What are the latest protocols for MI?
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2025 ACC AHA acute coronary syndrome guideline key changes STEMI NSTEMI
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I now have comprehensive data. Let me compile the full answer covering the 2025 ACC/AHA guideline plus textbook protocols.
Myocardial Infarction (MI) — Current Management Protocols
Key update: The 2025 ACC/AHA/ACEP/NAEMSP/SCAI Guideline for Management of Patients with Acute Coronary Syndromes (Rao SV et al., Circulation 2025; PMID 40014670) supersedes the prior 2013 STEMI and 2014 NSTE-ACS guidelines. Note: an erratum has been issued (PMID 41212941).
1. Initial Assessment & Diagnosis
- ECG within 10 minutes of first medical contact; repeat if initial is non-diagnostic
- High-sensitivity troponin (hs-cTn) is the biomarker of choice — serial measurements (0h/1h or 0h/2h/3h) for rapid rule-in/rule-out
- Classify as STEMI (≥1 mm ST elevation in ≥2 contiguous leads, or new LBBB) vs. NSTEMI/UA
- Evaluate Killip class, TIMI/GRACE risk scores
2. Pre-Hospital & Initial Pharmacotherapy (All ACS)
| Drug | Dose | Notes |
|---|---|---|
| Aspirin (ASA) | 162–325 mg chewed immediately | Continue 81 mg/day indefinitely |
| P2Y12 inhibitor | Ticagrelor 180 mg load or Prasugrel 60 mg load (PCI-planned); Clopidogrel 300–600 mg if fibrinolysis | Ticagrelor or prasugrel preferred over clopidogrel for PCI |
| Anticoagulation | UFH, LMWH (enoxaparin), or bivalirudin | Bivalirudin validated with PCI; LMWH/fondaparinux preferred with fibrinolytics |
| Nitroglycerin | 0.4 mg SL q5 min × 3, then IV | Avoid if SBP <90, RV infarct, or phosphodiesterase inhibitor use within 48h |
| Morphine | 2–4 mg IV | Reserved for refractory pain unresponsive to nitrates — use cautiously (may mask symptoms) |
| Beta-blockers (oral) | Start within 24h | Only if no HF, no Killip ≥II, no shock, SBP ≥120, HR 60–110, no advanced AV block |
3. Reperfusion Strategy (STEMI)
Early reperfusion is the top priority — all other therapies are secondary.
Primary PCI (preferred)
- Door-to-balloon ≤90 min from first medical contact at PCI-capable center
- Door-in-door-out ≤30 min if transfer needed (acceptable PCI time ≤120 min)
- Superior to fibrinolysis: better TIMI-3 flow, less reinfarction, less intracranial hemorrhage, lower mortality
- Indicated for symptom onset <12h; consider for 12–24h with ongoing symptoms
- Cardiogenic shock (Killip III/IV): PCI always preferred, even if delayed
- Culprit-lesion-only PCI in cardiogenic shock (CULPRIT-SHOCK trial): reduces mortality vs. multivessel PCI
- Complete revascularization of non-culprit lesions is recommended (reduces cardiovascular death + MI), timing flexible (pre-discharge or staged outpatient)
- Transradial access preferred — reduces bleeding, possible mortality benefit
- Drug-eluting stents (DES) preferred over bare-metal stents (BMS)
Fibrinolytic Therapy (when PCI not available in time)
- Use if PCI cannot be achieved within 120 min of first medical contact
- Administer within 30 min of hospital arrival ("door-to-needle")
- Preferred agents: tenecteplase, alteplase, reteplase
- Absolute contraindications: prior intracranial hemorrhage, ischemic stroke <3 months, structural brain lesion, suspected aortic dissection, active bleeding, significant facial trauma/head injury <3 months
- After fibrinolysis: transfer all patients to PCI-capable center; routine angiography within 3–24 hours reduces adverse events; immediate transfer for failed reperfusion or shock
4. NSTEMI / UA Management
- Antiplatelet + anticoagulation as above
- Risk stratification via GRACE score guides invasive strategy timing:
- Very high-risk (refractory ischemia, cardiogenic shock, life-threatening arrhythmia, mechanical complication): immediate angiography (<2h)
- High-risk (GRACE >140, dynamic ECG/troponin changes): early invasive (<24h)
- Intermediate-risk (GRACE 109–140): invasive within 24–72h
- Low-risk: non-invasive evaluation, selective invasive approach
5. Post-MI / Secondary Prevention (Long-term)
| Agent | Duration / Target | Evidence |
|---|---|---|
| ASA 81 mg/day | Indefinitely | 25% ↓ recurrent MI/stroke/CV death |
| P2Y12 inhibitor (ticagrelor 90 mg BID or prasugrel 10 mg/day or clopidogrel 75 mg/day) | 12 months minimum (DAPT); shorter (6 mo) may be acceptable with high bleeding risk | Standard of care post-ACS |
| Statin (high-intensity) | Indefinitely; target LDL <70 mg/dL (≥50% reduction) | If LDL goal not met, add ezetimibe or PCSK9 inhibitor |
| ACE inhibitor / ARB | Indefinitely if EF <40%, large anterior MI, HF, or diabetes | Most benefit within 24h initiation |
| Beta-blocker | Indefinitely post-MI (especially if EF <40%) | Start within 24h |
| Aldosterone antagonist (spironolactone/eplerenone) | If EF <40% + HF or diabetes | Avoid if K⁺ >5.0 or eGFR <30 |
| Cardiac rehabilitation | Begin in-hospital, continue outpatient | Reduces mortality, improves QoL |
6. Monitoring & In-Hospital Care
- CCU/ICU telemetry for ≥24h
- Daily ECG, assess for recurrent ischemia, new murmur (mechanical complication), HF
- Echocardiography (baseline): assess EF, wall motion, valvular lesions, LV thrombus
- LV thrombus: anticoagulate; routine anticoagulation for apical hypokinesis alone not recommended (increased bleeding risk)
- AV block with anterior MI: usually unstable (wide QRS escape), high mortality — may require temporary then permanent pacing
- AV block with inferior MI: usually transient and stable
- Uncomplicated STEMI: hospital stay 3–5 days; return to work at 2–4 weeks
7. Special Considerations
- MINOCA (MI with non-obstructive coronary arteries): comprehensive 2025 meta-analysis (PMID 40025434) confirms different prognosis and management — includes cardiac MRI, ACE inhibitors, statins; no routine antiplatelet unless ACS confirmed
- Older adults (>75 years): higher rates of atypical presentation (dyspnea >chest pain), more baseline elevated troponin, higher bleeding risk — individualize antiplatelet duration and reperfusion approach
- Contrast-induced AKI: limit contrast <100 mL for PCI; transradial access reduces CI-AKI; iodixanol (iso-osmolar) preferred over LOCM in CKD; pre-procedural volume expansion if eGFR <60
Sources:
- The Washington Manual of Medical Therapeutics
- Harrison's Principles of Internal Medicine, 22E (2025)
- Braunwald's Heart Disease, 11E
- 2025 ACC/AHA/ACEP/NAEMSP/SCAI Guideline for Management of ACS — Rao SV et al., Circulation 2025 (PMID 40014670)
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