The relationship between ambulatory arterial stiffness index and incident atrial fibrillation

Background: The ambulatory arterial stiffness index (AASI) is an indirect measure of blood pressure variability and arterial stiffness which are atrial fibrillation (AF) risk factors. The relationship between AASI and AF development has not been previously investigated and was the primary aim of this study. Methods: This was an observational cohort study of adults (aged 18-85 years) in sinus rhythm, who underwent 24-h ambulatory blood pressure monitoring (ABPM) for the diagnosis of hypertension or its control. Results: Eight hundred and twenty-one patients (49% men) aged 58.7 +/- 15.3 years were followed up for a median of 4.0 years (3317 patient-years). In total, 75 patients (9.1%) developed >= 1 AF episode during follow-up. The mean AASI was 0.46 +/- 0.17 (median 0.46). AASI values (0.52 +/- 0.16 vs. 0.45 +/- 0.17; p < .001) and the proportion of AASI values above the median (65.3% vs. 48.4%; p = .005) were greater among the patients who developed AF versus those that did not respectively. AASI significantly correlated with age (r = .49; 95% confidence interval: 0.44-0.54: p < .001). On Kaplan-Meier analysis, higher baseline AASI by median, tertiles, and quartiles were all significantly associated with AF development (X-2: 10.13; p < .001). On Cox regression analyses, both a 1-standard deviation increase and AASI > median were independent predictors of AF, but this relationship was no longer significant when age was included in the model. Conclusions: AASI is an independent predictor of AF development. However, this relationship becomes insignificant after adjustment for age which is higher correlated with AASI.