This is a prospective, single-center study. The primary purpose of this study is to evaluate the sensitivity and specificity of offline computational ultrasonic flow ratio (UFR) with conventional pressure wire-based fractional flow reserve (FFR) as the standard reference. The study will be conducted in Fuwai Hospital, and a total of 408 patients with coronary vessel diameter stenosis ≥30% and ≤80% are planned to be recruited. Participants who meet the inclusion criteria and do not meet the exclusion criteria will undergo intravascular ultrasound (IVUS) followed by FFR examination. IVUS imaging will be sent to an independent core laboratory for UFR calculation. UFR analyses were performed offline in a blinded fashion without awareness of FFR measurement. Using FFR≤0.80 as the gold standard, the sensitivity and specificity of UFR in the functional significance of coronary artery stenosis will be analyzed.

Inclusion Criteria:

• Stable angina pectoris, unstable angina pectoris, or after the acute phase of myocardial infarction
• Age ≥18 years
• Written informed consent
• Intermediated coronary lesions (diameter stenosis of 30%-80% by visual estimation from coronary angiography)

Exclusion Criteria:

• Ineligible for diagnostic IVUS or FFR examination
• Prior coronary artery bypass grafting of the interrogated vessels
• Myocardial infarction within 72 h of coronary angiography
• Severe heart failure
• Serum creatinine levels >150 umol/L, or glomerular filtration rates <45 ml/kg/1.73 m2
• Allergy to the contrast agent or adenosine
• Life expectancy < 2 years
• IVUS pullback not covering the entire lesion
• Severe myocardial bridge in the interrogated vessel

Patients ≥ 18 years of age who will be admitted for coronary angiography and had an indication for FFR measurement at the FuWai Hospital, Beijing, China, due to stable angina or unstable angina will be consecutively enrolled.