Ch18: Cardiomyopathy

Preparatory Mindset

Cardiomyopathy is "heart muscle disease not explained by coronary disease, hypertension, valvular disease or congenital heart disease" — classified by the 2023 ESC guidelines into hypertrophic (HCM), dilated (DCM), restrictive (RCM), arrhythmogenic (ACM), and non-classified forms. The exam skills: (1) match each phenotype to its echo signature — HCM = asymmetric septal hypertrophy ≥15 mm ± LVOT obstruction; DCM = dilated LV with EF <40%; RCM = normal wall thickness/EF with restrictive filling (LVEDP > RVEDP); (2) know the genetic component (HCM — sarcomere mutations; ACM — desmosomal DSP/FLNC/LMNA); (3) manage per phenotype — HCM with β-blockers and septal reduction for obstruction; DCM with GDMT (the heart-failure pillars) + ICD for EF ≤35%; and (4) recognise the poor-prognosis numbers (DCM 5-yr survival ~50%, 10-yr ~25%; amyloid restrictive ~2–4 years untreated). The HKHA covers cardiomyopathy through the CHF section (C 27–28) — GDMT, ICD/CRT criteria and CMR.

Core Concepts

Definition & classification (2023 ESC)

• Cardiomyopathy = myocardial disorder with structural/functional abnormality of the ventricular myocardium in the absence of coronary artery disease, hypertension, valvular disease or congenital heart disease sufficient to explain it.
• Classification: HCM (hypertrophic), DCM (dilated), RCM (restrictive), ACM (arrhythmogenic cardiomyopathy), and unclassified (left ventricular non-compaction, Takotsubo syndrome).

Hypertrophic cardiomyopathy (HCM)

• Definition: unexplained LV hypertrophy (not secondary to hypertension/aortic stenosis/athlete's heart).
• Genetics: autosomal dominant sarcomere gene mutations (β-myosin heavy chain MYH7, myosin-binding protein C MYBPC3); family screening essential.
• Pathophysiology: asymmetric septal hypertrophy → LVOT obstruction (peak gradient ≥30 mmHg rest/provocation) + diastolic dysfunction + myocardial ischaemia + arrhythmia risk (sudden cardiac death — SCD).
• Diagnostic criteria (AHA 2010 revised): primary — LV wall thickness ≥15 mm in any segment (adults) without other cause; secondary — ≥13 mm with positive family history or genetic mutation; first-degree relatives — ≥13 mm (adults) or ≥2 SD (children).
• Clinical: dyspnoea, angina, syncope (exertional), palpitations, SCD (young athletes); LVOT murmur — systolic ejection murmur at left sternal edge, louder on Valsalva/standing, softer on squatting; S4.
• Treatment: β-blocker (first-line; ↑ diastolic filling, ↓ obstruction, ↓ arrhythmia); non-dihydropyridine CCB (verapamil) if β-blocker fails; disopyramide for refractory obstruction; avoid vasodilators/inotropes (worsen obstruction); septal reduction — surgical myectomy (NYHA III–IV with gradient ≥50 mmHg) or alcohol septal ablation; ICD for high SCD risk (family history of SCD, LV thickness ≥30 mm, NSVT, abnormal BP response to exercise, prior arrest); anticoagulate if AF (CHA₂DS₂-VASc); genetic testing + family screening; exercise restriction.

Dilated cardiomyopathy (DCM)

• Definition: LV (or biventricular) dilatation + systolic dysfunction (EF <40% typically) not explained by ischaemia/valvular disease.
• Causes: genetic (30–40% — TTN, LMNA, MYH7, DSP, FLNC), viral myocarditis sequel, alcohol/toxic (anthracyclines, cocaine), peripartum, autoimmune, thyroid, sarcoidosis, haemochromatosis, tachycardia-induced.
• Pathophysiology: myocyte loss/fibrosis → LV dilatation + spherical remodelling → heart failure + arrhythmia + thromboembolism.
• Clinical: progressive heart failure (dyspnoea, fatigue, oedema), arrhythmias (VT, AF), sudden death; signs of biventricular failure.
• Diagnosis: echo — dilated LV, EF <40%; CMR (aetiology — LGE pattern: subepicardial/mid-wall suggests myocarditis/sarcoid); genetic testing; exclude ischaemia (angiography/CTCA); cardiac biopsy for specific causes.
• Treatment: GDMT — ACEi/ARB/ARNi + β-blocker + MRA + SGLT2i (see heart-failure chapter); diuretics; ICD for EF ≤35% (primary prevention); CRT for wide QRS ≥150 ms/LBBB; anticoagulation if AF; treat cause (alcohol abstinence, stop cardiotoxic drugs); advanced — transplant/MCS (5-year survival ~50%, 10-year ~25%).
• Peripartum cardiomyopathy: DCM in last month of pregnancy–5 months postpartum; treat with HF therapy (careful in pregnancy), bromocriptine controversial, recovery possible.

Restrictive cardiomyopathy (RCM)

• Definition: restrictive filling with normal or near-normal LV wall thickness and EF; LVEDP > RVEDP (vs constrictive pericarditis where LVEDP ≈ RVEDP — key distinguishing point).
• Causes: amyloidosis (AL, ATTR — most common), sarcoidosis, haemochromatosis, Loeffler/eosinophilic, endomyocardial fibrosis, radiation, glycogen storage, Fabry disease.
• Clinical: heart failure with preserved EF (HFpEF pattern), right-heart congestion disproportionate (JVD, oedema, ascites), low output; amyloid — thick walls with sparkling/granular echo, low voltage ECG, proteinuria, carpal tunnel, macroglossia, neuropathy.
• Diagnosis: echo/CMR (LGE patterns), cardiac amyloid — ECG low voltage + echo thick walls + elevated troponin/BNP; nuclear (DPD scan for ATTR); biopsy (EMB/abdominal fat pad) with Congo red; serum/urine free light chains (AL), genetic (TTR).
• Treatment: treat cause (AL — chemotherapy ± transplant; ATTR — tafamidis; sarcoid — steroids); diuretics cautiously (preload-dependent); rate control for AF; avoid high-dose β-blocker/ACEi (hypotension); prognosis poor untreated (amyloid ~2–4 years).

Arrhythmogenic cardiomyopathy (ACM)

• Definition: fibrofatty replacement of the RV (classically) or LV myocardium → ventricular arrhythmias, SCD, heart failure.
• Genetics: desmosomal mutations (DSP, FLNC, LMNA) — autosomal dominant; diagnosis per 2010 Task Force criteria (echo/CMR/ECG/arrhythmia/family).
• Clinical: palpitations, syncope, VT (LBBB morphology — RV origin), SCD in young athletes; ECG — epsilon wave, T-wave inversion V1–V3.
• Treatment: ICD (the cornerstone — arrhythmic risk), β-blocker, avoid strenuous exercise (provokes arrhythmia), antiarrhythmics (sotalol/amiodarone), ablation for VT storms, heart-failure therapy if involved.

Unclassified

• Left ventricular non-compaction: prominent trabeculations/deep intertrabecular recesses; heart failure, emboli, arrhythmia.
• Takotsubo (stress) cardiomyopathy: transient apical ballooning, post-menopausal women + emotional/physical stress; mimics ACS (no obstructive CAD); treat supportively, excellent recovery.

General principles

• Family screening + genetic counselling for all genetic forms (HCM, DCM, ACM).
• Exercise restriction in HCM/ACM (SCD risk).
• Anticoagulation for AF (CHA₂DS₂-VASc); heart-failure GDMT per phenotype.
• CMR is the key aetiological tool; EMB for infiltrative/specific diagnoses.

High-Yield Points

• Classification (ESC 2023): HCM, DCM, RCM, ACM, unclassified.
• HCM: septal ≥15 mm, LVOT gradient ≥30 mmHg; β-blocker first; myectomy if gradient ≥50 mmHg + NYHA III–IV; ICD for high SCD risk (thickness ≥30 mm, NSVT, family SCD).
• DCM: dilated LV + EF <40%; GDMT + ICD EF ≤35%; genetic (TTN, LMNA); 5-yr survival ~50%, 10-yr ~25%.
• RCM: normal thickness/EF, restrictive filling; LVEDP > RVEDP (vs constrictive ≈); amyloid (low voltage + thick walls), sarcoid, haemochromatosis.
• ACM: desmosomal (DSP, FLNC, LMNA); fibrofatty replacement; epsilon wave; ICD cornerstone; avoid exercise.
• Takotsubo: apical ballooning, stress, mimics ACS, reversible.
• Family screening + genetic testing; exercise restriction (HCM/ACM).
• HKHA: CMR for tissue characterisation; ICD EF ≤35%; CRT QRS ≥150 ms.

Topic Summary

Cardiomyopathies are myocardial diseases classified by phenotype (ESC 2023): HCM (asymmetric hypertrophy ± obstruction — β-blockers, septal reduction, ICD for SCD risk), DCM (LV dilatation + EF <40% — GDMT, ICD/CRT, genetic/toxin/viral causes), RCM (restrictive filling with preserved thickness/EF — amyloid/sarcoid/haemochromatosis; distinguish from constrictive pericarditis by LVEDP > RVEDP), ACM (fibrofatty replacement, desmosomal genetics, ICD cornerstone), and unclassified forms (non-compaction, Takotsubo). Management is phenotype-specific GDMT plus devices and family screening, with CMR as the key aetiological tool — the HKHA covers this through the heart-failure section (CMR, ICD/CRT criteria), an LMCHK priority.