Evaluation of serum nitric oxide synthase levels in patients with coronary slow flow based on corrected TIMI frame count

Introduction: The coronary slow flow phenomenon (CSFP) finding in angiography is characterized by the delayed filling of the terminal vessels without significant epicardial coronary disease. The endothelium performs a vital role in cardiovascular homeostasis by releasing vasoactive substances. Endothelial cells produce nitric oxide (NO) as one of these essential compounds. Three isoforms of nitric oxide synthase (NOS) are endothelial nitric oxide synthase (eNOS), neuronal nitric oxide synthase (nNOS), and induced nitric oxide synthase (iNOS). We aimed to determine the role of NOS in the development of CSFP as the first human study. Material and methods: A total of 129 patients who met the inclusion criteria were enrolled in the study. The patients were classified into five groups based on the results of coronary angiography: Group 1 without coronary artery disease (CAD) and without CSF, group 2 without CAD and with CSF, group 3 with CAD (< 50%) and without CSF, group 4 with CAD (50-90%) and without CSF, and group 5 with CAD and CSF. The serum level of NOS was determined in the participants. Coronary flow was quantified in patients with CSFP using the corrected TIMI frame count (CTFC) method, and the correlation between the levels of this biomarker and CTFC was investigated. Results: In this study, the NOS serum levels were not significantly correlated with the mean CTFC. Since the total amount of NOS was measured as a result of 3 isoforms of this enzyme, the lack of correlation could be related to increased iNOS level and decreased eNOS concentration. Conclusions: These results should be confirmed by more human studies.