Relationships of vascular function with measures of ambulatory blood pressure variation

Abstract

Background: Characteristics of short-term blood pressure (BP) variation may influence cardiovascular disease risk via effects on vascular function. Objective: In a cross-sectional study of a group of treated hypertensive and untreated largely normotensive subjects we investigated the relationships of measures of short-term BP variation with brachial artery vasodilator function. Methods: A total of 163 treated hypertensive (n = 91) and untreated largely normotensive (n = 72) men and women were recruited from the general population. Measures of systolic and diastolic BP variation were calculated from 24 h ambulatory BP assessments and included: (i) rate of measurement-to-measurement BP variation (SBP-var and DBP-var); and (ii) day-to-night BP dip (SBP-dip and DBP dip). Endothelium-dependent vasodilation was assessed as flow-mediated dilation (FMD) and endothelium-independent vasodilation was assessed in response to glyceryl trinitrate (GTN). Relationships were explored using univariate and multivariate linear regression. Results: The relationships of brachial artery vasodilator function with BP variation were not significantly different between treated hypertensive and untreated subjects, therefore these groups were combined for analysis. In univariate analysis, higher SBP-var (P < 0.001) and lower DBP-dip (P = 0.004) were associated with lower FMD; and higher SBP-var (P = 0.002) and lower SBP-dip (P = 0.003) and DBP-dip (P = 0.001) were associated with lower GTN-mediated dilation. In multivariate analysis, lower SBP-dip (P = 0.007) and DBP-dip (P = 0.03) were independently associated with lower GTN response.Conclusions: Our results indicate that a lower day-to-night BP dip is independently associated with impaired smooth muscle cell function. Although rate of BP variation was associated with measures of endothelial and smooth muscle cell function, relationships were attenuated after accounting for age and BP.