LINEAR ATRIAL ABLATIONS IN A CANINE MODEL OF CHRONIC ATRIAL-FIBRILLATION - MORPHOLOGICAL AND ELECTROPHYSIOLOGICAL OBSERVATIONS

Background - To test the hypothesis that susceptibility to sustained a trial fibrillation may be decreased by creation of linear atrial ablat ions, we established a canine model of chronic atrial fibrillation and used a novel catheter design to create atrial ablations. Methods and Results - Chronic atrial fibrillation was induced in 16 dogs by creati on of mitral regurgitation and rapid pacing of the atria, Temperature- controlled radiofrequency ablations were attempted along empirically d erived, preselected atrial target sites in 11 dogs (ablation group), a nd a sham procedure was performed in 5 dogs (control group). Follow-up electrophysiology study and pathological examination were conducted 1 3 +/- 5 days after the initial procedure Immediately after ablation, s ustained atrial fibrillation could be initiated in 1 of 9 surviving ab lation dogs and 5 of 5 controls (P = .004), Four dogs died within 24 h ours of the procedure. Permanent pacing was required in 4 dogs. At fol low-up, 0 of 7 ablation dogs and 5 of 5 controls had atrial fibrillati on ( P = .001). Furthermore, 2 of 7 ablation dogs had sustained atrial tachycardias, one of which was successfully ablated. Pathological exa mination demonstrated frequent incomplete lesion sets and discontinuou s lesions. Conclusions - In this model, a reduction in the susceptibil ity to sustained atrial fibrillation can be achieved by long linear at rial ablations created with specially designed coil electrode catheter s. Complete lesion continuity was not required to achieve a therapeuti c effect.