Validation of the 'Time to Notch' criterion in patients with left bundle branch block following transcatheter aortic valve replacement

Background Currently, the diagnostic criteria for left bundle branch block (LBBB) are based on recommendations from the American College of Cardiology (ACC)/American Heart Association (AHA)/Heart Rhythm Society (HRS) and the criteria proposed by Strauss. The left bundle branch is highly vulnerable to damage during transcatheter aortic valve replacement (TAVR), increasing the risk of periprocedural complications. This study evaluated whether a new Time-to-Notch criterion combined with the ACC/AHA/HRS guidelines outperforms the Strauss criteria. The goal of this study is to validate the new criterion using a Chinese cohort of patients with new-onset LBBB following TAVR. Methods In this retrospective cohort study, the subjects were patients who underwent TAVR between September 2017 and March 2025. Postprocedural electrocardiograms (ECGs) were analyzed to identify patients with new-onset LBBB after TAVR. Among them, a subset of patients had preprocedural ECGs exhibiting QRS widening fulfilling the standard ECG criteria for LBBB. Given the significant increase in QRS width observed in their postprocedural ECGs compared to their preprocedural ECGs, we reclassified their preprocedural ECGs as pseudo-left bundle branch block (pseudo-LBBB). Their preprocedural ECGs were categorized into the presence or absence of pseudo-LBBB. We additionally selected patients with preprocedural ECGs that met the above criteria as the pseudo-LBBB group, and the remaining patients whose preprocedural ECGs lacked pseudo-LBBB were classified into the LBBB group. The ECGs were analyzed using the Time-to-Notch and Strauss criteria. Results The 351 ECGs obtained from 157 consecutive patients who underwent TAVR were analyzed. A total of 52 patients with new-onset LBBB after TAVR were included in the study. Of these, 7 patients with preprocedural ECGs meeting the LBBB criterion and significant postprocedural prolongation of the QRS duration were assigned to the pseudo-LBBB group, and the remaining 45 patients were assigned to the LBBB group. Two professionally trained ECG doctors independently analyzed the ECGs of both groups. Combining the Time-to-Notch and the ACC/AHA/HRS criteria had a sensitivity of 73.3% and specificity of 85.7%, while the Strauss criteria had a sensitivity of 91.1% and specificity of 71.4%. Conclusions Our results indicate that the combined Time-to-Notch ACC/AHA/HRS criteria, with a notch time > 75 ms in lead I, demonstrate higher specificity compared to the Strauss criteria. Therefore, the Time-to-Notch criterion may offer significant value for diagnosing true LBBB in clinical practice.