Variable Arrangement of the Atrioventricular Conduction Axis Within the Triangle of Koch: Implications for Permanent
José-Ángel Cabrera1, Robert H Anderson2, Yolanda Macías3
1Unidad de Arritmias, Departamento de Cardiología, Hospital Universitario Quirón-Salud Madrid and Complejo Hospitalario Ruber Juan Bravo, Universidad Europea de Madrid, Centro de Investigación Biomédica en Red (CIBER), Enfermedades Cardiovasculares, Madrid, Spain.
Insights
Human heart conduction axis location varies significantly. Precise knowledge is crucial for selective atrioventricular pacing, especially concerning the bundle of His and triangle of Koch landmarks.
Area of Science:
- Cardiovascular anatomy
- Electrophysiology
- Cardiac conduction system
Background:
- Growing interest in selective atrioventricular (AV) pacing necessitates detailed anatomical understanding.
- Precise localization of the atrial and penetrating components of the AV conduction axis is critical for effective pacing.
Purpose of the Study:
- To provide a detailed angiographic, gross, and histological description of the human conduction axis.
- To clarify the anatomical variations of the AV conduction system relevant to electrophysiological procedures.
Main Methods:
- Serial histological sectioning of 41 human hearts and gross dissection of 3 hearts.
- Angiography in 60 patients undergoing electrophysiological studies.
- Comparison of anatomical findings with angiographic results.
Main Results:
- Significant variability in the location of the AV conduction axis transition (bundle of His) relative to the triangle of Koch.
- The penetration site was on the atrial aspect of the tricuspid valve hinge in over half of cases, with further variations.
- Marked variations in axis dimensions and right-sided endocardial adjacency were observed.
- Absence of the interventricular component of the fibrous membranous septum in nearly three-fifths of hearts.
Conclusions:
- The study highlights marked variability in the conduction axis location within the triangle of Koch.
- The interventricular component of the fibrous membranous septum is frequently absent, impacting anatomical reference points.
Objectives:
This study sought to describe, in detail, the angiographic, gross macroscopy, and histological dissection of the conduction axis in humans.
Background:
The recent upsurge of interest in specific pacing of the atrioventricular conduction axis has emphasized the need for precise knowledge of the location of the atrial and penetrating components of the atrioventricular conduction axis.
Methods:
A total of 41 human hearts were studied by serial histological sectioning and an additional 3 hearts by gross dissection. One of the hearts studied histologically was also dissected to show the location of the conduction axis prior to serial sectioning. The anatomical findings were then compared with the results of angiography undertaken in the catheter laboratory in 60 patients undergoing electrophysiological studies.
Results:
Marked variation of the location of the transition from atrioventricular conduction axis to the penetrating atrioventricular bundle, or the bundle of His, relative to the landmarks of the triangle of Koch was observed. In just over one-half of both the specimens and the patients, the site of penetration was on the atrial aspect of the hinge of the septal leaflet of the tricuspid valve, with further variation noted relative to the apex of the triangle of Koch. Based on measurements of the histological sections, marked variation in the dimensions of the axis and its adjacency to the right-sided endocardium were also found. In almost three-fifths of hearts, an interventricular component of the fibrous membranous septum was not able to be identified. The significance of these findings to those who seek to perform selective pacing of the atrioventricular conduction axis are discussed.
Conclusions:
Marked variability of the location of the conduction axis within the triangle of Koch is reported. In three-fifths of hearts, the interventricular component of the fibrous membranous septum is nonexistent.
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