---
title: Hypertrophic cardiomyopathy
description: What hypertrophic cardiomyopathy is, why it develops, how it is detected and which treatment approaches clinical guidelines describe.
type: disease
aliases:
  - HCM
sources:
  - tier: guideline
    org: esc
    title: 2023 ESC Guidelines for the management of cardiomyopathies
    year: 2023
    doi: 10.1093/eurheartj/ehad194
    url: https://doi.org/10.1093/eurheartj/ehad194
  - tier: guideline
    org: minzdrav-rf
    title: Гипертрофическая кардиомиопатия
    year: 2025
    doi: 10.15829/1560-4071-2025-6387
    url: https://cr.minzdrav.gov.ru/view-cr/283_2
  - tier: reference
    org: statpearls
    title: Hypertrophic Cardiomyopathy
    year: 2024
    url: https://www.ncbi.nlm.nih.gov/books/NBK430788/
sources_checked: 2026-10-11
review: null
---

Hypertrophic cardiomyopathy (HCM) is a mainly genetic disease in which the wall of the <Structure id="left-ventricle">left ventricle</Structure> thickens (to 1.5 cm or more in adults), usually unevenly, because of a thickened <Structure id="interventricular-septum">interventricular septum</Structure>.<Cite n={2} /> The thickening cannot be explained only by a higher load on the heart, such as high blood pressure.<Cite n={[1, 2]} /> HCM affects about one person in 500.<Cite n={[2, 3]} />

<Diagram name="hypertrophic-cardiomyopathy">
  <p slot="normal">
    Normally the walls of the left ventricle and the septum are not thickened, and the way out of
    the ventricle into the aorta is open. In adults, HCM is diagnosed when the left ventricular wall
    is 15 mm thick or more.<Cite n={[2, 3]} />
  </p>
  <p slot="disease">
    In HCM the septum is usually thickened unevenly, especially at its base.<Cite n={[2, 3]} /> As
    the heart contracts, a leaflet of the mitral valve can be pulled towards the septum: the outflow
    from the left ventricle narrows, and some blood goes back into the left atrium.<Cite
      n={[2, 3]}
    /> Not everyone has a narrowed outflow: HCM can be obstructive or non-obstructive.<Cite n={2} />
  </p>
</Diagram>

## Why it happens

<Patient>

HCM is most often caused by changes in genes: in about half of cases these are variants in genes for the contracting proteins of heart muscle cells.<Cite n={2} /> The disease often runs in families, passing from parent to child.<Cite n={[1, 2]} /> That is why doctors think not only about one person but about the whole family.<Cite n={1} />

In adults the disease shows itself at about 40 years of age on average.<Cite n={2} /> The thickened wall of the left ventricle becomes stiffer.<Cite n={3} />

</Patient>

<Student>

In about half of cases HCM results from pathogenic and likely pathogenic variants in genes encoding cardiomyocyte sarcomere proteins.<Cite n={2} /> In familial cases, 70–75% of probands show autosomal dominant inheritance in the pedigree; most Mendelian forms of cardiomyopathy are autosomal dominant.<Cite n={[1, 2]} />

LVH together with myocardial disarray and fibrosis increases left ventricular stiffness.<Cite n={3} /> Diastolic function can be impaired already in mutation carriers, before hypertrophy develops.<Cite n={2} /> Classic asymmetric LVH most commonly affects the basal interventricular septum; systolic anterior motion (SAM) of the mitral valve is common, and mitral regurgitation can be due to left ventricular outflow tract obstruction (LVOTO) or SAM.<Cite n={3} />

The Russian Ministry of Health guideline divides HCM into non-obstructive (LVOT pressure gradient below 30 mm Hg at rest and on exercise) and obstructive (above 30 (50) mm Hg at rest and on exercise).<Cite n={2} /> A gradient of 30 mm Hg or more is considered haemodynamically significant.<Cite n={3} /> Prevalence in the general population is about 0.2% (1 in 500).<Cite n={[1, 2, 3]} />

</Student>

## Symptoms

<Patient>

Up to half of people with HCM notice no symptoms or only mild ones.<Cite n={[1, 3]} /> Possible symptoms are breathlessness, weakness, tiredness, chest pain, palpitations, feeling faint and fainting.<Cite n={[2, 3]} />

A dangerous complication is sudden cardiac death caused by severe heart rhythm disturbances.<Cite n={2} /> It can happen at any age.<Cite n={2} /> HCM is the most common identifiable cause of sudden cardiac death in healthy people younger than 35.<Cite n={3} />

</Patient>

<Student>

Clinical features include dyspnoea, weakness, fatigue, presyncope and syncope, and arrhythmias; angina (including atypical chest pain) or silent ischaemia may occur.<Cite n={2} /> Syncope can have both arrhythmic and haemodynamic causes.<Cite n={2} />

Sudden cardiac death is caused by fatal arrhythmias due to myocardial ischaemia and electrical instability; it affects patients at any age, with a peak between 30 and 50 years.<Cite n={2} /> The most common arrhythmia in HCM is atrial fibrillation, present in about 25% of patients.<Cite n={3} /> Volume depletion decreases stroke volume and worsens the LVOT gradient.<Cite n={3} />

</Student>

## How it is diagnosed

<Patient>

The key tests are those that show the structure of the heart: a heart ultrasound (echocardiography) and, when needed, a heart MRI.<Cite n={[1, 3]} /> Ultrasound shows how thick the walls are and how the ventricle works, and MRI with contrast can find areas of scar tissue in the heart muscle.<Cite n={3} /> The ECG is often abnormal in HCM.<Cite n={3} />

The disease can be inherited, so the doctor asks in detail about illnesses in the family, and close relatives of a person with HCM are advised to be checked.<Cite n={[1, 3]} />

</Patient>

<Student>

A left ventricular wall thickness of 15 mm or more is the criterion for HCM in an adult proband.<Cite n={[2, 3]} /> The European guideline advises multimodality imaging to characterise the phenotype and identify abnormal ventricular morphology.<Cite n={1} /> Transthoracic echocardiography shows systolic and diastolic function; cardiac MRI with gadolinium detects myocardial fibrosis, an important prognostic indicator.<Cite n={3} /> The ECG is often abnormal, even if LVOTO is not present.<Cite n={3} />

A three- to four-generation family pedigree helps to identify Mendelian forms of inheritance.<Cite n={1} /> Testing eight genes with a proven role in HCM finds causal variants in 60–85% of index patients, depending on the cohort.<Cite n={2} /> Close family members of a patient with HCM should be screened.<Cite n={3} />

</Student>

## How it is treated

<Patient>

If there are symptoms, treatment usually starts with medicines that relieve them.<Cite n={3} /> Which treatment is right is decided by the doctor together with the patient.

If marked symptoms persist despite medicines, there is fainting caused by the narrowed outflow, or the outflow from the ventricle is severely narrowed, a procedure on the septum that relieves the narrowing may be discussed: an operation (myectomy) or alcohol septal ablation.<Cite n={3} /> People with risk factors for sudden death may be offered an implantable cardioverter-defibrillator.<Cite n={3} />

</Patient>

<Student>

Beta-blockers are the first line of management in most cases; calcium channel blockers (diltiazem, verapamil) relieve symptoms in obstructive HCM.<Cite n={3} /> Mavacamten is a first-in-class drug, an allosteric inhibitor of cardiac myosin ATPase, approved by the FDA in 2022.<Cite n={3} /> Certain medicines, including vasodilators, should be avoided or used very cautiously because they can worsen symptoms.<Cite n={3} />

Indications for surgery are NYHA class III–IV symptoms despite optimal medical therapy, syncope due to LVOT obstruction, or a gradient above 50 mm Hg; septal myectomy reduces the obstruction immediately.<Cite n={3} /> Alcohol septal ablation is performed for the same indications and has a faster recovery, but results are less uniform and the risk of complete heart block is higher.<Cite n={3} />

An implantable cardioverter-defibrillator is considered in patients with risk factors for sudden cardiac death, which include recent unexplained syncope, HCM-related sudden death in a close relative, extensive late gadolinium enhancement on MRI and massive LVH (more than 30 mm).<Cite n={3} /> The European guideline stresses that care for patients with cardiomyopathy requires the collaboration of different specialties.<Cite n={1} />

</Student>

## When to call an ambulance

In HCM, fainting can be caused by a rhythm disturbance, and sudden cardiac death is linked to severe arrhythmias.<Cite n={2} /> If a person with HCM faints, has severe chest pain, or has a fast heartbeat with feeling faint, call your local emergency number (112 in the EU, 911 in the US and Canada, 999 in the UK).

<Quiz />