Preprocedural Clinical Parameters Determining Perimitral Conduction Time During Mitral Isthmus Line Ablation

BACKGROUND—Achievement of complete conduction block across left mitral isthmus (MI) is challenging. Anticipation of perimitral conduction time (PMCT) associated with MI block may expedite this procedure. We evaluated the relationship between the preprocedural variables and the quantum of PMCT in patients with bidirectionally blocked MI. METHODS AND RESULTS—We reviewed clinical and echocardiographic parameters in 290 consecutive patients with confirmed bidirectional MI block during atrial fibrillation (AF) ablation. PMCT was defined as the temporal delay to the latest of the double potentials on the line of block while pacing posteroseptal to it in the left atrium (LA). LA size and type of AF significantly influenced PMCT in multivariate analysis. A cumulative score based on LA size (0≦45 mm; 1>45 mm) and type of AF (0paroxysmal; 1=nonparoxysmal) ranged from 0 to 2. PMCT was directly correlated to the cumulative score (0169 ms; n=78; 95% confidential interval, 156 to 181); 1187 ms; n=103; 95% confidential interval, 178 to 196; 2209 ms; n=109; 95% confidential interval, 200 to 217). In 61 patients who underwent AF ablation twice, the difference between 2 PMCT values was