What are the differences in treatment between STEMI (ST-Elevation Myocardial Infarction) and NSTEMI (Non-ST-Elevation Myocardial Infarction)?

STEMI vs NSTEMI: Differences in Treatment

The primary difference in treatment between STEMI and NSTEMI is the timing of reperfusion therapy - STEMI requires immediate reperfusion (ideally within 90 minutes of first medical contact) while NSTEMI typically follows an early invasive strategy within 24 hours for high-risk patients. 1

Pathophysiology and Diagnosis

• STEMI (ST-Elevation Myocardial Infarction) is characterized by a completely occlusive thrombus resulting in ST-segment elevation on ECG, indicating full-thickness myocardial damage 1
• NSTEMI (Non-ST-Elevation Myocardial Infarction) typically involves a partially occlusive thrombus leading to ST-segment depression, T-wave inversion, or nonspecific ECG changes 1, 2
• Both conditions are diagnosed by a combination of symptoms, ECG findings, and elevated cardiac biomarkers (troponin), but with different ECG patterns 1, 2

Initial Management (First 10 Minutes)

• For both STEMI and NSTEMI, a 12-lead ECG should be acquired and interpreted within 10 minutes of first medical contact 1
• Both conditions require immediate administration of aspirin 162-325 mg (chewed) by EMS providers 1
• Both require assessment of vital signs, focused history, and physical examination 1

Reperfusion Strategy Differences

STEMI Reperfusion:

• Immediate reperfusion therapy is mandatory for STEMI patients with symptom onset within 12 hours 1
• Primary PCI is the preferred method when it can be performed in a timely fashion (first medical contact-to-device time ≤90 minutes) 1
• If PCI cannot be performed within 120 minutes of first medical contact, fibrinolytic therapy should be administered within 30 minutes of arrival 1
• Patients should be transported directly to PCI-capable hospitals when possible 1

NSTEMI Management:

• Early invasive strategy (coronary angiography with intent to perform revascularization) within 24 hours is recommended for high-risk NSTEMI patients (GRACE score >140 or TIMI risk score >4) 1
• Immediate invasive approach (within 2 hours) is indicated for unstable patients with refractory angina, heart failure, or hemodynamic instability 1
• Medical therapy focuses on anti-ischemic medications, dual antiplatelet therapy, and risk factor modification 1, 3

Pharmacological Treatment

For Both STEMI and NSTEMI:

• Dual antiplatelet therapy with aspirin and a P2Y12 inhibitor (clopidogrel, ticagrelor, or prasugrel) 4, 1
• Clopidogrel is indicated for both STEMI and NSTEMI patients, administered in conjunction with aspirin 4
• Anti-ischemic therapy including nitrates, beta-blockers, and pain management with morphine as needed 5
• Anticoagulation with unfractionated heparin or low-molecular-weight heparin 1

STEMI-Specific:

• Loading dose of P2Y12 inhibitor (300-600 mg clopidogrel) prior to primary PCI 4
• Consideration for glycoprotein IIb/IIIa inhibitors, particularly in high thrombus burden cases 1, 6
• Therapeutic hypothermia for comatose STEMI patients after out-of-hospital cardiac arrest due to ventricular fibrillation or pulseless ventricular tachycardia 1

NSTEMI-Specific:

• Risk stratification using GRACE or TIMI scores to determine timing of invasive strategy 1, 2
• Management of underlying causes in Type 2 NSTEMI (supply-demand mismatch) 3

Post-Acute Management

• Both conditions require similar secondary prevention strategies including dual antiplatelet therapy, statins, beta-blockers, and ACE inhibitors 7
• STEMI patients typically receive more aggressive secondary prevention therapies at discharge compared to NSTEMI patients, though this difference is not supported by differences in disease severity 7
• Despite different initial management approaches, long-term outcomes (1-year mortality) are similar between STEMI (9.0%) and NSTEMI (11.6%) patients 7

Common Pitfalls to Avoid

• Delaying ECG acquisition beyond 10 minutes of first medical contact 1
• Failing to recognize STEMI equivalents (hyperacute T-waves, posterior MI, multilead ST depression with ST elevation in aVR) 1, 2
• Overlooking high-risk NSTEMI patients who need urgent invasive management 1
• Underestimating NSTEMI risk - outcomes are similar or worse compared to STEMI at 1 year 7
• Missing atypical presentations in women, elderly, and diabetic patients who may present without chest pain 1, 2

Remember that while initial management strategies differ significantly based on ECG findings, both conditions represent acute coronary syndromes requiring prompt diagnosis, risk stratification, and appropriate intervention to improve outcomes 8.