Dilated, hypertrophic and restrictive, each with a distinct physiology
Mnemonic
Three patterns, defined by what the ventricle does:
- Dilated - the commonest. Systolic failure with a dilated, thin walled, poorly contracting ventricle. Causes: idiopathic, alcohol, peripartum, myocarditis, doxorubicin, haemochromatosis, thiamine deficiency
- Hypertrophic - autosomal dominant sarcomeric mutation. Diastolic failure with asymmetric septal hypertrophy and outflow obstruction. Causes sudden cardiac death in the young. Murmur increases with Valsalva and standing, unlike aortic stenosis
- Restrictive - stiff, non-compliant ventricle with normal wall thickness and systolic function. Causes: amyloid, sarcoid, haemochromatosis, endomyocardial fibrosis
“Dilated cannot squeeze, hypertrophic and restrictive cannot fill.”
Hypertrophic cardiomyopathy versus aortic stenosis is the discrimination that matters: both give an ejection systolic murmur, but hypertrophic cardiomyopathy has a jerky pulse that rises quickly, and its murmur is louder with reduced preload, whereas aortic stenosis has a slow rising pulse and a quieter murmur.
Arrhythmogenic right ventricular cardiomyopathy is the fourth, with fibrofatty replacement, epsilon waves and sudden death in young athletes.
Expansion
| Type | Problem | Causes |
|---|---|---|
| Dilated | Systolic failure; large, poorly contracting ventricle | Alcohol, ischaemia, viral myocarditis, peripartum, doxorubicin, haemochromatosis, thiamine deficiency |
| Hypertrophic | Diastolic failure; thick, stiff ventricle with outflow obstruction | Autosomal dominant sarcomeric protein mutations (beta-myosin heavy chain) |
| Restrictive | Diastolic failure; stiff but not thickened | Amyloid, sarcoid, haemochromatosis, endomyocardial fibrosis |
Hypertrophic cardiomyopathy deserves particular attention: asymmetric septal hypertrophy with myocyte disarray, causing dynamic left ventricular outflow obstruction. The murmur increases with Valsalva and standing (reduced preload) and decreases with squatting, which is the opposite of aortic stenosis and is the key bedside discriminator. It is the commonest cause of sudden cardiac death in young athletes, and first degree relatives require screening.
Restrictive cardiomyopathy must be distinguished from constrictive pericarditis, since the latter is surgically curable. Imaging, the pattern of the jugular venous pulse and pericardial thickness help.
Takotsubo cardiomyopathy is the stress-induced form, with apical ballooning after emotional or physical stress, mimicking infarction with unobstructed coronary arteries.