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Factors affecting the efficacy of epicardial ablation using a cooled radiofrequency device
Yoshiyuki Watanabe, Timo Weimar, Toshinobu Kazui, Richard B. Schuessler, Ralph J. Damiano, Jr..
Washington University in St. Louis, St. Louis, MO, USA.
OBJECTIVE: A single epicardial ablation with a cooled radiofrequency (RF) device (AtriCure Coolrail AtriCure, Inc.) does not reliably create transmural lesion on the beating hearts in an animal model. Unexpectedly, transmurality of the thin tissue of the superior and inferior vena cava (SVC/IVC) was lower than the other areas. This study examined the efficacy of repeated epicardial ablations and the effects of cavitary blood flow (CBF) on the transmurality in an acute animal model.
METHODS:Twelve domestic pigs underwent a median sternotomy. In six pigs two epicardial ablations for 40 seconds each were made at six left (LA) and right atrial (RA) sites. Two lesions were made on the RA: two on LA atrial free wall; and two lesions were created on the lateral wall of SVC/IVC. In an additional 6 pigs a single ablation was performed on each vena cava at 40 seconds with or without occlusion of the SVC/IVC. All lesions were stained with 1% 2,3,5- triphenyl-tetrazolium chloride and sectioned at 5-mm intervals perpendicular to the long axis of the lesion for measurement of a transmurality.
RESULTS:Mean tissue thickness was 2.74±1.95 mm (range: 0.49-12.1). The blood flow of the SVC was 2.0 ± 0.4 m/s, and the IVC was 7.2 ± 1.2 m/s. 76% (160/211) of the cross-sections were transmural and 54% (19/35) of the entire lesions were transmural with two ablations. The transmurality of the SVC/IVC (33/69; 48%) lesions were significantly lower than the LA (65/71; 92%, p<0.01) and the RA (61/71; 86%, p<0.01). Only the LA lesions had a higher transmurality with a second ablation (single 71% and two ablations 92%, p<0.05). Occlusion of the SVC or IVC resulted in a significantly high transmurality in the occlusion group (OC: 81%) compared to the non-occlusion group (NO: 24%, p<0.01). On thin tissue sections (<2mm), the transmurality was significantly different between two groups (OC 91% vs NO 42%, p<0.01).
CONCLUSIONS:Using the Coolrail, two ablations created more reliable transmural lesions than a single ablation on the LA of the beating hearts. CBF decreases the performance of this device in the thin tissue of SVC/IVC.
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