We recruited 229 untreated essential hypertensive patients (HT) (age: 22–73 years) to evaluate augmentation index (AIx) and endothelial function in the presence (MS+) or absence (MS–) of the metabolic syndrome (MS). AIx was measured by applanation tonometry (Sphygmocor). Endothelium-dependent (FMD) and -independent dilation (25 μg sublingual glyceryl trinitrate, GTN) were evaluated by ultrasound and automatic computerized analysis of brachial artery diameter (BAD) changes. MS was defined using the ATP III criteria (2001).

No significant (p < 0.05) differences between MS+ (N = 71) or MS– (N = 162) were found for AIx (23.9±8.0 vs 25.9±10.4), FMD (4.8±2.6 vs 5.2±2.6%) or response to GTN (8.0±3.8 vs 7.7±3.3%). Age, systolic (SBP), diastolic blood pressure (DBP) and total cholesterol did not differ significantly (p < 0.05, or less). Body mass index (BMI) (29.0±3.3 vs 25.5±3.1 kg/m²), waist circumference (WC) (102.6±8.6 vs 90.8±9.2 cm), plasma glucose (103.4±23.0 vs 90.5±9.6mg/dl) and BAD (4.9±0.8 vs 4.4±0.9 mm) were significantly (p < 0.05, or less) higher in MS+ as compared to MS–, while HDL cholesterol was lower (41.9±11.5 vs 54.5±13.3 mg/dl, respectively). In the whole group, AIx correlated (p < 0.05 or less) with age (r = 0.37), SBP (r = 0.20), DBP (r = 0.17), BAD (r = −0.24), total cholesterol (r = 0.20), BMI (r = −0.17) and WC (r = −0.17). FMD correlated negatively with BAD (r = −0.43), age (r = −0.31), SBP (r = −0.16) and BMI (r = −0.13). In multivariate analysis, age, BAD and DBP resulted significant predictors of AIx (R² = 0.42), while age and BAD resulted as significant predictors for FMD (R² = 0.14). In hypertensive patients the presence of the metabolic syndrome does not account for a further deterioration of vascular function and structure.