This interesting case was provided by Dr. Bojana Uzelac, Emergency Medicine physician. We are paraphrasing a translation of her comments here.
The patient is a 50-year-old complaining of chest pain.
The ECG shows a rare occurrence – an isolated POSTERIOR WALL MI (PWMI). Note that leads V1 through V4 show the usual signs of posterior wall MI. We see ST segment depression, which represents a reciprocal view of the ST elevation present on the posterior wall of the left ventricle. The relatively tall, wide R waves in V2 and possibly V3 represent pathological Q waves on the posterior wall. (V2 R/S ratio > 1). What is unusual here is that there are no signs of inferior wall MI or lateral wall MI. Posterior wall MI usually occurs in conjunction with one of these.
PWMI is most often seen as an extension of inferior wall MI or lateral wall MI, because of shared blood supply. Usually, it is the right coronary artery that supplies both the posterior and inferior areas of the left ventricle (about 80% - 85% of the population). In some individuals, the circumflex artery supplies both areas. Posterior M.I. may also be seen in conjunction with lateral wall MI, when the circumflex supplies the posterior and lateral walls. In the case shown here, only the posterior wall is involved. Most cases of isolated PWMI involve either the circumflex or one of its marginal (OM) branches. Only about 3.3% - 5% of all MIs are isolated PWMI.
The second ECG shown here has Leads V7, V8, and V9 replacing V4 – V6. These posterior leads confirm the posterior M.I. with ST elevation. Posterior M.I. can be confirmed with STE of > .5 mm in two of the three leads. The sensitivity for this finding is not known, but specificity is almost 100%. Performance of posterior leads has been shown clinically to improve chances of recognizing IPWMI. It is generally considered to be a good idea to perform posterior leads on patients with symptoms of M.I., but no ST elevation on the standard 12-Lead ECG. For electrode placement, see HERE.
Followup The patient was taken to the cath lab, where the circumflex artery was found to be 100% occluded. The patient’s outcome was good.
Some additional resources: NIH, National Library of Medicine, Posterior myocardial infarction.
NIH, National Library of Medicine, Isolated posterior ST-elevation myocardial infarction: the necessity of routine 15-Lead electrocardiography: a case series. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9420295/
Thank to Dr. Bojana Uzelac of Serbia for sharing this important example with us. To follow her on Facebook, follow this link: https://www.facebook.com/profile.php?id=100090459765248&mibextid=ZbWKwL
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