title: Pathological aspects of radiofrequency catheter ablation of the canine atrioventricular node and bundle of His. With special reference to chronic incomplete atrioventricular block.
abstract: Radiofrequency catheter ablation of the atrioventricular (AV) node or bundle of His was performed in 12 adult mongrel dogs. The aim was to create chronic incomplete AV block (first- and second-degree AV block) and to examine the histopathology of the ablated lesions. However, the late electrophysiological results (2-4 weeks follow-up) were various: normal in 2 dogs, mild PR prolongation (less than 50%) in 2 dogs, first-degree AV block (PR prolongation greater than or equal to 50%) in 2 dogs, second-degree AV block in 2 dogs, complete AV block in 4 dogs. The maximally ablated area (%) of the atrioventricular conduction system in serial histologic sections from dogs with these conditions was 69%, 75%, 89.5%, 95% and 99.5%, respectively. The number of intact conduction cells at the maximally ablated site varied from 6 to 30 in the four cases of incomplete AV block. The mean ablated volume (%) of either the AV node or penetrating His bundle correlated roughly with the degree of AV block. The ablated lesions were well demarcated and almost replaced by dense fibrous tissue at 4 weeks. Interruption (3 dogs) or thinning (1 dog) of the endocardial elastic lamellae was detected, in association with endocardial thickening (mean 913 microns). Endocardial thrombi were found in 3 dogs (2 fresh, 1 organized). We conclude that radiofrequency catheter ablation does not cause severe complicated lesions. Several possible conditions for creating chronic incomplete AV block are discussed.
authors.affiliation: Department of Pathology, Tokyo Metropolitan Hiroo General Hospital, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Tanaka
authors.forename: S
authors.initials: S
authors.lastname: Satake
authors.forename: Y
authors.initials: Y
authors.lastname: Kawahara
authors.forename: M
authors.initials: M
authors.lastname: Sugiura
authors.forename: K
authors.initials: K
authors.lastname: Hirao
authors.forename: K
authors.initials: K
authors.lastname: Tanaka
authors.forename: T
authors.initials: T
authors.lastname: Kawara
authors.forename: A
authors.initials: A
authors.lastname: Masuda
authors.forename: T
authors.initials: T
authors.lastname: Nishikawa
authors.forename: T
authors.initials: T
authors.lastname: Kasajima
mesh_terms: D000818:Animals; D001283:Atrioventricular Node / Q000473:pathology*; D002036:Bundle of His / Q000473:pathology*; D002908:Chronic Disease; D004285:Dogs; D004564:Electrocoagulation; D004594:Electrophysiology; D006327:Heart Block / Q000473:pathology* / Q000503:physiopathology; D011846:Radio Waves