APLN and heart failure: Based on their generally favorable hemodynamic properties, apelin and apelin-based mimetics are currently in development for the treatment of several cardiovascular disorders, including heart failure, pulmonary hypertension, and ischemia/reperfusion injury (Wang et al., 2013; Brame et al., 2015; Gerbier et al., 2017; Mughal and O'Rourke, 2018).