Effect of blood pressure variability on endothelial function assessed by brachial artery flow mediated dilatation

Abstract

Purpose: To examine the influence of blood pressure variability on endothelial function assessed by brachial artery flow mediated dilatation. Methods: We screened 190 individuals without history of cardiovascular disease in a primary prevention program recording age (45,62±8,72 years), sex (48,4% males), body mass index (BMI = 27,03±4,79 kg/m2), waist circumference (94,42±14,16 cm), total cholesterol (214,30±41,87 mg/dl), LDL-cholesterol (136,59±37,73 mg/dl), HDL-cholesterol (47,99±13,24 mg/dl), triglycerides (150,02±108,15 mg/dl), blood glucose (92,28±28,18 mg/dl), number of smoked cigarettes/day. We determined the brachial artery FMD according to the guidelines for the ultrasound assessment of endothelial-dependent flow-mediated vasodilation. All subjects underwent a 24-hour Ambulatory Blood Pressure Monitoring (ABPM) on a working day, performing usual daily activities and avoiding heavy physical exercise. Blood pressure and heart rate readings were obtained every 15 minutes during daytime and every 30 minutes during nighttime. We recorded mean systolic and diastolic Blood Pressure (BP) and BP variability calculated as the Standard Deviation (SD) of mean blood pressure. After data collection we investigated the correlations (Pearson's r) between FMD values, classical risk factors and ABPM records, defining the magnitude of correlation as weak (r = 0,1 to 0,3), moderate (0,3 to 0,5) and high (0,5 to 1). Results: The uppermost observed correlations of brachial artery FMD values were in the moderate range, with systolic BP variability (r=-0,399, p<0,001), mean systolic BP (r=-0,372, p<0,001) and waist circumference (r=-0,360, p<0,001). We found weak significant correlations between FMD and mean diastolic BP (r=-0,288, p<0,001), age (r=-0,254, p<0,001), BMI (r=-0,290, p<0,001), number of smoked cigarettes/day (r=-0,223, p=002), HDL-cholesterol (r=0,168, p=0,021), triglycerides (r=-0,181, p=0,012) and blood glucose (r=-0,235, p=0,001). Moreover, the persons with endothelial dysfunction defined as a brachial artery FMD value less than 7,5% have significantly increased systolic blood pressure variability as compared with those with normal endothelial function (14,29±3,41 mmHg vs. 11,48±2,40 mmHg, p<0,001). Conclusions: Our study indicates that systolic blood pressure variability determined by ambulatory blood pressure monitoring is one of the most important factors that impacts on endothelial function.