A STUDY OF 24HOUR CENTRAL BLOOD PRESSURE VARIABILITY WITH MEASURES OF MACRO- AND MICROVASCULAR FUNCTION IN A POPULATION OF UNTREATED HYPERTENSIVE AND NORMOTENSIVE INDIVIDUALS

Abstract

Objective: Central blood pressure (cBP) has been more closely associated with target-organ damage compared with brachial BP, although a bidirectional interplay between central and peripheral arteries exists. Brachial short term BP variability (BPV) has been increasingly related to impaired macro- and microvascular function. However, scarce data exists regarding 24hour central BPV (cBPV) and its impact on organ damage. This study aimed to measure 24h cBPV in a population of untreated essential hypertensive (UHTs) and normotensive (NTs) individuals and evaluate its association with measures of macro- and microvascular function. Design and method: Newly-diagnosed UHTs and NTs were enrolled. 24hour cBP and 24h pulse wave velocity (PWV) were measured with the Mobil-O-Graph device. BPV including average real variability (ARV) of 24h central systolic BP (cSBP) and diastolic BP (cDBP) was calculated according to a standardized formula based on the ambulatory BP monitoring (ABPM) measurements. Urine albumin excretion (UAE) was measured in 24h samples. Results: We recruited 119 individuals including 79 UHTs and 40 NTs that didn’t differ in baseline characteristics. As expected, PWV was increased in UHTs compared to NTs [7.7 (1.5) vs 6.7 (1.2) m/s, p<0.001]. Similarly, in a subset of 60 individuals, UAE was increased [12.1 (9.7) vs 6.4 (4.5) mg/24h, p = 0.008]. UHTs presented higher ARV of 24h, daytime and nighttime cSBP/cDBP compared to NTs (p<0.05 for all comparisons). In total population, 24h PWV positively correlated with ARV of 24h cSBP (r = 0.353, p<0.001) and cDBP (r = 0.235, p = 0.010), ARV of daytime cSBP (r = 0.342, p<0.001) and cDBP (r = 0.235, p = 0.010), and nighttime cSBP (r = 0.297, p = 0.007). Furthermore, UAE correlated with ARV of nighttime cDBP (r = 0.372, p = 0.017). In multivariate analysis after adjusting for age, sex, and hypertension, ARV of 24h cSBP remained an independent predictor of PWV (beta = 0.109, p<0.001). Likewise, ARV of nighttime cDBP independently predicted UAE (beta = 0.480, p = 0.002). Conclusions: In a population of untreated hypertensives and normotensives, cARV indices are significantly and independently associated with measures of macro- and microvascular function including PWV and UAE, respectively. Further studies are warranted to ascertain the clinical value of cARV in terms of risk stratification and management.