Lit Matters 2: The EPIC trial (Electrode Position In Cardioverting AF)

Biphasic synchronized cardioversion for atrial fibrillation works better with anterior-lateral pad placement than anterior-posterior placement. In the EPIC trial, anterior-lateral positioning improved first-shock conversion, achieved higher overall success, and did not increase arrhythmias, skin injury, or procedural pain.

Pad Position for AF Cardioversion

• Anterior-lateral first-shock advantage: Anterior-lateral pad placement converted more patients on the first 100 J synchronized biphasic shock than anterior-posterior placement, with 54% versus 33% reaching sinus rhythm.
• Higher overall conversion success: Across up to four escalating shocks, anterior-lateral positioning still outperformed anterior-posterior, achieving 93% overall cardioversion versus 85%.
• No safety tradeoff detected: Arrhythmias, skin redness, and patient-reported periprocedural pain were similar between positions, so the efficacy edge for anterior-lateral did not come with a measurable safety penalty.
• Lower cumulative energy exposure: Anterior-lateral placement reached success with much less delivered energy, with a median total of 100 J versus 450 J for anterior-posterior.
• Shock vector rationale: Anterior-lateral positioning likely captures a larger mass of myocardium with the biphasic shock vector, a mechanistic clue that helps explain why it beats the left-atrium-targeted anterior-posterior approach. We get into the practice implications in the episode.
• Practical takeaway for ED practice: For synchronized biphasic cardioversion of atrial fibrillation, the best default pad position is anterior-lateral rather than anterior-posterior, though first-pass success still lands near only half of cases.