The associations between microalbuminuria and various parameters of flow-mediated vasodilatation (FMD) are not completely understood. We retrospectively analyzed 265 consecutive patients who underwent coronary angiography and in whom we could measure FMD and the urine albumin-creatinine ratio (UACR). Using 15 continuous measurement approaches, we measured FMD as the magnitude of the percentage change in the brachial artery diameter from baseline to peak (bFMD), the maximum FMD rate calculated as the maximal slope of dilation (FMD-MDR), and the integrated FMD response calculated as the area under the dilation curve during the 60- and 120-s dilation periods (FMD-AUC60 and FMD-AUC120). We divided the patients into two groups according to UACR: normoalbuminuria (NOR, n = 211) and microalbuminuria (MIC, n = 54). The MIC group showed a significantly higher percentage of coronary artery disease than the NOR group. FMD-AUC60 and FMD-AUC120, but not FMD-MDR, in the MIC group were significantly lower than those in the NOR group. On the other hand, bFMD in the MIC group tended to be lower than that in the NOR group, but this difference was not significant. A multiple regression analysis indicated that FMD-AUC120 and diabetes mellitus were predictors of MIC. Finally, we defined the cut-off value of FMD-AUC120 for the presence of MIC in all patients as 8.4 mm x second (sensitivity 0.640, specificity 0.588) by a receiver-operating characteristic curve analysis. In conclusion, this study provides more definitive evidence for the association of microalbuminuria with endothelial dysfunction. FMD-AUC120 may be a superior marker for MIC.
Keywords: Urinary albumin-creatinine ratio; area under the dilation curve; coronary artery disease.