cardiomyopathy

introduction

the term is usually reserved for conditions in which severe myocardial disease leads to cardiac failure
they can be classified as:
- “primary” or “intrinsic”
  - condition is primarily due to the cardiac muscle, although many of thee conditions now have identifiable extrinsic aetiologies
- “secondary” or “extrinsic”
  - cardiac muscle dysfunction is due to a cause outside the cardiac muscle
they can also be classified as either:
- dilated cardiomyopathy (DCM)
  - dilated cardiomyopathy is the most common form of non-ischaemic cardiomyopathy
  - accounts for 1/3rd of cases of congestive cardiac failure
  - most common in ages 20-60yr olds but may occur in children
  - 25-35% are familial
- restrictive cardiomyopathy (RCM)
  - a form of cardiomyopathy in which the walls are rigid, and the heart is restricted from stretching and filling with blood properly
- hypertrophic cardiomyopathy
  - hypertrophic cardiomyopathy (HCM or HOCM)

Genetic
- Hypertrophic cardiomyopathy (HCM or HOCM)
- Arrhythmogenic right ventricular cardiomyopathy (ARVC)
- Isolated ventricular non-compaction
- Mitochondrial myopathy
- familial cases of dilated cardiomyopathy
  - lamin heart disease
    - 1 in 5000 carry the LMNA gene mutation impacting lamin A and C proteins in the heart accounts for 10% of familial cardiomyopathy albeit with variable severity even with same mutation
  - those with a mutation in the TTN gene were 21 times more likely to develop the disease than family members who did not carry a mutation ¹⁾
Acquired
- Takotsubo cardiomyopathy (TCM) / stress cardiomyopathy / "broken heart"
- Loeffler endocarditis

cardiac dilation is a transversely isotropic, irreversible process resulting from excess strains on the myocardium.
may be caused by:
- ischaemic injury
- alcoholic cardiomyopathy
- chemotherapy - particularly doxorubicin (Adriamycin), and cobalt
- chronic tachycardias or excess catecholamines
  - stimulant use eg. cocaine
  - hyperthyroidism
  - Takotsubo cardiomyopathy (TCM) / stress cardiomyopathy / "broken heart"
- peri-partum cardiomyopathy
- infections such as:
  - HIV / AIDS
  - Lyme disease
- late sequelae of viral myocarditis
- autoimmune disease
  - polymyositis
- heavy metal exposure
- diabetes
- hypertension
- valvular heart disease
- in the tropics, Chagas disease is the most common infectious cause
- 25-35% are genetic such as:
  - gene mutations in the TTN gene (which codes for a protein called titin) are responsible for “approximately 25% of familial cases of idiopathic dilated cardiomyopathy and 18% of sporadic cases”
  - various autosomal dominant conditions
  - Alström syndrome (autosomal recessive)
  - Duchenne muscular dystrophy (X-linked)
many cases are “idiopathic” and thus regarded as “intrinsic”

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