What is the medical term for the absence of a heartbeat?

The medical term for the absence of a heartbeat is asystole.

Asystole is commonly described as a cardiac flatline: the heart has no effective ventricular electrical activity or contraction, so it cannot pump blood. It is a form of cardiac arrest and is generally associated with an extremely poor prognosis unless a reversible cause is quickly found.

The term comes from Greek roots meaning “without contraction.” On an electrocardiogram, asystole appears as a nearly flat tracing, although equipment problems, loose electrodes or fine ventricular fibrillation can sometimes imitate it. Clinicians therefore confirm the rhythm in more than one lead and check the patient rather than relying on the monitor alone.

Asystole differs from bradycardia, which means an abnormally slow heart rate, and ventricular fibrillation, in which the ventricles quiver chaotically rather than stop all activity. Standard resuscitation focuses on high-quality CPR, epinephrine and identifying reversible causes; defibrillation is not used for confirmed asystole.