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.
Key red flags
Cardiac syncope, resuscitated arrest, sustained VT, strong young sudden-death history or recurrent non-sustained VT requires prompt inherited-cardiac/EP review.
Investigation priorities
Detect hypertrophy patterns, pre-excitation, AF and ventricular arrhythmia.
Management branches
Increased wall thickness not fully explained by loading.
- Confirm measurements and history; quantify hypertension and exclude aortic stenosis, athlete remodelling and technical artefact.
- Obtain ECG, comprehensive echo with provocation and CMR; look deliberately for phenocopy and extracardiac clues.
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.
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.