Low-power radiofrequency application and intracardiac echocardiography forcreation of continuous left atrial linear lesions

Prediction of Left Atrial Linear Lesions; Introduction: Continuity bf radio frequency (RF) lesions for a catheter-based cure of atrial fibrillation is essential in order to avoid reentrant tachycardias. In the present study, w e assessed the value of intracardiac echocardiography and preablation elect rode-tissue interface parameters for creation of left atrial linear lesions . Methods and Results: In six healthy dogs, two left atrial linear lesions (l esion 1, along the inferior posterior left atrium; lesion 2, from the appen dage to the left atrial roof) were attempted via a transseptal approach usi ng a deflectable catheter with six 7-mm coil electrodes, In a randomized fa shion, one lesion was performed under echocardiographic guidance and one wi th blinded echocardiographic monitoring. The following preablation paramete rs were assessed for every coil electrode: (1) mean atrial electrogram ampl itude of six consecutive sinus beats; (2) diastolic pacing threshold; and ( 3) temperature response to application of 5 W for 10 seconds. After ablatio n (target temperature 70 degrees C, maximum power 50 W, duration 60 sec), t he excised left atrium was examined macroscopically and histologically for lesion length, continuity, and presence or absence of lesions associated wi th each coil. Out of 12 attempted RF lesions, 7 were continuous (length, 47 +/- 5 mm, les ion 2, n = 6) and 5 were discontinuous (lesion 1, n = 5). Fifty-two of 70 c oil electrodes (74%) had pathologic evidence of lesion creation. Intracardi ac echocardiography was superior to fluoroscopy with respect to the actual number of coil electrodes creating lesions, and lesion continuity was corre ctly predicted in 9 of 12 lesions. Intracardiac echocardiography was 85% se nsitive and 54% specific in predicting lesions created by individual coils. The correlation between the mean 60-second ablation temperature and the pr eablation parameters was 0.45 for the electrogram amplitude, -0.67 for the pacing threshold, and 0.81 for the temperature response to low-power applic ation. Sensitivity and specificity for prediction of lesions created by ind ividual coils, respectively, were 84% and 48% for the electrogram amplitude , 90% and 68% for the pacing threshold, and 96% and 76% for the low-power R F application. Conclusion: Long linear lesions can be safely and effectively performed in the canine left atrium, using a tip-deflectable multielectrode catheter. In tracardiac echocardiography may be helpful for positioning the ablation cat heter in some parts of the left atrium, and preablation parameters, especia lly a nontraumatic low-power RF application, are able to predict ultimate l esion creation with high accuracy. (J Cardiovasc Electrophysiol, Vol. 10, p p. 680-691, May 1999).