Lead aVR is beginning to get a little respect but still doesn't get the respect it deserves. Here is a recent review.
Recent attention to aVR has focused on arrhythmia diagnosis, pericarditis and ACS. Many recent publications emphasize ST elevation in aVR during ACS as a sign of global ischemia due to left main coronary artery involvement. As the review points out, however, the situation is more complex. From the abstract and introduction:
The 12-lead electrocardiogram (ECG) is a crucial tool in the diagnosis and risk stratification of acute coronary syndrome (ACS). Unlike other 11 leads, lead aVR has been long neglected until recent years..ST-segment elevation in lead aVR can be caused by (1) transmural ischemia in the basal part of the interventricular septum caused by impaired coronary blood flow of the first major branch originating from the left anterior descending coronary artery; (2) transmural ischemia in the right ventricular outflow tract caused by impaired coronary blood flow of the large conal branch originating from the right coronary artery; and (3) reciprocal changes opposite to ischemic or non-ischemic ST-segment depression in the lateral limb and precordial leads. On the other hand, ST-segment depression in lead aVR can be caused by transmural ischemia in the inferolateral and apical regions.
Background from some prior posts: