UMEM Educational Pearls


52 yo M with chest pain and shortness of breath, ECG as shown, do you activate cath lab?

The posterior descending artery (PDA) supplies the posterior third of the interventricular septum, including the posterior and inferior walls of the left ventricle. The vessel most commonly originates from either the right coronary artery (right dominant), left circumflex artery (left dominant), or both (codominant).


Posterior MI frequently occurs as an extension of an inferior or lateral infarct. Isolated posterior MI occurs in 3 - 5% of cases (1), and is frequently missed on ECGs.

The posterior myocardium is not directly visualized on a standard 12 lead ECG, but reciprocal changes of STEMI in the anteroseptal leads (V1- V3) are seen (the posterior electrical activity is recorded from the anterior side of the heart) 


If in V1- V3 you see 


* ST segment depression 

* Tall R wave

* Upright T waves




Consider posterior MI as a cause. You need to then obtain an ECG with posterior leads. If there is  0.5 mm elevation in any posterior lead this is diagnostic of posterior MI.






van Gorselen EO, Verheugt FW, Meursing BT, Oude Ophuis AJ. Posterior myocardial infarction: the dark side of the moon. Neth Heart J. 2007 Jan;15(1):16-21