Anatomy Relevant to Conduction System Pacing and Identifying the Level and Extent of Block
Raja Selvaraj
Professor of Cardiology
JIPMER
Overview
- Anatomy relevant to conduction system pacing
- Level and extent of block in LBBB
Late 19th Century - Kent vs His
- His W, Jr. Die Thätigkeit des embryonalen Herzens und deren Be-
deutung für die Lehre von der Herzbewegung beim Erwachsenen. Arb aus d med Klinik zu Leipzig 1893; 1:14–49.
- Kent AFS. Researches on the structure and function of the mam-
malian heart. J Physiol 1893; 14:233–254.
AV conduction axis
Triangle of Koch
Variable location of compact AVN
Cabrera J-Á, Anderson RH, Macías Y, et al. Variable Arrangement of the Atrioventricular Conduction Axis Within the Triangle of Koch: Implications for Permanent His Bundle Pacing. JACC Clin Electrophysiol. 2020;6(4):362-377.
Penetrating bundle - TV septal leaflet
Cabrera J-Á, Anderson RH, Macías Y, et al. Variable Arrangement of the Atrioventricular Conduction Axis Within the Triangle of Koch: Implications for Permanent His Bundle Pacing. JACC Clin Electrophysiol. 2020;6(4):362-377.
Longitudinal dissociation
Fine Structure of the His Bundle By THOMAS N. JAMES, M.D., AND LIBi SHEiw, M.D. Cifculation, Volume XLIV, July 1971
Branching bundle
Left bundle branch and fascicles
LBB - variability
Demoulin JC, Kulbertus HE. Histopathological examination of concept of left hemiblock. Br Heart J. (1972) 34:807–14
LBBB - Level and extent
"Incomplete LBBB"
How complete is LBBB ?
Barrett PA, Yamaguchi I. Jordan JL, et al. Electrophysiologicalfactors of left bundle-branch block. Br Heart J 1981;45:594-60 I
Level of block
Upadhyay GA, Cherian T, Shatz DY .. Roderick Tung. Intracardiac Delineation of Septal Conduction in Left Bundle-Branch Block Patterns. Circulation 2019;139:1876-88
Level of block
- Localized conduction block - 64%
- Within His bundle - 72%
- Proximal left bundle - 28%
- Intraventricular conduction delay with intact purkinje activation - Others
- Those with proximal CCB responded to HBP
Upadhyay GA, Cherian T, Shatz DY .. Roderick Tung. Intracardiac Delineation of Septal Conduction in Left Bundle-Branch Block Patterns. Circulation 2019;139:1876-88
Level of block determines correction with HBP
Identification with ECG
Activation after LBB transection
VENEROSE RS, SEIDENSTEIN M, STUCKEY JH, HOFFMAN BF. Activation of subendocardial Purkinje fibers and muscle fibers of the left septal surface before and after left bundle branch block. Am Heart J. 1962 Mar;63:346-61
Multilevel block - transseptal, endocardial, transmural
Characterization of Left Ventricular Activation in Patients With Heart Failure and Left Bundle-Branch Block. Angelo Auricchio et al. Circulation. 2004;109:1133–1139
Functional block due to wavefront propagation ?
Characterization of Left Ventricular Activation in Patients With Heart Failure and Left Bundle-Branch Block. Angelo Auricchio et al. Circulation. 2004;109:1133–1139
Practical Implications
- Anatomy
- More important for HBP
- Level of block
- Explains why HBP works
- LBP advantages over HBP
- Distal block
- Proximal LBP may not correct in all
- Additional CS lead ?