Electrophysiological Effects of Long, Linear Atrial Lesions Placed Under Intracardiac Ultrasound Guidance

BACKGROUND: A curative atrial fibrillation procedure will most likely rely on creating transmural linear ablative lesions. However, it is currently unknown whether endocardial radiofrequency lesions can create lines of conduction block. METHODS AND RESULTS: In six pigs, intracardiac echocardiography was used to guide the positioning of multiple coil array catheters to bridge endocardial structures in three right atrial locations: (1) from the crista terminalis to the tricuspid annulus; (2) from the fossa ovalis to the crista terminalis; and (3) from the inferior vena cava to the tricuspid annulus. Once the catheter was positioned, linear lesions were made by radiofrequency energy applied sequentially to each of the four coils. After 15 days, the chest was opened and a 112-electrode epicardial plaque was positioned over the atrial free wall lesion to determine activation patterns. Three lesions were placed in each animal, with a mean procedure time of 47+/-11 minutes. Once adequate contact was determined by intracardiac echocardiography, a single series of radiofrequency application was required to achieve tissue heating (65+/-4 degrees C) with a power of 21+/-10 W. Epicardial mapping demonstrated complete conduction block across the lesions in all animals, with split potentials and disparate activation times (64+/-16 ms) across the lesion. At autopsy, all lesions were discrete, continuous, and without evidence of charring. The lesions were within 0.3+/-0.5 mm of their targeted anatomic locations and measured 21+/-4 mm long and 2.8+/-0.6 mm wide. Histology revealed transmural fibrosis throughout the length of each lesion. CONCLUSIONS: Linear lesions that are electrophysiologically transmural and continuous can be placed in the right atrium of normal pigs. With intracardiac echocardiography, adequate tissue contact over several coil electrodes can be ensured, resulting in short procedure times, efficient energy application, and accurate anatomically linked lesion placement.