COMPARISON OF CATHETER ABLATION USING RADIOFREQUENCY VERSUS DIRECT-CURRENT ENERGY - BIOPHYSICAL, ELECTROPHYSIOLOGIC AND PATHOLOGICAL OBSERVATIONS

The effects of catheter ablation with radiofrequency versus direct current energy were compared in 18 dogs assigned to two groups (of 9 dogs each). Each dog underwent a single ablation at two sites in the left ventricle at energy levels of 100, 200 or 300 J delivered in unipolar configuration to six dogs each. A transient decrease in left ventricular systolic pressure (from 121.3 +/- 24.5 to 9.42 +/- 18.7 mm Hg, p < 0.01) and wall motion abnormality were noted in dogs with direct current shock. The left ventricular ejection fraction decreased (from 50 +/- 2% to 34 +/- 3%, p < 0.001) shortly after direct current ablation but improved 4 weeks later to 43 +/- 3%. There were no significant changes in left ventricular pressure, wall motion or ejection fraction in dogs in the radiofrequency ablation group. Sustained ventricular tachycardia (greater-than-or-equal-to 30 s) was seen immediately after direct current shock in all dogs, and one dog died of intractable ventricular fibrillation. A 24-h ambulatory electrocardiographic (ECG) monitor obtained immediately after the procedure showed multiple runs of ventricular tachycardia in all dogs exposed to direct current ablation but in only three dogs that underwent radiofrequency ablation. No differences were found in peak creatine kinase, complete blood count with smear and B-beta 15-42 fibrinopeptide levels. Pathologically, direct current-induced lesions were larger (mean length x width x depth 10.9 x 7.5 x 5.2 vs. 4.8 x 4.6 x 4.3 mm) and were poorly circumscribed with inhomogeneous margins of necrosis. Thus, compared with direct current ablation, radiofrequency current ablation created little ventricular dysfunction and fewer ventricular arrhythmias and induced more discrete and homogeneous necrosis with a smaller lesion size.