Ambulatory arterial stiffness index: a systematic review and meta-analysis

The dynamic relationship between 24 h diastolic and systolic ambulatory blood pressure (BP) expressed by the ambulatory arterial stiffness index (AASI) has been introduced as a novel measure of arterial function, which independently predicts cardiovascular mortality. This article reviews the published evidence on the features and the clinical relevance of AASI.

A systematic review and meta-analysis of the evidence on AASI from 51 cross-sectional and longitudinal studies in adults was conducted.

Studies of the reproducibility of AASI have shown a mean difference between assessments at 0.014 (95% CI -0.001, 0.028; 3 studies, n = 451) and repeatability coefficients ranging from 0.24 to 0.40. AASI appears to be independently associated with age, systolic BP and pulse pressure, and inversely with the nocturnal systolic and diastolic BP decline. A moderate pooled association of AASI with 24 h pulse pressure (pooled correlation coefficient r 0.47, 95% CI 0.40, 0.54; 20 studies, n = 29,186) and pulse wave velocity (pooled r 0.30, 95% CI 0.19, 0.42; 9 studies, n = 4123) was demonstrated, as well as with other measures of arterial function and target-organ damage. The adjusted pooled hazard ratio for stroke corresponding to a study-specific one standard deviation increase in AASI was 1.26 (95% CI 1.08, 1.45; 3 studies, n = 14,320).

The available evidence suggests that AASI, obtained by ambulatory BP monitoring, predicts future cardiovascular events, particularly stroke, and is associated with indices of arterial function. The precise pathophysiological mechanisms remain obscure. Research is required to determine the usefulness of AASI as a therapeutic target in clinical practice.