Kanic V, Kompara G, Suran D, Ekart R, Bevc S, Hojs R: Impact of KDIGO-Defined Acute Kidney Injury on Mortality after Percutaneous Coronary Intervention for Acute Myocardial Infarction. Cardiorenal Med 2018;8:332–339
Acute kidney injury (AKI), defined by rapid and often transient changes in serum creatinine concentration (with or without oliguria), is a common problem, especially in older hospitalized patients undergoing various surgical procedures, including coronary interventions for acute myocardial infarction (AMI). The impact of such episodes of AKI on subsequent mortality is a poorly understood issue, of great contemporary interest.
Kanic and colleagues have narrowed the knowledge gaps in this arena by conducting a retrospective, observational study of 5859 patients with an AMI who underwent percutaneous coronary intervention, of whom 499 (8.5 %) developed AKI (mild stage 1 in 73 %). The end-point examined was all-cause mortality after a median 4.2 years of follow-up. Models were constructed using logistic regression with adjustment of variables different among the groups at baseline.
The adjusted hazard ratio (HR) for cumulative mortality was 2.09 (95 % CI = 1.80 – 2.43) for all stages of AKI and was highest (HR – 6.30 – 95 % CI = 4.69 – 8.48) for stage 3 AKI. But even mild AKI (stage 1) was associated with two-fold increase in mortality risk. Several variables seemed to predict a higher risk of AKI and mortality. Unfortunately, the specific causes of death were not recorded and data on mediations were not collected. A study using propensity matched cohort would have been a better design for answering the questions posed. As with all such observational studies residual confounding could have impacted the results, and causal inferences cannot be made with much confidence.
Nevertheless, this and other studies seem to indicate that even a mild (and usually transient) increase in serum creatinine levels have a “legacy-like” effect lasting several years leading to enhanced mortality risk. The exact mechanism responsible for this apparent association remains obscure and needs further study. It will be important to validate this observation by prospective studies, and to identify possible interventions that might blunt or eliminate this apparent effect of AKI on mortality risk.