Hypertrophic cardiomyopathy

What is it?

In hypertrophic cardiomyopathy (HCM), the heart muscle cells grow larger and the walls of the heart thicken, sometimes only in one part.^2,1 The chambers inside become smaller and hold less blood, the walls can stiffen, and sometimes the thick muscle blocks blood leaving the heart.^2,1

It is thought to affect about 1 in 500 people and is seen at all ages.^2,1 Younger people tend to have a more severe form.¹ Most people inherit it from a parent: it comes from changes in the genes that control how the heart muscle grows.^2,1

The first signs

Some people have no symptoms and may first find out at a routine medical exam.¹

• chest pain;¹
• shortness of breath when active or lying down;¹
• dizziness, light-headedness or fainting, especially during exercise;¹
• a pounding or fluttering heartbeat (palpitations);¹
• tiredness.¹

In some young adults, the first sign is a sudden collapse, which can be fatal.¹

How doctors find out

The doctor listens to your heart, where a murmur may be heard.¹ Tests can include a heart trace (ECG), an ultrasound scan of the heart (echocardiogram), an MRI scan, a heart rhythm monitor worn for 24 hours or longer, and an exercise test.¹ Specialists may draw a detailed family tree.² If an inherited type is found, a genetic test can look for the faulty gene, and close relatives can then be checked, so that they can be watched and treated early if they have it.^2,1

Current treatment

Beta blockers or calcium channel blockers ease symptoms, other medicines treat rhythm problems, and some people need an implanted defibrillator (ICD), a myectomy or alcohol septal ablation.Source: MedlinePlus

Will it get worse?

For most people it does not affect daily life, and some live a normal lifespan without symptoms.^2,1 In others it gets worse, slowly or quickly.¹ It can lead to atrial fibrillation or a leaky heart valve, can worsen symptoms of heart failure, and raises the risk of sudden death, even at a young age.^2,1 It is the most common cause of sudden unexpected death in children and young athletes, and almost half of deaths from HCM happen during or just after physical activity.^2,1 If it is severe, you need regular checks.²

Medicines: what helps, and what to watch for

Not everyone needs treatment.² Beta blockers and calcium channel blockers can ease chest pain and breathlessness during exercise.¹ Other medicines treat heart rhythm problems, extra fluid and blood clots. If you have atrial fibrillation, you may be given blood thinners to lower the risk of blood clots.^2,1 For adults with symptoms from thick heart muscle that blocks blood flow (obstructive hypertrophic cardiomyopathy), the medicine mavacamten works so that the heart does not squeeze so hard.³

Good to know about mavacamten:

• you have heart scans (echocardiograms) before and during treatment;³
• it can stop hormonal contraception from working, so use another method during treatment and for 4 months after;³
• it may harm an unborn baby;³
• Side effects can include dizziness and fainting.³

Exercise and healthy habits help too

• sleep well, and get sleep apnoea treated if you have it;²
• manage stress, and keep other conditions such as diabetes under control.²

Procedures and surgery, for some people

If the thick muscle badly blocks blood leaving the heart, a surgeon can remove part of it (septal myectomy), sometimes repairing a leaky valve at the same time.^2,1 Another option is an alcohol injection into the artery that feeds the thick part, which shrinks it; many people improve a lot.^1,2 A pacemaker, or an implanted defibrillator (ICD) to stop dangerous heart rhythms, may be fitted; an ICD can be offered to people at high risk even before any rhythm problem.^1,2 Ablation treats the tissue causing rhythm problems.² A heart transplant is a last resort.²

Is there a cure?

There is usually no cure.^2,3 Treatment controls the symptoms and helps prevent complications.²

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Sources

Written in plain words by Frontlight from these pages:

1. MedlinePlus: Hypertrophic cardiomyopathy (Medical Encyclopedia)
2. NHS: Cardiomyopathy (hypertrophic cardiomyopathy section)
3. MedlinePlus: Mavacamten (Drug Information)