What is the primary difference between a STEMI and an NSTEMI?

The primary distinction between a STEMI (ST-Elevation Myocardial Infarction) and an NSTEMI (Non-ST-Elevation Myocardial Infarction) lies in the presence of ST segment elevation on an electrocardiogram (ECG). In a STEMI, there is a significant elevation in the ST segment, which signals a complete blockage of a coronary artery and indicates that there is an extensive area of heart muscle at risk due to lack of blood flow. This condition requires immediate intervention to restore blood flow and minimize heart damage.

In contrast, NSTEMI is characterized by the absence of ST segment elevation. While NSTEMI indicates some level of myocardial injury, it generally involves either partial blockage or transient ischemia. It can be associated with elevated cardiac biomarkers but does not produce the same urgent ECG changes that necessitate immediate revascularization procedures like a STEMI.

Thus, the correct answer effectively captures the critical difference between the two types of myocardial infarctions by highlighting the presence of ST segment elevation in STEMI, which is essential for understanding the urgency of treatment required for each condition.