To study the effect of myocardial microcirculation disturbance on coronary flow reserve fraction, compare the evaluation value of IMR, FFR and QCA on myocardial ischemia, and discuss the correlation among them.

In this study, 60 patients with critical lesions indicated by coronary angiography will be admitted. The investigators collected the basic clinical data (gender, age, body mass index, smoking history, hypertension, diabetes, hyperlipidemia), laboratory data (creatinine, cholesterol, triglycerides) and measured their FFR and IMR.

Inclusion Criteria:(1) Age: 18-75 years old, unlimited for men and women;

(2) Quantitative coronary angiography (QCA) showed that there was a critical lesion in the proximal or middle segment of the coronary artery (diameter stenosis rate was 50% - 70%), and the diameter of the artery was more than 2.5mm;

(3) Agree to participate in the study and sign informed consent

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Exclusion Criteria:(1) Patients with acute myocardial infarction within one month;

(2) Patients with congenital heart disease, severe valve disease, dilated cardiomyopathy, pulmonary heart disease and hypertrophic cardiomyopathy;

(3) With severe heart failure (NYHA cardiac function grade ≥ grade III or left ventricular ejection fraction < 35%);

(4) Patients with less than 1 year of stent implantation or with coronary artery bypass grafting;

(5) Patients with left main lesion, severe distorted calcification, open lesion, bifurcated lesion or complete occlusion;

(6) Patients with severe hepatorenal insufficiency;

(7) Contraindications to adenosine, aspirin and clopidogrel;

(8) Patients with advanced tumor or life expectancy less than 1 year;

(9) Patients with severe asthma or uncontrolled asthma;

(10) Women in pregnancy.

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