetic resonance imaging (MRI) scan may be required. Other possible tests include an exercise ECG and 24-hour ECG to record any palpitations or abnormal heart rhythms.
In some specialist centres, it is possible to pass a wire into the heart via the bloodstream and to take a small sample (biopsy) of the heart muscle to examine under a microscope. Even this can still miss ARVC and can be associated with some risk to the patient, and so is not used routinely.
If a specific genetic mutation has been identified as the cause of ARVC in an individual, family members can be tested for this same mutation with a blood test. However, since a significant proportion of people with ARVC do not have a gene identified, this is not always possible.
What treatment is available for ARVC?
Treatment for ARVC is aimed at preventing episodes of symptomatic palpitations and reducing the risk of sudden death. A specialist will advise on lifestyle modifications. It is most likely that this will include advice to not participate in competitive, strenuous physical activities since this can be a trigger for dangerous heart rhythm disturbances.
Medication including beta-blockers, sotalol and amiodarone can be used to reduce palpitations and abnormal rhythms.
If symptomatic episodes continue despite medication, a procedure called an ablation can be used. This targets the particular area of the heart causing the abnormal rhythm and this area is cauterised – or burnt – using wires passed into the heart via the bloodstream. While this is a very effective treatment for some types of heart rhythm problems, long-term success rates are lower in ARVC as new problematic areas of the heart can develop over time.
In people for whom medication is unsuccessful in controlling abnormal rhythms; or where blackouts, near blackouts or even a cardiac arrest have occurred, an implantable cardiac defibrillator (ICD) may be fitted to prevent sudden cardiac death.
Regular check-ups, often involving repeat investigations, are required for people diagnosed with ARVC.
Family screening and ARVC
Since the disease runs in families, all immediate blood relatives of people with ARVC should be screened for the condition. It is recommended that those first-degree blood relatives where the condition is not identified should return for repeat testing every 2 – 5 years.