Objective: This study analyzes the anatomic structure of the mitral and tricuspid annuli, their relationship with the coronary arteries and veins, and how this anatomic distribution may affect atrial ablation with bipolar radiofrequency clamps, the only technology that ensures transmurality.
Methods: Nine explanted fresh human hearts were studied, two of them with left coronary dominance. Two types of bipolar radiofrequency clamps were positioned to reach the mitral and tricuspid annuli, and relationships within the atrioventricular junction were analyzed, including coronary sinus and coronary arteries.
Results: In all hearts studied, the coronary arteries and veins within the adipose tissue of the right or left atrioventricular groove lay in the atrial side, 3 to 18 mm away from the mitral or tricuspid annuli. When the bipolar radiofrequency clamp was closed toward the mitral annulus, the coronary sinus was always included between the jaws, and in left coronary-dominant hearts, the circumflex artery was also included. Nevertheless, the clamp never reached the annulus owing to the increase in thickness of the adipose tissue around the groove and the ventricular mass, leaving 5 to 10 mm of atrial myocardium free from the radiofrequency electrodes. In the right atrium, clamp placement toward the tricuspid annulus excluding the right coronary left 8 to 18 mm of atrial muscle free from the bipolar electrodes.
Conclusions: Bipolar radiofrequency clamps are not sufficient to complete a Cox maze IV procedure. Moreover, they may compromise coronary arteries in patients with left coronary dominance. Lines to the atrioventricular annuli need to be completed with the cut-and-sew technique or with alternative monopolar energy devices.