The apelin receptor is also an important mediator in cardiovascular physiology, promoting vasodilatation and positive inotropy, as well as in pathophysiology including heart failure, and pulmonary arterial hypertension.6–12 In a key study, Chen et al.13 reported that the apelin receptor gene was the most significantly increased of the ∼12 000 genes measured following implantation of a left ventricular assist device. Here, APLNR is linked to pulmonary arterial hypertension.