Prognostic impact of the ambulatory arterial stiffness index in resistant hypertension

Abstract

The ambulatory arterial stiffness index (AASI), derived from ambulatory blood pressure (BP) monitoring recordings, is an indirect marker of arterial stiffness and a potential predictor of cardiovascular risk. Resistant hypertension is defined as uncontrolled office BP despite the use of at least three antihypertensive drugs. The aim of this prospective study was to investigate the AASI prognostic value in patients with resistant hypertension. At baseline, 547 patients underwent clinical-laboratory, and 24-h ambulatory BP monitoring examinations. AASI was defined as 1 minus the regression slope of DBP on SBP, and was calculated by standard and symmetric regression. Primary endpoints were a composite of fatal and nonfatal cardiovascular events and all-cause and cardiovascular mortalities. Multiple Cox regression was used to assess associations between AASI and subsequent endpoints. After median follow-up of 4.8 years, 101 patients (18.4%) reached the primary endpoint, and 65 all-cause deaths (11.9%) occurred (45 from cardiovascular causes). 24-h AASI was the best independent predictor of composite endpoint (hazard ratio 1.46, 95% confidence interval 1.12-1.92, for increments of 1-SD = 0.14), whereas cardiovascular mortality was best predicted by night-time AASI (hazard ratio 1.73, 95% confidence interval 1.13-2.65), after adjustments for cardiovascular risk factors, including mean ambulatory BPs and nocturnal BP reduction. Symmetric AASI was not superior to standard AASI. In sensitivity analysis, 24-h AASI was a better predictor of cardiovascular outcomes in women, in younger individuals, and in nondiabetic individuals. AASI is a predictor of cardiovascular morbidity and mortality in resistant hypertension, over and beyond traditional risk factors and other ambulatory BP monitoring parameters.