From the Guidelines
Non-ST-Elevation Myocardial Infarction (NSTEMI) is diagnosed when there is evidence of myocardial necrosis without ST-segment elevation on electrocardiogram (ECG), with elevated cardiac biomarkers, specifically troponin levels above the 99th percentile of the upper reference limit, in the context of clinical evidence of myocardial ischemia, as defined by the most recent guidelines 1. The primary criteria for NSTEMI include:
- Elevated cardiac biomarkers, specifically troponin levels above the 99th percentile of the upper reference limit
- Clinical evidence of myocardial ischemia
- Absence of ST-segment elevation on ECG Patients typically present with:
- Chest pain or discomfort that may radiate to the jaw, arm, or back
- Shortness of breath, nausea, diaphoresis, or fatigue The ECG findings in NSTEMI may include:
- ST-segment depression
- T-wave inversions
- Normal or unchanged ECG Risk factors that increase suspicion for NSTEMI include:
- Older age
- Male sex
- Family history of coronary artery disease
- Diabetes
- Hypertension
- Hyperlipidemia
- Smoking
- Obesity The pathophysiology involves partial occlusion of a coronary artery or temporary complete occlusion that has resolved, resulting in damage to heart muscle without the full-thickness injury seen in STEMI. Prompt recognition of NSTEMI is crucial as early intervention with antiplatelet therapy, anticoagulation, and consideration for cardiac catheterization can significantly improve outcomes and prevent further myocardial damage, as recommended by the 2020 ESC guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation 1.
From the Research
Criteria for Non-ST-Elevation Myocardial Infarction (NSTEMI)
The criteria for NSTEMI include:
- Elevated cardiac biomarkers of necrosis, such as troponin, in the absence of persistent ST-segment elevation on an electrocardiogram (ECG) 2
- Presence of anginal symptoms or other acute events 2
- High-sensitivity troponin measurements are the preferred test to evaluate for NSTEMI 3
- ECG changes, such as ST-segment depressions or T-wave inversions, may be present but are not required for diagnosis 3
Diagnostic Considerations
- Chest discomfort at rest is the most common presenting symptom of ACS, including NSTEMI 3
- Electrocardiography should be performed immediately (within 10 minutes of presentation) to distinguish between STEMI and non-ST-segment elevation ACS (NSTE-ACS) 3
- High-sensitivity troponin values less than the 99th percentile upper reference limit at 6 hours or greater from symptom onset may safely rule out acute coronary syndrome in patients who do not meet rapid rule-out criteria 4
Biomarker Evaluation
- Troponin assays are the most sensitive and specific biomarkers for cardiac injury 5
- Creatine kinase (CK) is not useful in the workup of patients with NSTEMI symptoms when troponin is negative 5
- CK should not be used to screen patients presenting to the emergency department with chest pain 5
Treatment Considerations
- Anti-ischemic therapy, including nitrates, beta-adrenergic blockers, and calcium channel blockers, may be administered to reduce myocardial oxygen consumption and improve oxygen supply 6
- Reperfusion therapy, such as primary percutaneous coronary intervention (PCI), may be indicated for patients with NSTEMI 6