Mapping of atrial activation patterns after inducing contiguous radiofrequency lesions: An experimental study

High resolution mapping techniques are used to analyze the changes in atria l activation patterns produced by contiguous RF induced lesions. In 12 Lang endorff-perfused rabbit hearts, left atrial activation maps were obtained b efore and after RF induction of epicardial lesions following a triple-phase sequential protocol: (phase 1) three separate lesions positioned verticall y in the central zone of the left atrial wall; (phase 2) the addition of tw o lesions loca ted between the central lesion and the upper and lower lesio ns; and (phase 3) the placement of four additional lesions between those in duced in the previous phases. In six additional experiments a pathological analysis of the individual RF lesions was performed. In phase 1 (lesion dia meter = 2.8 +/- 0.2 mm, gap between lesions = 3 +/- 0.8 mm), the activation process bordered the lesions line in two (250-ms cycles) and four experime nts (100-ms cycles). In phase 2, activation bordered the lesions line in ei ght (250-ms cycles, P < 0.01 vs control) and nine experiments (100-ms cycle s, P < 0.001), and in phase 3 this occurred in all experiments except one ( both cycles, P < 0.001 vs control). In the experiments with conduction bloc k, the increment of the interval between activation times proximal and dist al to the lesions showed a significant correlation to the length of the les ions (r = 0.68, P < 0.05, 100-ms cycle). in two (17%) experiments, sustaine d regular tachycardias were induced with reentrant activation patterns arou nd the lesions line. in conclusion, in this acute model, atrial RF lesions with intact tissue gaps of 3 mm between them interrupt conduction occasiona lly, and conduction block may be frequency dependent. Lesion overlap is req uired to achieve complete conduction block lines. Tachycardias with reentra nt activation patterns around a lesions line may be induced.