• The Sensitivity and Specificity of Current "STEMI" Criteria for Acute Coronary Occlusion. [ Time Frame: Up to 48 hours ]
  Determine the accuracy of current "STEMI" ECG criteria (as reported in the 4th universal definition of MI) in diagnosing acute coronary occlusion. Type 1a, 1c and 1d ECGs will be included in this group.
• The Sensitivity and Specificity of ECG Without ST-segment Elevation for Acute Coronary Occlusion [ Time Frame: Up to 48 hours ]
  Determine the accuracy of ECG interpretation of acute coronary occlusion without STEMI criteria. Only type 1b ECGs will be included in this group.
• The Specificity of ECG With STEMI Criteria [ Time Frame: Up to 48 hours ]
  Explore the rationale for correct ECG interpretation of false positive STEMI criteria. Only type 1c and 1d ECGs will be included in this group.
• The Sensitivity of ECG With STEMI Criteria [ Time Frame: Up to 48 hours ]
  Explore the rationale for correct ECG interpretation of false negative STEMI criteria. The occurrence of type 1c ECGs in subgroups will be compared.
• The Outcome (Mortality) According to ECG Subclassifications (STEMI/NSTEMI/Control Groups) [ Time Frame: Up to one year ]
  Compare the outcomes of the patients who are labeled as STEMI and the patients who are labeled as having NSTEMI but have acute coronary occlusion.

• The sensitivity and specificity of current criteria [ Time Frame: Up to 48 hours ]
  Determine the accuracy of current ECG criteria in diagnosing acute coronary occlusion
• The sensitivity and specificity of ECG without ST-segment elevation [ Time Frame: Up to 48 hours ]
  Determine the accuracy of ECG interpretation of acute coronary occlusion without STEMI criteria
• The Specificity of ECG With STEMI Criteria [ Time Frame: Up to 48 hours ]
  Explore the rationale for correct ECG interpretation of false positive STEMI criteria
• The Sensitivity of ECG With STEMI Criteria [ Time Frame: Up to 48 hours ]
  Explore the rationale for correct ECG interpretation of false negative STEMI criteria
• The outcome according to ECG subclassifications [ Time Frame: Up to one year ]
  Compare the outcomes of the patients who are labeled as STEMI and the patients who are labeled as having NSTEMI but have acute coronary occlusion.

In this retrospective, single-center, case-control study the investigators will seek to compare the diagnostic accuracy of various ECG criteria to identify acute coronary occlusion (ACO). The investigators will scan the charts of the patients presenting to emergency department with a clinical picture suggestive of acute coronary syndrome in the specified time period. Patients without any admission ECG will be excluded. Patients who had a final diagnosis of myocardial infarction (MI) with or without subsequent coronary intervention will be enrolled. These patients will be classified as ST-segment elevation (STEMI) group or non-ST-segment elevation (NSTEMI) group according to their final diagnosis. Patient who had been excluded for acute coronary syndrome with serial unchanging ECGs AND negative serial troponins will constitute a third group. Allocation to each group will be continued until the patient number in each group reaches up to 1000 patients. The dead or alive status of all included patients will be checked from the electronic national database.

All ECGs will be reviewed by two cardiologists blinded to the angiographic and clinical outcomes. The presence of predefined ECG findings of ACO (including, but not limited to, current established STEMI criteria) will be recorded. The coronary angiograms of the first two groups will be reviewed for ACO by independent investigators who are blinded to ECG parameters. The diagnosis of acute coronary occlusion will be dependent upon angiographic occlusion and rising cardiac biomarker levels. Because in some cases of ACO, the artery may spontaneously open by the time of the angiogram, the investigators will need to have surrogate endpoints: this will be culprit lesion OR acute occlusion on the angiogram AND a sufficiently elevated peak troponin, i.e., peak troponin I > 1.0 ng/mL with a 20% change within first 24 hours OR peak troponin T > 5.0 ng/mL, which have been shown to be highly correlated with ACO OR cardiac arrest in a clinical scenario compatible with ACO before blood could be withdrawn for troponin essay.

The sensitivity, specificity and diagnostic accuracy of all these predefined ECG criteria will be sought. Also, sensitivity, specificity and diagnostic accuracy of current established STEMI criteria will be defined. Both short- and long-term mortality of the patients with a diagnosis of STEMI with ACO, STEMI without ACO, NSTEMI with ACO, NSTEMI without ACO and chest pain without acute coronary syndrome will be compared.

• Myocardial Infarction
• Acute Coronary Syndrome
• Coronary Artery Disease

• STEMI
  Current international ECG criteria (New ST-segment elevation at the J-point in two contiguous leads with the cut-points: ≥0.1 mV millivolts (mV) in all leads other than leads V2-V3; for leads V2-V3: ≥2 mm in men ≥40 years; ≥2.5 mm in men <40 years, or ≥1.5 mm in women regardless of age) with troponin rise above 99th percentile in a clinical situation suggestive of myocardial ischemia.
  Intervention: Radiation: Coronary angiogram
• NSTEMI
  Troponin rise above 99th percentile in a clinical situation suggestive of myocardial ischemia without abovementioned criteria.
  Intervention: Radiation: Coronary angiogram
• Normal
  Emergency department admission with a clinical picture compatible with acute coronary syndrome, but no change in serial ECGs and no rise in cardiac biomarkers

Inclusion Criteria:

• Admission to emergency department with a clinical picture suggestive of acute coronary syndrome

Exclusion Criteria:

• Absence of documented ECG
• Age <18 years