ACLS ProMed Practice Test

In suspected ACS, the main purpose of the 12-lead ECG is to detect ST-segment elevation, which signals a STEMI. This pattern reflects acute transmural ischemia from a coronary artery occlusion and is the key finding that triggers immediate reperfusion therapy (like PCI or thrombolysis). The ST elevations appear in contiguous leads that map to the affected heart region, guiding urgent management.

If there’s no ST elevation, ACS may be NSTEMI or unstable angina, which are diagnosed with symptoms plus troponin elevation rather than ST-elevation changes. ECG can sometimes be abnormal in other conditions like pulmonary embolism or aortic dissection, but those diagnoses rely on imaging and other tests, not on ST-segment elevation patterns.