XDH and endothelial dysfunction: Although it is still unclear whether SUA plays a causal role or just acts as a biomarker in LVDD progression, hyperuricemia is generally considered to be associated with increased XO activity in purine metabolism, which presumably promotes excess production of reactive oxygen species (ROS), thereby leading to reduced nitric oxide bioavailability, inflammatory state, endothelial dysfunction, myocardial fibrosis, and finally LVDD [18–21].