The aim of this prospective, investigator-initiated study is to evaluate the diagnostic accuracy and correlations between mopphometric indices: luminal and qualitative parameters assessed by optical coherence tomography (OCT) including minimal lumen area, plaque type, presence of thin cap fibroatheroma and a functional index - angiography based vessel fractional flow reserve (vFFR) among patients with chronic coronary syndrome identified with intermediate grade coronary stenosis.

This is a prospective, single center, non-randomized, single-arm, investigator-initiated study evaluating diagnostic accuracy and correlations between morphometric indices: luminal and qualitative parameters evaluated by optical coherence tomography (OCT) including minimal lumen area, plaque stratification into fibrotic, calcific, lipidic plaque, or thin cap fibroatheroma and a functional index - angiography based vessel fractional flow reserve (vFFR) among patients with chronic coronary syndrome identified with intermediate grade coronary stenosis.

The additional objectives encompass assessing the influence of age, sex, diabetes mellitus, renal dysfunction on the relationship between vFFR results and morphometric indices of intermediate coronary stenosis.

We hypothesized that in patients with intermediate grade coronary stenosis in chronic coronary syndrome a positive correlation exists between vFFR and the morphometric parameters associated with coronary stenosis.

Inclusion Criteria:

• 18 years or older
• Chronic coronary syndrome defined as presence of chest pain ranked 2-3 in the Canadian Cardiovascular Society classification or positive ischemia test (exercise test, single photon emission tomography (SPECT)
• Intermediate grade coronary stenosis of 40-80% assessed visually in coronary angiography and OCT examination The patient is willing to participate in the study and has provided a written informed consent

Exclusion Criteria:

• Acute coronary syndrome
• Proximal left main lesion
• Ostial right coronary artery lesion
• Bypass of the assessed vessel
• Contraindications for adenosine administration
• Hemodynamic instability
• Heart insufficiency in New York Heart Association (NYHA) class IV scale
• Acute renal insufficiency
• Pregnancy

Patients undergoing coronary angiogram due to chronic coronary syndrome with intermediate grade coronary stenosis.