MMP9 and atrial fibrillation: Finally, SD rats treated with NaHS, DCA or 4-PBA were protected against Ang II-induced atrial fibrosis, evidenced by negative Masson staining, decreased MMP-9, collagen Iα and collagen III α expression (Figures 4C–M), and decreased susceptibility to AF, including reduced number of AF episodes and shortened AF duration, prolonged AERP and shortened AERPd, (Figures 4N–R), and improved LADS, including narrowed LAESVI and increased LAEF and LAFI(Figures 4S–U) compared with Ang-II injected SD rats.