Metabolic instability may persist after acute coronary syndrome (ACS) despite apparently stable conventional glycemic markers. A prospective multicenter observational study from the ORACLE program, published in Cardiovascular Diabetology, found that continuous glucose monitoring (CGM) identified worsening glycemic control from hospital discharge to approximately 4 months after ACS, including in patients without diabetes.

The study enrolled consecutive high-risk ACS patients who wore a FreeStyle Libre 3/3 Plus sensor for 14 to 15 days near discharge and again at follow-up. CGM metrics included time in range 70 to 180 mg/dL, tight range 70 to 140 mg/dL, time above and below range, and glycemic variability and risk indices. Of all enrolled patients, 213 had baseline recordings that met quality criteria.

During the early post-ACS period, median time in range 70 to 180 mg/dL was 96.57%, while median tight-range time was 85.00%. Mean glucose was 114.26 mg/dL, and the median glucose management indicator was 6.04%. CGM profiles showed marked inter-individual heterogeneity and a reproducible late-morning vulnerability window between 10:00 and 12:00, characterized by a lower range time and higher hyperglycemic exposure. This pattern was consistent across diabetes status and similar on weekdays and weekends.

From baseline to approximately 4 months, tight-range time decreased by 4.5% (P=0.008) and mean glucose increased by 4.67 mg/dL (P=0.03). Variability and glycemic risk indices also worsened, whereas HbA1c remained stable. Across CGM endpoints, approximately 20% to 40% of patients showed worsening trajectories. Hypertension and chronic obstructive pulmonary disease were independently associated with tight-range worsening.

The findings suggest CGM may detect clinically relevant post-ACS dysglycemia that static measures such as HbA1c can miss, supporting more refined metabolic surveillance after ACS.