Thrombus apposition on catheter ablation injuries

64 ablation catheter-induced injuries were studied macroscopically and microscopically to determine the incidence of endocardial thrombus formation. Ablation was performed in 16 mongrel dogs, 7 days before necropsy, 16 endocardial necroses were located in the right atrioventricular (AV) junction, 16 in the non-coronary cusp of the aortic valve or the subaortic valve area, 16 in the right and 16 in the left ventricle. Cathodal discharge at the distal electrode was employed against an external anodal plate for ventricular ablation. Necroses in the right AV junction and in the aortic area where the result of transseptal His bundle ablation. Energies ranged from 100–360 J. Pathologic examination was performed 1 week after ablation. 13 thrombi were observed attached to the endocardial necrosis area, of sizes ranging from 1–25 mm diameter (mean 6.9 mm). Six thrombi were found in the septal valve of the tricuspid valve, two in the aortic valve, two in the subaortic region, and three related to ventricular necroses. We conclude that the incidence of thrombosis is 20% in ablation injuries, the majority, 77%, having a diameter ≤ 10 mm. No correlation was found between thrombus formation and delivered energy or catheter polarity.