Surgical radiofrequency ablation induces coronary endothelial dysfunction in porcine coronary arteries

OBJECTIVES: Surgical radiofrequency ablation is increasingly used during open heart surgery for the treatment of chronic atrial fibrillation. The purpose of this study was to determine the effects of application of radiofrequency on coronary endothelial function and structure and establish the relationship between coronary lesions and distance of radiofrequency application. METHODS: Six Landrace swine (25.9+/-2.0 kg) were included in the study. With the heart kept beating, three epicardial radiofrequency lesions (20 W, 20 s duration, 60 degrees C) 2 cm in length each, were created 1, 5 and 10 mm away from the left anterior descending and the right coronary arteries. The circumflex artery served as control. Coronary rings were placed in organ chambers. After contraction to KCl and prostaglandin F2alpha, endothelium-dependent relaxations to bradykinin were studied. Gomori trichrome and hematoxylin-eosin safran staining were used for histological evaluation. RESULTS: Exposure to radiofrequency 1 mm from the coronary arteries caused a significant decrease in endothelium-independent contractions to KCl and endothelium-dependent relaxations to bradykinin compared to controls (P<0.05). No significant decrease of endothelium-dependent relaxations occurred for rings exposed to radiofrequency at a distance of 5 and 10 mm, compared to controls. Histological examination showed endothelial disruption and medial smooth muscle cells at different stages of necrosis up to 5 mm from the radiofrequency application site. CONCLUSIONS: Radiofrequency may induce coronary endothelial functional and morphological damages when applied less than 5 mm from the artery. Caution must be exerted during left atrial radiofrequency application due to the proximity of the circumflex artery.