What is the management difference between NSTEMI (Non-ST-Elevation Myocardial Infarction) and STEMI (ST-Elevation Myocardial Infarction) in patients presenting with acute coronary syndrome?

NSTEMI vs STEMI: Key Management Differences

The fundamental management difference is that STEMI requires immediate reperfusion therapy (primary PCI within 120 minutes or fibrinolysis if PCI unavailable), while NSTEMI is managed with early invasive strategy (coronary angiography within 24 hours for high-risk patients) rather than emergent reperfusion. 1, 2

Pathophysiology and ECG Distinction

STEMI represents acute total coronary occlusion with transmural myocardial ischemia, manifesting as persistent ST-segment elevation (>20 minutes) on ECG 1. Most patients develop Q-wave MI 1.

NSTEMI results from partial or intermittent coronary occlusion causing subendocardial ischemia, presenting with:

• Transient ST-segment elevation
• Persistent or transient ST-segment depression (31% of cases)
• T-wave inversions (12% of cases)
• Combined ST-depression with T-wave inversions (16%)
• Normal ECG (41% of cases) 1, 3

Both conditions require elevated cardiac biomarkers (high-sensitivity troponin above 99th percentile) for diagnosis 1.

Immediate Management: STEMI

Reperfusion is the cornerstone of STEMI treatment and must be initiated immediately:

• Primary PCI within 120 minutes of first medical contact reduces mortality from 9% to 7% 1, 3
• Administer aspirin 150-300 mg (non-enteric coating) immediately, followed by P2Y12 inhibitor 2, 4
• Activate catheterization laboratory immediately 2

If PCI cannot be achieved within 120 minutes:

• Administer fibrinolytic therapy (alteplase, reteplase, or tenecteplase at full dose for patients <75 years; half dose for ≥75 years) 3
• Transfer to PCI-capable facility with goal of catheterization within 24 hours 3

Immediate Management: NSTEMI

Risk stratification determines timing of invasive strategy:

Very High-Risk NSTEMI (requires immediate angiography <2 hours): 1, 2

• Hemodynamic instability or cardiogenic shock
• Recurrent or ongoing chest pain despite medical therapy
• Malignant ventricular arrhythmias or cardiac arrest
• Mechanical complications (acute mitral regurgitation, ventricular septal defect)
• Acute heart failure

High-Risk NSTEMI (early invasive strategy within 24 hours): 1

• Elevated troponin levels
• Dynamic ST-segment or T-wave changes
• GRACE risk score indicating high risk
• Diabetes mellitus
• Renal insufficiency
• Reduced left ventricular ejection fraction

Initial medical therapy for NSTEMI: 2, 5

• Aspirin 150-300 mg loading dose, then 75-100 mg daily
• P2Y12 inhibitor (prasugrel or ticagrelor preferred over clopidogrel for patients proceeding to PCI) 1, 4
• Parenteral anticoagulation (unfractionated heparin, enoxaparin, or bivalirudin)
• Beta-blockers, ACE inhibitors, statins

Critical Timing Differences

Parameter	STEMI	NSTEMI
ECG interpretation	Within 10 minutes [1,3]	Within 10 minutes [1,3]
Reperfusion goal	PCI within 120 minutes [1,2,3]	Not applicable
Angiography timing	Immediate [1]	<2 hours if very high-risk; within 24 hours if high-risk [1]
Fibrinolysis option	Yes, if PCI unavailable [3]	No [1]

Antiplatelet Therapy Nuances

For STEMI: Immediate dual antiplatelet therapy (aspirin + P2Y12 inhibitor) before catheterization 2, 4

For NSTEMI:

• Do NOT routinely pre-treat with P2Y12 inhibitors when coronary anatomy is unknown and early invasive management is planned 1
• Prasugrel should be considered over ticagrelor for patients proceeding to PCI 1, 4
• Pre-treatment may be considered only if early invasive strategy cannot be performed, depending on bleeding risk 1

Common Pitfalls to Avoid

STEMI mimics ("Pseudo-STEMI"): ST-elevation can occur without acute coronary occlusion in conditions like pericarditis, early repolarization, left ventricular hypertrophy, or Takotsubo cardiomyopathy 1, 6. Consider clinical context and other ECG features.

Occult total occlusion in NSTEMI: A significant proportion of NSTEMI patients actually have acute total occlusion on angiography despite lack of ST-elevation 7, 6. Maintain high suspicion in patients with ongoing symptoms, hemodynamic instability, or extensive ECG changes.

Delayed recognition: Approximately 40% of men and 48% of women present with atypical symptoms (dyspnea, epigastric pain) rather than classic chest pain 3. Maintain low threshold for ECG and troponin testing.

Monitoring Requirements

Both conditions require:

• Continuous cardiac monitoring for at least 24 hours 2
• High-sensitivity troponin at 0 and 1-2 hours (or 3-6 hours if conventional troponin) 2
• Echocardiography to assess LV function and exclude mechanical complications 2
• Renal function assessment for medication dosing 2

Mortality Context

STEMI mortality with primary PCI: 7% 3 High-risk NSTE-ACS mortality with early invasive strategy: 4.9% (vs 6.5% with conservative strategy) 3

The key distinction remains: STEMI = emergent reperfusion now; NSTEMI = risk-stratified invasive strategy within hours to days 1, 3.