[Efficacy and safety of various energy sources and application techniques for the surgical treatment of atrial fibrillation]. / Experimentelle Evaluierung verschiedener Energiequellen und Applikationsverfahren zur chirurgischen Therapie des Vorhofflimmerns.

We investigated efficacy and safety of different energy sources and application techniques for the treatment of atrial fibrillation in an experimental acute sheep model. In particular, we focused on thermal damage to the adjacent structures and tissues. We also attempted to evaluate the efficacy of different application techniques such as endocardial or epicardial approaches. Overall 64 young Merino sheep were examined. It could be shown that endocardial ablation with different energy sources on cardiopulmonary bypass consistently caused histomorphologically and electrophysiologically transmural lesions. Depending on the energy source, different amounts of endocardial damage were induced. Cryoapplication produces the smallest endocardial laceration without thrombus formation. Dry radiofrequency energy and microwave produced very wide and diffuse endocardial damage with carbonisation and disruption of the endothelium. Epicardial ablation on a beating heart (off-pump) with bipolar radiofrequency was consistently effective. Due to the energy flow between the two jaws of the bipolar clamp, no collateral damage was observed. All other energy sources were unable to produce transmural lesions epicardially (off-pump) because the nearby blood flow rewarmed or recooled the myocardium and caused the so called "heat sink phenomenon". Depending on the energy source, different histomorphological changes in the esophagus could be observed. Changes in intraluminal-measured esophageal temperatures were not observed during ablation.