Introduction: The ambulatory arterial stiff ness index (AASI) is a new method for estimating arterial stiffness, which is associated with cardiovascular (CV) prognosis. Our aim was to evaluate the prognostic significance of AASI for new CV events.
Methods: Casual and ambulatory blood pressure (BP) measurements were obtained in 1200 hypertensive patients (645 female, age 51 +/- 12 years, BMI 27 +/- 5 kg/m2), 53% under stabilized therapy, 47% untreated, all without previous CV events. The occurrence of CV events was determined for 9833 patient-years and analyzed by a Cox proportional hazard model adjusted for confounding variables. AASI was calculated from 24h ABPM data and all patients were classified from very high to average CV risk.
Results: There were 62 deaths and 152 new fatal and non-fatal CV events (79 strokes, 51 coronary events, 22 other CV events) during the 15.2 years of follow-up (mean 8.2 +/- 3.0 years). AASI correlated significantly (p < 0.001) with pulse wave velocity (PWV), casual and 24h ambulatory BP, age and BMI. In subjects with very high or high CV risk (n = 401), AASI was 0.338 +/- 0.178, while in those with low or moderate CV risk (n = 715), it was 0.291 +/- 0.173 and in those with average CV risk (n = 84), it was 0.219 +/- 0.170) (p < 0.002, ANOVA). The probability of event-free and stroke-free survival (Kaplan-Meier) was better for AASI values below vs. above the median. The adjusted relative risk (HR 95% CI) for CV events, stroke and coronary events associated with a 1-SD increment in AASI values was respectively 1.27 (1.01-1.59), 1.36 (95% CI 1.02-1.89) (p < 0.02) and 0.99 (95% CI 0.67-1.48) (NS), similar to that of 24h pulse pressure (PP) and PWV. AASI hazard ratios were no longer significant after additional adjustment for 24h PP, whereas the converse did not occur. However, AASI above the median increases the predictive value of 24h PP for CV events and stroke.
Conclusions: AASI correlates with PWV, stratifies CV risk and predicts total cardiovascular events and stroke but not coronary events. AASI may add predictive value to 24h PP for CV events and stroke.