Objective To investigate the impact of circumflex occlusion on the terminal part of QRS complex in ECG. Methods Eighteen patients diagnosed as acute myocardial infarction（AMI） and acute single LCX occlusion confirmed by coronary angiography（CAG） was enrolled to find the relationship between the occlusive vessel distribution and the abnormality of the terminal part of QRS complex in electrocardiogram（ECG）. Twenty-three cases with single right coronary artery（RCA） occlusion were enrolled at the same time as control. Results There are abnormalities at the end of QRS descending on Lead I and a VL

which is associated with the missing blood supply of obtuse marginal branch（LCX-OM）. It is rare that RCA occlusion can results in the abnormalities at the end of QRS descending on Lead I and a VL

while LCX often does

especially OM occlusion. Conclusions Abnormalities at the end of QRS complex descending are prevalent in patients with AMI

which has distribution inclination. When facing the ECG of an acute and continuous chest pain patient without obvious ST segment elevation or Q wave

the abnormality at the terminal part of QRS descending must be paid attention to.