Absence of any significant effects of circadian blood pressure variations on carotid artery elastic properties in essential hypertensive subjects

We sought in this study to examine the effects of diurnal blood pressure va riations upon common carotid artery (CCA) elasticity in selected subjects w ith uncomplicated moderate essential hypertension. Towards this end, 174 no n-smoker subjects with stage I-II essential hypertension and without diabet es mellitus, left ventricular hypertrophy and carotid atherosclerosis, were classified as dippers and non-dippers according to the diurnal variation o f >10% between mean daytime and night-time systolic and diastolic blood pre ssure (BP) in 24-h noninvasive ambulatory BP monitoring. CCA distensibility was derived by a combination of surface ultrasonographic data and simultan eous BP measurements at the brachial artery, The dippers and non-dippers we re similar with respect to demographic characteristics. Non-dippers had sig nificantly greater office systolic BP, 24-h systolic BP and ambulatory puls e pressure (PP) and significantly less (daytime-night-time) systolic and di astolic BP fall (by 16 mm Hg and 11 mm Hg respectively, P < 0.0001) compare d to dippers. CCA distensibility was significantly reduced in non-dippers c ompared to dippers (by 0.89 dyne(-1)/cm(2)/10(-6), P < 0.05). Multiple line ar regression analysis identified patient age and ambulatory PP as signific ant predictors of the CCA elasticity index. When patient age, 24-h systolic and diastolic BP were used as covariates in an analysis of covariance, the difference of CCA elasticity between dippers and non-dippers ceased to rea ch statistical significance. In contrast, when patient age, ambulatory PP, systolic (daytime-night-time) BP fall and diastolic (daytime-night-time) BP fall were used as covariates, the difference of CCA distensibility between dippers and non-dippers continued to be statistically significant. In conc lusion, the excessive impairment of CCA elastic properties in non-dippers c ompared to dippers hypertensive seems to be ascribed to the increased of to tal 24-h haemodynamic load and not to the circadian pattern of BP.