Ambulatory arterial stiffness index in chronic kidney disease stage 2–5. Reproducibility and relationship with pulse wave parameters and kidney function

BACKGROUND: Arterial stiffness contributes to the increased cardiovascular risk in patients with chronic kidney disease (CKD). Reproducible and easily obtainable indices of arterial stiffness are needed in order to monitor therapeutic strategies. The ambulatory arterial stiffness index (AASI) has been proposed as such a marker. The present study investigated the day-to-day reproducibility of AASI in CKD stage 2-5 and its relationship with other markers of arterial stiffness as well as with kidney function. METHODS: Eighty-three patients (29% female, median age 62 years) were studied by 24 h ambulatory blood pressure monitoring (ABPM), aortic pulse wave velocity (aPWV), augmentation index (AIx) and estimated glomerular filtration rate (eGFR) at a median interval of 7 days. Individual AASIs were calculated from 24 h ABPMs as 1 minus the regression slope of diastolic blood pressure over systolic blood pressure. RESULTS: Mean AASI, aPWV, AIx and 24 h pulse pressure (PP) were similar on repeated measurements. The intraclass correlation coefficients were between 72% and 78% for AASI calculated by three different methods, 87% for aPWV, 88% for AIx, and 96% for 24 h PP. The correlation coefficients between AASI and aPWV were from 0.48 to 0.53; with AIx it was between 0.19 and 0.34. After adjustment for covariates none of the arterial stiffness indices were significantly correlated to eGFR. CONCLUSIONS: In patients with CKD stage 2-5 AASI had a moderate, but acceptable reproducibility. The correlation between AASI and aPWV was good whilst the correlation between AASI and AIx was considerably lower. There was no significant correlation between AASI and eGFR.