Asystole is the absence of ventricular contractions in the context of a lethal heart arrhythmia, in contrast to an induced asystole on a cooled patient on a heart-lung machine, and general anesthesia during surgery necessitating stopping the heart. Asystole is the most serious form of cardiac arrest and is usually irreversible. Also referred to as cardiac flatline, asystole is the state of total cessation of electrical activity from the heart, which means no tissue contraction from the heart muscle and therefore no blood flow to the rest of the body.