Effect of left atrial-coronary sinus musculature connections on the coronary sinus activation pattern via retrograde conduction in patients with WPW syndrome

Background: Double potential (DP) activation patterns observed in coronary sinus (CS) electrograms recorded during left lateral atrial pacing, were explained by an initial low-frequency left atrial (LA) activation potential and secondary high-frequency CS musculature activation potential in canine hearts. Moreover, the connections between the LA and CS musculature vary greatly in size and location in the human heart. The purpose of this study was to investigate the relationship between the CS activation pattern during retrograde conduction via an accessory pathway (AP) and the location of left-sided APs. Methods and Results: Fifty-one patients (31 males, mean age 48.6 years) who underwent radiofrequency catheter ablation of left-sided APs were divided into two groups according to the successful ablation site. The CS electrograms during retrograde AP conduction were classified into 3 types; single, fractionated, and DP activation patterns. A DP pattern was identified in 10 of 12 patients (83.3%) with posteroseptal to posterolateral APs, and in particular, 9 had a divergent sequence. Twenty-six of 39 patients (66.7%) with lateral to anterolateral APs, demonstrated a single pattern. The number of radiofrequency applications was significantly higher in patients with a DP pattern than in those with a single pattern (3.4 +/- 3.3 vs. 7.8 +/- 6.8, p < 0.01). Conclusion: Misleading information obtained when mapping for optimal ablation sites might result from DP patterns with a divergent sequence produced by discrete muscular connections between the LA and CS musculature. Ablation around left posterior APs may require meticulous observation of the CS activation patterns.