Maximum-Fixed Energy Shocks for Cardioverting Atrial Fibrillation

Study Questions:

How safe and effective is transthoracic cardioversion of atrial fibrillation (AF) using 360 joule (J) shocks?


CHESS (Comparison of High vs. Escalating Shocks) was a randomized study of two different biphasic shock protocols that were compared in 276 patients (mean age 68 years, mean body mass index 30 kg/m2) with AF (duration <1 year in 70%) undergoing cardioversion using anterior-posterior adhesive electrodes: 1) 360 J with three attempts (n = 129); and 2) escalating shocks of 125, 150, and 200 J (n = 147). The primary endpoint was sinus rhythm at 1 minute. The safety endpoints were post-cardioversion arrhythmias, elevated troponin I concentration, skin burns, and pain.


The primary endpoint was achieved significantly more often in the 360-J group than in the escalating lower-energy group (88 vs. 66%). Sinus rhythm after the first shock also was more common in the 360-J group (75 vs. 34%). The median number of shocks delivered was one in the 360-J group and two in the other group. An arrhythmia occurred in 5% of both groups. There were no elevations in troponin I concentrations and no skin burns or patients who reported pain post-cardioversion.


The investigators concluded that 360-J shocks are more effective than a lower-energy escalating shock protocol for conversion of AF. The is no evidence of higher risk of adverse events using the 360-J protocol.


It has been known for many years that cardioversion efficacy is directly related to shock strength. However, there has been ongoing use of an escalating protocol of 125-200 J at some centers because of older studies suggesting a higher probability of adverse events with high-energy shocks. Neither the 2014 AHA/ACC/HRS nor the 2016 ESC AF management guidelines recommend a specific cardioversion protocol. This well-designed randomized study provides strong evidence that there is higher efficacy and no downside to using 360 J for the initial shock.

Clinical Topics: Arrhythmias and Clinical EP, Prevention, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias

Keywords: Arrhythmias, Cardiac, Atrial Fibrillation, Body Mass Index, Burns, Electric Countershock, Electrodes, Pain, Secondary Prevention, Shock, Troponin I

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