Key result
His bundle pacing revealed concealed fasciculo-ventricular pathways, with a delta wave observed in 32 of 34 patients, suggesting these connections are ubiquitous.
Why the study?
Paraspecific connections between the ventricular conduction axis and the muscular ventricular septum had yet to be considered as potential pathways for septal activation during His bundle pacing.
Do fasciculo-ventricular connections provide the substrate for septal activation during His bundle pacing?
Observational (n=56)
Do fasciculo-ventricular connections provide the substrate for septal activation during His bundle pacing?
Fasciculo-ventricular pathways are likely ubiquitous and become manifest as delta waves during His bundle pacing, explaining septal activation patterns.
Answers are grounded in this paper and cite their sources.
Should not yet change His bundle pacing practice; leaves open whether fasciculo-ventricular pathways are the septal activation substrate.
BACKGROUND: It is almost 100 years ago since Mahaim described the so-called paraspecific connections between the ventricular conduction axis and the crest of the muscular ventricular septum, believing such pathways to be ubiquitous. These pathways, however, have yet to be considered as potential pathways for septal activation during His bundle pacing. MATERIALS: So as to explore the hypothesis that specialised septal pathways might provide the substrate for septal activation during His bundle pacing, we compared the findings from 22 serially sectioned histological datasets and 34 different individuals undergoing His bundle pacing. RESULTS: We found histologically specialised pathways connecting the branching component of the atrioventricular conduction axis with the crest of the muscular ventricular septum in almost four-fifths of the histological datasets. In 32 of 34 patients undergoing His bundle pacing, the QRS complex closely resembled published images of known conduction through fasciculo-ventricular pathways. In only two patients was a delta wave not seen at any pacing voltages. Capture of these connections varied according to pacing voltage, a finding which correlated with the distance of the pathways from the site of penetration of the ventricular conduction axis. Ventricular activation times remained normal in the presence of the delta wave at higher pacing voltage but were prolonged at lower voltages. CONCLUSIONS: Our histologic findings confirm fasciculo-ventricular connections, initially described by Mahaim as being paraspecific, are likely ubiquitous. Analysis of 12-lead electrocardiograms leads us to conclude that fasciculo-ventricular pathways, concealed during sinus rhythm, become manifest with His bundle pacing.
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Mahmud et al. (2023) conducted an observational in His bundle pacing (n=56). His bundle pacing was evaluated on Presence of fasciculo-ventricular connections (delta wave). His bundle pacing revealed concealed fasciculo-ventricular pathways, with a delta wave observed in 32 of 34 patients, suggesting these connections are ubiquitous.
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