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In emergency cardiac care, any of the following cardiac rhythm disturbances: ventricular fibrillation, pulseless ventricular tachycardia or some poorly tolerated supraventricular tachycardias, e.g., some instances of rapid atrial fibrillation, atrial flutter, or AV nodal re-entrant tachycardia. By contrast, asystole, pulseless electrical activity, heart blocks, and the bradycardias are not shockable. Defibrillation or cardioversion of these latter rhythms may result in injury to the patient.
See also: rhythm