Observational StudyEKG Criteria and Identification of Acute Coronary Occlusion

a. Acute occlusion proven on angiogram (an acute culprit lesion with TIMI 0-1 flow, or description of acute total thrombotic occlusion) b. Acute culprit lesion (any TIMI score) with Peak cTNI > 10 ng/mL or cTnT > 1.0 ng/mL c. If no catheterization performed (contraindicated, not compatible with goals of care, etc), then highly elevated troponin as above plus a new/presumed new focal wall motion abnormality on echocardiography d. Positive ECG findings (by any criteria) with death occurring before attempted emergent coronary angiography and autopsy confirming ACO. For cases with positive ECG findings and death before cath but NO autopsy, these will be marked and saved in a separate group, not to be used in the primary analysis.

a. Acute occlusion proven on angiogram (an acute culprit lesion with TIMI 0-2 flow, or description of acute total thrombotic occlusion) b. Acute culprit lesion (any TIMI score) with Peak cTNI > 10 ng/mL or cTnT > 1.0 ng/mL c. If no catheterization performed (contraindicated, not compatible with goals of care, etc), then highly elevated troponin as above plus a new/presumed new focal wall motion abnormality on echocardiography d. Positive ECG findings (by any criteria) with death occurring before attempted emergent coronary angiography and autopsy confirming ACO. For cases with positive ECG findings and death before cath but NO autopsy, these will be marked and saved in a separate group, not to be used in the primary analysis.

1. Severe 3-vessel disease: >/=75% stenosis in all three major coronary vessels (or equivalents in the case of anatomic variants or preexisting bypass) with an acute culprit lesion (TIMI<3) or
2. Left main stenosis > 50% (see Smith review paper for reference): acute left main culprit of any TIMI score, or any lesion of the left main with TIMI<3 or
3. Any other cardiac catheterization findings prompting initiation of emergent coronary artery bypass grafting within the next 120 hours

1. At least three sequential negative cardiac biomarkers within 24 hours of presentation
2. cardiac catheterization showing no culprit lesion.
3. Angiogram showing an acute culprit lesion but both no occlusion (TIMI 2 or greater) and troponins not exceeding the cutoff above
4. If positive troponin values present but no angiography, then the patient must have echocardiography showing no wall motion abnormality and troponin values less than the above cutoff
5. If the patient has insufficient data to classify into one of these categories, the patient must be excluded from the study as they cannot be classified as ACO or non-ACO. For example, patients with extremely high troponin but no culprit seen on cath may have acute occlusion with complete autolysis of thrombus, myocarditis, spasm, etc. Thus the investigators cannot classify them as NO ACO when the possibility of ACO remains and cannot be disproven.

There will be no intervention as a part of this protocol.