Is lone AF lonely yet? What about the atrial fibrosis in lone AF and implications on the cryoablation success?

Abstract

Purpose: Structural (atrial fibrosis), electrical and contractile remodelling play major role in the development of a vulnerable atrial substrate for AF. Serum transforming growth factor (TGF)-β1 is the key mediator and related to the degree of atrial fibrosis. Although pulmonary vein isolation (PVI) is an effective therapetic method to eliminate triggers in the pathogenesis, the impact of atrial substrate on the PVI success remains unclear. In this study, we aimed to investigate the relation of serum TGF-β1 level and degree of left atrium (LA) fibrosis using delayed-enhanced magnetic resonance imaging (DE-MRI) and effects on the success of PVI in patients with lone paroxysmal AF. Methods: A total of 41 symptomatic lone paroxysmal AF patients (24 male, 58.5%; mean age: 49.2±7.6 years) underwent cryoballoon based catheter ablation. Cardiac DE-MRI to quantify atrial fibrosis, serum TGF- β1 levels, clinical and echocardiographic data were collected before cryoballoon ablation. Postablation blanking period was observed for 3 months. Results: Duration of the AF symptoms was median 60 months and mean EHRA score was 3.0±0.55. Mean LA anteroposterior diameter was 37.4±3.3 mm in all patients. DE-MRI revealed left atrial fibrosis in 27 (65.9%) patients [13 (31.7%) mild, 9 (22%) moderate and 5 (12.2%) severe fibrosis] with the median enhancement of 5% of the LA. At a median follow-up time of 18 months, 32 patients (78.1%) remained free of AF recurrence. While only serum TGF-β1 level (p=0.008) found as the predictor of the presence of LA fibrosis; both serum TGF-β1 level (p=0.001) and duration of AF episode (p=0.001) were found as the predictors of the extent of LA fibrosis. In multivariate cox regression analysis, extent of the LA fibrosis (p= 0.007) and early AF recurrence (p= 0.011) were found as the independent predictors of AF recurrence. Serum TGFβ-1 level of >15.894 pg/mL predicted the presence of LA fibrosis with a sensitivity of 70.37% and specificity of 100%. Also LA fibrosis extent of >20% predicted the development of AF recurrence with sensitivity of 100% and specificity of 93.75%. Conclusion: LA fibrosis determined by DE-MRI and increased serum TGFβ-1 level play major role in LA structural remodelling and has an impact on the success of PVI. Presence and extent of LA fibrosis using DE-MRI may help select appropriate patients for catheter based AF ablation and improve procedural outcome.