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Transseptal activation delta: A novel electrocardiographic criterion for left bundle branch capture
Nerea Torres González1, Diego Valdivia Miranda1, Julio Salvador Hernández Afonso2
1Department of Cardiology, Arrhythmia and Electrophysiology Unit, Hospital Universitario Nuestra Señora de la Candelaria, Santa Cruz de Tenerife, Canary Islands, Spain.
Insights
Transseptal activation delta (TAD) accurately distinguishes left bundle branch capture from septal pacing during implantation. A threshold of 25 ms offers high specificity for confirming conduction system capture.
Area of Science:
- Cardiology
- Electrophysiology
- Medical Devices
Background:
- Left bundle branch pacing (LBBP) implantation requires distinguishing true left bundle branch capture from septal myocardial pacing.
- Existing diagnostic criteria for LBBP may be limited by patient-specific factors or pacing maneuvers.
- Transseptal activation delta (TAD) was hypothesized to differentiate left bundle branch capture from septal pacing.
Purpose of the Study:
- To assess the diagnostic accuracy of TAD for confirming left bundle branch capture during LBBP implantation.
Main Methods:
- Prospective, observational, single-center study including 122 patients undergoing LBBP.
- Measurements of TAD were taken during septal pacing and confirmed left bundle branch capture.
- A validation cohort of 30 additional patients was analyzed.
Main Results:
- A TAD threshold of ≥25 ms demonstrated 78.9% sensitivity and 95.7% specificity for left bundle branch capture.
- Overall diagnostic accuracy for the TAD threshold was 84.5%.
- The identified threshold maintained diagnostic performance in the validation cohort.
Conclusions:
- Transseptal activation delta (TAD) is a practical and reproducible intraoperative criterion.
- A 25-ms TAD threshold reliably identifies left bundle branch capture with high specificity.
- TAD serves as a valuable confirmatory marker for conduction system capture in LBBP.
Background:
Distinguishing left bundle branch capture from septal myocardial pacing during left bundle branch pacing implantation remains challenging. Several diagnostic criteria have been proposed, including right bundle branch block morphology in lead V1 and timing measures such as V6 R-wave peak time or the V6-V1 interpeak interval, but these parameters may depend on baseline conduction characteristics or pacing maneuvers not always available. We hypothesized that the difference between V6 R-wave peak time during monopolar pacing from the proximal (ring) and distal (tip) electrodes, termed transseptal activation delta (TAD), would be greater when the distal electrode captures the left bundle branch than during septal myocardial pacing.
Objective:
This study aimed to evaluate the diagnostic accuracy of TAD in confirming the left bundle branch capture.
Methods:
In this prospective, observational, single-center study, 122 consecutive patients who underwent left bundle branch pacing were included. In 20 patients, measurements were obtained during septal pacing and after confirmation of left bundle branch capture, yielding 142 pacing observations. Left bundle branch capture was defined by electrocardiographic criteria and dynamic pacing maneuvers. A separate prospective validation cohort of 30 additional patients was analyzed.
Results:
A TAD threshold of ≥25 ms identified left bundle branch capture with 78.9% sensitivity, 95.7% specificity, and 84.5% overall diagnostic accuracy. In the prospective validation cohort, this threshold retained diagnostic performance.
Conclusion:
TAD is a practical, reproducible intraoperative criterion for identifying left bundle branch capture. A 25-ms threshold supports the role of TAD as a confirmatory marker of conduction system capture with high specificity.
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