Dilated cardiomyopathy (DCM) is the most common form of cardiomyopathy, accounting for 90% of cases. Most common cause of heart transplants.

Causes:

• idiopathic: the most common cause
• myocarditis: e.g. Coxsackie B, Parvovirus B19, HSV, HIV, diphtheria, Chagas disease
• ischaemic heart disease
• peripartum
• hypertension
• iatrogenic: e.g. radiation, doxorubicin (adriamycin)
• substance abuse: e.g. alcohol, cocaine
• Toxins (cobalt, lead, arsenic)
• inherited: either a familial genetic predisposition to DCM or a specific syndrome e.g. Duchenne muscular dystrophy
  • around a third of patients with DCM are thought to have a genetic predisposition
  • a large number of heterogeneous defects have been identified
  • the majority of defects are inherited in an autosomal dominant fashion although other patterns of inheritance are seen
• infiltrative e.g. haemochromatosis, sarcoidosis
  • these causes may also lead to restrictive cardiomyopathy
• nutritional e.g. wet beriberi (thiamine deficiency)
• Metabolic: chronic hypophosphatemia, hypokalemia, hypocalcemia, uremia

<aside> 💡

"ABCDE"

Alcohol, Beri beri, Chagas/Cocaine/Cockskie/Cyclophosphamide, Doxorubicin, Electrolyte disturbance

</aside>

Pathophysiology

• associated with mutations affecting cardiac cell cytoskeleton proteins and mitochondrial enzymes of oxidative phosphorylation in inherited forms which occupies about 35% of cases
• E.g, X-linked DCM involving the gene for dystrophin, which normally links the internal myocyte cytoskeleton with the external basement membrane. (similar process to Duchenne and Becker skeletal muscle dystrophies)
• dilated heart leading to predominately systolic dysfunction
• all 4 chambers are dilated, but the left ventricle more so than right ventricle