Cardiac arrest corresponds to the interruption of the heart’s contraction and pumping action, resulting from a sudden and drastic alteration in its electrical activity (ventricular fibrillation).
Cardiac arrest is an absolute medical emergency since, unless action is taken very quickly (on the order of tens of seconds or a few minutes) with appropriate cardiopulmonary maneuvers and/or electrical defibrillation, the outcome is fatal in 100% of cases.
Cardiac arrest is different from myocardial infarction, which depends on predominantly defects in blood supply to a more or less extensive portion of the heart muscle and, while representing a medical emergency, can be managed in a somewhat longer time frame, on the order of tens of minutes to several hours (depending on severity).