Ventricular Fibrillation with Background Pacing Masquerading as Pulseless Electrical Activity

Abstract

In the setting of cardiac arrest, emergency physicians (EPs) are faced with the difficult task of diagnosing arrhythmias within seconds, a challenge that is critical for optimal patient outcome. Below, I present the case of an 83-year-old man in cardiac arrest whose initial arrhythmia fooled 3 EP attendings and, most probably, a semiautomatic external defibrillator. The patient's rhythm was misdiagnosed as pulseless electrical activity (PEA; formerly termed electrical mechanical dissociation), but in fact the patient wai .in fine ventricular fibrillation (VF) with background pacemaker spikes, and hence a shockable rhythm was missed. Arrhythmia interpretation must consider the possibility of background (non-capturing) pacing, and EPs should not be biased by a prior automated defibrillator (computer) analysis.

Permanent Cardiac Pacemaker: an Emergency Perspective

“…However, the new semi-automatic defibrillation used by paramedics may fail to discharge in the presence of ventricular fibrillation as it oversense the pacing spike as acceptable rhythm. 20 Defibrillation or cardioversion can be done under standard indication. But the current may damage pacing and sensing circuit.…”