A comparison of contemporary definitions of contrast nephropathy in patients undergoing percutaneous coronary intervention and a proposal for a novel nephropathy grading system.

Contrast-induced nephropathy (CIN) after percutaneous coronary intervention (PCI) has multiple definitions. We attempted to identify the optimal definition of CIN. In 985 patients undergoing PCI (derivation group), we assessed the prognostic significance of 4 commonly used contemporary definitions of CIN (increases in serum creatinine after PCI [deltaCr] >1.0 mg/dl, >0.5 mg/dl, and >25% after PCI; and the American College of Cardiology National Cardiovascular Data Registry definition) with respect to 6-month major adverse cardiovascular events (MACEs) and all-cause mortality (at 863 +/- 324 days). Incidence of CIN ranged widely (2.0% to 15%) depending on the definition used. Only 2 definitions (deltaCr >0.5 mg/dl, >25%) consistently correlated with study outcomes. Using these 2 definitions, we devised a new grading system (grade 0 deltaCr <or=25% and <or=0.5 mg/dl; grade 1 deltaCr >25% but <or=0.5 mg/dl; and grade 2 deltaCr >0.5 mg/dl). Nephropathy grades (0 vs 1 vs 2) showed significant correlation with 6-month MACEs (12.4 vs 19.4 vs 28.6%, p = 0.003) and all-cause mortality (10.2 vs 10.4 vs 40.9%, p <0.0001). In multivariate analyses, the grading system showed an independent association with MACEs and mortality. The prognostic value of nephropathy grades was prospectively confirmed in an independent validation group of 539 patients. In conclusion, of the 4 contemporary definitions of CIN, only deltaCr >25% and >0.5 mg/dl consistently predicted adverse events after PCI. By unifying these 2 definitions, we devised a novel nephropathy grading system that is predictive of 6-month MACEs and all-cause mortality after PCI.