Hypertension and Increased Hindlimb Vascular Reactivity in Experimental Coarctation of the Aorta

• The cause of hypertension in human coarctation of the aorta is not well understood. The proponents of a mechanical hypothesis" suggest that the increase in blood pressure is due to the resistance offered by the coarctation and the collateral circulation, whereas those favoring a humoral explanation" postulate the existence of a generalized increase in peripheral resistance such as occurs in renal hypertension. Evidence for the increase in peripheral resistance is the finding, in some instances, of an elevated diastolic pressure below as well as above the aortic stricture. Experimental coarctation of the aorta has raised a similar problem. The results of Barcroft, Brotchner, and Gupta and Wiggers are in agreement with a purely mechanical origin of the hypertension. However, these workers used acute experiments, and there is evidence suggesting that in more prolonged studies the situation is different. Goldblatt et al. postulated a renal origin for the hypertension. Other authors have arrived at a s i mil a r con cl usi on. 3~ McQueen has shown an increased vascular reactivity in the hindquarters of hypertensive rats with renal artery constriction. If the hypertension in experimental coarctation of the aorta were of renal origin, similar results could be expected. However, there is an interesting hemodynamic difference between renal artery constriction and aortic coarctation. In the latter, while the blood pressure above the constriction is elevated, the blood pressure below is close to normal, and some-