Asystole
Also calledCardiac standstill · Flatline · Ventricular asystole · Cardiac arrest (asystolic)
Definition
Absence of detectable ventricular electrical activity, so no QRS complexes are seen; it is one of the four cardiac-arrest rhythms (with ventricular fibrillation, pulseless ventricular tachycardia and pulseless electrical activity). Atrial activity (P waves) may continue without any QRS complexes, and the 2010 AHA guidelines note that the rhythm is perhaps better described as ventricular asystole. A flat line in one lead is not proof of asystole: fine ventricular fibrillation can also look like a flat line, and ventricular fibrillation can show no activity in a single lead while being obvious in others, so the rhythm is confirmed in another lead.
Sources
- Neumar RW, Otto CW, Link MS, et al. Part 8: adult advanced cardiovascular life support: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2010;122(18 Suppl 3):S729-S767. doi.org/10.1161/CIRCULATIONAHA.110.970988
- Ewy GA. Ventricular fibrillation masquerading as asystole. Ann Emerg Med. 1984;13(9 Pt 2):811-812. doi.org/10.1016/s0196-0644(84)80445-x
- Ornato JP, Gonzales ER, Garnett R. Atrial fibrillation with high degree atrioventricular block masquerading as ventricular fibrillation masquerading as asystole during cardiac arrest. Crit Care Med. 1987;15(4):334-335. doi.org/10.1097/00003246-198704000-00013
Last reviewed 2 October 2026. Every definition in the EKG Dictionary cites the guideline, consensus statement or original paper it comes from.