RLN2 and atrial fibrillation: Nowadays, it is considered that the pleiotropic hormone relaxin-2 could be beneficial for atrial fibrillation (AF) management due to (a) its remarkable antiarrhythmic and cardioprotective properties, such as its anti-inflammatory, antiapoptotic, antifibrotic, anti-hypertrophic and antioxidant effects, (b) its capacity to inhibit angiotensin II (Ang II), or (c) its role regulating extracellular matrix (ECM) turn-over and reducing collagen excessive deposition in cardiac tissues1–5.