Histological findings induced by different energy sources in experimental atrial ablation in sheep

Abstract

The aim of this study was a detailed comparative investigation of acute cardiac alterations induced by different energy sources and approaches in a sheep model. Experiments were performed on 39 sheep. Circular lesions were created endo- or epicardially in the left atrium and at the pulmonary veins using different energy sources: cryo, microwave, laser and unipolar or bipolar radiofrequency (RF). Electrophysiological examinations were performed immediately post treatment and 2 h after ablation to prove conduction block. Altered areas of the atria and pulmonary veins were investigated histopathologically. Endocardial ablation resulted in transmural lesions, confirmed by electrophysiological examinations. However, endocardial microwave and laser induced intensive thrombus formation, whereas radiofrequency and cryoablation induced more circumscribed necrosis and led to little endocardial thrombi. Epicardial cryoablation and microwave energy were not successful in acute phase in 8 of 9 animals. In contrast, epicardial bipolar RF was efficient and resulted in well demarcated slim lesion lines but induced marked thrombus formation. It can be summarized that surgical ablation techniques using different energy sources and approaches in this acute animal model resulted in different electrophysiological effectiveness and histomorphological lesions. Further mid and long term studies are necessary to confirm these results.

Complete left atrial ablation with bipolar radiofrequency☆☆☆

“…The clamping design of bipolar devices clears out heat sink due to convective cooling exerted endocardially by circulating blood, thus rendering transmurality of the lines highly predictable after both epicardial and endocardial ablation [4,8,9,21]. Temperature or impedance feedback featured by bipolar radiofrequency devices improves the reproducibility of complete tissue penetration.…”

“…This is, on one hand, not costeffective especially in Europe where no reusable ablation device is available for cardiac use; on the other hand, ablations performed with any unipolar surgical device are not as reliably transmural as those achieved with bipolar radiofrequency [21]. In past years, we have also used a second unipolar radiofrequency device to complete the lesion set on the mitral annulus in a series of 33 patients undergoing bipolar ablation of the left atrium (control group), basically before devising a way to perform all the ablation with bipolar radiofrequency.…”

Histopathology of Bipolar Radiofrequency Ablation in the Human Atrium

“…These changes are known to resolve after ablation, conceivably allowing a return of conduction through the gaps. Bipolar RF energy has been found to have advantages over other energy sources for surgical ablation of the atria, as it is associated with less collateral damage to surrounding structures and has the ability to indicate when the lesion has reached transmurality [4,10].…”

“…Prior studies have reported the histopathology of the human and animal atria after surgical unipolar ablation as well as percutaneous unipolar RF catheter ablation [4][5][6][7]. To our knowledge, histopathologic effects of surgical bipolar RF ablation on human atria have not been reported.…”

Thermography in laser ablation control

“…Usage of cryoenergy is high effective, especially in atrial fibrillation correction procedures in pulmonary veins zone, but technically complicated and relatively expensive. Microwave weren't useful in clinical practice because of huge thrombogenesis, uneven endocardial lesions and high perforation rate [4] . In the 1980s, were developed and tested successfully laser ablation methodology [5,5] .…”