Paradoxical distribution of augmentation index level in chronic kidney diseases

Pulse wave velocity (PWV) and augmentation index (AI) are used as indexes of arterial stiffness and cardiovascular survival. Although PWV is known to increase as the stage of chronic kidney disease (CKD) advances, how this is related to AI and CKD stage has not yet been well defined. A sub-analysis was performed using the data from the Antihypertensive and Blood Pressure of Central Artery in Japan study. This was a cross-sectional study on hypertensive patients. All the patients with available serum creatinine levels were selected, and estimated glomerular filtration rate (eGFR) was calculated according to the modification of diet in renal disease equation for a Japanese population. Augmentation indexes at different stages of CKD were compared. Data from 1392 patients were pooled and analyzed. In addition to eGFR, there were differences in age (P<0.0001), pulse rate (P<0.0001), vasodilator antihypertensive drugs (P<0.005), systolic (P<0.005) and diastolic (P<0.01) blood pressure at 5 CKD stages. Multivariate regression showed that AI correlated to age (0.19%/year), pulse rate (-0.54% /bpm), systolic blood pressure (0.18%/mmHg) and vasodilator antihypertensive drugs (-2.42%/class). Therefore, AI was adjusted for these confounding factors. Adjusted AI in stage 5 (77±20%) was lower than that in stage 1 (84±19%, P<0.05). These data indicate that AI varies according to CKD stage, and suggest that a cut-off value of AI should be set for each stage of CKD to detect cardiovascular disease.