Creation of isthmus lesions with a novel sliding electrode
Betts TR., Gallgher PJ., Morgan JM.
Simple and rapid achievement of permanent bi-directional conduction block in the tricuspid valve annulus (TVA)-inferior vena cava isthmus is desired for successful cure of common atrial flutter. Procedural failure may occur from incomplete ablation lines (a result of the uneven isthmus contour and difficulty in ensuring lesion continuity). We report the use of a novel sliding electrode for creation of transmural isthmus lesions. Methods: The sliding catheter consists of a coaxially moving ovoid electrode (able to achieve close isthmus contact whatever its contours) and a flexible "annular hook" for TVA anchorage. In 6 anaesthetised pigs bi-directional isthmus conduction was recorded before and after lesion creation. After securing the catheter tip, radiofrequency (RF) energy was applied for 20-30 seconds with a target temperature of 65°C. Starting at the TVA, the sliding electrode was moved in 2mm increments and RF energy applied until fluoroscopy and contact electrograms confirmed the electrode was in the IVC. Bi-directional conduction block was then assessed. If isthmus conduction was still present a second sequence was performed in the same position. The hearts were excised and examined macroscopically for lesion size and presence of coagulum and microscopically for lesion depth. Results: Complete bi-directional isthmus block was achieved in 5/6 animals after a median of 6 (range 5-8) RF applications taking 12+/-3.2 minutes. One animal required two sequences. 1 pig had a small visible gap at the TVA due to the distal margin of the sliding electrode tract being too far from the annular hook. This design fault was subsequently corrected. Excessive coagulum was seen in one animal where 2 sequences of 30-second burns were applied. One sequence of 20-second burns is enough to create complete isthmus block. Macroscopically the lesions were discrete, narrow and continuous. Histological examination confirmed lesion transmurality Conclusion: This novel sliding electrode is capable of performing discrete, transmural isthmus lesions both rapidly and efficiently. Electrode geometry and sliding mechanism ensure lesion continuity and depth.