Background Contrast-induced nephropathy (CIN) is a serious complication of cardiac catheterization, and is associated with a significant increase in morbidity, mortality. To evaluate the value of the contrast volume to creatinine clearance (V/CrCl) ratio for predicting CIN and to determine a safe V/CrCl cut-off value to avoid CIN in patients with chronic total occlusions (CTOs) undergoing cardiac catheterization.

Methods We prospectively enrolled 728 consecutive patients with CTOs undergoing cardiac catheterization. Receiver-operator characteristic (ROC) curves were used to identify the optimal sensitivity for the observed range of V/CrCl. The predictive value of V/CrCl for CIN was assessed using multivariate logistic regression.

Results Twenty-one patients (2.88%) developed CIN. There was a significant association between a higher V/CrCl ratio and CIN risk (p < 0.001) of contrast, respectively (p < 0.001). ROC curve analysis indicated that a V/CrCl ratio of 2.76 was a fair discriminator for CIN (C-statistic = 0.77). After adjusting for other known CIN predictors, V/CrCl ratios >2.76 remained significantly associated with CIN (OR 5.04; 95% CI 1.62–15.65, p = 0.005) or worse long-term outcomes (death: hazard ratio [HR] = 2.87, 95% CI 1.39–5.93, p = 0.004; major adverse cardiac events: HR = 1.47, 95% CI: 1.04–2.08, p = 0.029).

Conclusions A V/CrCl ratio > 2.76 was a significant independent predictor of CIN and was independently associated with long-term outcomes.