23-06: Left Main Lesion

ECG Findings

• ST elevation in aVR ≥ 1 mm.

• ST elevation in V₁ ≥ 1 mm is common as well.

• Widespread ST depression, typically in at least six to eight other leads.

Pearls

1. The left main coronary artery branches into the left anterior descending artery and the circumflex artery. It supplies blood to the ventricular septum and the anterior and lateral aspects of the left ventricle, usually sparing the posterior and inferior portion.

2. Risk of cardiogenic shock is high since so much of the left ventricle is served by the left main coronary artery. Patients with a 100% LMCA occlusion often suffer a pre-hospital cardiac arrest and may present in cardiogenic shock.

3. ST segment elevation in lead aVR may also be seen in severe triple vessel disease, proximal left anterior descending occlusion and diffuse subendocardial ischemia.

4. Other causes of diffuse myocardial ischemia, such as aortic dissection or profound anemia, can also produce this ECG pattern. ST elevation in lead aVR is not specific for left main disease, as there are many other potential causes of this finding.