Vein of Marshall Cannulation for the Analysis of Electrical Activity in Patients With Focal Atrial Fibrillation

BACKGROUND: Whether or not the muscle bundle within the ligament of Marshall (LOM) can serve as the origin of focal atrial fibrillation (AF) is unknown. METHODS AND RESULTS: A total of 28 consecutive patients with paroxysmal AF underwent balloon-occlusion coronary sinus angiograms to identify the vein of Marshall (VOM). Attempts were then made to advance a 1.5-French electrophysiological catheter into the VOM via the coronary sinus orifice. In 17 of the 28 patients (10 of 17 were men aged 38+/-15 years), cannulation was successful. Double potentials were registered in 8 of these 17 patients. The first potential corresponded with local left atrial activation. The second potential was shorter and narrower than the first. The sequence of activation in the second potential in the VOM was proximal to distal. In 6 patients with direct VOM recordings, we documented that the origin of AF was in the muscle bundle within the LOM. Radiofrequency catheter ablation aimed at the insertion site of the VOM successfully terminated AF in 4 of these 6 patients. CONCLUSIONS: (1) It is possible to cannulate and to record electrical potentials from the VOM. (2) The characteristics of the double potentials within the VOM suggest that the second potential is from the muscle bundle (Marshall bundle) within the LOM. (3) The Marshall bundle may be the origin of focal AF in some patients.