Augmented resting beat-to-beat blood pressure variability in young, healthy, non-Hispanic black men.

Abstract

What is the central question of this study? The prevalence of hypertension in black individuals exceeds that in other racial groups. Despite this well-known heightened risk, the underlying contributory factors remain incompletely understood. We hypothesized that young black men would exhibit augmented beat-to-beat blood pressure variability compared with white men and that black men would exhibit augmented total peripheral resistance variability. What is the main finding and its importance? We demonstrate that young, healthy black men exhibit greater resting beat-to-beat blood pressure variability compared with their white counterparts, which is accompanied by greater variability in total peripheral resistance. These swings in blood pressure over time might contribute to the enhanced cardiovascular risk profile in black individuals. The prevalence of hypertension in black (BL) individuals exceeds that in other racial groups. Recently, resting beat-to-beat blood pressure (BP) variability has been shown to predict cardiovascular risk and detect target organ damage better than ambulatory BP monitoring. Given the heightened risk in BL individuals, we hypothesized young BL men would exhibit augmented beat-to-beat BP variability compared with white (WH) men. Furthermore, given studies reporting reduced vasodilatation and augmented vasoconstriction in BL individuals, we hypothesized that BL men would exhibit augmented variability in total peripheral resistance (TPR). In 45 normotensive men (24 BL), beat-to-beat BP (Finometer) was measured during 10-20min of quiet rest. Cardiac output and TPR were estimated (Modelflow method). Despite similar resting BP, BL men exhibited greater BP standard deviation (e.g. systolic BP SD; BL, 7.1±2.2mmHg; WH, 5.4±1.5mmHg; P=0.006) compared with WH men, which was accompanied by a greater TPR SD (P=0.003), but not cardiac output SD (P=0.390). Other traditional measures of variability provided similar results. Histogram analysis indicated that BL men exhibited a greater percentage of cardiac cycles with BPs higher(> +10mmHg higher) and lower (< -8mmHg lower) than mean systolic BP compared with WH men (interaction, P<0.001), which was accompanied by a greater percentage of cardiac cycles with high/low TPR (P<0.001). In a subset of subjects (n=30), reduced sympathetic baroreflex sensitivity was associated with augmented BP variability (r=-0.638, P<0.001), whereas cardiac baroreflex sensitivity had no relationship (P=0.447). Herein, we document an augmented beat-to-beat BP variability in young BL men, which coincided with fluctuations in vascular resistance and reduced sympathetic BRS.