STEMI vs NSTEMI/Unstable Angina: Clinical Presentation Differences
No, patients with STEMI do not present the same way as those with NSTEMI or unstable angina - they have distinct clinical presentations, ECG findings, pathophysiology, and management requirements.
Key Differences in Presentation
STEMI Presentation
- Sudden, severe chest pain lasting >30 minutes
- Minimal or no relief with rest or nitroglycerin
- Complete coronary artery occlusion
- ST-segment elevation on ECG
- Transmural myocardial necrosis
- Requires immediate reperfusion therapy
NSTEMI/Unstable Angina Presentation
- Chest discomfort often more prolonged (>20 minutes) than stable angina
- May occur at rest or with minimal exertion
- Partial or intermittent coronary occlusion
- ST depression, T-wave inversion, or normal ECG
- NSTEMI shows elevated cardiac biomarkers; unstable angina does not
- Management based on risk stratification
Pathophysiological Differences
The fundamental difference lies in the coronary artery occlusion:
- STEMI: Complete occlusion of an epicardial coronary artery requiring immediate reperfusion 1
- NSTEMI/UA: Partial or intermittently occluding thrombus, often with subtotal occlusion 1, 2
ECG Findings
| STEMI | NSTEMI/UA |
|---|---|
| ST-segment elevation | ST depression, T-wave inversion, or normal ECG |
| Typically leads to Q-wave MI | Usually leads to non-Q-wave MI |
| Diagnostic for immediate reperfusion | Requires biomarkers for differentiation |
Biomarker Patterns
- STEMI: Elevated cardiac biomarkers (troponin)
- NSTEMI: Elevated cardiac biomarkers (troponin)
- Unstable Angina: Normal cardiac biomarkers
Management Priorities
STEMI Management
- Immediate reperfusion therapy is critical
- Primary PCI within 120 minutes (preferred) or fibrinolytic therapy if PCI not available within timeframe
- Reduces mortality from 9% to 7% 3
NSTEMI/UA Management
- Risk stratification using validated tools (TIMI, GRACE scores)
- High-risk patients: early invasive strategy within 24-48 hours
- Lower-risk patients: initial conservative strategy with possible delayed invasive approach
- Focus on antiplatelet, anticoagulant, and anti-ischemic therapies 2
Clinical Pearls and Pitfalls
Diagnostic Challenge: Initial presentation cannot reliably distinguish between STEMI and NSTEMI/UA until ECG is performed
Time-Critical Decision: ECG should be obtained within 10 minutes of presentation for all suspected ACS patients 2
Atypical Presentations: More common in:
- Older adults (≥75 years)
- Women
- Patients with diabetes
- Those with chronic renal failure or dementia
Atypical Symptoms: May include:
- Jaw, neck, ear, arm, or shoulder pain
- Back or epigastric discomfort
- Unexplained dyspnea
- Nausea, vomiting, diaphoresis
- Unexplained fatigue 2
Reperfusion Decision: For STEMI, the decision for reperfusion therapy must be made rapidly, with primary PCI preferred when available within 120 minutes 1, 3
Remember that prompt recognition of the specific type of acute coronary syndrome is essential for appropriate management and optimal outcomes. The initial ECG is the critical differentiating tool that guides immediate management decisions.