Clinical Implications of Contrast-Induced Nephropathy in Patients Without Baseline Renal Dysfunction Undergoing Coronary Angiography.

BACKGROUND: The clinical implications of different definitions of contrast-induced nephropathy (CIN) in patients without baseline renal dysfunction are not well defined. METHODS: Consecutive patients at a single centre without baseline renal dysfunction (estimated glomerular filtration rate, eGFR≥60ml/min/1.73m2) undergoing coronary angiography or percutaneous coronary intervention (PCI), were systematically evaluated for long-term risk of mortality following CIN using two broad definitions: an absolute increase from baseline in serum creatinine (SCr) ≥0.3mg/dl (mild to severe absolute CIN) and a relative increase from baseline of 25% (mild to severe relative CIN) within 72hours. RESULT: Of 2,823 subjects alive before discharge following coronary angiography there were 320 episodes of mild to severe relative CIN (11.3%) and 125 of mild to severe absolute CIN (4.4%). During a median follow-up of 2.3years, 73 patients (3.2%) died. After adjustment for confounders, mild to severe absolute CIN was associated with an adjusted hazard ratio (HR) (95% confidence interval) for all-cause mortality of 3.31 (1.74-6.30) (p<0.0001) and relative CIN with an adjusted HR of 1.92 (1.09, 3.38) (p=0.024). The risk of mortality rose with severity of CIN. Two commonly used definitions of CIN combining absolute and relative terms (increase ≥ 0.3mg/dl or 50%, and ≥ 0.5mg/dl or 25% from the baseline) confirmed these results. CONCLUSION: Among patients without baseline renal dysfunction undergoing coronary angiography, the incidence of CIN can range widely depending on definition. Absolute CIN is less common than relative CIN. Regardless of definition, CIN is associated with a markedly increased risk of long-term mortality. This finding requires confirmation in multicentre studies.