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Normalization of bundle branch block patterns by distal His bundle pacing. Clinical and experimental evidence of
Insights
Distal His bundle pacing effectively normalized bundle branch block patterns in patients and dogs. This pacing method corrected conduction delays within the His bundle, suggesting a new therapeutic approach.
Area of Science:
- Cardiology
- Electrophysiology
- Cardiac Conduction System
Background:
- Bundle branch block patterns (BBBP) can arise from various cardiac conditions.
- Conduction delays within the His bundle (IHCD) may contribute to BBBP.
- His bundle pacing is an emerging technique for cardiac rhythm management.
Purpose of the Study:
- To investigate the efficacy of distal His bundle (H) pacing in normalizing BBBP.
- To explore the role of intra-His conduction delay (IHCD) in BBBP.
- To provide clinical and experimental evidence for His bundle pacing in BBBP.
Main Methods:
- Reported clinical cases of patients with acute and chronic BBBP.
- Conducted experimental studies in dogs with induced IHCD and BBBP.
- Utilized distal His bundle pacing with electrode catheters and plunge wire electrodes.
- Monitored His-His (H-H) and His-ventricular (H-V) intervals, and stimulus-to-QRS (PI-V) intervals.
Main Results:
- Distal His bundle pacing normalized BBBP in 6 out of 7 clinical patients.
- Pacing normalized BBBP in 12 out of 18 experimental dog models (67%).
- Pacing-ventricular intervals (PI-V) were shorter than H-V intervals and matched H'-V intervals in IHCD cases.
- Selective His bundle pacing was confirmed by electrogram monitoring.
Conclusions:
- Distal His bundle pacing is effective in normalizing BBBP, particularly when IHCD is present.
- Functional longitudinal dissociation may explain conduction abnormalities in the His bundle.
- His bundle pacing offers a potential therapeutic strategy for specific conduction disorders.
Abstract:
Clinical and experimental observations in which bundle branch block patterns (BBBP) in ECG leads were normalized by distal His bundle (H) pacing are reported. The clinical material includes four patients with acute right BBBP secondary to anterior wall myocardial infarction and three patients with chronic left BBBP. Six of the seven patients had a prolonged H-V interval (60-85 msec) including three who showed evidence of an intra-H conduction delay (IHCD) with split H (H and H'). Distal H pacing from a right-sided electrode catheter normalized the BBBP with a stimulus-to-QRS (PI-V) interval 20-35 msec shorter than the H-V interval and almost identical to the H'-V interval in the three patients with documented IHCD. In 18 dogs ligation of the anterior septal artery resulted in IHCF with split H associated with right or left BBBP. Distal H pacing from catheter and/or plunge wire electrodes normalized the BBBP in 12 experiments (67%) with a PI-V interval identical to the H'-V interval. H pacing was selective and direct stimulation of myocardium was excluded by monitoring the high ventricular septal electrogram. The clinical and experimental observations are discussed as evidence that functional longitudinal dissociation is probably only operative in the pathologic H due to selectively greater depression of conduction in the transverse interconnections.