Acute coronary syndrome.
ECG in 10 min. hs-troponin 0/1-2 h. PCI on the clock. STEMI vs NSTE-ACS pathways, the high-sensitivity troponin algorithm, antiplatelet + anticoagulation choices, and reperfusion windows.
Reviewed June 2026 · verify against current guidelines
Diagnosis & Workup
Recognize. Confirm. Stage.
First 10 minutes
- ECG ≤10 min from FMC (incl. prehospital).
- Repeat ECG: recurrent sx · hemodynamic change · high suspicion.
- hs-cTn at 0 and 1-2 h (conventional cTn: 0 and 3-6 h).
STEMI ECG criteria
| Most leads | ST elevation ≥1 mm in ≥2 contiguous leads (outside V2-V3). |
|---|---|
| V2-V3 | ≥2 mm men ≥40 y · ≥2.5 mm men <40 y · ≥1.5 mm women. |
| Posterior MI | ST depression ≥0.5 mm in V1-V3 → obtain V7-V9. STE ≥0.5 mm in V7-V9 confirms. |
| LBBB or paced | NOT a STEMI equivalent in isolation. Requires clinical correlation. |
NSTE-ACS ECG (any of; normal does NOT exclude)
| ST depression | ≥0.5 mm in ≥2 contig leads, horizontal/downsloping · new or dynamic. |
|---|---|
| T-wave inversion | >1 mm in ≥2 contig leads with dominant R. |
| Transient STE | Self-resolving ST elevation. |
STEMI = ECG criteria met above.
NSTE-ACS = symptoms without persistent STE; ↑ troponin (NSTEMI).
UA = symptoms + non-diagnostic ECG + normal troponin (historical category; now largely reclassified as NSTE-ACS in the hs-cTn era).
NSTE-ACS = symptoms without persistent STE; ↑ troponin (NSTEMI).
UA = symptoms + non-diagnostic ECG + normal troponin (historical category; now largely reclassified as NSTE-ACS in the hs-cTn era).
FMC first medical contacths-cTn high-sensitivity cardiac troponinSTE ST elevationLBBB left bundle branch blockNSTE-ACS non-ST-elevation ACSNSTEMI non-ST-elevation MIUA unstable angina
ECG Pearls
OMI patterns to know.
Standard ED teaching, not in the 2025 ACS guideline. Useful when ECG looks "not quite STEMI" but artery is occluded.
Patterns
| Posterior MI | STD ≥0.5 mm in V1-V3 + tall R waves → V7-V9 (STE ≥0.5 mm confirms). |
|---|---|
| deWinter T | Upsloping STD at J point + tall symmetric T waves V1-V6 → proximal LAD. |
| Wellens | Biphasic (Type A) or deeply inverted (Type B) T in V2-V3 during pain-free interval → critical LAD; AVOID stress. |
| aVR + diffuse STD | STE aVR + diffuse STD → LMCA, proximal LAD, or 3-vessel disease. |
Sgarbossa criteria (LBBB or paced rhythm)
| Concordant STE | ≥1 mm in any lead with positive QRS (highly specific). |
|---|---|
| Concordant STD | ≥1 mm in V1, V2, or V3 (highly specific). |
| Discordant STE | Original: ≥5 mm with negative QRS. Modified (Smith): ST/S ratio ≥ 0.25 (more sensitive). |
Recognize OMI even when STEMI criteria are not met. Activate cath, get a second read, get an echo.
OMI occlusion myocardial infarctionLAD left anterior descendingLMCA left main coronary arterySTE ST elevationSTD ST depressionLBBB left bundle branch block
Acute Management
Antiplatelet + anticoagulation.
DAPT
| Aspirin | 162-325 mg chewed nonenteric load → 75-100 mg daily. |
|---|---|
| Ticagrelor | 180 mg load → 90 mg BID. Preferred P2Y12. |
| Prasugrel | 60 mg load → 10 mg daily. 5 mg if <60 kg or ≥75 y. PCI only. |
| Clopidogrel | 300-600 mg load → 75 mg daily. Fibrinolysis: 300 mg if ≤75 y; no load if >75 y. |
Anticoagulation
| UFH | 60 U/kg bolus (max 4000 U) → 12 U/kg/h (max 1000 U/h). aPTT goal 60-80 sec. |
|---|---|
| Enoxaparin | 1 mg/kg SC q12h → q24h if CrCl <30. |
β-blocker
| Within 24 h | Oral β-blocker (metoprolol, carvedilol, or bisoprolol) unless: acute HF/low output · shock risk · severe bradycardia · PR >0.24 s · 2°/3° AV block · severe asthma. Metoprolol: tartrate acutely → succinate long-term. |
|---|
Prasugrel is contraindicated in prior stroke or TIA.
In NSTE-ACS without an invasive plan, ticagrelor is preferred over prasugrel.
If CABG is possible, defer the P2Y12 load until coronary anatomy is known (pre-op washout: ticagrelor 3-5 d · clopidogrel 5 d · prasugrel 7 d).
In NSTE-ACS without an invasive plan, ticagrelor is preferred over prasugrel.
If CABG is possible, defer the P2Y12 load until coronary anatomy is known (pre-op washout: ticagrelor 3-5 d · clopidogrel 5 d · prasugrel 7 d).
DAPT dual antiplatelet therapyP2Y12 platelet ADP-receptor inhibitorUFH unfractionated heparinaPTT activated partial thromboplastin timeCrCl creatinine clearanceHF heart failureTIA transient ischemic attackCABG coronary artery bypass graftNSTE-ACS non-ST-elevation ACS
Reperfusion
On the clock.
STEMI timing
| PCI direct | FMC-to-device ≤90 min. |
|---|---|
| PCI transfer | FMC-to-device ≤120 min. |
| Fibrinolysis | Anticipated PCI delay >120 min · no contraindications · sx <12 h. |
| Post-lysis | Transfer ALL for angio 2-24 h, even if successful. |
NSTE-ACS invasive timing
| Immediate <2 h | Very high-risk: refractory angina · hemodynamic/electrical instability · shock · acute HF. |
|---|---|
| Early <24 h | High-risk: GRACE >140 · dynamic ST · rising troponin. |
| <72 h before d/c | Intermediate-risk: GRACE 109-140 · stable troponin · no ongoing ischemia. |
| Routine or selective | Lower-risk: GRACE <109 · TIMI <2. |
Procedural standards
| Access | Radial > femoral. |
|---|---|
| Imaging | IVUS or OCT for complex PCI. |
| Complete revasc | Stable STEMI + MVD → revasc non-IRA. Shock → culprit-only. |
FMC first medical contactGRACE Global Registry of Acute Coronary EventsTIMI Thrombolysis In Myocardial InfarctionHF heart failured/c dischargeMVD multi-vessel diseaseIRA infarct-related arteryIVUS intravascular ultrasoundOCT optical coherence tomography
Pitfalls
What gets missed.
Common errors
- Supplemental O2 when SpO2 ≥90% — no benefit, possible harm.
- Prasugrel after prior stroke or TIA — contraindicated.
- Loading P2Y12 pre-cath when CABG possible → delays urgent surgery.
- Skipping CrCl before enoxaparin or contrast.
- Calling new LBBB a STEMI equivalent.
- Treating posterior or deWinter pattern as "just ST depression."
- Forgetting post-lysis transfer for 2-24 h angio.
Transfusion (MINT)
| Threshold | Hb ~10 g/dL reasonable in ACS + acute/chronic anemia, no active bleeding. |
|---|
Normal troponin and a non-diagnostic ECG do NOT rule out NSTE-ACS. Repeat the ECG. Repeat the troponin. Risk-stratify.
CrCl creatinine clearanceLBBB left bundle branch blockTIA transient ischemic attackP2Y12 platelet ADP-receptor inhibitorCABG coronary artery bypass graftHb hemoglobinMINT Myocardial Ischemia and Transfusion trialNSTE-ACS non-ST-elevation ACS
Long-term
DAPT strategy + discharge.
DAPT duration & de-escalation
| Default | DAPT ≥12 mo if not HBR. |
|---|---|
| Ticagrelor mono | DAPT → ticagrelor alone ≥1 mo post-PCI is reasonable to ↓ bleeding. |
| De-escalate | Ticagrelor or prasugrel → clopidogrel after 1 mo may be reasonable to ↓ bleeding. |
| HBR | Single antiplatelet after 1 mo may be considered. |
| OAC + PCI | Drop aspirin at 1-4 wk; continue P2Y12 (clopidogrel preferred) + OAC. |
Secondary prevention
| Statin | High-intensity. Add ezetimibe if LDL-C ≥70 on max statin. |
|---|---|
| ACEi / ARB | Indicated if LVEF ≤40%, HTN, DM, or anterior STEMI. Reasonable in other ACS. |
| MRA | If LVEF ≤40% with HF or DM, on ACEi/ARB + β-blocker. |
| Cardiac rehab | Refer all. Home-based acceptable. |
Ticagrelor monotherapy at 1 mo = practice-changing 2025 update. Reasonable to ↓ bleeding in patients tolerating ticagrelor.
DAPT dual antiplatelet therapyP2Y12 platelet ADP-receptor inhibitorHBR high bleeding riskOAC oral anticoagulantLDL-C low-density lipoprotein cholesterolACEi angiotensin-converting enzyme inhibitorARB angiotensin receptor blockerMRA mineralocorticoid receptor antagonistLVEF left ventricular ejection fractionHF heart failure
Sources
Verify against current guidelines and local protocol before acting.
- Rao SV et al. 2025 ACC/AHA/ACEP/NAEMSP/SCAI Guideline for the Management of Patients With Acute Coronary Syndromes. Circulation 2025;151:e771-e862 (copublished JACC 2025;85:2135-2237).
- Thiele H et al. CULPRIT-SHOCK: culprit-only vs multivessel PCI in cardiogenic shock. NEJM 2017.
- Carson JL et al. MINT: restrictive vs liberal transfusion in MI + anemia. NEJM 2023.
- Mehran R et al. TWILIGHT: ticagrelor monotherapy after PCI. NEJM 2019.
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