Arrhythmogenic right ventricular cardiomyopathy (ARVC)

An introduction to ARVC or arrhythmic cardiomyopathy

• A problem with the proteins that hold heart muscle cells together causes these cells to be lost and replaced by fibrous scar tissue and fatty cells, causing the ventricle walls to become thin.
• ARVC can affect the electrical activity of the heart and causes arrhythmias.
• As ARVC affects both the right and left ventricle it is also known as arrhythmic cardiomyopathy.

What is ARVC?

Arrhythmogenic right ventricular cardiomyopathy, or ARVC, is a type of cardiomyopathy that affects
the ventricles (lower pumping chambers) of the heart and causes arrhythmias (abnormal heart rhythms). It affects the right ventricle, and often also affects the left ventricle. For this reason it is sometimes called arrhythmic cardiomyopathy (as the main symptoms are arrhythmias). It doesn’t affect the atria (upper chambers) of the heart.

The structure of the heart, showing the atria and ventricles

In ARVC there is a defect in the proteins that join the cells of the heart muscle (myocytes) together. This means that the proteins do not develop properly and cannot keep the muscle cells together. When this happens the muscle cells detach and die, the area of the heart becomes inflamed, and the lost cells are replaced with fibrous scar tissue and fat deposits. This affects the structure of the heart muscle, and it becomes thin and stretched. This causes two main problems:

• the electrical pathways through the heart that coordinate the heart beat may be affected, causing arrhythmias; and
• the thin walls of the ventricles of the heart are unable to pump blood as effectively as normal.

What causes ARVC?

ARVC is often a genetic condition (caused by an altered or ‘mutated’ gene) and can be inherited (passed from parent to child). However, the genetics of ARVC are complicated.

ARVC is often ‘autosomal dominant’. This means that the mutated gene is found on one of the non-sex
chromosomes (called the autosomes). A child of an affected parent will have a 50% chance of inheriting the gene mutation. In some cases it is ‘recessive’ (and it therefore only develops into the
condition if both parents pass on the gene). 

Who gets ARVC?

ARVC is rare compared to some other types of cardiomyopathy (such as dilated and hypertrophic
cardiomyopathy). Around 1 in 10,000 people are thought to have ARVC, although it is likely that there
are more people living with the condition than this figure suggests.

What are the symptoms of ARVC?

ARVC can be a progressive condition, and symptoms may become worse over time. The symptoms are
related to the electrical activity of the heart as well as the structure of the heart and how well it pumps.
Symptoms can include the following.

• Palpitations (feeling your heart beating too fast, too hard or like it is ‘fluttering’) – this is caused by
  arrhythmias (when the electrical messages which control the heart’s rhythm are disrupted).
• Light-headedness and fainting (loss of consciousness) – reduced oxygen levels or blood flow to the brain, due to arrhythmias, can cause light-headedness or dizziness and, in some cases, loss of consciousness.
• Swollen legs, ankles and tummy – build-up of fluid in the tissues, because the heart isn’t pumping
  effectively, can cause swelling (called ‘oedema’).
• Breathlessness (or dyspnoea) – fluid builds-up around the lungs, making it harder to breathe. Due to the effect of ARVC on the electrical signalling the in the heart, it often causes arrhythmias.

As ARVC affects the electrical signalling the in the heart, it often causes arrhythmias.

Arrhythmias

Arrhythmias are caused by the disruption of the normal electrical signalling in the heart that controls the heart beat. This disruption causes a change in the heart’s rhythm, which means it beats too fast, too slow or erratically. Types of arrhythmias that can happen in ARVC include the following.

• Atrial fibrillation (AF) – caused by disruption of the electrical messages that normally cause the heart muscle to contract. In AF the atria beat very quickly and are uncoordinated. This can make the flow of blood around the atrium ‘turbulent’, and the heart less efficient at pumping out blood. AF can cause palpitations and increase the risk of blood clots forming, which can increase the risk of a stroke. 
• Ventricular premature beats (VPB) – this is an extra heart beat that happens when electrical impulses start in one of the ventricles, and it contracts before it receives the normal signal via the atria. ARVC can sometimes cause an increase in the number and frequency of these extra beats.
• Ventricular tachycardia (VT) – VT starts due to abnormal electrical activity in the ventricles, where
  the heart contracts abnormally quickly (over 100 beats per minute). It can lead to loss of consciousness.
• Ventricular fibrillation (VF) – the contraction of the ventricles is uncoordinated, and they ‘quiver’ rather than contract normally, so blood is not pumped out of the heart effectively. This condition is
  life-threatening and requires urgent treatment with a defibrillator (see treatment below).

What are the complications of ARVC?

ARVC can be very serious as it can cause complications.

• Heart block – where the normal electrical activity that controls the heart beat is slowed or stopped, and stops the heart contacting normally. Heart block might require a pacemaker if the heart is unable to keep a normal rhythm.
• Heart failure – when the heart is not working effectively and it ‘fails’ to pump enough blood, at
  the right pressure, to meet the body’s needs. It describes a collection of symptoms caused by a
  heart that is struggling to work effectively, such as weight gain (due to fluid retention), shortness of
  breath, a cough, oedema, palpitations, dizziness and tiredness.
• Sudden cardiac death (SCD) – this can happen due to dangerous arrhythmias, such as ventricular
  fibrillation (VF), where the contraction of the ventricles is uncoordinated, and they ‘quiver’ rather
  than contracting normally, so blood is not pumped out of the heart effectively. Although it is relatively
  rare, if VF is not controlled (using a defibrillator to shock the heart back into normal rhythm), it can
  cause the heart to stop beating (a cardiac arrest).

How is ARVC diagnosed?

ARVC can be difficult to diagnose as the changes in the heart can be subtle and the fat deposits can
be hard to see. Because the heart chambers can become enlarged, it is sometimes misdiagnosed as
dilated cardiomyopathy.

• Medical history – to look at symptoms and whether other family members have this condition (as it can be genetic).
• Physical exam – to see what physical symptoms, if any, are happening.
• ECG (electrocardiogram) – this looks at the electrical activity of the heart and whether arrhythmias
  (abnormal heart rhythms) are happening. A ‘signal -averaged ECG’ might be used to look for particular electrical signals that are common to ARVC. An ECG might also be done during exercise.
• Echo (echocardiogram) – this is a type of ultrasound scan, which uses sound waves to create echoes when they hit different parts of the body. This looks at the structure of the heart and how it is working. 
• Exercise tests – these are tests done during exercise, such as on an exercise bike or a treadmill, to look at how the heart works during exertion (where it is under increased pressure to work) and measure oxygen consumption during exercise.
• Holter monitoring – this is when an ECG is recorded over a period of time (such as a few days), while carrying on with normal activities. The ‘holter’ is a ECG device which is worn on the waist or in a pocket which makes it possible to move and walk around.
• Electrophysiology study (EPS) – this test involves having a long tube called a catheter inserted into
  a blood vessel and fed up to the heart. Electrical signals are sent through the catheter to the heart
  which makes it beat at different rates, which is recorded. This can be used to find where in the
  heart arrhythmias are starting (and can be used to identify treatment options).
• Implantable loop recorder – this is a small device, implanted under the skin, that records the electrical activity of the heart to identify any arrhythmias. Implantable loop recorders can be in place for up to a couple of years, if this is helpful.
• MRI (magnetic resonance imaging) scan – this scan produces high quality images and is used to look at the structure of the heart and blood flows through it.
• Radionuclide test and CT test – this involves having a radioactive dye (called a contrast dye) injected into a blood vessel. A CT scan, which uses x-rays, is done to produce images of the heart. The dye helps to see the structure of the heart and how blood flows around it.

How is ARVC treated and managed?

Although there is no cure for ARVC, treatments are used to reduce and control symptoms, and reduce the risk of complications. Treatment focuses on improving the pumping of the heart, controlling arrhythmias and reducing the risk of cardiac arrest.

Medication and devices

• ACE inhibitors (angiotensin-converting enzyme inhibitors) – relax the smooth muscle around the
  blood vessels to reduce the workload on the heart, and reduce the volume of the blood, making it
  easier for the heart to work. 
• Anti-arrhythmic medication – reduces abnormal heart rhythms and helps to control the normal
  rhythm.
• Anticoagulants (blood thinners) – may be used in people with arrhythmias to reduce the risk of blood clots forming, which could lead to a stroke.
• Angiotensin II Receptor Blockers (ARBs) – dilate (enlarge) the blood vessels which helps to reduce
  blood pressure and may be used if the person is not able to tolerate ACE inhibitors. 
• Beta-blockers – reduce the rate and force of the heart’s contraction, by reducing stimulation of
  adrenalin (which would normally make the heart beat faster).
• Diuretics (water tablets) – reduce the build-up of fluid on the lungs or the ankles by encouraging the kidneys to get rid of water as urine. 
• Pacemaker – may be recommended for people who have heart block (which makes the heart
  rate slow down). Pacemakers control the electrical signalling of the heart to keep a normal heart rhythm.
• Cardioversion – this is a when an electric shock is given to the heart to try and control arrhythmias,
  most commonly atrial fibrillation, and put the heart back into a normal rhythm. This is similar to what an ICD does (see below) but is a procedure done in hospital.
• Catheter ablation – this uses radio waves to treat areas of the heart where the electrical pathways
  cause arrhythmias. It stops the transmission of electrical signals that affect the normal heart rhythm.
• ICDs (implantable cardioverter defibrillator) – this may be recommended due to the risk of life-threatening arrhythmias. ICDs detect and correct any dangerous arrhythmias which could otherwise lead to a cardiac arrest.

Lifestyle management

In addition to medication and devices, there may be ways to reduce the effect of ARVC through lifestyle. The following are examples of what might help.

• Healthy eating – a balanced diet can help to keep a healthy weight, which will reduce the impact on the heart as well as helping with general health.
• Keeping a healthy weight – as this can help to reduce any extra pressure on the heart and lungs.
• Minimise alcohol – alcohol can raise your heart rate and increase blood pressure. You may not need to completely avoid it, but keeping within recommended guidelines can reduce any potential affects.
  The Chief Medical Officer reviewed these guidelines in 2016.
• Minimise caffeine – caffeine can raise your heart rate and increase blood pressure. As everyone is
  different in how they react to it, you might like to talk to your specialists about how to manage your caffeine intake.
• If you smoke – stopping smoking is important to help your overall health as well as your heart and
  lung function (as it can reduce oxygen levels in the blood as well as narrowing blood vessels). Your GP or an NHS stop smoking service may be able to help.

A note on exercise

Although exercise is often recommended for people with a heart condition, it can trigger arrhythmias and heart failure symptoms, and can be dangerous if the condition is unstable. Exercise for people with ARVC needs to be considered carefully, and be part of a discussion between the individual and their cardiologist or specialist nurse.