Excellent illustrative example by Dawn of acute infero-postero MI. I'd add the following points to her explanation:

• The RCA (Right Coronary Artery) - generally supplies the right ventricle and posterior and inferior walls of the left ventricle. This explains why inferior & posterior MI's are commonly seen together.
• While right-sided precordial leads would be needed to know for sure about acute RV infarction - I'd be less suspicious of this in this case (unless the patient was hypotensive or became hypotensive after NTG) because there is ST depression in lead V1. Often you'll see either a flat or slightly elevated ST segment in V1 (but not in V2,V3) when there is associated RV involvement.
• In theory - acute infero-postero MI could be due to either: i) acute RCA occlusion; or ii) acute circumflex (LCx) occlusion in a dominant-left circulation (in which the RCA is a smaller less dominant vessel). Approximately 80-90% of individuals have a right-dominant circulation - so acute RCA occlusion is far more common.
• Clues in this tracing that the lesion is in the RCA are: i) ST elevation in lead III>II; and ii) marked ST depression in lead aVL >lead I.
• Note that in addition - there are small q waves in V4,V5,V6 - and ST elevation (!) also in leads V5,V6. Although one might be tempted to suspect a left-dominant circulation (due to infero-poster-"lateral") involvement - LEAD V6 ST elevation may also be a "reciprocal change" from posterior infarction (and it is not necessarily due to "lateral" infarction). Given how much more marked ST elevation is in lead III>II - I'd suspect RCA occlusion in this case (confirmed by Dawn's revelation that RCA occlusion was in fact the "culprit" artery).
• Practically speaking - it doesn't matter all that much what the "culprit artery" will be (as fun as it is to predict) - since it is obvious from this ECG that the patient needs acute cath - and definitive answers will then be obtained (sometimes collateralization and anatomic variants may account for unusual patterns).
• Finally - as Dawn suggests - there IS an important differential diagnosis to keep in mind for the "Tall R wave in lead V1". I totally agree in this case that the disproportionately tall R waves in V2,V3 are undoubtedly the result of acute posterior MI given the changes described above. Moreover, the R wave in V1 is really not taller than the S wave - so this example is really not consistent with things like RVH, RBBB, etc.
• Additional educational material that may be of interest include: i) Brief pdf on the "Mirror Test" (which is positive in lead V2 of this tracing!) and which also contains the List of Causes for a Tall R in Lead V1 - and ii) Review of How to PREDICT the CULPRIT ARTERY.