Congenital thickening of the muscle of the heart (hypertrophic cardiomyopathy)

What is it about ?

Hypertrophic cardiomyopathy (CMH) is an inherited heart disease characterized by abnormal thickening of the muscle of the heart of unknown origin. The disease is the leading cause of sudden cardiac death in young people and athletes. It has few or no symptoms, and most people have a normal life expectancy.

In half of the cases, it is about anomalies in the manufacture of fibers of the heart muscle (myocardium), which prevents it from contracting properly. Metabolic disorders,obesity and theamyloidosis are rare causes of hypertrophic cardiomyopathy.

In individuals whose heart muscle is thickened for other causes, eg hypertension or valve disease (heart valve disease), we are not talking about hypertrophic cardiomyopathy.

What is its frequency?

It is the most common genetic heart disease, affecting 1 in 500 people. More than 1000 mutations have already been identified in 23 different genes. The disease is said to be “autosomal dominant”; this means that if one of the two parents suffers from it, it will also affect half of the offspring.

Among people with hypertrophic cardiomyopathy, less than 5% develop a problem with heart function. In addition, the thickening of the heart muscle usually stops after the age of 20 to 30 years.

How to recognize it?

A large number of people do not have (many) symptoms, especially if they are otherwise in good health. Usually, the disease does not manifest itself until middle age. The first manifestation is often sudden cardiac death or the need for intensive care following a serious arrhythmia. About 1/5 of people with hypertrophic cardiomyopathy are at this risk.

Young and middle-aged people who have the following symptoms should think about hypertrophic cardiomyopathy:

• a shortness of breath to the effort;
• difficulty doing activities that were once okay;
• chest pain;
• a fainting to the effort;
• from heart rhythm disturbances : palpitations, extrasystoles (pause too long before the next beat, tachycardia (too fast heartbeat), atrial fibrillation transient.
  The most serious form is ventricular fibrillation, where the muscle of the heart (myocardium) appears to vibrate and is not no longer able to pump blood through the body. The patient loses consciousness and is in cardiac arrest.

How is the diagnosis made?

If there are cases of hypertrophic cardiomyopathy in the family, it is important that all family members are examined. The doctor makes the diagnosis on the basis of a heart auscultation. By listening to the heart, he can perceive a murmur, abnormal noise or change of rhythm. The doctor measures the blood pressure and checks for signs ofheart failure. An EKG can show abnormalities.

On chest x-rays, the doctor may notice a thickened heart. The most important consideration is theultrasound heart (echocardiography). It allows the cardiologist (heart specialist) to measure the thickness of the myocardium and see the heart in action. Sometimes a CT scan is done to get an even sharper image of the heart. In very exceptional cases, the doctor will take a biopsy (a piece of tissue) from the heart muscle and send it to the laboratory for analysis.

What can you do ?

• Focus on a healthy lifestyle and get enough exercise.
• Never practice a competitive sport and avoid extreme physical exertion at all costs.
• Don’t smoke, limit your salt intake and keep your weight under control.
• Be vigilant in your professional choices: night or shift work is not recommended.

What can your doctor do?

People with hypertrophic cardiomyopathy are looked after by a cardiologist. Screening for cardiovascular risk factors is important because the combination of several heart conditions increases the risk of death.

There is no evidence that the drugs work. People who have no symptoms should therefore not take medication. In some cases, medications can ease symptoms.

In case of atrial fibrillation, a treatment medicated will be attempted in order to normalize the heart rate. a anticoagulant therapy can also be started.

In hypertrophic cardiomyopathy, major treatment involves the use of an automatic implantable defibrillator (AID). As the pacemaker, this small device is implanted under the skin and is equipped with electrodes, which are connected to the heart and which monitor the heart rate. If it does not register a normal rhythm for 15 seconds, the ICD will give an electric shock and repeat it, if necessary. This is an excellent method of preventing sudden cardiac death in people with hypertrophic cardiomyopathy.

The doctor estimates the risk of sudden cardiac death based on the patient’s story, the results of theecho and electrocardiogram observations. An implantable automatic defibrillator is also indicated in people who have previously had to be resuscitated following a serious arrhythmia.

A heart transplant is only necessary in very rare situations.

The patient’s family members (children, brothers, sisters and parents) should be examined by a cardiologist to rule out the disease. If the doctor knows the genetic mutation that causes the disease, he or she can look for the specific mutation using a DNA test on a simple sample of blood from family members. People who have a known genetic mutation should be reviewed every 3 to 5 years.

Want to know more?

www.mongeneraliste.be/nos-dossiers/maladies-cardiovasulaires-infarctus-avc-arthmie-cardiaque

Sources

Foreign clinical practice guide ‘Hypertrophic cardiomyopathy’ (2000), updated on 14.03.2017 and adapted to the Belgian context on 25.10.2019 – ebpracticenet