A reduced elastic modulus of vascular wall components in hypertension?

1have demonstrated two features of a conduit artery in the vasculature of essential hypertensive patients. First, that the diameter of the radial artery of essential hypertensive patients is similar to or greater than that of well-matched, normotensive control subjects. Second, if compared under conditions of similar transmural pressure, the compliance and distensibility of the artery (for definitions see "Appendix") are not decreased in the essential hypertensive patients. The finding that the diameter of this conduit artery is normal or increased in essential hypertension confirms a number of previous reports, 2 in particular those concerning the brachial 3 - 4 artery. However, the results reported by Hayoz et al 1 seem particularly clear-cut, for the measurements have been made with a resolution (based on signal averaging) of 1 fim. The finding that compliance and distensibility characteristics of conduit arteries are not decreased in essential hypertension is more controversial. 2 - 5 Most previous measurements in vivo of arterial compliance have, however, been made indirectly on the basis of measurements of pulse-wave velocity with the classic Moens-Kortewig equation for tubes with perfectly elastic walls. 6 By contrast, Hayoz et al 1 measured compliance by determining the time course of the diameter change throughout the cardiac cycle and plotting this against the corresponding pressure change, measured with a finger plethysmograph, to obtain a direct assessment of the diameter-pressure relation and thus of compliance and distensibility. 7 The experimental basis for the finding seems therefore strong, and Hayoz et al 1 obtained further support for their finding by also showing that in the carotid artery of spontaneously hypertensive rats (SHR), compliance and distensibility were similar to or greater than those of arteries from normotensive Wistar-Kyoto (WKY) rats if compared at the same transmural pressure. The implication is therefore that the mechanical properties of conduit arteries are not functionally altered in hypertension; this editorial comment will consider briefly the consequences of this implication regarding vascular development in hypertension.