Infarction of the posterior* left ventricular wall is also caused by occlusion of the posterior descending coronary artery and, frequently occurs in association with an inferior wall infarction. It is also occasionally associated with a lateral wall infarction and rarely is an isolated event. It is also difficult to diagnose from the routine 12 lead ECG because electrodes are not usually placed on the patient’s back. The presence of ST segment depression in leads V1 and V2 in association with the ST segment elevation in leads II, II. aVF and/or V6 that is consistent with an inferior and/or lateral wall infarction implies posterior wall* involvement. The ST segment depression in Leads V1 and V2 is the opposite, or reciprocal of ST elevation that would have been recorded had leads been placed on the posterior chest wall in positions referred to as V7,V8 and V9
Note, Currently, there is a bit of a controversy as to appropriate terminology. Some prefer the term “lateral” or “postero-lateral wall infarction” rather than “posterior wall infarction” because studies employing contemporary imaging techniques suggest that the posterior surface of the heart is comprised mainly of the left atrium and not the left ventricle and that the infarcted region in the left ventricle is primarily lateral rather than posterior. However, I prefer the original term “posterior wall infarction” because most physicians are familiar with the term and because leads placed on the posterior chest wall are required to demonstrate the ST segment elevation.