Association between stress hyperglycemia ratio and mortality in acute myocardial infarction patients with and without atrial fibrillation: a retrospective cohort study from the MIMIC-IV database.

Background: The stress hyperglycemia ratio (SHR) potently predicts adverse outcomes in patients with acute myocardial infarction (AMI), and previous studies reported U-shaped relationships between SHR and adverse prognosis. However, the relationship between SHR and mortality risk in AMI patients with or without atrial fibrillation (AF) remained unknown, and which factors affect the mortality in lower SHR patients were unclear. This study aims to research the relationship between SHR and mortality risk in AMI patients with or without AF, and whether AF affects the mortality in lower SHR patients.

Methods: We conducted a cohort study using data from 3233 patients with a first diagnosis of AMI from the MIMIC-IV (version 2.2) database. Patients were divided into two groups based on AF. The study outcome was 1-year all-cause mortality. SHR was defined as the index calculated by the formula: SHR = (admission glucose) (mmol/L) / (1.59 * HbA1c [%] - 2.59).

Results: U-shaped association between SHR and all-cause mortality was found only in AMI patients with AF, not in AMI patients without AF. For AMI patients with AF, the inflection point for the curve was found to be a SHR of 1.09, either lower (OR, 0.30; 95%CI, 0.10, 0.94) or higher (OR, 3.28; 95%CI, 2.01, 5.34) SHR is associated with increased mortality. However, a linear relationship was found in patients without AF, higher (OR, 1.95; 95%CI, 1.52, 2.51) SHR is associated with increased mortality. For patients with SHR ≤ 1.09, AF increased the risk of all-cause mortality(OR, 1.50; 95%CI, 1.10, 2.05), while this effect was not found in patients with SHR > 1.09.

Conclusion: The association between SHR and mortality in AMI patients with or without AF is different: U-shaped association between SHR and all-cause mortality only in AMI patients with AF, not in AMI patients without AF. AF is a factor that make the difference by increasing the risk of mortality in AMI patients with low SHR. Lower SHR may increase mortality through the onset of AF. This study emphasizes avoiding "relative hypoglycemia", SHR = 1.09 is the moderately tight glycemic control, which means glucose level is about (1.59 * HbA1c [%] - 2.59) * 1.09 mmol/L.

Trial Registration: Clinical trial number: not applicable.