Conal branch of anterior interventricular artery

The conal branch (Conus artery) of the anterior interventricular artery referred to as the left conal branch is a small arterial branch that arises from the proximal segment of the LAD and courses toward the right ventricular outflow tract (Conus arteriosus; Infundibulum of the right ventricle). It supplies the anterior surface of the RVOT and the adjacent myocardium.

Anatomical details

The anterior interventricular artery (LAD) gives rise to three main types of branches: the left conus branch, septal perforator arteries, and diagonal arteries (Anterior ventricular branches). The left conal branch is typically the first or one of the earliest branches of the LAD, directed rightward toward the pulmonary outflow tract.

It is important to distinguish the left conal branch (from the LAD) from the more commonly discussed right conal branch, which arises from the right coronary artery (RCA) or, in approximately 40% of individuals, directly from the right aortic sinus as an independent vessel. Both left and right conal arteries supply the conus arteriosus (RVOT), and together they may form an anastomotic ring around the outflow tract known as the circle of Vieussens (annulus of Vieussens). This anastomosis serves as an important collateral pathway: in cases of proximal LAD or RCA occlusion, the conal artery can provide functionally significant collateral blood flow to the territory of the occluded vessel.

Clinical significance

The conal branch has particular clinical relevance in several settings:

• Collateral circulation: In patients with severe LAD or RCA disease, the conus artery can serve as a principal source of collateral flow, preserving myocardial function in the territory of the occluded vessel. Case reports have demonstrated functionally significant collateral supply from the conus artery to an occluded LAD, with preserved left ventricular contractility.

• Anterior wall myocardial infarction: The size of the conal branch correlates with ECG patterns during anterior wall acute MI. A large conal branch reaching the interventricular septum provides "double circulation" to the septum (alongside LAD septal perforators), which may protect the right paraseptal area and is associated with absence of ST elevation in lead V1.

• Congenital heart disease: Recognition of the conal artery is essential in conditions such as tetralogy of Fallot, where surgical repair involving the RVOT must account for its course.

• Coronary angiography: In approximately 20% of patients, the conus artery may not be visualized during RCA angiography because contrast is injected distal to its origin, potentially causing collateral pathways to go undetected.