Arrhythmogenic cardiomyopathy

What is arrhythmogenic cardiomyopathy?

Note: this section contains a general description of the disease and might not apply to your personal situation. Please refer to your medical professional for details and questions regarding your personal situation.

Arrhythmogenic cardiomyopathy, abbreviated as ACM, is a heart muscle disease with an increased risk of life-threatening arrhythmias (heart rhythm abnormalities) and a progressively decreasing pump function of the heart. Patients with ACM are often young and physically active, but this isn’t essential for disease development. The medical terminology is very descriptive: ‘arrhythmogenic’ means ‘abnormal rhythm’ and ‘cardio-myo-pathy’ means heart muscle disease. ACM is also known as ARVC (arrhythmogenic right ventricular cardiomyopathy): in the classical disease presentation of ACM the disease starts on the right side of the heart (the right ventricle).
Approximately 1 in 5000 people have ACM. This is a broad estimation since ACM is not well recognized. This makes ACM one of the most common heart muscle diseases in the Netherlands. ACM has an inheritable cause and it’s often present in multiple family members.
To understand ACM, we first need to understand the function of the (healthy) heart.

The heart is a powerful muscle, that is constantly contracting in a regular rhythm. By contracting it pumps the blood, with all its oxygen and nutrients, through all the parts of the body. For example, during exercise the body needs more oxygen. Therefore, during exercise the heart rate increases to facilitate oxygen delivery to the muscles. Just like the rest of the body, the heart consists of thousands of microscopically small cells. To make an efficient pumping motion, the heart cells need to cooperate in a synchronized manner. This is only possible by cell to cell connections. These connections provide neighbouring cells with the electrical pulses which cause the neighbouring cell to contract. Besides this electricity, these connections are important to keep the cells aligned with each other. Special connection proteins are responsible for resisting the pressures of the contracting heart muscle.

In patients with ACM, the connection between the heart muscle cells is changed in specific places of the heart. Often, a DNA mutation (an error in the inheritable ‘code’) causes inefficient and weak connections between heart cells. When this is the case, the electrical signals aren’t appropriately distributed along the heart muscle. Fortunately, the majority of the heart muscles are able maintain the correct heart rhythm. But sometimes, the abnormal electrical signals can cause heart rhythm abnormalities. The heart can contract too fast or too slow to pump enough blood to the rest of the body. In worst case scenario, the heart rhythm stops in total and cardiac arrest occurs. Sometimes, this can happen at young age during exercise for example. For patients with ACM it is essential that doctors recognize the disease in an early stage to prevent life-threatening rhythm abnormalities to occur.

Another important effect of abnormal cell connections is the formation of scar tissue between the heart cells. This loss of connection between the heart cells causes damage to the heart muscle. The body will try to repair the damaged part of the heart. Unfortunately, the heart can’t make new heart cells. Therefore, the lost heart cells are replaced by fatty- and fibrotic tissue. This scar tissue can’t contract, which has a negative effect on the pump function of the heart. The overall function is preserved for a long time. Only when very large parts of the heart muscle are replaced with fatty and fibrotic tissue the overall heart function will slowly decrease. This process can result in heart failure. That is why long-term medical follow-up is very important.

ACM can’t be cured (yet). But, certain life style interventions can significantly reduce the risk of heart rhythm abnormalities. Strenuous exercise is discouraged in patients with ACM, because this has a negative effect on the cell-cell connections of the heart. Furthermore, some drugs can lower the risk of arrhythmias. In case of a life-threatening arrhythmia or cardiac arrest, a lifesaving shock can be delivered by using an Automated External Defibrillator (AED). The sooner the abnormal heart rhythm is restored, the better. The cardiologist can decide to advice an ICD (Implantable Cardioverter Defibrillator) for high risk patients. This ICD can monitor the heart rhythm 24 hours a day and when an arrhythmia occurs the ICD can restore the rhythm immediately by delivering a shock. ICDs aren’t able to prevent heart rhythm disturbances but can terminate abnormal heart rhythms as quickly as possible.
An ICD is a small device which is implanted just below the collarbone under the skin of the chest. The implantation requires minor surgery and can be performed under local anaesthesia (numbing medication) which is injected into the skin. Unfortunately, an ICD can also have physical and emotional disadvantages. Patients can be anxious, because they fear experiencing ICD shocks. Therefore, we think that an ICD should only be implanted in those patients who really need one.