STEMI vs NSTEMI questions love to hide in plain sight: the patient looks the same (chest pain, diaphoresis, risk factors), but management hinges on one fast decision—is there an occlusive coronary thrombus you need to open now? Here’s a 5‑second rule you can run on every vignette to choose the right pathway.
The 5‑Second Rule (Say it out loud)
“STEMI = ST‑Elevation? Send to the lab.”
- STEMI → immediate reperfusion (PCI preferred; fibrinolysis if PCI can’t happen fast enough)
- NSTEMI/Unstable angina → no lytics; treat medically + risk‑stratify for early invasive approach
One-liner:
STEMI is an “open the artery now” problem; NSTEMI is a “stabilize + stratify” problem.
Quick Visual / Mnemonic Device: “ELEVATE → ELEVATOR”
When you see ST‑ELEVation, put the patient in the ELEVATOR straight to the cath lab.
- ELEVATE (STEMI) → ELEVATOR → PCI
- No elevation (NSTEMI/UA) → NO lytics → risk score → early cath if high risk
Step 1: Recognize the Pattern (ECG + Biomarkers)
STEMI
ECG:
- ST elevation in contiguous leads or new LBBB with ischemic symptoms (classic board trigger)
Path: Usually complete coronary occlusion → transmural ischemia/infarction.
NSTEMI vs Unstable Angina (UA)
ECG:
- ST depression and/or T‑wave inversion or even normal ECG
Biomarkers:
- NSTEMI: troponin positive
- UA: troponin negative
Path: Usually partial/subtotal occlusion or severe demand ischemia → subendocardial injury.
Step 2: Immediate Actions Everyone Gets (“MONA-ish + antithrombotics”)
High-yield reality: MONA is not the algorithm, but several components are still commonly used early. Think anti-ischemic + antiplatelet + anticoagulation.
Initial stabilization for suspected ACS (both STEMI and NSTEMI/UA)
- Aspirin (chewed)
- P2Y12 inhibitor (e.g., clopidogrel, ticagrelor) when appropriate per strategy
- Anticoagulation (e.g., heparin) unless contraindicated
- High-intensity statin
- Nitroglycerin for pain (avoid in certain settings below)
- Oxygen only if hypoxemic (boards love to punish routine O₂)
- Morphine is no longer “automatic” (can be used selectively; can reduce absorption of oral P2Y12)
USMLE “don’t miss” contraindications to nitrates:
- Right ventricular infarct (inferior MI + hypotension, JVD, clear lungs) → preload dependent
- Recent PDE‑5 inhibitor use (sildenafil, tadalafil)
- Severe hypotension
Step 3: The Fork in the Road = Reperfusion Strategy
If STEMI: Reperfuse—FAST
Goal: restore flow to prevent myocardial death.
Preferred: Primary PCI
- Door-to-balloon goal: typically ≤ 90 minutes at PCI-capable center
- If transferring: keep total time short (boards often emphasize “if PCI can’t be performed rapidly…”)
If PCI isn’t timely available: Fibrinolysis
- Best if within 12 hours of symptom onset (earlier is better)
- Follow with transfer for angiography (“pharmaco-invasive” strategy)
Absolute/major fibrinolysis contraindications (high yield)
- Any prior intracranial hemorrhage
- Known intracranial neoplasm/AVM
- Ischemic stroke within 3 months
- Active bleeding/significant bleeding diathesis
- Suspected aortic dissection
- Severe uncontrolled hypertension (classically SBP > 180 or DBP > 110)
Board pitfall: NSTEMI ≠ lytics (risk of bleeding without clear benefit).
If NSTEMI/UA: No lytics—Risk stratify
Treat with:
- Antiplatelet therapy (ASA + P2Y12 per strategy)
- Anticoagulation
- Anti-ischemic meds (beta-blocker if no contraindication, nitrates, statin)
Then decide on early invasive (angiography ± PCI) vs ischemia-guided approach using clinical risk.
Clues that push NSTEMI toward early cath (common USMLE triggers):
- Hemodynamic instability, cardiogenic shock
- Recurrent/persistent chest pain despite medical therapy
- Malignant arrhythmias
- Dynamic ST changes
- Very elevated troponin
- High risk scores (TIMI/GRACE themes)
“5 Seconds on Test Day” Checklist
If you see ST elevation + ischemic symptoms:
- Activate cath lab (primary PCI)
- If PCI delay is too long and no contraindications → fibrinolysis
- Give ASA + anticoagulation + statin (plus P2Y12 when indicated)
If you see ST depression/T inversion or no ST elevation:
- No fibrinolysis
- ASA + anticoagulation + statin (often + P2Y12)
- Risk stratify → early invasive if high risk
High-Yield Comparison Table (STEMI vs NSTEMI/UA)
| Feature | STEMI | NSTEMI | Unstable Angina |
|---|---|---|---|
| Occlusion | Usually complete | Usually partial | Partial / transient |
| ECG | ST elevation (contiguous leads) ± new LBBB | ST depression / T inversion / nonspecific | Similar to NSTEMI or normal |
| Troponin | Positive | Positive | Negative |
| Immediate reperfusion? | Yes (PCI or lytics) | No lytics; consider early invasive if high risk | No lytics; consider early invasive if high risk |
| Core meds | ASA, P2Y12, anticoagulation, statin, nitrates (if ok) | Same (no lytics) | Same (no lytics) |
Mini-Mnemonic: “STEMI = ST‑ELEVATE the urgency”
- ELEVATE → Emergent reperfusion
- No ELEVATION → Evaluate risk (TIMI/GRACE vibe), treat medically first
USMLE-Style “Trap Doors” to Watch For
- Inferior MI + hypotension + JVD + clear lungs → think RV infarct → avoid nitrates/diuretics, give fluids, confirm with right-sided leads (V4R).
- New diastolic murmur + tearing pain → suspect aortic dissection → do NOT give anticoagulation/lysis; control BP/HR and image.
- Post-MI day 3–5 sudden hypotension + new harsh murmur → mechanical complications (papillary muscle rupture, VSD) → not “more nitro,” needs urgent management.
- Troponin can rise in non-ACS (myocarditis, PE, CKD). ACS management follows the whole picture—ECG + symptoms + risk profile.
Your “Shareable” One-Liner to Memorize
STEMI: “See ST elevation? Open the artery.”
NSTEMI/UA: “No elevation? No lytics—stabilize, anticoagulate, and cath based on risk.”