Diabetes-Related Differences in the Predictive Value of the Physiological Assessment of Myocardial Ischemia for Long-Term Clinical Outcomes

Background/Objectives: Physiological assessment of borderline coronary lesions is recommended by current guidelines for revascularization decision-making. The aim of our study was to assess the prognostic utility of physiological indices and determine whether their predictive value differs between patients with and without diabetes (DM). Methods: A physiological assessment was conducted in 381 patients with borderline coronary artery disease. The study cohort was divided according to the presence or absence of DM, and all individuals were followed over a four-year period. Results: Of the 381 patients, 154 (40.4%) had DM. Patients with DM had a higher BMI (30.1 kg/m2 vs. 27.8 kg/m2, p < 0.0001) and a lower left ventricular ejection fraction at the time of enrollment (50% vs. 55%, p = 0.0414) compared to the non-diabetic group. Patients diagnosed with DM had significantly more positive FFR results for ischemia, regardless of the assessed vessel, positive non-hyperemic evaluation of LAD and more PCI procedures, including PCI of the LAD. The mortality rate in FU among diabetics was 23.4%, while in patients without diabetes, it was 16.8%; (p = 0.1081). The clinical profile of deceased patients was largely comparable between groups. In patients with diabetes, the non-hyperemic physiological assessment by RFR/iFR (OR 0.68, 95%CI: 0.49–0.96; p = 0.0261) as well as iFR alone (OR 0.55, 95%CI: 0.32–0.97; p = 0.0388) was strongly correlated with the risk of death. In contrast to patients with DM, in the non-DM group, the non-hyperemic assessment using RFR (OR 0.37, 95%CI: 0.18–0.78; p = 0.0085) proved to be a significant prognostic factor. Conclusions: Non-hyperemic physiological indices (RFR/iFR) demonstrated a strong prognostic value in both diabetic and non-diabetic populations. Higher RFR/iFR values were consistently associated with a reduced risk of death. In the group of patients with DM, the iFR value may be considered a significant prognostic factor for long-term mortality. In the group without DM, the RFR assessment is such a factor.