Acute kidney injury after myocardial infarction: prognostic implications via dual robust methods.

Background: Acute kidney injury (AKI) following acute myocardial infarction (AMI) notably affects patient outcomes. The impact of KDIGO AKI staging on post-discharge short- and long-term outcomes, particularly early-stage AKI, is not well understood. This study evaluates the prognostic implications of various KDIGO stages in AMI patients. Methods: Utilizing the Medical Information Mart for Intensive Care IV (version 3.0) database, this retrospective cohort study included adult patients primarily diagnosed with AMI. Statistical analyses, including doubly robust estimation, propensity score matching, logistic regression, and Cox regression, were performed. The study compared Non-AKI (KDIGO stage 0) with Mild-AKI (maximum KDIGO stage 1 during hospitalization), and Normal-or-mild AKI (KDIGO stages 0-1) with Moderate-to-severe AKI (KDIGO stages 2-3). Results: Among 5,715 patients analyzed, 4,306 (75.36%) developed AKI. Doubly robust analysis revealed no significant differences in outcomes between Non-AKI and Mild-AKI groups (28-day mortality: OR 0.97, 95% CI 0.68-1.38; 180-day mortality: HR 0.94, 95% CI 0.76-1.18; 1-year mortality: HR 0.98, 95% CI 0.81-1.20). However, Moderate-to-severe AKI was significantly associated with worse outcomes compared to Normal-or-mild AKI (28-day mortality: OR 1.67, 95% CI 1.36-2.05; 180-day mortality: HR 1.06, 95% CI 1.02-1.10; 1-year mortality: HR 1.22, 95% CI 1.07-1.38; all Conclusions: Patients with Mild-AKI can be considered as having "subclinical AKI," with prognoses similar to Non-AKI patients. In contrast, Moderate-to-severe AKI significantly worsens prognosis compared to Normal-or-mild AKI.