Maximum-Fixed Energy Shocks for Cardioverting Atrial Fibrillation
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.
Keywords: Arrhythmias, Cardiac, Atrial Fibrillation, Body Mass Index, Burns, Electric Countershock, Electrodes, Pain, Secondary Prevention, Shock, Troponin I
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