Objective To analyze heart rate threshold of myocardial ischemia due to different coronary artery stenosis rate on cardiac end-systolic in patients with coronary myocardial bridge. Methods A total of 765 patients coronary angiography（CAG） were performed from January 2015 to December 2016

25 patients were founded coronary myocardial bridge

removed 3 patients with coronary myocardial bridge combine coronary artery occlusive disease. 22 patients with coronary myocardial bridge were divided into 3 groups according to coronary artery stenosis rate on cardiac end-systolic by quantitative coronary angiography（QCA）

A group coronary artery stenosis rate≤50%

50%<B group coronary artery stenosis rate ≤75%

75%< C group coronary artery stenosis rate ≤99%; 22 patients performed ambulatory Holter electrocardiogram

according to diagnostic criteria of myocardial ischemia

R-wave lead ST segment horizontal depression or downhill depression ≥0.1 mV

duration of each time ≥1 minute

two adjacent intervals at least 1 minute

observe heart rate threshold of myocardial ischemia in different groups. Results A group 5 patients coronary artery stenosis rate ≤50%

basic mean heart rate was 68±0.30 beat per minute

mean heart rate that lead to myocardial ischemia was 103 ±1.50 beat per minute; 50%< B group 2 patients coronary artery stenosis rate ≤75%

basic mean heart rate was 70±1.10 beat per minute

mean heart rate that lead to myocardial ischemia was 95±2.40 beat per minute; 75%< C group 15 patients coronary artery stenosis rate≤99%

basic mean heart rate was 70±2.30 beat per minute

mean heart rate that lead to myocardial ischemia was 86±1.60 beat per minute; statistically test

the difference of basic mean heart rate among ABC groups was not significant（p >0.05）; mean heart rate that lead to myocardial ischemia between A group and C group was statistically significant（p <0.05）; mean heart rate that lead to myocardial ischemia between A group and B group was not significant（p>0.05）; mean heart rate that lead to myocardial ischemia between B group and C group was not significant（p >0.05）; Conclusions Heart rate threshold of myocardial ischemia of patients with coronary myocardial bridge decreased along with coronary artery stenosis rate increased on cardiac end-systolic; the stenosis rate was more obvious

heart rate threshold of myocardial ischemia was more slow

it show that coronary flow reserve decreased.