Radiofrequency Ablation of Accessory Pathways Guided by the Location of the Ligament of Marshall

INTRODUCTION: In humans, complex muscle connections are present near the junction between the coronary sinus (CS) and the ligament of Marshall. We hypothesize that these complex muscle connections participate in accessory pathway conduction. METHODS AND RESULTS: Electrophysiologic studies and radiofrequency ablation were performed in four patients with refractory AV reciprocating tachycardia. Case 1 was a 19-year-old male. Marshall bundle potentials were recorded by a catheter in the vein of Marshall. Radiofrequency energy application from that catheter resulted in successful ablation. Case 2 was a 43-year-old male who had undergone two unsuccessful radiofrequency ablation procedures of a left free-wall accessory pathway by conventional techniques. Coronary sinus electrography during tachycardia and ventricular pacing showed a long V-A interval. Radiofrequency energy application directed toward the ligament of Marshall eliminated the pathway conduction. Case 3 was a 17-year-old male who had undergone three unsuccessful ablation procedures. Radiofrequency energy application directed toward the stump of the vein of Marshall successfully eliminated the pathway conduction. Case 4 was a 20-year-old female who underwent one unsuccessful ablation procedure. Successful ablation was achieved in the left atrial free wall, approximately 1 cm above the AV annulus, at a location near the ligament of Marshall. CONCLUSION: We report four patients in whom successful accessory pathway ablation was achieved by targeting the ligament of Marshall. These findings suggest that the complex muscle connections among the coronary sinus, ligament of Marshall, and left atrium is important in accessory pathway conduction and maintenance of circus movement tachycardia in these patients.