The objective of this study was to evaluate the usefulness of the fractional flow reserve (FFR)measurements in determining the degree of atherosclerotic stenosis in coronary arteries and toestablish the predictive value of FFR in the context of preventing the occurrence of a majoradverse cardiac event (MACE) in patients with diabetes mellitus (DM) as compared to thepatients without DM. Patients and MethodsThe sample was collected at the Centre Hospitalier Universitaire, CHU Henri Mondor inParis, France. The study included a total of 286 patients undergoing coronary angiographyand/or percutaneous coronary intervention (PCI) due to suspected or established coronaryartery disease (CAD). There were 103 patients with diabetes mellitus and 183 withoutdiabetes mellitus (the control group). At the time of the inclusion and during the study itself,we measured demographic and clinical data, laboratory findings and parameters of singlephoton emission computed tomography (SPECT). The duration of the designed clinicalfollow-up with analysing MACE was 24 months. Mace was defined by the occurrence of: 1)unstable angina pectoris; 2) myocardial infarction; 3) cerebrovascular insult or transitoryischemic attack; 4) fatal outcome; 5) subsequent PCI of the observed vessel or observedlesion and 6) subsequent coronary artery bypass graft (CABG). Immediately after performingthe coronary angiography, the FFR was measured in order to evaluate one or moreintermediary stenoses and decide on further treatment. VI ResultsIn comparison with the control group, patients with DM had a significantly longer stay inhospital, significantly higher values of ITM, while a notably greater number of them sufferedfrom dyslipidemia and arterial hypertension.As far as the medication therapy is concerned, patients with DM used significantly moreangiotensin convertase inhibitors I (ACE inhibitors) and beta blockers (BB). Patients withDM and FFR values ≥ 0,8, did not have statistically more MACEs than patients without DM,regardless of the reference diameter of the culprit coronary artery during the two-year follow-up. A higher FFR after the completion of PCI correlated with a smaller incidence of MACEsin patients with DM. FFR in patients with DM has a better sensitivity and specificity thanSPECT in recognising ischemia of the heart muscle. The incidence of complications duringthe FFR measurement is markedly low.ConclusionFFR is a safe and reliable invasive method, characterised by a low incidence of complicationsand used for screening significant atherosclerotic stenoses in patients with DM. FFR ≥ 0,8excludes a possible occurrence of MACE in patients with DM in a two-year time period. FFR≥ 0,9 measured after PCI is a safe prognostic factor in lowering the incidence of MACE in atwo-year time period.