For patients with acute myocardial infarction (AMI), the acute-to-chronic (A/C) glycemic ratio predicts in-hospital morbidity and mortality better than glycemia at admission, according to a new study. The A/C is calculated by dividing the presenting (acute) glucose level value by estimated chronic glucose levels (which are calculated using the formula (28.7 × HbA1c) – 46.7).
In an observational study at a single facility in Italy, researchers prospectively measured glycemia at admission and calculated A/C glycemic ratio in consecutive patients with AMI to determine which indicator had better prognostic value. Patients were considered to have diabetes if diabetes or use of antidiabetes treatment was noted in the admission history, and unknown diabetes was diagnosed if patients had an HbA1c of 6.5% or greater at admission and no history of the disease. The primary end point of the study was a composite of in-hospital mortality, acute pulmonary edema, and cardiogenic shock. The study results were published Jan. 30 by Diabetes Care.
Overall, 1,553 patients were included in the study, 747 with ST-elevation MI (STEMI) and 806 with non-ST-elevation MI (NSTEMI). Mean age was 67 years, and most patients (74%) were men. Four hundred seventeen patients (27%) had diabetes, 233 (15%) had acute hyperglycemia according to a glucose cutoff of 198 mg/dL (11 mmol/L), and 583 (37%) had acute hyperglycemia according to a glucose cutoff of 144 mg/dL (8 mmol/L). Rate of the primary end point increased along with tertiles of A/C glycemic ratio (P<0.0001 for trend), and a parallel increase was seen in troponin I peak value (P<0.0001). A/C glycemic ratio remained an independent predictor of both the primary end point and troponin I peak value in multivariable analysis, with and without adjustment for major confounders. Reclassification analyses were performed and found that A/C glycemic ratio had the best prognostic power for the primary end point in the overall study population (12% net reclassification improvement; P=0.003) and especially in patients with diabetes (27% net reclassification improvement; P<0.0001).
The authors noted that most of the patients in their study were treated with percutaneous coronary intervention and that their results may not apply to patients with AMI who do not undergo that procedure. The study may also have been limited by its observational design and by the possibility that average chronic glucose level was underestimated in patients who had low hemoglobin levels at admission, among other factors, they said. However, they concluded that the A/C glycemic ratio appears to be closely associated with morbidity and mortality rates during hospitalization in patients with AMI. “Use of the A/C glycemic ratio may be particularly valuable in patients with diabetes with chronically elevated glycemic levels because it may identify true stress hyperglycemia, which has been associated with larger infarct size and worse in-hospital outcome,” the authors wrote.