Ambulatory arterial stiffness index is not correlated with the pressor response to laboratory stressors in normotensive humans

BACKGROUND: Ambulatory arterial stiffness index (AASI) is a novel estimate of arterial stiffness, which independently predicts cardiovascular mortality, even in normotensive individuals. Additionally, other markers derived from ambulatory blood pressure (BP) monitoring, including variability, pulse pressure, nocturnal dipping, and morning BP surge, have all been shown to be predictive of end-organ damage and cardiovascular disease. Exaggerated cardiovascular reactivity to sympathoexcitatory stimuli may also predict future incidence of hypertension. The purpose of this investigation was to test the hypothesis that AASI and other derivations of ambulatory BP, including pulse pressure, 24-h blood pressure variability, dipping, and morning surge, would be correlated with the pressor response to common physiological stress maneuvers. METHOD: We measured continuous heart rate and arterial BP during head-up tilt, mental stress, cold pressor test, and isometric handgrip to fatigue in 67 healthy, normotensive, nonobese individuals (43 women, 24 men, mean age +/- SD: 28 +/- 6 years). Then, 24-h ambulatory BP was obtained, and AASI was defined as 1 minus the slope of diastolic on systolic BP in individual 24-h ambulatory BP recordings. RESULTS: Although all measures were widely variable among patients, there was no relationship between AASI, pulse pressure, blood pressure variability, dipping, and morning surge with the pressor responses. CONCLUSION: We conclude that in the absence of aging, cardiovascular, or autonomic disease, the novel stiffness index (AASI) or other ambulatory BP indices are either poorly correlated with or mechanistically unrelated to the complex pressor response to common provocations of sympathoexcitation.