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Atrial fibrillation is the most prevalent tachyarrhythmia in clinical practice, with very high cardiovascular morbidity and mortality with a high-cost impact in health systems. Currently, it is one of the main causes of stroke and subsequent heart failure and sudden death. miRNAs mediate in several processes involved in cardiovascular disease, including fibrosis and electrical and structural remodeling. Several studies suggest a key role of miRNAs in the course and maintenance of atrial fibrillation. In our study, we aimed to identify the differential expression of circulating miRNAs and their predictive value as biomarkers of recurrence in atrial fibrillation patients undergoing catheter pulmonary vein ablation. To this effect, 42 atrial fibrillation patients were recruited for catheter ablation. We measured the expression of 84 miRNAs in non-recurrent and recurrent groups (45.2%), both in plasma from peripheral and left atrium blood. Expression analysis showed that miRNA-451a is downregulated in recurrent patients. Receiver operating characteristic curve analysis showed that miR-451a in left atrium plasma could predict atrial fibrillation recurrence after pulmonary vein isolation. In addition, atrial fibrillation recurrence is positively associated with the increment of scar percentage. Our data suggest that miRNA-451a expression plays an important role in AF recurrence by controlling fibrosis and progression.

Cardiac resynchronization therapy represents a therapeutic option for heart failure drug-refractory patients. However, due to the lack of success in 30% of the cases, there is a demand for an in-depth analysis of individual heterogeneity. In this study, we aimed to evaluate the prognostic value of circulating miRNA differences. Responder patients were defined by a composite endpoint of the presence of left ventricular reverse remodelling (a reduction ≥15% in telesystolic volume and an increment ≥10% in left ventricular ejection fraction). Circulating miRNAs signature was analysed at the time of the procedure and at a 6-month follow-up. An expression analysis showed, both at baseline and at follow-up, differences between responders and non-responders. Responders presented lower baseline expressions of miR-499, and at follow-up, downregulation of miR-125b-5p, both associated with a significant improvement in left ventricular ejection fraction. The miRNA profile differences showed a marked sensitivity to distinguish between responders and non-responders. Our data suggest that miRNA differences might contribute to prognostic stratification of patients undergoing cardiac resynchronization therapy and suggest that preimplant cardiac context as well as remodelling response are key to therapeutic success.