Significant left main coronary artery disease in patients with acute coronary syndrome (ACS) generally is managed with bypass surgery. Treatment before surgery often includes anti-platelet therapy using a combination of aspirin and clopidogrel. Clopidogrel therapy seems to improve clinical outcomes in patients with ACS but may lead to increased morbidity, especially among patients who undergo bypass surgery. Avoiding the use of clopidogrel five days before surgery may be associated with decreased morbidity, making it more important to identify patients with ACS who may need to have cardiovascular surgery at an early stage. Gaitonde and associates studied the use of electrocardiographic (ECG) evidence, specifically a lead aVR ST-segment elevation greater than the ST-segment elevation seen in lead V₁, in predicting significant left main coronary artery disease.

ECG changes in four patients presenting with ACS demonstrated ST-segment elevation in lead aVR that was greater than ST-segment elevations in lead V₁. Clopidogrel therapy was withheld in these patients, and emergency angiography was performed, which confirmed significant left main disease. All patients were successfully treated with emergency coronary bypass surgery.

Vectorcardiography may explain the ECG changes seen in patients with ACS. Vectors of different myocardial areas counteract forces from other areas, resulting in the final electrocardiographic tracing. It is unclear whether the same ECG changes would be seen in patients with left main disease who also have other factors that can affect ECG vectors, such as left circumflex artery stenosis, right coronary artery stenosis, vessel dominance, or prior myocardial infarction.

The authors conclude that an aVR ST-segment elevation greater than the V₁ ST-segment elevation can predict left main stenosis in patients with ACS, and its early recognition can improve clinical outcomes in these patients.