Definition of Sudden Cardiac Death and associated Risk Factors

In this article, we will discuss the Definition of Sudden Cardiac Death and associated Risk Factors. So, let’s get started.


It is defined as the unexpected natural death due to cardiac causes within a short period of time (usually within one hour) from the start of symptoms in an individual who may have pre-existing heart disease but in whom the time and mode of death are unexpected. Death means irreversible loss of all biological functions.

Cardiovascular collapse means loss of sufficient cerebral blood flow to maintain consciousness due to acute dysfunction of the heart and/or peripheral vasculature.

Sudden and unexpected cardiac death is usually due to development of catastrophic arrhythmia (ventricular fibrillation, pulseless VT) and accounts for 25-30% of cardiovascular deaths.

Risk Factors

  • Advanced age: The incidence of sudden cardiac death increases with age in both the sexes and in all races; though it is more common in males.
  • Altered altered coronary anatomy such as atheroma, plaque rupture or both.
  • Depressed left ventricular function: There is an increased risk of sudden cardiac death in patients with cardiac disease having ejection fraction less than 30%.
  • Reversible risk factors: Certain factors such as transient myocardial ischemia and reperfusion, electrolyte disturbances (hypokalemia, hypomagnesemia), drugs (diuretics, digitalis), alteration in pH or blood gas may provoke SCD if not taken care of immediately.
  • Other risk factors are hypertension, LVH, conduction defects, hyperlipidemia, smoking, glucose intolerance and decreased vital capacity.
  • In Framingham study, the incidence of SCD in smokers was two and half times more than in non-smokers.

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