[Vascular dysfunction in hypertension evaluated by nonivasive assessment of arterial impedance]. / Evaluacion de las alteraciones circulatorias de la hipertension arterial mediante la determinacion no invasiva de la impedancia arterial.

The effects of high blood pressure on arterial vessels has become an important topic of research. These effects can be evaluated by analyzing three major components: systemic vascular resistance, arterial compliance and wave reflection. The increase in systemic vascular resistance and arterial stiffness produces modifications of left ventricular afterload and morphologic changes of pressure and flow waves. These effects can eventually cause structural changes of the left ventricle, an increase in oxygen consumption and a decrease in coronary perfusion. Until recently, invasive methods were the only means to evaluate arterial function. The aim of this review is to assess the usefulness of non invasive methods to determine the components of arterial impedance in order to evaluate the hemodynamic changes due to high blood pressure.

Carotid wall viscosity increase is related to intima-media thickening in hypertensive patients.

Increases in arterial wall viscosity and intima-media thickness (IMT) were found in hypertensive patients. Because smooth muscle cells are responsible for the viscous behavior of the arterial wall and they are involved in the process of thickening of the intima-media complex, this study evaluates the relationship between carotid thickness and wall viscosity. The simultaneous and noninvasive assessment of the intima-media complex and arterial diameter waveform was performed using high-resolution ultrasonography. This technique was contrasted against sonomicrometry in sheep, showing that the waveforms obtained by both methods were similar. The common carotid arteries of 11 normotensive subjects (NTA) and 11 patients with mild to moderate essential hypertension (HTA) were measured noninvasively by using tonometry and an automatic densitometric 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 criteria. In NTA, eta was 2.73+/-1.66 (mm Hg x 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 between eta and IMT holding constant pressure was r=.59 (P<.05). In conclusion, wall viscosity increase was associated with a higher IMT even maintaining blood pressure fixed, suggesting that the intima-media thickening might be related to smooth muscle alterations manifested as an increase in viscous behavior.