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.