Hypertrophic obstructive cardiomyopathy (HOCM) involves thickening (hypertrophy) of the left ventricle muscle, particularly affecting the ventricular septum. The thickening reduces the space inside the ventricle and blocks blood flow up to the aorta, referred to as left ventricular outflow tract (LVOT) obstruction.
HOCM is associated with an increased risk of heart failure, myocardial infarction, arrhythmia and sudden cardiac death. Arrhythmia and sudden death often occur during exertion, when there is extra demand on the heart. It is a notable cause of sudden cardiac death in young people, including high-performing athletes.
HOCM is an autosomal dominant genetic condition resulting from a defect in the genes for sarcomere proteins. It occurs in about 1 in 500 people. A family history of heart disease and sudden death is very relevant. However, a de novo mutation (new mutation) may occur in patients without a family history.
Presentation
Most patients are asymptomatic. Patients can present with non-specific symptoms, which may occur with exertion:
- Shortness of breath
- Fatigue
- Dizziness
- Syncope (loss of consciousness)
- Chest pain
- Palpitations
Severe cases may present with symptoms of heart failure (e.g., cough, shortness of breath, orthopnoea, paroxysmal nocturnal dyspnoea and oedema).
Examination findings:
- Ejection systolic murmur at the lower left sternal border (louder with the Valsalva manoeuvre)
- Fourth heart sound
- Thrill at the lower left sternal border
Diagnosis
An echocardiogram or cardiac MRI is used to establish the diagnosis.
Genetic testing may be considered to establish the affected genes.
Management
Management depends on the severity and symptoms. Options include:
- Beta blockers
- Surgical myectomy (removing part of the heart septum to relieve the obstruction)
- Implantable cardioverter defibrillator (for those at risk of sudden cardiac death or ventricular arrhythmias)
- Heart transplant
Patients are advised to avoid intense exercise, heavy lifting and dehydration. ACE inhibitors and nitrates are avoided as they can worsen LVOT obstruction.
Complications
Most patients have minimal symptoms and a normal lifespan. Possible complications include:
- Arrhythmia
- Mitral regurgitation
- Heart failure
- Sudden cardiac death
Last updated January 2025
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