What is the main difference between STEMI and NSTEMI management?

STEMI usually reflects an acutely occluded coronary artery, so it needs immediate reperfusion: primary PCI within 90 minutes of first medical contact, or fibrinolysis within 30 minutes of arrival when PCI cannot be done within 120 minutes. NSTEMI is never treated with fibrinolytics. It is managed with aspirin plus a P2Y12 inhibitor, a parenteral anticoagulant and coronary angiography timed by risk: within 2 hours if unstable, within 24 hours if high risk, otherwise before discharge.

When is fibrinolysis used instead of PCI for STEMI?

Fibrinolysis is used when primary PCI cannot be performed within 120 minutes of first medical contact, symptoms began less than 12 hours earlier, and there is no contraindication such as prior intracranial hemorrhage, recent ischemic stroke, active bleeding or suspected aortic dissection. It should be given within 30 minutes of arrival together with clopidogrel and an anticoagulant, followed by transfer for angiography 2 to 24 hours later, or immediately if reperfusion fails.

Why are fibrinolytics not used in NSTEMI?

Fibrinolytics are not indicated in NSTEMI or unstable angina because their bleeding risk outweighs any potential benefit. These patients receive antiplatelet and anticoagulant drugs, and the culprit lesion is treated with coronary angiography and revascularization timed by risk: within 2 hours for shock, refractory angina, acute heart failure or sustained ventricular arrhythmias, within 24 hours for high-risk features such as a GRACE score above 140, and otherwise before discharge.

Which P2Y12 inhibitor is preferred in acute coronary syndrome?

Under the 2025 ACC/AHA guideline, prasugrel or ticagrelor is preferred over clopidogrel for patients with STEMI or NSTE-ACS who undergo PCI, and ticagrelor is recommended for NSTE-ACS managed medically. Clopidogrel is used when the others are unavailable, not tolerated or contraindicated, and it is the P2Y12 inhibitor given with fibrinolytic therapy. Prasugrel is contraindicated after a prior stroke or TIA. Dual antiplatelet therapy continues for at least 12 months unless bleeding risk is high.

What is a STEMI equivalent?

A STEMI equivalent is an ECG pattern treated like STEMI because it suggests an acute coronary occlusion without classic ST elevation. Examples include posterior MI (ST depression in V1 to V3, confirmed by ST elevation in V7 to V9), right ventricular MI seen in right-sided leads, hyperacute or de Winter T waves, and a new or presumed new LBBB or RBBB accompanied by other signs of ischemia. A new LBBB on its own is not treated as a STEMI equivalent.

What replaced type 1 and type 2 MI in the 2026 definition?

The 2026 Fifth Universal Definition of MI replaced the numbered types with three clinical ones. Primary MI is caused by an acute coronary problem such as plaque rupture, spontaneous coronary artery dissection, embolism or spasm. Secondary MI, the old type 2, results from a supply-demand imbalance caused by another acute condition such as a tachyarrhythmia, severe hypertension, hypotension, hypoxia or anemia, and treatment targets that trigger. Procedure-related MI follows PCI or cardiac surgery within 30 days.

STEMI vs NSTEMI Management: PCI, Lytics & 2025 Updates

STEMI and NSTEMI are both myocardial infarctions (a rise and/or fall in cardiac troponin, with at least one value above the sex-specific 99th percentile, plus evidence of ischemia), and the ECG decides how each is treated. STEMI (new ST elevation in two contiguous leads, or a STEMI equivalent) usually means an acutely occluded coronary artery and needs immediate reperfusion: primary PCI within 90 minutes of first medical contact, or fibrinolysis within 30 minutes of arrival when PCI can't happen within 120 minutes. NSTEMI (ST depression, T-wave inversion or a normal ECG with a troponin rise) never gets fibrinolytics; it gets dual antiplatelet therapy, an anticoagulant and coronary angiography timed by risk: within 2 hours if unstable, within 24 hours if high risk, otherwise before discharge. Management follows the 2025 ACC/AHA ACS guideline; definitions follow the Fifth Universal Definition of MI (2026).

STEMI vs NSTEMI vs unstable angina

	STEMI	NSTEMI	Unstable angina
ECG	New ST elevation in ≥2 contiguous leads, or an equivalent	ST depression, T-wave inversion or normal	Same as NSTEMI, or normal
Troponin	Rise and/or fall, at least one value above the sex-specific 99th percentile	Rise and/or fall, at least one value above the sex-specific 99th percentile	No acute rise on serial testing
Usual picture	Acute coronary occlusion, transmural injury	Subendocardial infarction; up to 1 in 4 still have an occluded culprit artery	Same mechanism as primary MI, without acute myocardial injury
Reperfusion	Immediate: primary PCI, or fibrinolysis if PCI is too far away	Angiography by risk: <2 h, <24 h or before discharge	Same risk-based approach
Fibrinolytics	Yes, within 12 h of symptom onset if PCI is delayed	No	No
P2Y12 inhibitor	Prasugrel or ticagrelor with PCI; clopidogrel with fibrinolysis	Prasugrel or ticagrelor with PCI; ticagrelor if managed medically	As for NSTEMI

Diagnosis: ECG first, troponin second

ECG within 10 minutes of arrival.
STEMI criteria (Fifth UDMI): new ST elevation at the J point in at least two contiguous leads: ≥1 mm in most leads; in V2-V3, ≥2 mm in men 40 or older, ≥2.5 mm in men under 40 and ≥1.5 mm in women, in the absence of LVH or LBBB. Localize the territory with the STEMI patterns guide.
STEMI equivalents:
- Posterior MI: ST depression ≥1 mm in V1-V3, especially with a dominant R wave, confirmed by ST elevation in V7-V9 (the 2025 ACC/AHA guideline wants posterior leads from ≥0.5 mm).
- Right ventricular MI: ST elevation in right-sided leads (V3R-V6R). Get right-sided leads in every inferior STEMI.
- New or presumed new LBBB or RBBB with other signs of ischemia. Classic teaching counted any new LBBB; the 2025 guideline says a new LBBB is not diagnostic of MI in isolation. In known LBBB or a paced rhythm, use the Sgarbossa criteria (LBBB vs RBBB table).
- Other occlusion patterns such as hyperacute T waves and de Winter T waves.
NSTE-ACS ECG: new horizontal or downsloping ST depression ≥0.5 mm in two contiguous leads, new T-wave inversion ≥1 mm, or a normal tracing.
Troponin: high-sensitivity troponin on arrival and 1-2 hours later, judged against sex-specific cut-offs (lower in women). Rises are small in the first 3 hours, larger at 3-12 hours and peak at 12-24 hours, so one early normal value does not exclude MI (cardiac biomarkers).

MI types under the 2026 definition

The Fifth Universal Definition replaced the numbered types with three clinical ones:

Fifth UDMI (2026)	Mechanism	Older label
Primary MI	Spontaneous acute coronary pathology: atherothrombosis, spontaneous coronary artery dissection, coronary embolism, vasospasm, or stent or graft failure >30 days after the procedure	Type 1 (SCAD, embolism and spasm were type 2; late stent failure was 4b/4c)
Secondary MI	Supply-demand imbalance from another acute condition: tachyarrhythmia (most common), severe hypertension, hypotension, hypoxia, anemia	Type 2
Procedure-related MI	Coronary complication within 30 days of PCI or cardiac surgery	Types 4 and 5

STEMI and NSTEMI still drive the first hours of care; the clinical type guides what follows. Review books may still say "type 2": for a secondary (type 2) MI, treat the trigger. A troponin rise without ischemia (myocarditis, sepsis, Takotsubo syndrome, cardiotoxic drugs) is myocardial injury, not MI.

First steps in every ACS

Aspirin 162-325 mg chewed (non-enteric-coated), then 75-100 mg daily.
Oxygen only if SpO₂ <90%; routine oxygen is not recommended.
Nitroglycerin for pain, but not with systolic BP <90 mm Hg (or a fall >30 mm Hg from baseline), suspected RV infarction, or a PDE-5 inhibitor (sildenafil, tadalafil, vardenafil).
Opioids sparingly: morphine and fentanyl blunt some oral P2Y12 inhibitors.
High-intensity statin for everyone.
Oral beta-blocker within 24 hours unless contraindicated (e.g., bradycardia, heart block, hypotension, asthma).
P2Y12 inhibitor + parenteral anticoagulant, chosen by strategy (antiplatelets breakdown).

STEMI: reperfuse now

Primary PCI is preferred. EMS should go straight to a PCI-capable hospital with a first-medical-contact-to-device goal of ≤90 minutes; if a transfer is needed, the limit is 120 minutes.
Timing: primary PCI is the default within 12 hours of symptom onset and is still used at 12-24 hours. After 24 hours, urgent PCI is for hemodynamic instability or malignant arrhythmias.
Fibrinolysis if PCI can't be done within 120 minutes, symptoms began <12 hours ago and there is no contraindication: tenecteplase, alteplase or reteplase within 30 minutes of arrival (Merck's 2026 review: 30-60 minutes), plus clopidogrel (not prasugrel or ticagrelor) and an anticoagulant.
After fibrinolysis, transfer to a PCI center for angiography 2-24 hours later; do rescue PCI immediately if chest pain or ST elevation persists 60 minutes or more after the lytic starts, or recurs.
With primary PCI: aspirin + prasugrel or ticagrelor (clopidogrel if neither can be used; prasugrel is contraindicated after stroke or TIA) plus unfractionated heparin or bivalirudin. Fondaparinux is not used for PCI.
Procedure: radial over femoral access; complete revascularization is recommended, except that in cardiogenic shock only the culprit vessel is treated at the time (a microaxial flow pump is reasonable in selected patients).

Absolute contraindications to fibrinolysis: any prior intracranial hemorrhage; ischemic stroke within 3 months (except acute ischemic stroke); cerebrovascular malformation or malignant intracranial tumor; intracranial or intraspinal surgery within 2 months or head or facial trauma within 3 months; active bleeding (not menses) or bleeding diathesis; suspected aortic dissection; and BP >180/110 mm Hg that does not respond to treatment. Relative ones include pregnancy, oral anticoagulation, active peptic ulcer, major surgery within 3 weeks and traumatic or prolonged CPR.

NSTEMI: antithrombotics, then angiography by risk

No fibrinolytics: in unstable angina and NSTEMI the bleeding risk outweighs any benefit.
DAPT: aspirin + ticagrelor or prasugrel if PCI is done, ticagrelor if managed medically, clopidogrel if neither can be used. If angiography will be more than 24 hours away, upstream clopidogrel or ticagrelor may be considered (Class 2b).
Anticoagulant: unfractionated heparin or enoxaparin; bivalirudin during PCI when bleeding risk is high; fondaparinux only without an early invasive strategy.
Invasive strategy: the 2025 guideline recommends angiography with intent to revascularize during the admission for intermediate- and high-risk NSTE-ACS. Timing by risk (Merck):

Risk	Features	Coronary angiography
Very high	Cardiogenic shock, heart failure symptoms, refractory angina, hemodynamic or electrical instability (e.g., sustained VT or VF)	Immediate (<2 h)
High	GRACE >140, steeply rising troponin, dynamic ST changes	<24 h
Intermediate	GRACE 109-140, no ongoing symptoms, stable or falling troponin	Before discharge (<72 h)
Low	GRACE <109, no ongoing ischemia, troponin below the 99th percentile, no dynamic ST changes	Before discharge, or a stress test or coronary CT angiography first

Secondary prevention

DAPT for at least 12 months if bleeding risk isn't high. To lower bleeding: ticagrelor monotherapy after ≥1 month of DAPT with ticagrelor, or de-escalation from ticagrelor or prasugrel to clopidogrel after 1 month.
Lipids: high-intensity statin (ezetimibe can start at the same time). Add a nonstatin (ezetimibe, PCSK9 inhibitor, inclisiran, bempedoic acid) if LDL-C stays ≥70 mg/dL on maximal statin; it is reasonable at 55-69 mg/dL. Recheck a fasting lipid panel 4-8 weeks after any change.
Beta-blocker long-term when LVEF ≤40%; benefit with preserved EF is uncertain.
ACE inhibitor or ARB with LVEF ≤40%, heart failure, hypertension, diabetes, chronic kidney disease or anterior MI; MRA for LV dysfunction with heart failure or diabetes; SGLT2 inhibitor for heart failure after MI.
Cardiac rehabilitation referral before discharge.

How USMLE tests it

Stem clue	Best answer	Trap
ST depression or T inversion + rising troponin	DAPT, anticoagulant, angiography by risk	Fibrinolytics
ST elevation, PCI not possible within 120 min	Fibrinolytic within 30 min + clopidogrel, then transfer	Sending for PCI anyway
Inferior STEMI + hypotension + clear lungs	Right-sided ECG; IV saline (1-2 L)	Nitroglycerin or diuretics
ST depression V1-V3 with tall R waves	Posterior leads V7-V9; treat as STEMI	Calling it NSTEMI
Suspected aortic dissection	Image first; no fibrinolytics (dissection breakdown)	Fibrinolytics
Troponin rise during rapid atrial fibrillation or severe anemia	Secondary (type 2) MI: treat the trigger	Fibrinolytics

Post-MI complications and their timing are drilled in the acute MI complications breakdown.

Practice question

A 58-year-old man has had crushing substernal chest pain for 2 hours. He is at a rural hospital without a catheterization lab; the nearest PCI-capable center is 3 hours away and air transport is unavailable. BP is 148/90 mm Hg, pulse 92/min, SpO₂ 97% on room air, and his lungs are clear. The ECG shows 3-mm ST elevation in II, III and aVF with ST depression in I and aVL; right-sided leads show no ST elevation. He has no history of stroke, bleeding or recent surgery, and he has chewed aspirin 325 mg. Which is the most appropriate next step?

A. Tenecteplase now with clopidogrel and an anticoagulant, then transfer to the PCI center B. Transfer for primary PCI without fibrinolysis C. Heparin infusion and coronary angiography within 24 hours D. Repeat troponin in 1 hour before choosing a reperfusion strategy E. Supplemental oxygen and serial ECGs

Answer: A. This is an inferior STEMI (ST elevation in II, III and aVF with reciprocal depression in I and aVL), 2 hours from onset, with no contraindication. A first-medical-contact-to-device time well over 120 minutes means fibrinolysis within 30 minutes of arrival, with clopidogrel and an anticoagulant, then transfer for angiography in 2-24 hours, or immediately if reperfusion fails.

B: transfer pushes reperfusion far past the 120-minute limit.
C: that is the NSTE-ACS pathway; ST elevation needs immediate reperfusion.
D: troponin lags behind injury; the ECG already makes the diagnosis.
E: routine oxygen is not recommended at SpO₂ 97%, and observation wastes the reperfusion window.

Key takeaways

Both are MIs (troponin rise and/or fall with a value above the sex-specific 99th percentile, plus ischemia); the ECG splits them.
STEMI → reperfuse: primary PCI ≤90 min from first medical contact (≤120 min with transfer), or fibrinolysis within 30 min plus clopidogrel if symptoms <12 h, then angiography at 2-24 h.
NSTEMI → no lytics: DAPT, heparin or enoxaparin, angiography <2 h if unstable, <24 h if high risk, otherwise before discharge.
STEMI equivalents: posterior MI (V7-V9), RV MI (right-sided leads), new LBBB or RBBB with other signs of ischemia.
2026 definition: primary, secondary (type 2) and procedure-related MI.
Traps: no nitrates with RV infarction or PDE-5 inhibitors; no lytics for NSTEMI or suspected dissection; oxygen only if SpO₂ <90%.