Aetiology

The old classification of dilated, restricted and hypertrophic cardiomyopathy has been largely abandoned due to the high degree of overlap. The latest classification of cardiomyopathy by the WHO and American Heart Association reflect this.

The tables below shows a very limited set of exam related facts for the various cardiomyopathies:

Primary cardiomyopathies - predominately involving the heart

Genetic - both conditions listed below are autosomal dominant. An implantable cardioverter-defibrillator is often inserted to reduce the incidence of sudden cardiac death.

Type of cardiomyopathySelected points
Hypertrophic obstructive cardiomyopathyLeading cause of sudden cardiac death in young athletes
Usually due to a mutation in the gene encoding β-myosin heavy chain protein
Common cause of sudden death
Echo findings include MR, systolic anterior motion (SAM) of the anterior mitral valve and asymmetric septal hypertrophy
Arrhythmogenic right ventricular dysplasiaRight ventricular myocardium is replaced by fatty and fibrofatty tissue
Around 50% of patients have a mutation of one of the several genes which encode components of desmosome
ECG abnormalities in V1-3, typically T wave inversion. An epsilon wave is found in about 50% of those with ARV - this is best described as a terminal notch in the QRS complex

Mixed - rather confusingly most of the causes of dilated and restrictive cardiomyopathy are now listed separately in the 'secondary' causes. This category servers as a reminder that many patients will have a genetic predisposition to cardiomyopathy which is then triggered by the secondary process, hence the 'mixed' category

Type of cardiomyopathySelected causes/points
Dilated cardiomyopathyClassic causes include
  • Alcohol
  • Coxsackie B virus
  • Wet beri beri
  • Doxorubicin
Restrictive cardiomyopathyClassic causes include
  • Amyloidosis
  • Post-radiotherapy
  • Loeffler's endocarditis

Acquired

Type of cardiomyopathySelected points
Peripartum cardiomyopathyTypical develops between last month of pregnancy and 5 months post-partum
More common in older women, greater parity and multiple gestations
Takotsubo cardiomyopathy'Stress'-induced cardiomyopathy e.g. patient just found out family member dies then develops chest pain and features of heart failure
Transient, apical ballooning of the myocardium
Treatment is supportive


Secondary cardiomyopathies- pathological myocardial involvement as part of a generalized systemic disorder

Type of cardiomyopathySelected causes/points
InfectiveCoxsackie B virus
Chagas disease
InfiltrativeAmyloidosis
StorageHaemochromatosis
ToxicityDoxorubicin
Alcoholic cardiomyopathy
Inflammatory (granulomatous)Sarcoidosis
EndocrineDiabetes mellitus
Thyrotoxicosis
Acromegaly
NeuromuscularFriedreich's ataxia
Duchenne-Becker muscular dystrophy
Myotonic dystrophy
Nutritional deficienciesBeriberi (thiamine)
AutoimmuneSystemic lupus erythematosis

Clinical features