Causes of Cardiac Arrest

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Cardiac arrest may be caused by almost any known heart condition.

Most cardiac arrests occur when a diseased heart’s electrical system malfunctions. This malfunction causes an abnormal heart rhythm such as ventricular tachycardia or ventricular fibrillation. Some cardiac arrests are also caused by extreme slowing of the heart’s rhythm (bradycardia).

Irregular heartbeats such as these that can cause cardiac arrest should be considered life-threatening arrhythmias.

Other causes of cardiac arrest include:

  • Scarring of the heart tissue Such scarring may be the result of a prior heart attack or another cause. A heart that’s scarred or enlarged from any cause is prone to develop life-threatening ventricular arrhythmias. The first six months after a heart attack represents a particularly high-risk period for sudden cardiac arrest in patients with atherosclerotic heart disease.
  • A thickened heart muscle (cardiomyopathy) Damage to the heart muscle can be the result of high blood pressure, heart valve disease or other causes. A diseased heart muscle can make you more prone to sudden cardiac arrest, especially if you also have heart failure. Learn more about cardiomyopathy
  • Heart medications Under certain conditions, various heart medications can set the stage for arrhythmias that cause sudden cardiac arrest. (As odd as it may sound, antiarrhythmic drugs used to treat arrhythmias can sometimes produce ventricular arrhythmias even at normally prescribed doses. This is called a “proarrhythmic” effect.) Significant changes in blood levels of potassium and magnesium (from using diuretics, for example) also can cause life-threatening arrhythmias and cardiac arrest.
  • Electrical abnormalities Certain electrical abnormalities such as Wolff-Parkinson-White syndrome and Long QT syndrome may cause sudden cardiac arrest in children and young people.
  • Blood vessel abnormalities In rare cases, congenital blood vessel abnormalities, particularly in the coronary arteries and aorta, may cause cardiac arrest. Adrenaline released during intense physical activity often acts as a trigger for sudden cardiac arrest when these abnormalities are present.
  • Recreational drug use Use of certain recreational drugs can cause sudden cardiac arrest, even in otherwise healthy people.