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

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"ABCDE"

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

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**Selenium deficiency** is known to cause Keshan disease, a type of dilated cardiomyopathy. This condition is named after the region in China where it was first identified and there, it was linked to low selenium levels in the soil. Selenium is an essential trace element that plays a critical role in protecting cells from oxidative damage and infection. It's incorporated into selenoproteins which have various functions including antioxidant defence and thyroid hormone metabolism.

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