After patient arrival, the MICN or research assistant will log patient and retain paramedic and base record for the study investigator. The following information will be obtained regarding patient EMS and ED phase: patient sequence number and medical record number, age, gender, race, initial prehospital vital signs (blood pressure, heart rate, pain scale), treatment with nitroglycerin in the field (number of doses), initial triage vital signs (heart rate, blood pressure, pain scale), ECG findings (location of ST elevations if present), disposition to the cath lab (yes/no). On follow up, a study investigator will enter whether percutaneous coronary intervention (PCI) was performed, the location of the culprit lesion(s) for patients treated in the cath lab, and final diagnosis and disposition for all patients. This information will be obtained via chart review and discussion with the cath lab team as required. There will be no follow-up of patients beyond hospital discharge. A second investigator will review a random 10% sample of records for key data elements.