A prospective DE-MRI study evaluating the role of TGF-β1 in left atrial fibrosis and implications for outcomes of cryoballoon-based catheter ablation: new insights into primary fibrotic atriocardiomyopathy.

BACKGROUND: Transforming growth factor (TGF)-β1 mediated atrial fibrosis plays a major role in the development of vulnerable atrial substrate for atrial fibrillation (AF). Although cryoablation effectively eliminates the triggers for AF, the impact of atrial substrate on the success of cryoablation remains unclear.
OBJECTIVE: We aimed to investigate the association of plasma TGF-β1 level with extent of left atrium (LA) fibrosis using delayed-enhanced magnetic resonance imaging (DE-MRI) and also effects of LA fibrosis on the success of cryoablation.
METHODS: A total of 41 symptomatic lone paroxysmal AF patients (58.5% male; age: 49.2 ± 7.6 years) underwent initial cryoablation. Cardiac DE-MRI at 1.5-Tesla scanner to quantify atrial fibrosis, plasma TGF-β1, clinical and echocardiographic data were collected before cryoablation. Postablation blanking period was observed for 3 months.
RESULTS: DE-MRI revealed LA fibrosis in 27 (65.9%) patients with a median enhancement of 5% of the LA surface area. A total of 179 pulmonary veins (PV) were successfully isolated without any major complication. At median 18 months follow-up, 32 patients (78.1%) remained free of AF recurrence. Only plasma TGF-β1 level (P = 0.001) was found to be the predictor of the extent of LA fibrosis. Multivariate Cox regression analysis pointed out that the extent of LA fibrosis (HR: 1.127, P = 0.007) and early AF recurrence (HR: 1.442, P = 0.011) were the independent predictors of AF recurrence in late follow-up.
CONCLUSION: Higher levels of TGF-β1 are associated with more extensive LA fibrosis and extent of LA fibrosis predict recurrences in patients undergoing cryoablation for lone AF.