Do surgical clips interfere with radiofrequency thermal ablation?

OBJECTIVE. This study sought to evaluate whether surgical clips affect tissue conductivity and thereby alter the induction of radiofrequency ablation lesions and to determine whether therapy is safe after previous placement of clips in the liver. MATERIALS AND METHODS. An ex vivo porcine hepatic model was used. Three clips were placed around a radiofrequency electrode at 10, 20, and 30 mm from the point of insertion. Clips were arranged in a plane either perpendicular or parallel to the electrode track. After placement of the liver specimen on a grounding pad, radiofrequency energy was applied in a standardized manner for 5 min. Lesion growth and morphology were documented for each minute. RESULTS. Radiofrequency lesions appeared circular and homogeneous after 5 min. Lesion diameter perpendicular to the radiofrequency electrode averaged 30 mm. However, lesion formation was irregular during the early phase of the radiofrequency ablation. The lesion extended irregularly toward the 1-cm clip after 60 sec of ablation. During the second minute, a distinct lesion was observed around the clip 1 cm from the electrode; the primary lesion had not yet reached the clip. During the final 3 min, the primary lesion reached the 1-cm clip and ultimately incorporated the satellite lesion. No lesions were detected surrounding the more distant clips. CONCLUSION. Our data suggest that with the parameters applied in our study, radio-frequency ablation can be safely performed in patients with implanted clips. No aberrant conduction is observed around surgical clips that are located 20 mm and further from the radiofrequency electrode.