Using a novel graded outcomes scale, the investigators evaluated whether left atrial (LA) volume measured by cardiac computed tomographic angiography is a predictor of pulmonary vein isolation success in patients with nonparoxysmal atrial fibrillation (AF) and paroxysmal AF (PAF). Data from 45 patients who underwent electrocardiographically gated computed tomographic angiography before pulmonary vein isolation for AF were used. LA volume was measured in the ventricular systolic and diastolic phases, defined as 40% and 75% of the interval between consecutive R waves. Outcomes were graded at 0 to 3, 3 to 6, 6 to 12, and 12 to 24 months after pulmonary vein isolation and scored on a 5-point scale: 1 = no AF recurrence off antiarrhythmic drug, 2 = no AF recurrence on antiarrhythmic drug, 3 = rare AF (<1 episode in 3 months), 4 = asymptomatic recurrent AF, and 5 = no reductions in AF frequency or severity. LA volumes were significantly larger in the nonparoxysmal AF group compared with the PAF group in systole (159.2 vs 128.2 ml, p <0.001) and diastole (137.1 vs 104.0 ml, p <0.001). In patients with PAF, larger LA volume was correlated with worse clinical outcomes in the first 12 months, but the results did not reach statistical significance (systole r = 0.25 to 0.41, diastole r = 0.20 to 0.34). In conclusion, these results show a significant difference in LA volume in patients with nonparoxysmal AF and PAF in systole and diastole. Additionally, there was a correlation between LA volume and clinical outcomes in patients with PAF, although this did not reach statistical significance.