Non-atherosclerotic causes of myocardial infarction

Classification of Myocardial infarction

Type I: Spontaneous myocardial infarction related to ischaemia due to a primary coronary event
Type II: Secondary ischaemia due to increased oxygen demand or decreased supply

Non-atherosclerotic causes of a type I MI:

(a) Coronary dissection

Mechanism of tear poorly understood
Occurs most commonly in women (pregnancy and peripartum) ?hormonal or haemodynamic factors
Detailed intravascular USS demonstrates occult atheroma
Rx: stent insertion

(b) Procoagulant states

Rare reports associated with antiphosholipid syndrome, protein C, factor V leiden deficiency
Rx: lifelong anticoagulation

Non-atherosclerotic causes of type II MI:

(a) Cocaine

Powerful coronary vasoconstrictor that raises BP and HR
Thrombogenic and atherogenic
Common in demographic groups where cocaine is used widespread (young males)
Rx: (avoid B-blockers acutely as this may aggravate coronary constriction), abstinence from cocaine

(b) Coronary embolism

MI with unobstructed coronaries

TREATMENT

Secondary prevention should only be prescribed if there is evidence of atherosclerotic disease

Non-MI causes for troponin-positive chest pain with normal coronaries

(a) Takotsubo cardiomyopathy

In patients with ST-elevation chest pain 1-2% have normal coronaries and impaired ventricular function
Syndrome is known as apical ballooning (Takitsubo cardiomyopathy) ?due to adverse effects of catecholamines on the heart
Syndrome occurs after a stressful event such as bereavement - many patients make a full recovery of LV function over a period of weeks

(b) Atypical myocarditis: may present with classic sudden onset angina-liek pain at any age (demonstrated on cardiac MRI in 50% cases)

(d) Cardiac trauma

(e) Sepsis

(f) Renal failure

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