Race against time: Understanding NSTEMI-ACS VS STEMI ACS Management.

Dr. Zayed | Published : 21, April 2025.

The management of acute coronary syndromes (ACS) encompassing both ST-elevation myocardial infarction (STEMI) and Non–ST-elevation ACS (NSTE-ACS) is grounded in early diagnosis, risk stratification, and timely reperfusion or ischemia-guided interventions. The fundamental goal across the ACS spectrum is to restore myocardial perfusion and minimize infarct size, as our title says "time is Muscle and the muscle here is myocardium."

STEMI MANAGEMENT AHA/ACC GUIDELINE

STEMI: Urgent Reperfusion-Based Approach

STEMI diagnosis hinges on ST-segment elevation in at least 2 contiguous leads or a STEMI equivalent such as a new left or right bundle branch block (LBBB/RBBB). Once identified, "Code STEMI" is activated, prompting immediate cardiology consultation and expedited decision-making regarding reperfusion strategy.

A crucial branch point in STEMI management is the time to percutaneous coronary intervention (PCI), which is door-to-balloon time ≤ 90 minutes, and first medical contact to PCI ≤ 120 minutes, "DOOR" here is hospital entrance.

Total acceptable time from first contact to opening the artery = 120 minutes

📍 First Medical Contact (FMC) i.e EMS→ Hospital Door = ~30 mins (EMS time for traveling)
🏥 Hospital Door → Balloon (PCI) = ≤90 min

Interesting to Know: Since ACS originates from ruptured atherosclerotic plaque causing thrombus formation, we use adjuvant therapy which includes statins to stabilize the atherosclerotic plaque and reduce future risk rupture, while simultaneously addressing the thrombus with antiplatelets and anticoagulants to prevent progression and recurrence.

  • Adjunctive therapy should not delay irrespective of the primary intervention (PCI or Fibrinolysis):

    • Aspirin

    • An ADP receptor inhibitor (prasugrel, ticagrelor, or clopidogrel)

    • An anticoagulant (typically UFH or bivalirudin)

    • High Intensity Statin

    • Consideration of a glycoprotein IIb/IIIa inhibitor in selected high-risk cases

  • If PCI can be achieved within 120 minutes, the patient is transferred directly to the cath lab for primary PCI.

  • If PCI cannot be performed within 120 minutes, a fibrinolysis-first strategy is pursued provided there are no absolute contraindications like active bleeding or known coagulopathy. Fibrinolysis is immediately followed by:

  • Followed by Secondary PCI, ensuring transfer to a PCI-capable center even after successful lysis (pharmaco-invasive approach).

Once reperfusion is achieved via PCI or fibrinolysis all patients transition to supportive therapy and secondary prevention. 

PCI is preferred over fibrinolysis for patients with acute STEMI, as long as it can be performed quickly, safely, and expertly. If PCI cannot be performed within 120 minutes of first medical contact, Fibrinolysis should be administered, provided that the patient has no contraindications to its use. After Fibrinolysis is administered, the patient should be transferred immediately to a center where PCI can be performed within 24 hours, even if the patient is stable and has evidence of successful reperfusion.

Supportive Therapy, which is famously known by the "MONA-BASH"

Initial medical management across all ACS types before and after invasive procedures is standardized by MONA-BASH:

  • Morphine: For severe chest pain refractory to nitrates

  • Oxygen: If SpO₂ < 90%

  • Nitroglycerin: Sublingual or IV for chest pain or hypertension

  • Antiplatelets:

    • Aspirin (loading dose followed by maintenance)

    • ADP receptor inhibitors (clopidogrel, prasugrel, or ticagrelor)

  • Beta blockers: Unless contraindicated (e.g., heart block, hypotension)

  • ACE inhibitors: Particularly beneficial in anterior infarction or LV dysfunction

  • Statins: High-intensity, initiated early regardless of LDL levels

  • Heparin: UFH or LMWH, depending on reperfusion strategy and bleeding risk

NSTE-ACS: Risk-Stratified Strategy

In contrast, NSTEMI/unstable angina do not mandate immediate reperfusion unless high-risk features are present (e.g., refractory angina, hemodynamic instability, arrhythmias, or dynamic ECG changes). Management begins with early pharmacologic therapy, guided by troponin levels, ECG findings, and risk scores (e.g., GRACE, TIMI).

  • In conservative (non-invasive) management, LMWH (enoxaparin) is often preferred over UFH due to more stable pharmacokinetics and superior efficacy in reducing recurrent ischemic events.

  • In patients planned for early invasive strategies (PCI), UFH or bivalirudin may be selected.

  • Dual antiplatelet therapy (DAPT), anticoagulation, and MONA-BASH remain core.

INTERESTING TO KNOW: UFH vs LMWH in ACS.

Several trials (e.g., ESSENCE, SYNERGY, and EXTRACT-TIMI 25) have consistently shown LMWH to be superior or at least non-inferior to UFH in NSTEMI patients who had non invasive strategy i.e fibrinolysis (vs UFH is more Efficacious in invasive strategy i.e PCI) , with a comparable or slightly increased bleeding risk depending on renal function and dosing.

REFERENCES:

2013 ACCF/AHA Guideline for the Management of ST-Elevation Myocardial Infarction
 O'Gara PT, et al. Circulation. 2013;127:e362–e425.

2020 ESC Guidelines for the Management of Acute Coronary Syndromes in Patients Presenting Without Persistent ST-Segment Elevation
Collet J-P, et al. European Heart Journal. 2021;42(14):1289–1367.

Time to Treatment and Mortality after Prehospital Fibrinolysis or Primary PCI
Armstrong PW, et al. New England Journal of Medicine. 2013;368(10):888–897.
https://doi.org/10.1056/NEJMoa1211588

Impact of Door-to-Balloon Time on Mortality in STEMI Patients
Rathore SS, et al. New England Journal of Medicine. 2009;361:901–909.
https://doi.org/10.1056/NEJMoa0903810

Comparison of Enoxaparin and Unfractionated Heparin in NSTEMI: SYNERGY Trial
Ferguson JJ, et al. JAMA. 2004;292(1):45–54.
https://doi.org/10.1001/jama.292.1.45

ESSENCE Trial: Enoxaparin versus UFH in NSTE-ACS

Cohen M, et al. New England Journal of Medicine. 1997;337(7):447–453.
https://doi.org/10.1056/NEJM199708143370701

Meta-analysis: UFH vs LMWH in NSTE-ACS
Eikelboom JW, et al. BMJ. 2002;325(7360):1320.
https://doi.org/10.1136/bmj.325.7360.1320

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