Acute Inferior ST-Elevation Myocardial Infarction (STEMI) — Diagnosis & Management

Key Points

• Inferior STEMI: ST elevation in II, III, aVF, usually due to RCA occlusion.
• Check for RV infarction with V4R; avoid nitrates if present.
• Reperfusion strategy: PCI preferred; fibrinolysis if PCI unavailable.
• Administer DAPT, anticoagulation, and high-intensity statin therapy.
• Monitor for bradyarrhythmias, hypotension, and mechanical complications.

Algorithm

1. Obtain ECG and confirm ST elevation in II, III, aVF.
2. Assess hemodynamics; suspect RV infarction if hypotension with clear lungs.
3. Place right-sided leads (V4R) if RV involvement suspected.
4. Activate PCI team or initiate fibrinolysis if PCI not available.
5. Administer aspirin + P2Y12 inhibitor, heparin, and statin.
6. Avoid nitrates if RV involvement; support preload with fluids.
7. Monitor rhythm and treat bradyarrhythmias as needed.

Clinical Synopsis & Reasoning

Acute inferior STEMI results from acute occlusion of the right coronary artery (RCA) in most patients, or the left circumflex artery (LCx) when left-dominant circulation exists. ECG shows ST elevation in II, III, aVF, with reciprocal ST depression in aVL. ST elevation greater in lead III than II suggests RCA involvement. Evaluate for right ventricular (RV) infarction—suspect when hypotension, clear lungs, and marked ST elevation in III > II are present; confirm with right-sided leads (V4R). Early recognition and rapid reperfusion improve survival and reduce complications such as AV block, bradyarrhythmias, and cardiogenic shock.

Treatment Strategy & Disposition

Immediate reperfusion with primary PCI is preferred when it can be performed within guideline-directed time frames. If PCI is not available within 120 minutes, initiate fibrinolysis unless contraindicated. Administer dual antiplatelet therapy (aspirin plus P2Y12 inhibitor), anticoagulation (unfractionated heparin or bivalirudin during PCI), and high-intensity statin therapy. For suspected RV infarction, avoid nitrates and diuretics to prevent worsening preload-dependent hemodynamics. Treat bradycardia or AV block with atropine; temporary pacing may be required. Admit to a coronary care unit for continuous monitoring.

Epidemiology / Risk Factors

• Inferior STEMI accounts for 30–40% of all STEMIs.
• Most commonly due to RCA occlusion.
• Mortality is lower than anterior STEMI but complications—especially bradyarrhythmias—are more common.

Investigations

ECG Features of Inferior STEMI

Pharmacology

Prognosis / Complications

• Generally favorable survival with timely reperfusion.
• Complications include AV block, RV dysfunction, papillary muscle rupture, and hypotension.
• Long-term prognosis improves with adherence to secondary prevention guidelines.

Patient Education / Counseling

• Explain the need for urgent reperfusion and close monitoring.
• Discuss lifestyle modification: smoking cessation, diet, exercise, and cardiac rehab.
• Stress adherence to long-term medications: antiplatelets, statins, beta-blockers, ACE inhibitors.
• Review warning signs of recurrent ischemia and importance of follow-up.

Notes

Inferior STEMI requires rapid diagnosis and reperfusion to minimize infarct size. Recognition of right ventricular involvement is critical, as inappropriate vasodilator therapy can worsen hemodynamics. Continuous monitoring and early secondary prevention improve long-term outcomes.

References

1. Ibanez B et al. 2017 ESC Guidelines for the management of acute myocardial infarction in patients presenting with ST-segment elevation. — Link
2. O'Gara PT et al. 2013 ACCF/AHA Guideline for the Management of ST-Elevation Myocardial Infarction. — Link
3. Thygesen K et al. Fourth Universal Definition of Myocardial Infarction (2018). — Link