Abstract
Background: The purpose of this study was to test the feasibi-lity and effectiveness of cryoablation
therapy (SurgiFrost™ CryoCath, Endocare Inc., Irvine, California, USA) for linear
epicardial treatment of atrial fibrillation in an acute off-pump sheep model. Methods: After thoracotomy, we performed epicardial cryoablation (2 min intervals at - 160
°C) with pacing electrodes positioned at the left atrial appendage (LAA), the pulmonary
veins (PVs), the right atrial appendage (RAA), and the vena cava cranialis (VCC) in
8 sheep. Circular epicardial ablations were performed with online temperature measurement
in the ascending aorta and in the esophagus. The sheep were sacrificed two hours after
ablation procedure, and heart, lungs, and esophagus were retrieved for histological
examination. Out of all 8 sheep, histo-pathological analysis was performed on the
RAA and VCC in 6 sheep and on the CAA and PV in all 8 sheep. Results: Thin-walled structures such as PVs and VCC showed electrical isolation. No significant
changes in temperature in the descending aorta and the esophagus were observed. There
was evidence of extensive transmural alteration including vascular lesions, myocardial
degeneration and necrosis as well as epi- and endocardial necrosis in the left atria
in three of 8 cases, in the right atria in 5 of 6 cases, in the VCC in 6 of 6 cases,
and in the PV in 5 of 8 cases. Mild lesions of the muscular layer of the esophagus
were found in 7 of 8 cases. Conclusions: Epicardial cryoablation is not effective on thicker tissues like LAA and RAA due
to the rewarming of the current blood flow. However, thin tissues like VCC and PV
can be isolated. Further chronic studies are necessary to evaluate the potential for
regeneration of adjacent structures.
Key words
Cryoablation - atrial fibrillation - surgery
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Dr. Nicolas Doll
Heart Center, Department of Cardiac Surgery, University of Leipzig
Strümpellstrasse 39
04289 Leipzig
Germany
Fax: + 49-341-8651452
Email: dolln@medizin.uni-leipzig.de