This study clarified the influence of myocardial bridge on coronary hemodynamics by clarifying FFR and d-FFR to guide clinical intervention and treatment.

Myocardial bridge is a congenital anatomical abnormality, which is generally considered to be a benign change, but individual can cause angina, myocardial infarction and even sudden death. Previously, it was believed that the degree of myocardial ischemia induced by myocardial bridge was related to factors such as the location, length, and systolic stenosis of the myocardial bridge shown by coronary angiography.However, in recent years, more and more evidence has suggested that there is a high degree of mismatch between anatomical stenosis and its function.Studies have shown that FFR and d-FFR can accurately evaluate the functional significance of stenotic lesions.This study intends to enroll patients who underwent coronary angiography due to chest pain and confirmed the left anterior descending artery (LAD) simple myocardial bridge systolic stenosis ≥30%, and the pressure guide wire was used to measure the FFR and d-FFR of the myocardial bridge lesion under static and dobutamine stress.Analyze the relationship between these functional parameters and the anatomical morphological characteristics of the myocardial bridge and other possible clinical influencing factors, and explore the influence of the morphological characteristics of the myocardial bridge on myocardial hemodynamics，so as to clarify the degree of myocardial bridge shown by angiography may induce obvious myocardial ischemia, which requires clinical intensive intervention.

Inclusion Criteria:

• Patients with chest pain aged ≥18 years old, regardless of gender;
• Coronary angiography shows a solitary myocardial bridge with systolic diameter stenosis ≥30% in LAD;
• Have the ability to complete an ECG exercise test;
• Sign informed consent and are willing to participate in the intended study.

Exclusion Criteria:

• Patients with acute coronary syndrome;
• Coronary angiography shows that the diameter of atherosclerosis in the non-myocardial bridge area of LAD is ≥30%;
• RCA or LCX has severe fixed stenosis, diameter stenosis ≥70% or FFR<0.75, and no interventional therapy is accepted;
• Hypertrophic obstructive cardiomyopathy or more than moderate heart valve disease;
• Atrial fibrillation or severe slow or rapid arrhythmia;
• Heart failure with NYHA ≥ Grade III;
• Uncontrolled hypertension or systolic blood pressure <100mmHg;
• Asthma or severe chronic obstructive pulmonary disease;
• Severe liver and kidney dysfunction;
• Allergic to contrast agents.

The investigators enrolled patients with LAD simple myocardial bridge after other interventional treatments for vascular lesions or FFR testing to exclude functionally significant lesions.