Dynamic Changes of the S Wave in Lead V6: A Novel Visual Indicator for Left Bundle Branch Capture.

BACKGROUND

During the electrode screwing process in left bundle branch pacing (LBBP), the significance of the S wave in lead V6 remains elusive. In this study we analyzed the change of the S wave in lead V6 under different patterns of capture and explore its mechanisms.

METHODS

Our study included 243 patients with selective LBBP (SLBBP). We used the continuous pacing technique and classified the electrophysiologic characteristics observed during the screwing process into 4 patterns: left ventricular septal pacing (LVSP), nonselective LBBP (NSLBBP) in low output and in lower output, and selective LBBP. The change of the S-wave morphology in lead V6 and R-wave peak time in leads V6 and V1 were evaluated according to these 4 patterns.

RESULTS

In all 243 cases, the presence of S wave in V6 gradually increased in the 4 patterns as follows: 35.4% in LVSP, 77.0% in NSLBBP low output, 82.7% in NSLBBP lower output, and 97.9% in SLBBP. From the LVSP to the NSLBBP (low output) pattern, there were 60 (69.8%) cases of deepening of the S wave and 101 (64.3%) cases showing a newly emerged S wave. From the NSLBBP lower output to the SLBBP pattern, there were 171 (85.1%) cases with a deepening S wave and 37 (88.1%) cases with a newly emerged S wave. Sensitivity and specificity of the S wave in lead V6 were 97.9% and 100% in SLBBP, respectively.

CONCLUSIONS

The dynamically changing S wave in lead V6 serves as a novel visual indicator of left bundle branch capture.