Cardiomyopathy

Also called Heart muscle disease, HCM, DCM

Disease of the heart muscle itself, often inherited. It is the commonest cause of sudden cardiac death in young people, and relatives need testing.

What it is

A group of conditions affecting the heart muscle rather than its arteries. The main types are hypertrophic, where the muscle thickens; dilated, where it stretches and weakens; and arrhythmogenic, where muscle is replaced by fat and scar.

Many are inherited, usually in a pattern where each child of an affected parent has a one in two chance. That is the fact this entry exists for: a diagnosis in one person is a diagnosis question for the whole family, and cascade screening of first-degree relatives is standard care that is frequently not arranged.

It is the commonest cause of sudden cardiac death in people under 35, including in athletes. Sudden death in a young relative, or an unexplained drowning or single-vehicle crash, is part of the family history and should be mentioned.

Many people live normal lives with it. Treatment includes medication, implantable defibrillators for those at high risk, and sometimes surgery, and outcomes have improved considerably.

Signs you might notice

Breathlessness on exertion or lying flat.

Palpitations, or a racing or irregular heartbeat.

Chest pain, particularly on exertion.

Fainting or near-fainting, especially during or straight after exercise. This is the symptom that must never be dismissed.

Swollen ankles and legs, and fatigue. See heart failure and oedema.

Urgent: fainting on exertion, chest pain with exertion, or palpitations with collapse.

999: collapse with no pulse. Start CPR and send for a defibrillator.

A family history of sudden unexplained death under 40 needs assessment even with no symptoms at all.

How it can affect day-to-day life

The genetic dimension changes what this is like. People carry not only their own diagnosis but the question of their children, and telling relatives is a burden that lands on the patient.

Exercise advice is individual and depends on the type. Blanket bans are outdated; so is carrying on regardless. Get it specified.

An implantable defibrillator prevents sudden death and brings its own anxiety, particularly after a shock. Support for that exists and is worth asking for.

Driving rules apply after certain diagnoses and after a device is fitted. Ask rather than assume.

Some cardiomyopathy is not inherited: it can follow pregnancy, chemotherapy, alcohol or a viral illness, and the outlook and the family implications are then different.

Supporting someone well

Ask for family screening for first-degree relatives, and for genetic testing where a mutation has been found. This is standard and it is often not organised.

Never dismiss fainting during exercise in a young person.

Get exercise advice specific to the type and the person, in writing.

Learn CPR and know where the nearest public defibrillator is.

Ask about the inherited cardiac conditions service rather than staying under general cardiology.

Ask about pregnancy specifically before conceiving; some types carry significant risk and pre-pregnancy planning matters.

Where to get help

A GP practice, then cardiology and an inherited cardiac conditions clinic.

999 for collapse; start CPR immediately.

Cardiomyopathy UK run a support line and are the specialist charity.

British Heart Foundation on 0808 802 1234.