Investigators will enroll consecutive patients with NSTE-ACS with a culprit intermediate stenosis between 40 and 70% and in whom FFR evaluation will result negative (>0.80). In these patients, the operator will perform IVUS-NIRS and OCT and a blood sample to evaluate endothelial function as per our previous experience (5). The study has no control group. Endothelial function and inflammatory state will be evaluated in all patients and will be compared to those obtained by patients enrolled in the NATHAN NEVER study (NCT02519608, Study ID: 150497)(5).