OBJECTIVEThe infarct-related artery (IRA) could not always be identified by electrocardiogram (ECG). In the present study, we attempted to explore the reason for failed IRA identification by ECG based on the comparison between ECG records and coronary angiographic findings.

METHODSAll 18-lead ECG records were compared with respective angiographic findings in 1024 consecutive patients with ST elevation myocardial infarction (STEMI) between October 2004 and July 2009. More than two continuous 18-lead ECG records were performed within 12 hours of the symptom onset in all patients. Patients with previous myocardial infarction, coronary artery bypass surgery, pacemaker implantation or ECG evidence of left bundle branch block and angiography was performed more than 12 hours time from symptom onset were excluded.

RESULTSOf all 1024 patients enrolled, the IRA were correctly identified in 854 cases and identified wrong in 96 cases and could not be identified in 74 cases by ECG. Of the failed identification in these 170 cases, IRA was left circumflex coronary artery in 76 (44.7%)cases, right coronary artery in 66 (38.8%) cases, left anterior descending branch in 20 (11.8%) cases, ramus medianus branch in 7 (4.1%) cases, and left main in 1(0.6%) case. Double-vessel and triple-vessel diseases were recorded in 27(15.9%) patients and 47(27.6%) patients respectively. Early repolarization syndrome occurred in 8 (4.7%) patients, and dextrocardia in 1 patient (0.6%). Angiographic study showed acute occlusion of a small branch in 6 (3.5%) patients.

CONCLUSIONCoronary collateral vessel can mislead judgments of the IRA by ECG. When the IRA can not be determined by ECG, left circumflex coronary artery is most likely to be the culprit vessel. Occasionally, early repolarization syndrome and anatomic variation of the coronary artery or heart and a small branch occlusion could be causes of misjudgments of IRA by ECG.