Left main coronary artery

**Definition:** Diagonal branches of the left anterior descending coronary artery supply blood flow to the anterior and anterolateral walls of the left ventricle. There are usually denoted as D1, D2, D3, etc. There are termed "diagonal" due to them branching from their parent vessel at acute angles. They extend over the left ventricle in a diagonal fashion toward the acute margin and the cardiac apex. They often run parallel to one another and are variable in number (often 2 to 9).