Acute Coronary Syndromes and Myocardial Infarction
Core concepts
Differentiate STEMI, NSTEMI, and unstable angina by ECG and troponin. Know reperfusion strategy: primary PCI within 120 minutes of first medical contact for STEMI; fibrinolysis only if PCI is unavailable within 120 minutes and symptom onset <12 h, followed by transfer for angiography. Understand the Fourth Universal Definition of MI (type 1–5), including type 2 (supply-demand mismatch) and type 4a (PCI-related, troponin >5× URL). Master antithrombotic regimens: aspirin plus a P2Y12 inhibitor (ticagrelor/prasugrel preferred over clopidogrel in ACS), parenteral anticoagulation (heparin, enoxaparin, bivalirudin), and GP IIb/IIIa for bailout. Know complete vs. culprit-only revascularization in multivessel STEMI (complete is generally preferred in hemodynamically stable patients).
Traps
- Using fibrinolysis in cardiogenic shock or when PCI is timely.
- Missing right ventricular infarction (inferior STEMI with hypotension)-avoid nitrates and give fluids.
- Confusing type 2 MI with type 1; treat the underlying stressor.
- Forgetting that prasugrel is contraindicated in prior stroke/TIA and ticagrelor in severe hepatic impairment.
- Overlooking stent thrombosis as a cause of recurrent STEMI.
Rule of thumb
Time is muscle: door-to-balloon <90 min at PCI centers, <120 min from first medical contact when transferring. In inferior STEMI with hypotension, obtain right-sided leads; if RV involvement, volume-load and avoid nitrates.
Worked example
A 58-year-old with 3 hours of chest pain has inferior ST elevation and BP 82/50. Right-sided lead V4R shows ST elevation, confirming RV infarction. Give a fluid bolus and avoid nitrates; proceed to primary PCI.