Posterior Myocardial Infarction

Introduction

Posterior myocardial infarction (PMI) is a type of heart attack that affects the back (posterior) wall of the left ventricle. It is often underdiagnosed because the typical ECG leads do not directly record electrical activity from the posterior wall.

Causes

PMI is usually caused by occlusion of the posterior descending artery (PDA), which is most commonly a branch of the right coronary artery (RCA) or, in some cases, the left circumflex artery (LCX).

ECG Diagnosis

Detecting PMI requires careful ECG interpretation: - Signs in standard leads: - ST-segment depression in leads V1-V3 (reciprocal changes) - Prominent R waves in V1-V2 - T wave inversion in V1-V3 - Use of posterior leads (V7-V9): - ST-segment elevation of at least 0.5 mm is considered significant

Symptoms

Like other types of myocardial infarctions, PMI presents with: - Chest pain (which may radiate to the back) - Shortness of breath - Nausea and diaphoresis (sweating)

Treatment

Management is similar to other STEMIs and should follow guideline-directed therapy: 1. Acute Revascularization: - Immediate percutaneous coronary intervention (PCI) is the preferred strategy - If PCI is unavailable, fibrinolytic therapy may be considered 2. Pharmacological Treatment: - Aspirin and P2Y12 inhibitors (e.g., clopidogrel, ticagrelor) - Anticoagulation (e.g., heparin) - Beta-blockers (if no contraindications) - Nitrates (for symptom relief, while monitoring for hypotension) - Statins (high-intensity therapy) 3. Monitoring & Complications: - Risk of cardiogenic shock, arrhythmias, and ventricular dysfunction must be assessed

Conclusion

Posterior MI requires a high index of suspicion for early diagnosis, appropriate ECG recognition, and rapid treatment with reperfusion therapy to improve outcomes.

Source recommendations

1. American Heart Association (AHA) STEMI Guidelines

1. https://www.heart.org/en/professional/quality-improvement/mission-lifeline/mission-lifeline-hospital-stemi-and-nstemi-recognition
2. https://www.ahajournals.org/doi/10.1161/CIR.0000000000001309
3. https://www.heart.org/en/professional/quality-improvement/mission-lifeline
4. https://cpr.heart.org/en/resuscitation-science/cpr-and-ecc-guidelines/algorithms
5. https://professional.heart.org/en/science-news/2025-guideline-for-the-management-of-patients-with-acute-coronary-syndromes

2. European Society of Cardiology (ESC) Guidelines for Myocardial Infarction

1. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Acute-Coronary-Syndromes-ACS-Guidelines
2. https://academic.oup.com/eurheartj/article/44/38/3720/7243210
3. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Fourth-Universal-Definition-of-Myocardial-Infarction
4. https://academic.oup.com/eurheartj/article/39/2/119/4095042
5. https://pubmed.ncbi.nlm.nih.gov/28886621/