ELASTIC-MODULUS OF THE RADIAL ARTERY WALL MATERIAL IS NOT INCREASED IN PATIENTS WITH ESSENTIAL-HYPERTENSION

Hypertension is known to decrease arterial distensibility and systemic compliance. However, the arterial tree is not homogeneous, and it has been shown that the medium-size radial artery does not behave like th e proximal, elastic, large, common carotid artery. Indeed, radial arte ry compliance in hypertensive patients (HTs) has been shown to be para doxically increased when compared with that in normotensive control su bjects (NTs) at the same blood pressure level. To determine whether th is increase was due to hypertension-related hypertrophy of the arteria l wall, radial artery functional and geometric parameters from 22 NTs (mean+/-SD, 44+/-11 years) were compared with those from 25 age- and s ex-matched never-treated essential HTs (48+/-12 years) by using a high -precision ultrasonic, echo-tracking system coupled to a photoplethysm ograph (Finapres system), which allows simultaneous arterial internal diameter, intima-media thickness, and finger blood pressure measuremen ts. When the values for HTs were compared with those of NTs at their r espective mean arterial pressures, HTs had similar internal diameter ( 2.50+/-0.56 versus 2.53+/-0.32 mm, mean+/-SD) and greater intima-media thickness (0.40+/-0.06 versus 0.28+/-0.05 mm, P<.001) measurements an d increased arterial wall cross-sectional areas (3.79+/-1.14 versus 2. 45+/-0.57 mm(2), P<.001). Circumferential wall stress was not signific antly different between the two groups. Compliance calculated for a gi ven blood pressure, ie, 100 mm Hg (E(inc)), was greater in HTs than NT s (3.46+/-2.41 versus 2.10+/-1.55 m(2) . kPa(-1) . 10(-8), P<.05). In both groups, C-100 was positively correlated with arterial wall cross- sectional area (P<.05) but not with age or mean arterial pressure. The incremental modulus of elasticity (E(inc)), which evaluates the elast ic properties of the wall material, was calculated from intima-media t hickness and pulsatile changes in diameter and blood pressure. E(inc) in HTs was not significantly different from that in NTs at their respe ctive mean arterial pressures or for a given level of circumferential stress. For a given blood pressure level (100 mm Hg), E(inc) was signi ficantly reduced in HTs compared with NTs (1.84+/-1.65 versus 3.28+/-2 .11 kPa . 10(3), P<.01). These results indicate that the stiffness of the radial artery wall material is not increased in HTs, despite wall hypertrophy, and that the structural and functional changes of arteria l wall material that occur during sustained hypertension could be a me ans by which medium-size arteries maintain their distensibility charac teristics despite wall hypertrophy.