Risk stratification according to the type of impaired renal function in patients with acute myocardial infarction treated with percutaneous coronary intervention.

Background: It has been shown that successful reperfusion improves in-hospital and long-term outcome of patients with acute myocardial infarction (AMI). Nevertheless, some patients are still at high risk due to AMI despite achievement of reperfusion. Impaired renal function (IRF) is one of the recently recognised risk factors in this population. However, the prognostic value of different types of IRF in patients with AMI treated with percutaneous coronary intervention (PCI) has not been well characterised.

Aim: To evaluate the prognostic value of different types of IRF in AMI patients treated with PCI.

Methods: The single centre AMI registry encompassed 1486 consecutive AMI patients treated with PCI, who were followed for a mean of 29.7 months. Subjects with at least 1 measurement of serum creatinine >133 micromol/l (>1.5 mg/dl) during hospitalisation were selected (n=194; 13.1%) and incorporated into the IRF group. The control group consisted of 1292 (86.9%) subjects with normal renal function. The IRF patients were divided into subgroups: contrast-induced nephropathy--CIN (n=90; 6.1%); and chronic kidney disease--CKD (n=66; 4.4%). Thirty-eight patients from the IRF group (2.6%) had normal value of serum creatinine on admission and did not match criteria of CIN. Patients with creatinine value >133 micromol/l on admission were incorporated into the CKD group. CIN was defined as a serum creatinine level <134 micromol/l on admission and a 25% increase of that parameter, with a value >133 micromol/l within 48 hours after PCI. Among CIN patients 2 subgroups were identified with respect to coexisting diabetes mellitus: CIN-DM and CIN-nDM (both n=45; 3.05%).

Results: Remote mortality rate was significantly higher in the IRF group (38.7%) and in particular subgroups--CKD (51.5%), CIN-DM (46.7%), CIN-nDM (28.9%)--than in controls (10.3%, p <0.001 for all study groups vs. controls). Multivariate analysis identified IRF as an independent predictor of any-cause death in the whole population [hazard ratio (HR) 2.23; 95% CI 1.99-2.47, p <0.001]. All defined types of IRF had a significant and independent influence on remote survival in the study population (CIN-DM - HR 3.52; 95% CI 3.23-3.81; CIN-nDM--HR 2.60; 95% CI 2.29-2.91; CKD--HR 1.98; 95% CI 1.68-2.28).

Conclusions: Impaired renal function and all defined types of renal impairment have been shown to worsen the long-term prognosis of AMI patients treated with PCI. The most important risk factor of mortality is CIN in diabetic patients, which is associated with an over 3.5-fold increase of death hazard in this study population.