THE INCREMENTAL VALUE OF RENAL FUNCTION-ADJUSTED CONTRAST VOLUME OVER PRE-PROCEDURAL ESTIMATION OF RISK TO PREDICT CONTRAST INDUCED-ACUTE KIDNEY INJURY AFTER PRIMARY PCI

Purpose: We have demonstrated that age, renal function and ejection fraction, summarized into the AGEF Score, are pre-procedural predictors of Contrast-Induced Acute Kidney Injury (CI-AKI) after primary PCI, whereas the impact of renal function-adjusted contrast volume (CV) remains not fully explored. To date, Maximum Accepted Contrast Dose (MACD) from Cigarroa formula and CV to eGFR ratio (CV/eGFR) have been proposed to calculate a maximum CV not to be overcome, although a threshold for CV/eGFR has not been yet established. We investigated the association between CV/eGFR and CI-AKI in a consecutive population of patients undergoing primary PCI. Methods: CI-AKI was defined as an absolute increase in serum creatinine ≥0.5mg/dL or an increase ≥25% from baseline within 72 hours. Multivariate logistic regression and receiver-operating characteristic (ROC) curve analyses were used to assess whether CV/eGFR was an independent predictor of CI-AKI and the cutoff value was identified according to the Youden index. Finally, the increased discriminative value of CV/eGFR over the pre-procedural model based on the AGEF score was examined using the net reclassification improvement (NRI). Results: 470 patients were consecutively enrolled and 25 (5.3%) cases of CI-AKI occurred. These patients were older, had higher troponin, more severe impairment of hemodynamic status at admission and worse basal renal function than patients without CI-AKI. Mean procedural CV was 164±63 ml; the incidence of CI-AKI was not higher across different quartiles of CV and no patient exceeded the MACD. Despite patients developing CI-AKI had not received an absolutely higher total CV (165±79 Vs 163±62 mL), they had received a much higher renal function-adjusted CV (CV/eGFR 3.62 Vs 1.96, p<0.001). Conversely, the difference in CV/MACD was not significant (0.52 Vs 0.40, p=0.07). CI-AKI incidence was much higher (15%, p<0.001) in patients in the highest quartile of CV/eGFR, corresponding to the cutoff indicated by the ROC curve (>2.5, AUC 0.77, 72% sensitivity and 78% specificity). At multivariate analysis CV/eGFR above the cutoff or in the highest quartile (OR 5.13, p=0.004) remained an independent predictor of CI-AKI. The model with CV/eGFR demonstrated a statistically significantly NRI of 23% (p=0.021) over the baseline pre-procedural model, largely driven by a significant improvement in classification of patients not experiencing CI- AKI. Conclusions: CV remains a key risk factor for CI-AKI in patients undergoing primary PCI and our study supports the need for minimizing CV, independently from baseline pre-procedural risk