Pathological effects of extensive radiofrequency energy applications in the pulmonary veins in dogs

Introduction-The long-term complications of catheter ablation within the pu lmonary veins are unknown. The development of pulmonary vein stenosis has r ecently been described after catheter ablation to treat either chronic or p aroxysmal atrial fibrillation, The purpose of this study was to examine the pathological and hemodynamic effects of radiofrequency (RF) energy applica tion within the pulmonary veins. Methods and Results-Right heart and transseptal catheterization were perfor med in 9 anesthetized mongrel dogs. The pulmonary vein ostia were cannulate d and pulmonary venous pressure was measured before RI; energy application in up to 4 separate pulmonary veins. Animals were euthanized at intervals o f 2 to 4 weeks (n=3), 6 to 8 weeks (n=3), or 10 to 14 weeks (n=3) after abl ation, Repeat catheterization before euthanasia demonstrated statistically significant differences in pulmonary capillary wedge pressure, cardiac outp ut, pulmonary vascular resistance, and systemic vascular resistance (P<0.05 ) compared with the baseline. Luminal narrowing was observed in 3,3 Of 33 p ulmonary veins to which RF energy was applied. Of these, 7 were totally occ luded, 7 had severe stenosis, and 8 were only minimally narrowed. Histologi cal examination revealed intimal proliferation with organizing thrombus, ne crotic myocardium in various stages of collagen replacement, endovascular c ontraction, and a proliferation of elastic lamina. Conclusions-Applications of RF current within the pulmonary veins may resul t in pulmonary vein narrowing or complete occlusion, These observations sho uld be considered in treatment of arrhythmias originating within the pulmon ary veins.