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Pathophysiology and etiology of sudden cardiac arrest

Philip J Podrid, MD, FACC
Section Editors
Brian Olshansky, MD
Scott Manaker, MD, PhD
Deputy Editor
Brian C Downey, MD, FACC


Sudden cardiac arrest (SCA) and sudden cardiac death (SCD) refer to the sudden cessation of cardiac activity with hemodynamic collapse, typically due to sustained ventricular tachycardia/ventricular fibrillation. These events mostly occur in patients with structural heart disease (that may not have been previously diagnosed), particularly coronary heart disease.

The event is referred to as SCA (or aborted SCD) if an intervention (eg, defibrillation) or spontaneous reversion restores circulation. The event is called SCD if the patient dies. However, the use of SCD to describe both fatal and nonfatal cardiac arrest persists by convention. (See "Overview of sudden cardiac arrest and sudden cardiac death", section on 'Definitions'.)

The cardiac diseases that lead to the genesis of the arrhythmia resulting in cardiac collapse and sudden death are varied, and the association with sudden death in some cases is poorly understood [1]. Identification of the patient at risk for sudden death and identification of the factors that precipitate the fatal arrhythmia continue to represent a major challenge. This topic will review the mechanisms and etiology of SCA. Treatment for SCA, the evaluation of survivors, and the outcomes of SCA are discussed separately. (See "Advanced cardiac life support (ACLS) in adults" and "Evaluation of the survivor of sudden cardiac arrest" and "Prognosis and outcomes following sudden cardiac arrest in adults".)


The exact mechanism of collapse in an individual patient is often impossible to establish since, for the vast majority of patients who die suddenly, cardiac activity is not being monitored at the time of their collapse. As a result, the mechanism can only be inferred, based upon information obtained after the process has been initiated.

However, there have been many cases in which the initiating event has been witnessed or recorded [2-4]. This has usually occurred in patients being continually monitored in the coronary care unit or with a 24-hour ambulatory ECG recording device or an implantable cardioverter-defibrillator (ICD). Ventricular tachycardia (VT) or ventricular fibrillation (VF) account for the majority of episodes [2,4]. However, a bradyarrhythmia is responsible for some cases of SCD.

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Literature review current through: Nov 2017. | This topic last updated: Aug 22, 2016.
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