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Electrophysiological delineation of the specialized conduction system under cardiotomy and its clinical role
Insights
Identifying the His bundle
Area of Science:
- Cardiac Electrophysiology
- Congenital Heart Surgery
- Anatomy
Background:
- The specialized conduction system's anatomy is crucial for preventing conduction disturbances during congenital heart defect repair.
- Accurate intraoperative localization of the His bundle and its branches is essential for minimizing iatrogenic injury.
Purpose of the Study:
- To electrophysiologically delineate the specialized conduction system in patients undergoing cardiotomy for congenital heart defects.
- To correlate electrophysiological findings with anatomical landmarks to improve surgical safety and reduce conduction abnormalities.
Main Methods:
- Electrophysiological mapping was performed during cardiotomy in 64 patients with ventricular septal defect (VSD), tetralogy of Fallot (TOF), and transposition of the great arteries (TGA).
- Histological studies were conducted for confirmation of electrophysiological findings.
- Specific deflection patterns were analyzed in relation to anatomical structures like the muscle of Lancisi (ML) or its equivalent (LES).
Main Results:
- A superficial His bundle location was identified in large VSDs (types II/III), correlating with a high incidence of conduction disturbance.
- Distinct electrophysiological characteristics were observed in TOF, aligning with the His bundle's anatomical course.
- The muscle of Lancisi (ML) or its equivalent (LES) was identified as a reliable landmark for the right bundle branch (RBB) course, aiding in surgical navigation.
Conclusions:
- The muscle of Lancisi (ML) or its equivalent (LES) can serve as a practical landmark for the right bundle branch (RBB) during congenital heart surgery.
- Utilizing these landmarks has led to a significant reduction in surgically induced complete right bundle branch block.
- Understanding variations in the conduction system's course is vital for refining surgical techniques and diagnostic accuracy.
Abstract:
Electrophysiological delineation of the specialized conduction system was performed under cardiotomy on 64 patients: 51 with ventricular septal defect (VSD), 11 with tetralogy of Fallot (TOF) and 2 with transposition of the great arteries (TGA, III). Some histological study was done for confirmation. In large VSD of type II or III, superficial location of the His bundle was shown by a tall H deflection recorded along the inferior rim, coinciding with a high incidence of conduction disturbance in this malformation. One characteristic in TOF was a deflection recorded along the posteroinferior rim rather exclusively on the left ventricular side, coinciding with the anatomic course of the His bundle. A deflection was frequently recorded at an area a few mm posterior to the muscle of Lancisi (ML) or the Lancisi equivalent structure (LES); it was relatively common in ordinary types of VSD, and presumed as the penetrating site of the right bundle branch (RBB) and/or near the bifurcated portion of the His bundle. The second portion of the RBB was not clearly delineated in general, particularly in TOF, but always found within the septomarginal trabecle when delineated. Our conclusion, together with histological study, was that one may use the ML or the LES as a rough marking for the course of the RBB. By this recognition, the surgically induced complete right bundle branch block has been diminished significantly. Variation of the course of conduction system as well as limits of this diagnostic measure are described herein.