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 the proximal, elastic, large, common carotid artery. Indeed, radial artery compliance in hypertensive patients (HTs) has been shown to be paradoxically increased when compared with that in normotensive control subjects (NTs) at the same blood pressure level. To determine whether this increase was due to hypertension-related hypertrophy of the arterial wall, radial artery functional and geometric parameters from 22 NTs (mean+/-SD, 44+/-11 years) were compared with those from 25 age- and sex-matched never-treated essential HTs (48+/-12 years) by using a high-precision ultrasonic, echo-tracking system coupled to a photoplethysmograph (Finapres system), which allows simultaneous arterial internal diameter, intima-media thickness, and finger blood pressure measurements. When the values for HTs were compared with those of NTs at their respective 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 and increased arterial wall cross-sectional areas (3.79+/-1.14 versus 2.45+/-0.57 mm(2), P<.001). Circumferential wall stress was not significantly different between the two groups. Compliance calculated for a given blood pressure, ie, 100 mm Hg (E(inc)), was greater in HTs than NTs (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 elastic properties of the wall material, was calculated from intima-media thickness and pulsatile changes in diameter and blood pressure. E(inc) in HTs was not significantly different from that in NTs at their respective mean arterial pressures or for a given level of circumferential stress. For a given blood pressure level (100 mm Hg), E(inc) was significantly 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 arterial wall material that occur during sustained hypertension could be a means by which medium-size arteries maintain their distensibility characteristics despite wall hypertrophy.