Figure 1
![Figure 1](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2F1471-2482-14-32/MediaObjects/12893_2013_Article_473_Fig1_HTML.jpg)
Radiofrequency ablation by a urine catheter-guided bipolar radiofrequency clamp technique. (A) Left and right pulmonary veins were separated and circled with a urine catheter. (B) The bipolar radiofrequency clamp arm was inserted into the catheter. (C) The bipolar radiofrequency clamp was directed by the catheter to go through the back wall of the left and right pulmonary veins. Then the circled ablation of the pulmonary veins was performed. (D) Diagram of surgery shown in A. (E) Diagram of surgery shown in B. (F) Diagram of surgery shown in C.