Electrophysiological characterization of cardiac veins in humans

Background: The coronary sinus is a complex structure with a surrounding myocardial coat and muscle bundles that course within it. The purpose of this study was to evaluate the electrical activity of the coronary sinus (CS), great cardiac vein (GCV) and related structures, such as the Vein of Marshall (VOM). Methods and Results: Data obtained from adult (n = 114) and pediatric patients (n = 16) were analyzed. The width of atrial electrograms (EGMs) within the CS at a basic pacing cycle length of 600 ms was 46 +/- 7.4 ms (mean +/- SD) vs. 29.7 +/- 6.3 ms in the GCV (p < 0.01). With decremental pacing the width of the EGM within the CS at 300 ms increased to 66.6 +/- 8.5 ms (p < 0.1 compared to CS EGM at pacing cycle length of 600 ms). The width of the EGM within the GCV increased from 29.7 +/- 6.3ms at a pacing cycle length of 600 ms to 34.6 +/- 6.0 at 300 ms (p = NS). There were no significant differences in the atrial EGM width between CS and GCV in the pediatric patients. Conclusions: We conclude that atrial electrograms are wider in the CS but not in the GCV. This finding can be explained by the presence of a myocardial coat around the CS. The rate response characteristics of the atrial electrograms within the CS are consistent with a lack of tight coupling between muscle bundles and the CS musculature. Further, the absence of such differences in pediatric patients could partly explain relative differences in types of supraventricular arrhythmias seen in different age groups.