How cardiomyopathies are tested on Step 1
Vignettes give a cause (heavy drinking, recent viral illness, chemotherapy, family history of sudden death, systemic infiltrative disease) and ask for the type, the histology, or the management.
Dilated = cannot squeeze (systolic). Hypertrophic = thick, may obstruct outflow (diastolic ± obstruction). Restrictive = cannot relax and fill (diastolic) with normal wall thickness or infiltrated walls.
The three types
Each type has a typical shape on echocardiography and a characteristic list of causes.
| Type | Causes | Physiology | Exam |
|---|---|---|---|
| Dilated | Idiopathic, genetic, alcohol, myocarditis (coxsackie B), doxorubicin, trastuzumab, peripartum, Chagas, wet beriberi, cocaine | Systolic dysfunction, ↓ EF | S3, displaced apex, MR murmur from dilation |
| Hypertrophic | Autosomal dominant sarcomere gene mutations; Friedreich ataxia | Diastolic dysfunction ± dynamic LVOT obstruction | S4, systolic murmur louder with Valsalva, bifid pulse |
| Restrictive | Amyloidosis, sarcoidosis, hemochromatosis, radiation, endomyocardial fibrosis, Löffler | Diastolic dysfunction, normal EF | Elevated JVP, Kussmaul sign, S4; low-voltage ECG in amyloid |
Cardiac amyloid: thick walls on echo but low voltage on ECG — a classic mismatch.
Hypertrophic cardiomyopathy
Sarcomere mutations cause hypertrophy, myocyte disarray, and fibrosis. In about two-thirds, the thick septum and anterior mitral leaflet obstruct LV outflow.
| Management | Rationale |
|---|---|
| β blockers or non-DHP CCBs (verapamil) | Slow HR → longer filling → larger LV; ↓ contractility |
| Avoid diuretics, nitrates, vasodilators, dehydration | Shrink the LV and worsen obstruction |
| Mavacamten | Cardiac myosin inhibitor reduces hypercontractility |
| Septal myectomy or alcohol septal ablation | Refractory obstruction |
| ICD | High sudden-death risk (prior arrest, VT, massive hypertrophy, family history) |
| Screen first-degree relatives | Autosomal dominant |
Sudden death in HCM is usually ventricular fibrillation, often during exertion.
Restrictive cardiomyopathy vs constrictive pericarditis
Both impair filling and raise venous pressure, but the problem lies in different tissue.
Clinical application
Causes of dilated cardiomyopathy are frequently tested through history.
Five weeks after delivery, a 31-year-old develops progressive dyspnea, orthopnea, and leg swelling. Echocardiography shows a dilated LV with EF 30% and no valve disease. What is the diagnosis, and what is a key counseling point?
- Heart failure with a dilated, poorly contracting LV in the last month of pregnancy or within 5 months postpartum, without another cause, defines peripartum cardiomyopathy.
- It is a form of dilated cardiomyopathy.
- Many patients recover, but recurrence risk in later pregnancies is substantial, especially if EF does not normalize.
Answer. Peripartum cardiomyopathy (dilated). Treat as HFrEF, avoiding ACE inhibitors during pregnancy, and counsel about high risk with future pregnancies.