Experimentelle Untersuchungen zur chirurgischen Therapie des Vorhofflimmerns am Tiermodell Schaf

Zusammenfassung

Gegenstand und Ziel: Vorhofflimmern ist die häufigste Ursache für kardiale Arrhythmien beim Menschen. Die Erzeugung zirkulärer transmuraler Läsionen mittels verschiedener Energieformen dient der elektrischen Isolation der autonomen Foci. Ziel der Studie war daher, am Tiermodell Schaf die Effektivität und die Risiken verschiedener Ablationstechniken systematisch zu vergleichen. Material und Methoden: Bei 39 Merinoschafen wurden zirkuläre Läsionen im Bereich des linken Atriums und der Pulmonalvenen erzeugt. Kryotechnik (n = 12), Mikrowellen (n = 9), Laser (n = 6) sowie unipolare (n = 6) und bipolare (n = 6) Hochfrequenz (HF) wurden von endokardial bzw. von epikardial eingesetzt und die Temperatur im Lumen des Ösophagus gemessen. Elektrophysiologische Untersuchungen unmittelbar sowie zwei Stunden nach der Ablation dienten dem Nachweis der erfolgreichen Reizleitungsblockade. Repräsentative Proben von linkem Atrium, Pulmonalvenen und Ösophagus wurden histopathologisch untersucht. Ergebnisse: Alle endokardialen Ablationstechniken führten zu elektrophysiologisch effektiven transmuralen Nekrosen. Im Gegensatz zu Kryoablation und unipolarer HF erzeugten Mikrowellen- und Laserenergie starke Thromben. Die epikardiale Ablation mit Kryotechnik und Mikrowellen war in acht von neun Fällen nicht effektiv, während die bipolare HF zu effektiven transmuralen Läsionen, jedoch mit deutlichen Thromben führte. In 24 von 39 Fällen wurden histologisch auch Alterationen des Ösophagus nachgewiesen. Insbesondere von endokardial applizierte unipolare HF und Kryotechnik führten zu Nekrosen der Ösophaguswand. Schlussfolgerung: Epikardial applizierte bipolare HF war das Verfahren zur Vorhofablation, das von den getesteten Methoden die geringsten Risiken der Ösophagusperforation bei bester Effektivität der Ablation aufwies. Diese Ergebnisse aus den Akutversuchen sollten jedoch noch in Langzeitversuchen überprüft werden.

Summary

Objective: Atrial fibrillation is a common cause of cardiac arrhythmia in humans. Creation of circular transmural lesions by the use of different energy sources results in the insulation of autonomous focal triggers or macro re-entry circuits. The aim of this study was the evaluation of the effectiveness and risks of various ablation methods in a sheep model. Material and methods: Experiments were performed in 39 Merino sheep. Circular lesions were created endo- and epicardially in the oesophagus, left atrium and pulmonary veins using different energy sources: Cryo (n = 12), microwave (n = 9), laser (n = 6), unipolar radiofrequency (RF) (n = 6) and bipolar RF (n = 6). The temperatures inside the oesophagus were measured. Electrophysiological examinations were performed post treatment and two hours after ablation to prove the conduction block. Specimens of the atria and pulmonary veins were investigated histopathologically. Results: Endocardial ablation resulted in transmural lesions, confirmed by electrophysiological examinations in all cases. In contrast to cryoablation and unipolar RF, microwave and laser induced intensive endocardial thrombus formation. Epicardial cryoablation and microwave energy were not successful in eight of nine animals. However, epicardial bipolar RF was efficient but induced marked thrombi. In 24 of 39 sheep alterations of the oesophagus were detected histologically. Especially endocardial unipolar RF and cryoablation induced necroses of the oesophagus wall. Conclusion: Epicardial bipolar RF was the method in our study, which resulted in best effectiveness of ablation and smallest risk of oesophagus perforation. Further mid- and long-term studies are necessary to confirm these results.

Schlüsselwörter

Vorhofflimmern - atriale Ablation - Tiermodell - Schaf

Keywords

Atrial fibrillation - atrial ablation - animal model - sheep

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