Background: Contrast-induced nephropathy (CIN) has been traditionally associated with increased mortality and adverse cardiovascular events. We sought to determine whether CIN has a negative impact on the long-term outcome of patients with non-ST segment elevation myocardial infarction (NSTEMI). Methods: A total of 312 consecutive patients (mean age 59 years, 76% male) who presented with NSTEMI and had undergone an early invasive procedure were retrospectively included. CIN was defined as either a 25% or 0.5-mg/dl increase in baseline serum creatinine (Cr) 72 h after the procedure. The primary endpoint of the study was mortality in the long-term follow-up (38 months, interquartile range 30-40). The secondary endpoint consisted of mortality and myocardial infarction (MI). Results: CIN developed in 30 (9.6%) patients. Independent predictors of CIN were the contrast volume-to-Cr clearance ratio, left ventricular ejection fraction and hemoglobin concentration. The primary (20 vs. 8.5%, p = 0.042) and secondary endpoints (33.3 vs. 17%, p = 0.029) were observed more frequently in patients with CIN during long-term follow-up. The unadjusted odds ratio (OR) of CIN was 2.55 [95% confidence intervals (CI) 1.04-6.24, p = 0.040] for mortality and 2.15 (CI 1.09-4.25, p = 0.028) for mortality/MI. However, after adjustment for confounding factors, CIN was not an independent predictor of either mortality (OR 1.62, CI 0.21-12.57, p = 0.646) or mortality/MI (OR 1.12, CI 0.31-4.0, p = 0.860). Conclusion: The effect of CIN on the long-term outcome of patients with NSTEMI was substantially influenced by confounding factors. CIN was a marker, rather than a mediator, of increased cardiovascular risk, and the baseline renal function was more conclusive as a long-term prognosticator.
