Can posterior STEMI (elevation in V8/V9) activate STEMI bypass?
Question #25
Answer:
The short answer to your question is yes, you can activate PCI with isolated posterior STEMI (>1 mm elevation in the posterior leads).
Posterior myocardial infarction (MI) is relatively rare compared to anterior and inferior infarctions. It often occurs alongside inferior or lateral MIs, with isolated posterior MIs being less common. The incidence of isolated posterior MI is estimated to be between 3% and 7%. Conversely, posterior involvement is observed in approximately 15-20% of cases when associated with inferior or lateral infarctions.
Under Ontario's STEMI bypass protocol, paramedics can transport a patient directly to a Percutaneous Coronary Intervention (PCI) center when a 15-lead ECG indicates an isolated posterior STEMI, even if the initial 12-lead ECG appears normal. This approach ensures timely access to reperfusion therapy for patients with posterior myocardial infarctions, which are often underdiagnosed due to their subtle presentation on standard 12-lead ECGs.
Identification of Posterior STEMI:
- Posterior myocardial infarctions may not present with typical ST-elevation on a standard 12-lead ECG.Instead, they often show:
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- Horizontal ST depression in leads V1-V3.
- Tall, broad R waves in V2-V3.
- Upright T waves in the anterior leads.
yle="font-family: inherit; font-size: 1rem;">To confirm a posterior STEMI, a 15-lead ECG is performed by repositioning leads to the posterior chest:
- Optional V7: Left posterior axillary line, same horizontal plane as V6.
- V8: Tip of the left scapula, same horizontal plane as V6.
- V9: Left paraspinal region, same horizontal plane as V6.
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Remember to label your leads!
