ECG in a person with persistent anginal pain for the past several hours showing significant ST segment depression anterolateral leads along with sinus tachycardia. ST segment elevation is noted in aVR. Such a pattern is consistent with significant left main coronary artery stenosis. Clinical evaluation and X-Ray chest showed features of pulmonary edema. Angiography done after initial stabilization with intensive medical management showed severe stenosis of distal left main coronary artery along with multiple lesions in all the three vessels, making a standard indication for an urgent coronary artery bypass grafting. A similar ECG pattern can also occur in severe proximal triple vessel disease. The previous ECG is given below for comparison, which shows minimal changes. But the ST segment elevation (minimal) in aVR is seen. This highlights the need for serial ECGs in acute coronary syndrome as initial ECGs may be normal even in those with severe disease.
Classical electrocardiographic pattern in left main coronary artery disease is ST segment elevation in aVR with extensive ST depression in other leads, most prominent in I, II and V4-V6 . ST elevation may be noted in V1, but ST elevation in aVR is more than or equal to that in V1 . ST segment elevation in aVR greater than or equal to that in V1 distinguished left main stenosis from left anterior descending coronary artery (LAD) stenosis with 81% sensitivity, 80% specificity. ST segment elevation in aVR in proximal left LAD occlusion before first septal is thought to be due to transmural ischemia of the basal part of the septum . Injury current of basal part of septum is directed towards right shoulder and aVR. ST segment elevation in aVR noted in left main disease is also likely due to the same mechanism as flow to first septal is blocked in this case as well. Mortality was more frequently observed in left main obstruction patients with higher degree of ST elevation in aVR .