From the Guidelines
STEMI and NSTEMI differ primarily in their presentation, ECG findings, and laboratory markers, with STEMI typically involving complete blockage of a coronary artery and NSTEMI involving partial occlusion or temporary blockage, as noted in the 2017 guidelines 1. The key differences between STEMI and NSTEMI are:
- Presentation: STEMI patients typically present with persistent chest pain lasting more than 30 minutes, while NSTEMI patients may have similar chest pain but with varying durations.
- ECG findings: STEMI is characterized by ST-segment elevation of ≥1 mm in two or more contiguous leads, indicating complete coronary artery occlusion, whereas NSTEMI shows ST-segment depression, T-wave inversion, or may be normal without ST elevation.
- Laboratory markers: Cardiac biomarkers like troponin and CK-MB are elevated in both STEMI and NSTEMI, but to a greater extent in STEMI, reflecting more significant myocardial damage. The pathophysiological difference between STEMI and NSTEMI is that STEMI involves complete blockage of a coronary artery causing full-thickness myocardial damage, while NSTEMI typically involves partial occlusion or temporary blockage resulting in less extensive damage, as described in the 2014 guidelines 1. Both conditions require immediate medical attention, though STEMI typically necessitates more urgent reperfusion therapy, ideally within 90 minutes of first medical contact through primary percutaneous coronary intervention (PCI), as recommended in the 2011 focused update 1. It is essential to note that the management of STEMI and NSTEMI has evolved over time, with updates in guidelines and recommendations, such as the use of antiplatelet and antithrombin therapy, and the importance of early risk stratification, as discussed in the 2010 guidelines 1 and the 2003 application of current guidelines 1. In clinical practice, the differentiation between STEMI and NSTEMI is crucial, as it guides the treatment approach and determines the level of urgency required, with STEMI patients requiring immediate reperfusion therapy and NSTEMI patients undergoing early invasive or noninvasive strategies, as outlined in the 2012 focused update incorporated into the 2007 guidelines 1.
From the Research
Signs and Symptoms
- Chest discomfort at rest is the most common presenting symptom of acute coronary syndromes (ACS), including STEMI and NSTEMI, affecting approximately 79% of men and 74% of women 2
- Approximately 40% of men and 48% of women present with nonspecific symptoms, such as dyspnea, either in isolation or in combination with chest pain 2
- STEMI and NSTEMI can present with similar symptoms, making diagnosis based on symptoms alone challenging
Lab Tests and Diagnosis
- Electrocardiography (ECG) is used to distinguish between STEMI and non-ST-segment elevation ACS (NSTE-ACS), with STEMI characterized by significant ST-segment elevation on ECG 2, 3
- High-sensitivity troponin measurements are the preferred test to evaluate for NSTEMI 2
- Coronary catheterization and percutaneous coronary intervention (PCI) within 2 hours of presentation can reduce mortality in STEMI patients 2
- Invasive coronary angiography and percutaneous or surgical revascularization within 24 to 48 hours can reduce mortality in high-risk patients with NSTE-ACS 2
Key Differences between STEMI and NSTEMI
- STEMI is caused by complete coronary artery occlusion, while NSTEMI is caused by partial or intermittent occlusion of the artery 2
- STEMI accounts for approximately 30% of ACS, while NSTEMI accounts for approximately 70% of ACS 2
- STEMI is characterized by significant ST-segment elevation on ECG, while NSTEMI may present with ST-segment depressions, T-wave inversions, or no significant ECG changes 2