Vein of Marshall Activity During Sustained Atrial Fibrillation

Background: The human vein of Marshall (VOM) activation patterns during sustained (persistent or permanent) atrial fibrillation (AF) have not been studied in detail. Methods: VOM was cannulated via coronary sinus in six patients (67.3 ± 7.5 years old) having either persistent (N = 4) or permanent (N = 2) AF presenting for radiofrequency catheter ablation. Results: At sinus rhythm in patients with persistent AF, there were frequent ectopic beats from the VOM as well as from left and right pulmonary veins (PVs). The ectopic activity originating from the VOM was highly fragmented. The P wave morphology associated with VOM ectopy was isoelectric in leads I and aVL, positive in leads II, III, aVF, and V2‐V5, which is similar to the P wave morphology associated with left PV ectopic beats. During AF the activation cycle length at VOM was 140 ± 31 msec, which was significantly shorter than that in other atrial sites (P < 0.05). Similarly, the dominant frequency at VOM (9.71 Hz ± 1.52 Hz) was significantly higher than that at other atrial sites (P < 0.0001). In one patient, VOM ablation was associated with AF termination during radiofrequency energy application. Conclusions: Ectopic activity with complex local electrogram originating from VOM is commonly seen in patients with sustained AF. The P wave morphology associated with the ectopic beats from VOM and from the left PVs was similar. The rate of activation at VOM is significantly faster than other atrial and PV sites during AF. These findings show that rapid activation is present in the VOM during sustained AF in human patients.