The left circumflex coronary artery arises from the left main coronary artery and supplies the lateral and inferolateral segments of the myocardium. In approximately 10% of individuals the left circumflex coronary artery is considered dominant and it supplies a left posterior descending artery. This is considered a “left dominant” system.
The most common congenital anomaly of the circumflex coronary artery is when it arises from the right coronary cusp. This is a benign anomaly and does not result in myocardial ischemia.
When occluded, the circumflex coronary artery can cause a lateral myocardial infarction resulting in ST elevation in the lateral leads. The lateral ECG leads are considered lead V5-V6 and the “high lateral” ECG leads are lead I and aVL.