The humoral theory postulates activation of the renin-angiotensin system secondary to reduction of renal blood flow but plasma renin activity has not been consistently found to be elevated in these subjects and, while it is reasonable to hypothesize that an increase in the renine angiotensin system contributes to hypertension in patients with coarctation, its role in the development of hypertension at rest and during exercise after a successful repair is still unclear [113]. Here, REN is linked to Hypertension.