NSTEMI is a True Heart Attack
Yes, Non-ST-Elevation Myocardial Infarction (NSTEMI) is definitively a true heart attack characterized by myocardial necrosis with detectable cardiac biomarkers in the absence of ST-segment elevation. 1
Understanding NSTEMI as a Myocardial Infarction
NSTEMI is distinguished from unstable angina by the presence of myocardial necrosis, which is the hallmark of a true heart attack. According to the American College of Cardiology Foundation/American Heart Association guidelines, the key difference between unstable angina and NSTEMI is the release of detectable quantities of cardiac biomarkers of myocardial necrosis, most commonly troponin I (TnI), troponin T (TnT), or CK-MB 2.
The pathophysiology of NSTEMI typically involves:
- A non-occlusive thrombus that develops on a disrupted atherosclerotic plaque, reducing myocardial perfusion 1
- Microembolization of platelet aggregates and components of the disrupted plaque 2
- Subtotal occlusion of a coronary artery, as opposed to the complete occlusion seen in STEMI 1
Diagnostic Criteria for NSTEMI
The diagnosis of NSTEMI requires:
- Detection of an increase and/or decrease of cardiac troponin with at least one value above the 99th percentile of the upper reference limit
- Symptoms of myocardial ischemia
- New ischemic ECG changes, development of pathological Q waves, or imaging evidence of new loss of viable myocardium 1
Comparison with Other Acute Coronary Syndromes
| Feature | Unstable Angina | NSTEMI | STEMI |
|---|---|---|---|
| Cardiac Biomarkers | Normal | Elevated | Elevated |
| Myocardial Necrosis | Absent | Present | Present (transmural) |
| ECG Changes | May show ischemic changes | ST depression/T-wave inversion | ST-segment elevation |
| Coronary Occlusion | Partial/transient | Partial/subtotal | Complete |
This table clearly demonstrates that NSTEMI shares the critical feature of myocardial necrosis with STEMI, confirming its status as a true heart attack 1.
Clinical Implications
The recognition of NSTEMI as a true heart attack has important clinical implications:
- Requires aggressive antiplatelet therapy, including aspirin and a P2Y12 inhibitor such as clopidogrel or ticagrelor 3
- Necessitates consideration of early coronary angiography and revascularization 4
- Carries significant mortality risk, with long-term outcomes often worse than STEMI due to higher burden of comorbidities, older age, and more extensive coronary artery disease 1
Important Considerations
- Approximately 30% of NSTEMI cases are associated with a total occlusion of a coronary artery, representing a high-risk subgroup that may benefit from immediate invasive strategy 5
- Risk stratification using validated tools such as TIMI and GRACE scores is essential for determining optimal management 1
- High-sensitivity cardiac troponin levels >50 ng/L appear to be an effective strategy to identify high-risk NSTEMI at presentation 6
Conclusion
NSTEMI is unequivocally a true heart attack characterized by myocardial necrosis with elevated cardiac biomarkers. While it differs from STEMI in terms of ECG presentation and the degree of coronary occlusion, it represents a serious acute coronary syndrome requiring prompt diagnosis and appropriate therapy to improve outcomes.