ACS protocol
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"acute coronary syndrome" AND management
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PMID: 40014670
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I now have enough comprehensive content from multiple authoritative textbooks. Let me compile the full ACS protocol response.
Acute Coronary Syndrome (ACS) Protocol
Overview
ACS is a spectrum of myocardial ischemia/infarction defined by three entities:
| Entity | Troponin | ST Changes | Definition |
|---|---|---|---|
| Unstable Angina (UA) | Negative | No ST elevation | Chest pain at rest/new-onset/crescendo, no necrosis |
| NSTEMI | Positive | ST depression or T-wave changes | Myonecrosis without transmural occlusion |
| STEMI | Positive | Persistent ST elevation >20 min | Complete transmural occlusion; medical emergency |
The key mechanism in type 1 MI: atherosclerotic plaque rupture/erosion → platelet aggregation → thrombus → partial (UA/NSTEMI) or complete (STEMI) coronary occlusion.
Step 1 - Initial Assessment (within 10 minutes of arrival)
History: Classic = chest pain/pressure radiating to arm/jaw, diaphoresis, nausea. Atypical presentations are more common in elderly, women, diabetics, and postoperative patients (dyspnea, confusion, abdominal pain, syncope, unexplained hypotension).
Immediate workup:
- 12-lead ECG within 10 minutes of presentation (first priority)
- Cardiac biomarkers: high-sensitivity troponin (serial at 0, 1, 3 hours)
- CBC, BMP, coagulation studies (aPTT, PT/INR), lipid panel, magnesium
- Portable CXR (assess for pulmonary edema, exclude aortic dissection)
- Continuous cardiac monitoring / telemetry
STEMI ECG criteria (2 or more contiguous leads):
- Men >40 yr: ≥2 mm in V2-V3; ≥1 mm all other leads
- Men <40 yr: ≥2.5 mm in V2-V3
- Women: ≥1.5 mm in V2-V3; ≥1 mm all other leads
- Right-sided leads (V4R): ≥0.5 mm (for RV infarction in inferior STEMI)
- Posterior leads (V7-V9): ≥0.5 mm
ECG-Territory-Artery correlation:
| ST Elevation | Territory | Culprit Artery |
|---|---|---|
| V1-V6 / LBBB | Anterior/septal | Proximal LAD or left main |
| V2-V4 | Anterior wall | LAD |
| V5-V6 | Lateral wall | LCX |
| II, III, aVF | Inferior | RCA or LCX |
| I, aVL | High lateral | Diagonal or proximal LCX |
STEMI mimics to exclude: Pericarditis, LV aneurysm, Brugada syndrome, aortic dissection, LV hypertrophy, early repolarization, Prinzmetal angina, hyperkalemia, PE, myocarditis.
Step 2 - Initial Medical Therapy (All ACS)
ASA: 162-325 mg orally (chewed) or rectally immediately. 325 mg preferred if ASA-naive. Maintenance 81 mg/d after PCI.
Supplemental O2: Only if SpO2 <90%.
Nitroglycerin: 0.4 mg SL q5 min × 3 doses for ongoing chest pain (avoid if hypotension, right ventricular infarction, or PDE5 inhibitor use within 24-48 h).
Beta-blockers (e.g., metoprolol 25 mg PO qid): Reduce O2 demand and arrhythmia risk. Contraindicated in heart failure, hemodynamic instability, advanced AV block, significant bradycardia, or active bronchospasm.
Morphine: Used cautiously for refractory chest pain (note: the 2025 ACC/AHA guideline emphasizes avoiding routine morphine in NSTEMI due to potential slowing of P2Y12 inhibitor absorption).
Step 3 - Antiplatelet and Anticoagulant Therapy
DAPT (Dual Antiplatelet Therapy)
ASA + one P2Y12 inhibitor:
| Agent | Loading Dose | Maintenance | Notes |
|---|---|---|---|
| Clopidogrel | 600 mg (PCI) / 300 mg (lysis) | 75 mg/d | Prodrug; variable response |
| Ticagrelor | 180 mg | 90 mg BID | Mortality benefit vs clopidogrel; reversible; preferred if PCI |
| Prasugrel | 60 mg | 10 mg/d | Avoid if prior stroke/TIA, age ≥75, or weight <60 kg |
| Cangrelor | 30 µg/kg IV bolus | 4 µg/kg/min infusion | IV only; FDA-approved for PCI only |
DAPT duration: 12 months standard for DES; may be shortened if high bleeding risk.
Anticoagulation
| Agent | Dose | Notes |
|---|---|---|
| UFH | 60 units/kg IV bolus (max 4000 units), then 12 units/kg/h | All PCI patients; thrombolysis (except streptokinase) |
| Enoxaparin (LMWH) | 30 mg IV bolus, then 1 mg/kg SC q12h | Age >75: no bolus, 0.75 mg/kg SC q12h |
| Bivalirudin | 0.75 mg/kg bolus, then 1.75 mg/kg/h | Direct thrombin inhibitor; alternative at time of PCI |
| Fondaparinux | 2.5 mg IV, then 2.5 mg SC daily | Superior to UFH with thrombolytics; NOT for PCI alone (catheter thrombosis risk) |
Step 4 - Reperfusion Strategy
This is the cornerstone of STEMI management. Mortality is directly proportional to total ischemia time.
STEMI: Reperfusion
Primary PCI is the preferred strategy:
- Door-to-balloon (D2B) time goal: ≤90 minutes (if first medical contact at PCI-capable center)
- FMC-to-device time: ≤120 minutes (if transfer required)
- If transfer expected to delay >120 min from FMC: thrombolytics within 30 minutes (door-to-needle ≤30 min), then transfer for angiography (pharmacoinvasive strategy)
Thrombolytics (if PCI not available within time window):
- Alteplase (tPA), reteplase, tenecteplase (fibrin-specific agents preferred)
- Absolute contraindications: Prior intracranial hemorrhage, ischemic stroke <3 months, active internal bleeding, aortic dissection, known intracranial neoplasm
STEMI Alert should be activated prehospital or in ED - catheterization lab team mobilized analogously to trauma alert.
UA/NSTEMI: Invasive vs. Conservative Strategy
Risk stratify using TIMI risk score (0-7 points):
- Age ≥65 years
- ≥3 CAD risk factors
- Known CAD (stenosis ≥50%)
- ST-segment deviation on admission ECG
- ≥2 anginal events in prior 24 hours
- ASA use in prior 7 days
- Elevated cardiac markers
Higher TIMI score = higher 14-day risk of death/MI/urgent revascularization → prefer routine invasive strategy.
| Strategy | Timing | Indications |
|---|---|---|
| Immediate invasive (<2h) | <2 hours | Refractory ischemia, hemodynamic instability, sustained VT/VF, heart failure |
| Early invasive (<24h) | <24 hours | GRACE score >140, troponin rise/fall, new ST depression |
| Delayed invasive (24-72h) | 24-72 hours | Stabilized moderate-to-high risk |
| Ischemia-driven (conservative) | Selective | Low TIMI score, EF >40%, no recurrent ischemia |
Step 5 - Secondary Prevention (Discharge Medications)
| Drug Class | Agent | Goal |
|---|---|---|
| Antiplatelet | ASA 81 mg/d indefinitely + P2Y12 for 12 months | Reduce stent thrombosis / recurrent MI |
| Statin | High-intensity (atorvastatin 40-80 mg or rosuvastatin 20-40 mg) | LDL <55 mg/dL ideally |
| Beta-blocker | Metoprolol succinate or carvedilol | Reduce mortality, especially if EF reduced |
| ACE inhibitor / ARB | Ramipril, lisinopril, or equivalent | If EF ≤40%, diabetes, hypertension, CKD |
| Aldosterone antagonist | Eplerenone / spironolactone | If EF ≤40% + HF symptoms or diabetes |
Special Populations
Elderly (>75 years): Higher atypical presentations; AHA guidelines support revascularization with no absolute age cutoff; higher bleeding risk - adjust LMWH dosing (no IV loading dose in enoxaparin).
RV Infarction (complicating inferior STEMI): Hypotension + clear lungs + JVD triad; avoid nitrates, diuretics; treat with IV fluids and maintain RV preload.
Cardiogenic Shock: Early revascularization; consider mechanical circulatory support (IABP, Impella, ECMO). Inotropes (dobutamine) if needed.
Key Time Targets (2025 ACC/AHA Guideline)
| Metric | Target |
|---|---|
| First ECG after ED arrival | ≤10 minutes |
| Door-to-balloon (PCI center) | ≤90 minutes |
| FMC-to-device (transfer) | ≤120 minutes |
| Door-to-needle (thrombolytics) | ≤30 minutes |
Sources
- The Washington Manual of Medical Therapeutics (ACS protocol, Tables 4-14, 4-17, Figures 4-3 & 4-4)
- Goldman-Cecil Medicine International Edition (Chapters 57-58, NSTEMI/STEMI management)
- Rosen's Emergency Medicine (Chapter 64, ECG adjuncts, ACS management)
- Goodman & Gilman's Pharmacological Basis of Therapeutics (ACS pharmacology)
- 2025 ACC/AHA/ACEP/NAEMSP/SCAI Guideline for Management of ACS (Rao SV et al., Circulation, 2025) - [PMID 40014670] - Note: An erratum was published (PMID: 41212941); verify specific recommendations against the corrected version.
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