Cardiac arrest refers to the loss of heart function. The heart’s main function is to pump blood towards the arteries so that they transport oxygen and other nutrients to the tissues. The main cause for cardiac arrest is heart attack. There are other extracardiac causes that may lead to cardiac arrest such as hypoxia when drowning or hypovolemic shock when hemorrhaging.
The most frequent body mechanism during cardiac arrest—after having a heart attack—is a serious arrhythmia called ventricular fibrillation. This arrhythmia might occur as a consequence of a sudden lack of oxygen caused by the obstruction of a coronary artery. Ventricular fibrillation causes chaos in the heart’s electrical activity which becomes mechanically inefficient and, as a consequence, the heart pumps little or no blood.