Coagulum index predicts coagulum formation in right atrial radiofrequency energy delivery to ablate atrial fibrillation

An ongoing multicenter U.S. clinical study evaluates the safety and effecti veness of creating linear lesions with radiofrequency (RF) energy using (a 3.7 Fr microcatheter used with a 9 Fr steerable guiding catheter in the rig ht atrium CRA) to treat paroxysmal atrial fibrillation (PAF). Study entry c riteria were symptomatic, drug refractory PAF. RF energy was delivered in 6 0-second episodes at 30 W or 50 W power settings. Electrode tissue contact was ascertained by sharp electrograms of high amplitude. Coagulum Index (C. I.), a new calculation to predict the probability of coagulum development, was derived analytically from measurements of RF power, RF current, and tim e to reach maximum temperature in each ablation episode. The RF data from 3 98 separate ablation episodes in 15 patients were used to calculate C.I. Co agulum presence wets determined by postablation visual inspection of the mi crocatheter electrodes. A logistic model was used to estimate the probabili ty of coagulum occurrence, with C.I. as the predictive variable. When C.I. greater than or equal to 12, the probability of coagulum formation increase d significantly in this model (P < 0.0001). Prolonging the power delivery r ise time and limiting maximum RF power setting to 30 W effectively lowers C .I. and minimizes coagulum formation. These results should also apply to le ft atrium ablation, where minimizing coagulum formation may decrease the ri sk of stroke or mortality.