Atrial fibrillation with high degree atrioventricular block masquerading as ventricular fibrillation masquerading as asystole during cardiac arrest.

Ventricular fibrillation (VF) can masquerade as asystole. We report a 54-yr-old male in cardiac arrest who, on surface ECG, appeared to be in VF or asystole. A bedside intracardiac recording using a transmyocardial pacing wire showed the true rhythm to be atrial fibrillation (AF) with high grade atrioventricular block. AF with a high degree block can masquerade as VF, which simultaneously masquerades as asystole, and can be correctly diagnosed by bedside intracardiac monitoring. Patients who have a flat line rhythm which may represent asystole, fine ventricular fibrillation, or atrial fibrillation with a high degree atrioventricular block may warrant a trial of electrical countershock, high-dose atropine, or transthoracic pacing.