From the Guidelines
ST elevation in leads II, III, and aVF without reciprocal changes in leads I and aVL typically indicates an inferior wall myocardial infarction (MI) without lateral wall involvement, suggesting occlusion of the right coronary artery (RCA) and requiring immediate evaluation for acute coronary syndrome. This finding is significant because it may indicate a less extensive infarction or could suggest a more proximal RCA occlusion 1. The absence of reciprocal ST depression in leads I and aVL is important to note, as it may influence the diagnosis and treatment of the patient.
Key Considerations
- The patient should undergo immediate evaluation for acute coronary syndrome, including cardiac biomarkers (troponin) and additional ECG leads (particularly right-sided leads V3R-V6R to check for right ventricular involvement) 1.
- Right ventricular involvement occurs in approximately 30-50% of inferior MIs and can cause hypotension, especially when patients receive nitrates or preload-reducing medications.
- Treatment typically includes aspirin (325mg loading dose), P2Y12 inhibitors like clopidogrel (600mg loading dose), anticoagulation, and urgent coronary angiography with potential percutaneous coronary intervention 1.
- Careful fluid management is essential if right ventricular involvement is present, as these patients may require volume expansion rather than the typical preload reduction strategies used in other MI types.
Diagnostic Implications
- The spatial vector of the ST segment in the frontal plane is more likely to be directed to the right when the RCA is occluded, resulting in greater ST-segment elevation in lead III than in lead II 1.
- The absence of ST-segment depression in leads I and aVL is more suggestive of RCA than LCx occlusion 1.
- The use of right-sided chest leads (V3R-V6R) can help diagnose right ventricular involvement and distinguish between RCA and LCx occlusion 1.
From the Research
ST Elevation in Leads II, III, and aVF
- ST elevation in leads II, III, and aVF is typically associated with inferior wall myocardial infarction 2, 3, 4
- The presence of ST elevation in these leads without reciprocal changes in leads I and aVL may indicate a specific type of inferior wall myocardial infarction 2
- Studies have shown that patients with ST elevation in leads II, III, and aVF may have a lower peak CK level and less left ventricular dysfunction compared to those with anterior ST elevation 2
Clinical Significance
- The absence of reciprocal changes in leads I and aVL may suggest a more localized area of infarction 5
- ST elevation in leads II, III, and aVF without reciprocal changes may be associated with a benign clinical course in some cases 5
- However, it is essential to consider other clinical and electrocardiographic factors to determine the severity and prognosis of the infarction 3, 4
Diagnostic Value
- The ratio of ST elevation in lead III to lead II (III/II > 1) has been proposed as a diagnostic criterion for right ventricular infarction 4
- This criterion has a high specificity and positive predictive value, although it may not be as sensitive as other diagnostic methods, such as right-chest leads V3R to V7R 4
- Further studies are needed to fully understand the diagnostic value of ST elevation in leads II, III, and aVF without reciprocal changes in leads I and aVL 6, 2, 3, 5, 4