Acute and Chronic Effects of Epicardial Radiofrequency Applications Delivered on Epicardial Coronary Arteries

Abstract

Background-Epicardial coronary injury is by far the most feared complication of epicardial ablation. Little information is available regarding the chronic effects of delivering radiofrequency in the vicinity of large coronary vessels, and the long-term impact of this approach for mapping and ablation on epicardial vessel integrity is poorly understood. Therefore, the aim of this study was to characterize the acute and chronic histopathologic changes produced by in vivo epicardial pulses of radiofrequency ablation on coronary artery of porcine hearts. Methods and Results-Seven pigs underwent a left thoracotomy. The catheter was sutured adjacent to the left anterior descending artery and left circumflex artery, and 20 pulses of radiofrequency energy were applied. Radiofrequency lesions located no more than 1 mm of the vessel were used for this analysis. Three animals were euthanized 20 days (acute phase) after the procedure and 4 animals after 70 days (chronic phase). The following parameters were obtained in each vessel analyzed: (1) internal and external perimeter; (2) vessel wall thickness; (3) tunica media thickness, and (4) tunica intima thickness. The presence of adipose tissue around the coronary arteries, the distance between the artery and the epicardium, and the anatomic relationship of the artery with the coronary vein was also documented for each section. Sixteen of 20 (80%) sections analyzed, showed intimal thickening with a mean of 0.18Ϯ0.14 mm compared with 0.13Ϯ0.16 mm in the acute phase (Pϭ0.331). The mean tunica media thickness was 0.25Ϯ0.10 mm in the chronic phase animals compared with 0.18Ϯ0.03 mm in the acute phase animals (Pϭ0.021). A clear protective effect of pericardial fat and coronary veins was also present. A positive correlation between depth of radiofrequency lesion and the degree of vessel injury expressed as intimal and media thickening (Pϭ0.001) was present. A negative correlation was identified (rϭϪ0.83; Pϭ0.002) between intimal thickening and distance between epicardium and coronary artery. Conclusions-In this porcine model of in vivo epicardial radiofrequency ablation in proximity to coronary arteries leads to acute and chronic histopathologic changes characterized by tunica intima and media thickening, with replacement of smooth muscle cells with extracellular matrix, but no significant stenosis was observed up to 70 days after the ablation. The absence of acute coronary occlusion or injury does not preclude subsequent significant arterial damage, which frequently occurs when epicardial radiofrequency applications are delivered in close vicinity to the vessels. (Circ Arrhythm Electrophysiol. 2011;4:526-531.)

Chronic Left Coronary Artery Stenosis After Radiofrequency Ablation of Idiopathic Premature Ventricular Contraction Originating From Left Coronary Sinus Cusp

“…In a porcine model, RF ablation proximal to the coronary arteries led to chronic histopathologic changes, characterized by tunica intima and media thickening with replacement of the smooth muscle cells with extracellular matrix; however, no significant stenosis was observed up to 70 days after ablation. 5 In the present study, significant LMCA and LAD stenoses developed 4 months after RF ablation. Intravascular ultrasound showed positive remodeling characteristics in the LAD lesion.…”

Characterization of Catheter–Tissue Contact Force During Epicardial Radiofrequency Ablation in an Ovine Model

“…17 Several studies have demonstrated that acute vascular wall changes, including endothelial disruption, neointimal thickening, and intravascular thrombosis, occur when delivering RFA in the vicinity of a coronary artery with risk of chronic vascular damage inversely proportional to vessel size. 19,20 Moreover, more significant changes were noted to only occur in vessels of small calibre with the suggestion that larger vessels are protected from such changes due to greater blood flow. 13 RF application over or immediately adjacent to a coronary artery is best avoided, and based on our data, coronary injury is greater when CF is high.…”

Epicardial Interventions in Electrophysiology

“…Viles-Gonzalez and co-workers delivered RF lesions within 1 mm of the coronary arteries in seven pigs, and examined the acute (20 days) and chronic (70 days) effects. 103 In both the acute and chronic specimens, intimal and medial thickening was seen, with replacement of smooth muscle cells by extracellular matrix. No significant stenosis was observed up to 7 days after ablation.…”