Secondary electrocardiographic stratification of NSTEMI to identify an acutely occluded culprit artery

In the United States, approximately 720 000 adults will experience a myocardial infarction (MI) every year. The 12-lead electrocardiogram (ECG) is quintessential for the classification of a MI. About 30% of all MIs exhibit ST-segment elevation on the 12-lead ECG and is therefore classified as an ST-Elevation Myocardial Infarction (STEMI), which is treated emergently with percutaneous coronary intervention to restore blood flow. However, in the remaining 70% of MIs, the 12-lead ECG lacks ST-segment elevation and instead exhibits a motley of changes, including ST-segment depression, T-wave inversion, or, in up to 20% of patients, have no changes whatsoever; as such, these MIs are classified as a Non-ST Elevation Myocardial Infarction (NSTEMI). Of this larger classification of MIs, 33% of NSTEMI actually have an occlusion of the culprit artery consistent with a Type I MI . This is a serious clinical problem because NSTEMI with an occluded culprit artery have similar myocardial damage like STEMI and are more likely to suffer from adverse outcomes compared to NSTEMI without an occluded culprit artery. In this review article, we review the extant literature on NSTEMI with an occluded culprit artery. Afterward, we generate and discuss hypotheses for the absence of ST-segment elevation on the 12-lead ECG: (1) transient occlusion (2) collateral blood flow and chronically occluded artery and (3) ECG-silent myocardial regions. Lastly, we describe and define novel ECG features that are associated with an occluded culprit artery in NSTEMI which include T-wave morphology abnormalities and novel markers of ventricular repolarization heterogeneity.