Renal Function-Adjusted Contrast Volume Redefines the Baseline Estimation of Contrast-Induced Acute Kidney Injury Risk in Patients Undergoing Primary Percutaneous Coronary Intervention

Background—Age, estimated glomerular renal function (eGFR), and ejection fraction are preprocedural predictors of contrast-induced acute kidney injury (CI-AKI) after primary percutaneous coronary intervention. The effect of renal function–adjusted contrast volume (CV) remains not totally explored, and a threshold has not yet been established. Methods and Results—Logistic regression and receiver-operating characteristic curve analyses were used to assess whether CV/eGFR was an independent predictor of CI-AKI. The increased discriminative value of CV/eGFR over the preprocedural model based on age, eGFR, and ejection fraction was examined using the net reclassification improvement analysis. Of 470 patients enrolled, we observed 25 (5.3%) cases of CI-AKI. Patients with CI-AKI had received a higher renal function–adjusted CV (CV/eGFR 3.62 versus 1.96; P<0.001), and CI-AKI incidence was higher (15%; P<0.001) in patients in the highest quartile of CV/eGFR, corresponding to the cutoff indicated by the receiver-operating characteristic curve (>2.5; area under the curve, 0.77). At multivariable analysis, CV/eGFR above the cutoff (odds ratio, 5.57; P=0.002) remained an independent predictor of CI-AKI. The model with CV/eGFR demonstrated a statistically significantly net reclassification improvement of 0.23 (P=0.021) over the baseline preprocedural model, largely driven by a correct decrease in risk estimates for patients not experiencing CI-AKI, with a likelihood ratio χ2 of 5.973 (P=0.029). Conclusions—CV remains a key risk factor for CI-AKI after primary percutaneous coronary intervention and our study supports the need for minimizing CV, independently from baseline preprocedural risk. A CV restricted to no more than twice and a half the baseline eGFR might be valuable in reducing the risk of CI-AKI.