Transforming Growth Factor-(1) and Atrial Fibrillation IntroductionTransforming growth factor-(1) (TGF-(1)) is an important factor that induces atrial fibrosis and atrial fibrillation (AF). The purpose of this study was to evaluate the association between TGF-(1) level and clinical factors before catheter ablation (CA), and to investigate the impact of TGF-(1) level on the outcome after CA for AF. Methods and ResultsThis prospective study included 151 patients (persistent AF group: n = 59, paroxysmal AF [PAF] group: n = 54, and control group: n = 38). All patients who underwent CA for AF were followed up for 12 months. The PAF group had the highest TGF-(1) levels in all patients. An early recurrence of AF (ERAF: defined as episodes of atrial tachyarrhythmia within a 3-month blanking period) was detected in 60 patients (53%). Recurrent AF after the blanking period was detected in 36 patients (32%). On multivariate analysis, low TGF-(1) level was the only independent factor associated with recurrent AF. Moreover, the AF recurrence ratio was higher in the low TGF-(1) group (< 12.56 ng/mL) than in the high TGF-(1) group (16 of 29 patients, 55% vs. 20 of 84 patients, 24%, P = 0.002 by log-rank test). ConclusionsPAF was associated with a higher TGF-(1) level. Moreover, lower TGF-(1) level in AF patients could be a cause of recurrent AF after CA.