Visualization of Electrophysiologically Defined Superior Vena Cava-Right Atrium Junction With High-Resolution Mapping...

Recent studies have identified diagonal conduction block lines at the electrophysiologically defined superior vena cava (SVC)-right atrium (RA) junction using three-dimensional mapping systems and reported the utility of SVCI using these lines. However, these block lines are not always observed, requiring the use of a conventional horizontal isolation approach.

This study aimed to visualize the electrophysiologically defined SVC-RA junction using high-resolution mapping with atrial extrastimulus pacing.

Twenty-five patients underwent high-resolution mapping during sinus rhythm (Sinus map) and extrastimulus pacing (S2 map) using a three-dimensional mapping system (CARTO 3, version 8). Slow conduction or conduction block along the SVC-RA junction was assessed by adjusting the lower threshold cut-off value in the "early meets late" analysis. The length of slow or conduction block lines was compared between the two maps.

The S2 map revealed significantly longer slow or conduction block lines compared to the Sinus map (52.5 ± 18.0 mm vs. 35.6 ± 16.1 mm, p = 0.0013). The adjusted lower threshold values were comparable between the two maps: 26.4 ± 3.7% for the S2 map and 25.2 ± 3.8% for the Sinus map (p = 0.2819). In the S2 map, a slow or block line covering more than half of the junction was observed in all patients. Furthermore, the sinus node was consistently located inferior to this line.

High-resolution mapping with atrial extrastimulus pacing more clearly visualizes the SVC-RA junction, potentially enabling more effective SVCI and estimation of the sinus node location.