Acute Inferior-Posterior Myocardial Infarction:
ECG Findings:
• ST segment elevation in inferior leads (II, III, aVF)
• ST segment depressions in the anterior leads (V1-V3) and possibly high lateral leads (I, aVL)
Important Points:
1. The right coronary artery supplies blood to the right ventricle, the sinoatrial (SA) node, the inferior portions of the left ventricle, and usually to the posterior portion of the left ventricle and the atrioventricular (AV) node.
2. Infarctions involving the SA node may produce sinus dysrhythmias including tachycardias, bradycardias, and sinus arrest.
3. Infarctions involving the AV node may produce AV blocks.
4. In the presence of acute inferior injury, a right-sided ECG should be obtained to look for right ventricular involvement. The administration of nitroglycerin in the presence of acute right ventricular infarction can precipitate profound hypotension, as these patients are preload-dependent.
5. Since the right coronary artery so often supplies the posterior left ventricle, look for evidence of a posterior infarction (as present in the example) and consider obtaining an ECG with posterior leads.
