What EKG finding defines STEMI?

The correct answer identifies a critical criterion for diagnosing STEMI (ST-Elevation Myocardial Infarction). In the context of an EKG, the presence of one mm of ST segment elevation in two contiguous leads serves as a significant marker for myocardial injury. This finding suggests that there is sufficient damage to the heart muscle due to insufficient blood flow, typically caused by a blockage in a coronary artery.

Contiguous leads refer to those that are anatomically connected and reflect the same area of the heart. When ST segment elevation is noted in two contiguous leads, it indicates that a larger area of the heart muscle is at risk, reinforcing the diagnosis of STEMI. This specific evidence of prolonged myocardial ischemia necessitates immediate medical intervention to restore blood flow and limit heart damage.

In contrast, the other options either refer to insufficient elevation in one lead or do not appropriately capture the clinical relevance needed for confirming STEMI diagnosis. Therefore, the requirement for ST segment elevation in two contiguous leads is crucial because it increases the likelihood of significant coronary artery occlusion, ultimately guiding urgent therapeutic decisions.