Abstract
BACKGROUND: During left bundle branch (LBB) area pacing, it is important to confirm that the capture of the LBB is achieved, not just the capture of only the adjacent left ventricular (LV) myocardium. OBJECTIVE: Our aim was to establish ECG criteria for LBB capture.
We hypothesized that since LBB pacing results in physiologic depolarization of the LV then the native QRS can serve as a reference for the diagnosis of LBB capture in the same patient. METHODS: Only patients with evidence of LBB capture (QRS morphology transition) were included.
Several QRS characteristics were compared between the native rhythm and different types of LBB area capture. RESULTS: A total of 357 ECGs (124 patients) were analyzed: 118 with native rhythm, 124 with non-selective LBB capture, 69 with selective LBB capture and 46 with LV septal capture.
Our hypotheses that during LBB capture the paced V6 R-wave peak time (RWPT, measured from QRS onset) equals the native V6 RWPT and that the paced V6 RWPT (measured from the stimulus) equals the LBB potential to V6 R-wave peak interval were positively validated. Criteria based on these rules had sensitivity and specificity of 88.2-98.0% and 85.7-95.4%, respectively.
Moreover, 100% specific V6 RWPT cut-off for LBB capture diagnosis in patients with narrow QRS/right bundle branch block was determined to be 74 ms. CONCLUSION: We showed equivalency of LV activation times in ECG during native and paced LBB conduction, consequently, if V6 RWPT is longer during pacing, this is indicative of lack of LBB capture.