Conal branch of right coronary artery

The conal branch of right coronary artery (Conus artery) is typically the first branch of the right coronary artery (RCA), supplying the right ventricular outflow tract (infundibulum or conus arteriosus). It arises at or near the origin of the RCA and courses over the right ventricular infundibulum toward the interventricular septum.

Anatomy and Origin Patterns

A comprehensive study of 600 specimens (300 cadaveric hearts and 300 coronary angiograms) identified five main patterns of origin for the conal artery:

• Type A (32.1%): Arises as a direct branch of the RCA

• Type B (16%): Arises from a common coronary ostium shared with the RCA

• Type C (40.3%): Arises independently from the right aortic sinus as a separate vessel (the most common pattern)

• Type D (8%): Multiple conal arteries are present

• Type E (3.6%): Arises from the right ventricular branch or the acute marginal artery

Clinical Significance

The conal artery has important clinical relevance in several settings:

• Collateral circulation: In patients with occlusion of the left anterior descending artery (LAD) or the RCA, the conus artery often serves as a principal source of collateral circulation. Failure to visualize it during coronary arteriography (which occurs in approximately 19.5% of cases due to contrast injection distal to its origin) may lead to underestimation of collateral flow, affecting medical and surgical decision-making.

• Myocardial protection: The size of the conal branch influences the extent of myocardial injury during anterior wall acute myocardial infarction. A large conal branch that reaches the interventricular septum can provide a "double circulation" to the septum (alongside the LAD septal perforators), offering protection and modifying the ECG pattern specifically, the 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 its course may be surgically relevant.