- Presenting to the ED within 6 hours from onset of chest discomfort (pain, pressure, tightness, etc) consistent with a possible diagnosis of AMI or ACS and with an initial ECG non-diagnostic for injury (or injury equivalent resulting in emergent reperfusion therapy). (NOTE: Subjects who have chest discomfort that is episodic or stuttering in nature may be included if the ED presentation is within 6 hours of symptom onset.)