02/05/2026
A STEMI (ST-elevation myocardial infarction) occurs when a coronary artery becomes acutely occluded, causing full-thickness myocardial ischemia. Electrically, injured heart cells can’t maintain normal membrane potentials, creating a current of injury that shifts the ST segment upward in the leads viewing that affected wall of the heart.
In simple terms: the heart muscle is starving for oxygen, its electrical behavior changes, and the EKG shows it. But not all ST elevation is a true STEMI.
Common STEMI mimics include early repolarization (commonly seen in athletic patients), pericarditis, left bundle branch block, ventricular aneurysm from an old MI, hyperkalemia, and left ventricular hypertrophy. These can produce ST changes without an acute coronary occlusion — and treating them as a STEMI can lead to unnecessary cath lab activation or missed alternative diagnoses.
This 35yo M patient presented to EMS with central, sub-sternal chest pain x 30 minutes while on scene at an outdoor law enforcement operation in January. He denied medical history, nausea, back pain, radiation of pain, but did have some mild associated shortness of breath.