Asystole is the complete absence of electrical and mechanical activity in the heart, appearing as a flatline on an ECG monitor. It represents one of the most serious forms of cardiac arrest, because there is no organized rhythm for a defibrillator to convert — it is a non-shockable rhythm.

Treatment focuses on high-quality CPR, administration of epinephrine, and aggressive identification and correction of underlying reversible causes (commonly remembered as the Hs and Ts, such as hypoxia, hypovolemia, and toxins). Because survival from asystole is low, rapid recognition and uninterrupted chest compressions are critical, and providers should confirm the flatline in more than one ECG lead to rule out fine ventricular fibrillation or equipment error.

CPR Certification Labs provides hands-on, American Heart Association–aligned CPR, BLS, ACLS, and PALS certification training to help providers master these life-saving skills.