CardiologyTier 2Disease (DEADMAN)

Cardiomyopathy - hypertrophic

Description

Unexplained LV hypertrophy not explained by loading conditions
- Wall thickness >=15 mm (>=13 mm if a first-degree relative is affected)
Sarcomeric, autosomal dominant, incomplete and age-dependent penetrance
Patterns: asymmetric septal (commonest), apical, concentric, mid-cavity
Obstructive (HOCM) in ~1/3 at rest, more on provocation
- Septal hypertrophy + SAM of the mitral valve -> dynamic LVOT obstruction + MR
Diastolic dysfunction is universal; systolic function preserved until burnout

Genetics

Sarcomere gene mutations, autosomal dominant
- MYH7 (beta-myosin heavy chain) and MYBPC3 (myosin-binding protein C) = majority
- Also TNNT2, TNNI3
~40-60% have no identified mutation

Mechanism

Mutant sarcomere -> inc actin-myosin cross-bridging
- -> hypercontractility, inc energy demand
- -> myocyte hypertrophy + myofibrillar disarray + interstitial fibrosis
- -> arrhythmic substrate + diastolic stiffness

Phenocopies - exclude before labelling HCM

Fabry disease, ATTR/AL amyloid, Danon, Noonan/RASopathies, mitochondrial disease
Athlete's heart, hypertensive LVH, aortic stenosis
Different diseases with different treatments

Exam - obstructive

Bifid (jerky) carotid pulse, double apical impulse, palpable S4
Ejection systolic murmur at LLSE with no carotid radiation +/- pansystolic MR murmur
Louder with Valsalva/standing; softer with squatting/handgrip
- The opposite of AS - the key bedside discriminator

Investigations

ECG abnormal in >90% - LVH, deep T inversion (giant T inversion in apical HCM), pathological Q waves
TTE - wall thickness, LVOT gradient at rest, with Valsalva and on exercise, SAM, MR, diastolic function
CMR - detects apical and lateral hypertrophy missed on echo; LGE quantifies fibrosis for risk
Holter for NSVT; exercise test for blunted or hypotensive BP response
Genetic testing in the proband -> cascade predictive testing of relatives
- If no mutation is found, relatives need lifelong clinical surveillance instead

Symptomatic obstruction

Beta blocker first line - non-vasodilating; verapamil if intolerant; disopyramide as add-on
*Avoid vasodilators, nitrates, dihydropyridine CCBs, digoxin and aggressive diuresis* - all increase the gradient
Mavacamten (cardiac myosin inhibitor) - reduces gradient and symptoms
- Serial echo required - EF can fall
Refractory: surgical septal myectomy (preferred, younger patients) or alcohol septal ablation

Non-obstructive symptoms

SCD prevention

Family and lifestyle

Cascade screening of first-degree relatives - clinical +/- genetic
Competitive high-intensity sport - now individualised rather than a blanket ban

Most patients have normal or near-normal life expectancy with modern care
Annual SCD risk ~0.5-1% overall, substantially higher in defined high-risk groups
Four trajectories:
- Sudden cardiac death
- Progressive heart failure
- AF -> stroke
- "Burnt-out" dilated phase (~5%)

Monitor

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