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Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.

Hypertrophic cardiomyopathy

Cardiology · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

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Escalate

Exertional syncope, sustained ventricular arrhythmia, resuscitated arrest, acute pulmonary oedema or AF with haemodynamic compromise needs urgent monitored cardiology assessment.

Synopsis

Diagnose unexplained hypertrophy, define obstruction and sudden-death risk, and direct family and symptom management.

  • HCM is otherwise-unexplained increased LV wall thickness; first exclude hypertension, aortic stenosis and phenocopies.
  • LV outflow obstruction is dynamic: measure gradients at rest and with Valsalva; use exercise stress echo when symptoms and resting testing disagree.
  • A harsh systolic murmur that increases with Valsalva/standing supports dynamic obstruction but absence of a murmur does not exclude HCM.
  • Sudden-death prevention uses integrated risk, including syncope, family history, wall thickness, LV function, apical aneurysm, rhythm and CMR fibrosis.
  • AF is often poorly tolerated and materially increases embolic risk; detect it actively and anticoagulate when confirmed.
  • Offer genetic counselling and testing when it will clarify diagnosis or family management; screen first-degree relatives clinically.
  • Mavacamten and, from July 2026, NICE-recommended aficamten are specialist options for symptomatic obstructive HCM with mandatory systolic-function surveillance.
  • Avoid dehydration and unreviewed vasodilators or high-dose diuresis when significant obstruction is present.

Key red flags

Arrhythmic red flags

Cardiac syncope, resuscitated arrest, sustained VT, strong young sudden-death history or recurrent non-sustained VT requires prompt inherited-cardiac/EP review.

Unstable AF

Fast AF can sharply reduce filling and output; hypotension, ischaemia, pulmonary oedema or syncope requires immediate cardioversion assessment.

Investigation priorities

01
12-lead ECG and ambulatory monitoringFirst step

Detect hypertrophy patterns, pre-excitation, AF and ventricular arrhythmia.

Management branches

DiagnosisUnexplained LV hypertrophy

Increased wall thickness not fully explained by loading.

  1. Confirm measurements and history; quantify hypertension and exclude aortic stenosis, athlete remodelling and technical artefact.
  2. Obtain ECG, comprehensive echo with provocation and CMR; look deliberately for phenocopy and extracardiac clues.
  3. Build a three-generation pedigree and refer for inherited-cardiac genetic counselling/testing when appropriate.
  4. At diagnosis, assess symptoms, AF, ventricular arrhythmia, sudden-death risk and exercise/pregnancy needs rather than deferring these to later follow-up.

Key medicines

MavacamtenCYP2C19 poor metaboliser or phenotype pending: start 2.5 mg orally once daily, maximum 5 mg; other phenotypes: start 5 mg once daily, maximum 15 mg, with SmPC-directed echo titration.Do not start if LVEF is below 55%; interrupt if LVEF falls below 50%. Genotype CYP2C19, check every new prescription including OTC CYP2C19/CYP3A4 interactions, and avoid in pregnancy; effective contraception is required during treatment and for 6 months after.
AficamtenStart 5 mg orally once daily; consider 10 mg once daily when the Valsalva LVOT gradient is at least 100 mmHg. Increase by 5 mg at intervals of 2-8 weeks to a maximum 20 mg once daily, guided by LVEF and Valsalva LVOT gradient.Do not initiate or up-titrate if LVEF is below 55%. If LVEF is 40 to below 50%, reduce by 5 mg (interrupt for 7 days if already taking 5 mg); if LVEF is below 40%, interrupt for at least 7 days, with label-directed echo before resumption. Check every prescription for CYP2C9/CYP2D6/CYP3A interactions and use effective contraception during treatment; pregnancy requires expert benefit-risk review.
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Sources and review status6 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • 2023 ESC Guidelines for the management of cardiomyopathiesDiagnosis, LVOTO assessment, sudden-death risk and family care.
  • NHS Genomics Education: Hypertrophic cardiomyopathyPhenotype and inherited-disease context.
  • NICE TA913: Mavacamten for obstructive HCMNHS eligibility for mavacamten.
  • Mavacamten BMS SmPCExact genotype-based dose, LVEF, interaction and pregnancy safeguards.
  • NICE TA1181: Aficamten for symptomatic obstructive HCMPublished 30 July 2026; new NHS treatment recommendation.
  • MHRA Products: Myqorzo (aficamten)UK product information for exact dose, LVEF monitoring, interaction and pregnancy safeguards.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateRapid draftClinical stateAwaiting reviewJurisdictionUnited Kingdom