CAROTID WALL VISCOSITY INCREASE IS RELATED TO INTIMA-MEDIA THICKENINGIN HYPERTENSIVE PATIENTS

Increases in arterial wall viscosity and intima-media thickness (IMT) were found in hypertensive patients, Because smooth muscle cells are r esponsible for the viscous behavior of the arterial wall and they are involved in the process of thickening of the intima-media complex, thi s study evaluates the relationship between carotid thickness and wall viscosity. The simultaneous and noninvasive assessment of the intima-m edia complex and arterial diameter waveform was performed using high-r esolution ultrasonography. This technique was contrasted against sonom icrometry in sheep, showing that the waveforms obtained by both method s were similar, The common carotid arteries of 11 normotensive subject s (NTA) and 11 patients with mild to moderate essential hypertension ( HTA) were measured noninvasively by using tonometry and an automatic d ensitometric analysis of B-mode images to obtain IMT and instantaneous pressure and diameter loops. A viscoelastic model was used to derive the wall viscosity index (eta) using the hysteresis loop elimination c riteria. In NTA, eta was 2.73+/-1.66 (mm Hg . s/mm) and IMT was 0.58+/ -0.08 (mm), whereas in HTA, eta was 5.91+/-2.34 (P<.025) and IMT was 0 .70+/-0.12 (P<.025), respectively. When all data of eta versus IMT of NTA and HTA were pooled in a linear regression analysis, a correlation coefficient of r=.71 (P<.05) was obtained, Partial correlation betwee n eta and IMT holding constant pressure was r=.59 (P<.05). In conclusi on, wall viscosity increase was associated with a higher IMT even main taining blood pressure fixed, suggesting that the intima-media thicken ing might be related to smooth muscle alterations manifested as an inc rease in viscous behavior.