I'm on work experience clonazepam 1mg tablet pur The American Heart Association explains that cardiac arrest is the sudden loss of heart function in someone who may or may not have been diagnosed with heart disease. It's caused when the heart's electrical system malfunctions, causing the heart to stop suddenly. Death usually occurs within minutes. However, cardiopulmonary resuscitation (CPR) and use of a defibrillator to shock the heart and restore a normal rhythm can sometimes prevent death if performed within a few minutes.