Anterior ventricular branches of anterior interventricular artery

The anterior ventricular branches of the anterior interventricular artery (Diagonal branches of the left anterior descending artery) are a series of epicardial vessels that arise from the anterior interventricular artery (LAD) and course obliquely over the anterior and anterolateral free wall of the left ventricle to supply the myocardium of that region.

Definition and Anatomy

The anterior interventricular artery (LAD) originates from the left main coronary artery at the left coronary sinus and travels along the anterior interventricular sulcus toward the cardiac apex. Along its course, it gives off three main categories of branches: septal perforator branches (which penetrate the interventricular septum), the left conus branch, and the anterior ventricular (diagonal) branches, which extend laterally over the epicardial surface of the left ventricle.

Key characteristics:

• Number: Typically one to three diagonal branches arise from the LAD. According to the ACC/AHA data standards, they are designated as the first, second, and third diagonal branches, defined as the three longest branches originating from the LAD to supply the anterolateral wall of the left ventricle.

• Course: These branches diverge from the LAD in a parallel fashion at their point of origin and then course obliquely across the anterior and anterolateral surface of the left ventricle toward the lateral cardiac border.

• Caliber and length: A meta-analysis of 25,602 hearts found that diagonal branches average approximately 2.21 mm in diameter (95% CI: 2.022.39) and a mean length of 49.1 mm (95% CI: 37.860.5).

• Territory of supply: The diagonal branches supply the anterior and anterolateral free wall of the left ventricle. Myocardial perfusion studies have confirmed that the anterior, anteroseptal, and apical segments are the most specific territories of the LAD and its branches. Isolated occlusion of a diagonal branch characteristically produces ST-segment elevation in leads I and aVL, reflecting ischemia of the high anterolateral wall.

• Ramus intermedius variant: In approximately 25% of hearts, the left main coronary artery trifurcates, giving rise to an additional branch between the LAD and circumflex arteries known as the ramus intermedius (RI). This vessel supplies a territory similar to that of a large first diagonal branch and is considered part of the same "diagonal artery" family.

Clinical Significance

The diagonal branches are important targets in coronary revascularization. Complete absence of diagonal branches is exceedingly rare (0.5% of cases), and when no diagonal branches are visualized angiographically, ostial occlusion of one or more such branches should be suspected. The papillary muscles of the left ventricle typically receive blood supply from more than one segmental artery, including contributions from the diagonal branches, which explains why anatomical variations in these vessels can play a role in ischemic papillary muscle dysfunction.