Septal branches of inferior interventricular artery

The septal branches of the inferior interventricular artery (Posterior descending septal perforators) are small-caliber perforating arteries that arise from the Inferior interventricular artery (Posterior descending artery). These branches penetrate the interventricular septum from its inferior (diaphragmatic) surface to supply the posterior and inferior third of the interventricular septum.

Parent vessel and origin

The inferior interventricular artery (PDA) most commonly arises from the right coronary artery (RCA) in right-dominant circulations (~87% of individuals), or from the left circumflex artery in left-dominant circulations (~9.5%). In co-dominant systems, the RCA supplies the PDA while the circumflex supplies the posterolateral artery. The ACC/AHA formally defines the posterior descending septal perforator as a "septal perforator vessel originating from the PDA."

Territory of supply

The interventricular septum has a dual blood supply: the anterior two-thirds is supplied by the anterior septal perforators arising from the left anterior descending artery (LAD), while the posterior third is supplied by the posterior septal perforators arising from the inferior interventricular artery (PDA). These posterior septal branches supply the inferior and basal portions of the septum.

Relationship to the conduction system

The posterior septal branches are of particular clinical importance because they provide the arterial supply to the atrioventricular (AV) node, the penetrating bundle of His, and the branching atrioventricular bundle at the base of the ventricles. Histologic studies have confirmed that the conduction tissues at the base of the ventricles tend to receive their blood supply from arteries arising from the inferior interventricular artery. The AV nodal artery, which ascends within the inferior pyramidal space at the crux of the heart, typically originates from the dominant RCA or one of its branches in this region.

Morphology and caliber

Compared to the anterior septal perforators (the first of which is typically the largest septal branch in the heart), the posterior septal perforators are generally smaller in caliber and more numerous. They penetrate the septum at roughly right angles from the posterior interventricular groove.

Clinical significance

• Inferior myocardial infarction: Occlusion of the RCA proximal to the PDA can compromise these branches, leading to posterior septal ischemia, AV conduction disturbances (first-, second-, or third-degree AV block), and posterior fascicular block.

• Collateral circulation: In the setting of significant atherosclerotic disease, the anterior and posterior septal perforators can serve as important collateral pathways between the LAD and RCA territories.

• Cardiac surgery: Knowledge of the location of these perforating arteries is essential during operations involving the ventricular septum, as incisions and sutures in this region can jeopardize these vessels.