The incidence of arrhythmogenic right ventricular cardiomyopathy (ARVC) is now thought to be higher than previously believed (affecting 1 in every 1000 individuals), due to the availability of better diagnostic techniques and general awareness of the disorder amongst the medical profession. ARVC was first recognised in the late 1970’s. It is anticipated that even more information regarding ARVC will be available in the coming years, to help us understand the natural history of the condition.
What causes ARVC?
ARVC is caused by a defect in the ‘glue’ that holds the muscle cells of the heart together, working as a unit. When stretched the ‘glue’ breaks down, the muscle cells separate and an inflammatory process begins to repair the break. In a way the heart muscle sustains an injury that the body attempts to repair. As this process is repeated there is a progressive replacement of the normal heart muscle cells by scar tissue and fat. Initially this may only involve small areas of the right heart but later on it becomes global and may even involve the left side.
ARVC is inherited, passed on in the genes from one generation to the next. The pattern of inheritance is such that the child of an affected parent has 50% chance of inheriting the condition. The disease affects men and women equally and has been recognised in people of diverse ethnic origin.
What are the symptoms?
Clinical presentation is usually with symptoms of palpitations (feeling the heart pounding) because of a fast and irregular heart rhythm. The irregular heart rhythm may be associated with light-headedness or fainting episodes. Unlike most cardiomyopathies, shortness of breath and chest pains are unusual symptoms and tend to occur at the later stages of the disease.
How is it diagnosed?
The diagnosis of ARVC can be extremely difficult and usually requires specialist expertise. Your doctor will usually start by asking you some questions and examining you. Most of the investigations are painless and non-invasive, similar to those performed in the diagnosis of hypertrophic and other cardiomyopathies. Initial investigations include a tracing of the electrical activity of the heart (ECG) and an ultrasound scan (echocardiogram). As with hypertrophic cardiomyopathy (HCM), the ECG is very sensitive in picking-up ARVC since up to 80% of individuals with the disease will have an ECG abnormality. The echocardiographic features, however, can be very subtle in the early stages of the condition, often confined only to the right ventricle and therefore further imaging of the right side of the heart is required in most cases with a magnetic resonance imaging scan (MRI). Further evaluation includes an exercise treadmill test and a 24-hour Holter monitor (tape) in an attempt to capture the irregular heart rhythms. In some specialist centres further invasive investigations are performed in an attempt to identify the electrical faults of the heart muscle associated with ARVC (electrophysiological studies) and to biopsy part of the heart muscle and examine it under the microscope. These investigations, however, are not widely accepted, they are still being developed, can still miss ARVC, which affects some areas of the heart but not others and can be associated with potentially serious complications.
Advances in molecular genetics (DNA) means that in some centres, the condition may be diagnosed using a blood test. This test, however, is not available in every hospital, it is expensive, the results may take up to several months and it is not always positive in ARVC patients (we are able to identify a defective gene in 60% of clinically confirmed ARVC patients). It can be used after the clinical evaluation to confirm the diagnosis or in the context of family screening.
Treatment and advice
The majority of patients with this condition have no symptoms for many years unless irregular heart rhythm develops. Treatment in the majority of cases aims to prevent or at least control the irregular heart rhythms.
If your tests prove positive your specialist will advise you on lifestyle modifications. You will most likely be advised not to participate in competitive, strenuous activities.
Watch CRY’s myheart cardiologist, Dr Michael Papadakis talk about things to avoid with cardiomyopathy below.
Drug treatment may also be used to control the irregular heart rhythms. Drugs may include beta-blockers, amiodarone or sotalol.
In cases where drug treatment is unsuccessful in controlling rapid heart beats, an implantable cardioverter defibrillator (ICD) may be fitted. This is similar to a pacemaker where a box is implanted under the skin in the chest. The box has a fine wire which is attached to the heart to record and deliver electrical impulses in the presence of an abnormal heart rhythm.
It will be necessary for you to have at least annual check-ups which usually will include a repeat of the initial investigations. Since the disease runs in families, all first degree relatives of the affected patients have to be screened with ECG and Echocardiogram.