High-resolution mapping and histologic examination of long radiofrequency lesions in canine atria.
BACKGROUND
Catheter ablation may prevent conduction of multiple atrial wavefronts and/or reduce the critical mass of atrial myocardium required to sustain fibrillation. The purpose of this study was to examine the effect of radiofrequency (RF) energy application on conduction in canine atria by performing high-density epicardial mapping and careful histologic examination of the ablation zone.


RESULTS
RF energy was applied to the right atrial endocardium in nine anesthetized mongrel dogs in an attempt to create a line of conduction block spanning the vertical length of a 504-channel epicardial mapping plaque. The mean length and width of the histologically determined ablation zone was 34 +/- 4 and 7.3 +/- 2.6 mm, respectively. No thrombus was present. Conduction block that spanned the mapping plaque in 6 of 9 animals was matched histologically by continuous transmural necrosis in five. In one, only a portion of the ablation zone was transmural; the remainder was wide but nontransmural. In 2 of 3 animals with conduction, a narrow region was present where continuous transmural necrosis was absent. In the other animal, conduction was present despite continuous transmural necrosis.


CONCLUSIONS
Conduction block usually occurred when continuous transmural necrosis was present, and conduction usually persisted when continuous transmural necrosis was absent. However, important exceptions were observed, including block when the ablation zone was wide but nontransmural, and conduction despite a thin line of continuous transmural necrosis.
Taylor
G W
GW
Department of Medicine, University of Alabama at Birmingham 35294-0019, USA.
Walcott
G P
GP
Hall
J A
JA
Bishop
S
S
Kay
G N
GN
Ideker
R E
RE
D000818:Animals; D016275:Atrial Function; D002304:Cardiac Pacing, Artificial; D006348:Cardiac Surgical Procedures; D017115:Catheter Ablation; D004285:Dogs; D004699:Endocardium / Q000601:surgery*; D005260:Female; D006327:Heart Block / Q000473:pathology; D006329:Heart Conduction System / Q000503:physiopathology; D008297:Male; D009206:Myocardium / Q000473:pathology*; D009336:Necrosis