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Cardiac arrest overview

Published: June 19, 2009. Updated: July 29, 2009

In a cardiac arrest normal circulation of the blood stops due to failure of the ventricles of the heart to contract effectively during systole. The resulting lack of blood supply results in cell death from oxygen starvation. Cerebral hypoxia, or lack of oxygen supply to the brain, causes victims to immediately loose consciousness and stop breathing. Cardiac arrest is a medical emergency that, untreated, leads to death within minutes.


Cardiac arrest directly results from a variety of arrhythmias which include asystole (known colloquially as a flatline), ventricular fibrillation, ventricular tachycardia, severe bradycardia and complete heart block with a slow ventricular escape rate.

These arrhythmias can result from:

  • Ischemic heart disease: In apparently healthy adults, cardiac arrest is often caused by ventricular fibrillation during myocardial
  • infarction.
  • Non-ischemic cardiomyopathy: Dilated and hypertrophic cardiomyopathy
  • Congenital heart diseases
  • Valvular heart disease: Aortic stenosis
  • Long QT syndrome: Congenital or acquired
  • Brugada syndrome
  • Primary ventricular fibrillation


The state of cardiac arrest is diagnosed in an unconscious (unresponsive to vigorous stimulation) person who does not have a pulse.

An ECG clarifies the exact diagnosis and guides treatmen, but treatment should begin without awaiting an ECG. The ECG may reveal:

  • asystole,
  • ventricular fibrillation,
  • ventricular tachycardia
  • severe bradycardia,
  • complete heart block with a slow ventricular escape rate
  • or even normal electrical activity (pulseless electrical activity, formerly called electromechanical dissociation).

Potentially treatable causes of pulseless electrical activity include:

  • cardiac tamponade
  • tension pneumothorax
  • toxins or drug overdoses
  • lack of oxygen (hypoxia)
  • potassium disturbance (hypokalemia or hyperkalemia)
  • decreased blood volume (hypovolemia) due to haemorrhage or dehydration
  • hypothermia


Cardiopulmonary resuscitation (CPR)

Seconds count. Call for help immediately or send someone for help. Begin cardiopulmonary resuscitation (CPR) immediately. CPR only buys time for advanced responders to arrive and does not restart the heart. If an automated external defibrillator (AED) is available, apply it to the patient at once and follow the instructions on the device.

Code blue

In many hospitals, cardiac arrest results in one of the healthcare providers announcing a "Code Blue" for immediate response by an appropriately trained team of nurses and physicians. The resuscitating team continues advanced cardiac life support until the patient recovers or a doctor declares the patient's death.

Advanced Cardiac Life Support (ACLS)

As soon as appropriately trained personnel arrive they apply advanced cardiac life support protocols, unless there is a valid do not resuscitate (DNR) order or a valid advance health directive in accord with local protocols. If so it is ethically appropriate to permit natural death to occur in accordance with the wishes of the patient.

Previous: Brugada syndrome Next: Cardiac tamponade

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