Posterior Myocardial Infarction

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Posterior myocardial infarction is commonly confused with anterior subendocardial ischemia; however, the T waves are expected to be negatively deflected with anterior subendocardial ischemia (unless early on when they can mirror posterior hyperacute T waves). 5-10% of all myocardial infarctions are isolated posterior and not associated with inferior ST elevation. Isolated posterior myocardial infarctions are associated with longer door-to-balloon times and worse outcomes because they are frequently missed. ST elevation of at least 0.5 mm in posterior leads can help secure the diagnosis.

 

Posterior leads placed under the left scapula and designated as V7, V8, and V9.

Examples

ECG Showing Posterior Myocardial Infarction

Posterior Myocardial Infarction

Posterior myocardial infarction with ST-segment depression and upright T waves in the precordial leads V2 through V4. This patient had percutaneous coronary intervention to an occluded left circumflex artery.
ECG Showing Posterior Myocardial Infarction

Posterior Myocardial Infarction

V4-V6 represent posterior leads. At least 0.5mm ST-segment elevation can be seen in V6, confirming the diagnosis of posterior myocardial infarction. This patient had percutaneous coronary intervention to an occluded left circumflex artery.

References

  1. Ayer A, Terkelsen CJ. Difficult ECGs in STEMI: Lessons learned from serial sampling of pre- and in-hospital ECGs. Journal of Electrocardiology. 2014;47(4):448-458.
  2. Waldo SW, Brenner DA, Li S, Alexander K, Ganz P. Reperfusion times and in-hospital outcomes among patients with an isolated posterior myocardial infarction: Insights from the National Cardiovascular Data Registry (NCDR). American Heart Journal. 2014;167(3):350-354.