Endocardial and Epicardial Rhythmia HDx™ Mapping Verifies Surgical Cox Maze IV Lesion Pattern

: Atrial fibrillation (AF) remains the most common cardiac dysarrhythmia, with a significant impact on the health-care economy. AF occurs as a result of electrical conduction delays within the atrial tissue, which may stem from fibrosis or other mediators that alter atrial tissue conduction substrate. The Cox maze III and IV procedures block these reentry circuits by directly dividing, or breaking, the self-perpetuating circuit and by isolating these circuits away from the intrinsic cardiac conduction pathway. The Convergent procedure, a hybrid approach to AF ablation, coordinates the electrophysiologist and the cardiac surgeon in a simultaneous or sequential endocardial and epicardial procedure. Because the heart remains electrically active, electroanatomical maps, not anatomical landmarks, guide therapy. However, lesion transmurality and contiguity remain inconsistent. The Rhythmia HDx™ mapping system (Boston Scientific, Natick, MA, USA) offers detailed maps of acute lesion patterns during the ablation procedure. However, these maps require instrumentation and technology found in the electrophysiology laboratory, not in the operating room. We herein present a case during which we performed a Cox maze IV procedure and also applied the Rhythmia HDx™ electroanatomical mapping system (Boston Scientific, Natick, MA, USA) at the time of operation. Through this novel approach, we were able to verify the completeness of the lesions created and reach a procedural endpoint confirmed by both epicardial and endocardial maps of successful electrical isolation of the left atrium posterior wall and pulmonary vein pedicle.