Posterior Interventricular Branch

Overview

The posterior interventricular branch - also known as the posterior descending artery (PDA) - is a critical artery that runs in the posterior interventricular sulcus of the heart. It supplies blood to the posterior third of the interventricular septum and adjacent areas of the right and left ventricles. It is typically a branch of the right coronary artery (RCA) in a right-dominant heart and of the left circumflex artery (LCx) in a left-dominant heart. The PDA plays a major role in maintaining the vitality of the conduction system and the muscular septum.

Location

The posterior interventricular branch is located on the diaphragmatic (inferior) surface of the heart, within the posterior interventricular sulcus. It originates from:

• The right coronary artery (RCA) in about 85% of individuals (right-dominant circulation)

• The left circumflex artery (LCx) in about 8–10% (left-dominant circulation)

• Both RCA and LCx in the remainder (codominant circulation)

The artery descends toward the apex of the heart and may anastomose with the anterior interventricular branch (left anterior descending artery) at or near the apex.

Structure

The posterior interventricular branch is a medium-caliber muscular artery. Its characteristics include:

• Course: Travels in the posterior interventricular groove, accompanied by the middle cardiac vein

• Wall type: Composed of endothelial lining, smooth muscle, and elastic tissue typical of coronary arteries

• Branches: Gives rise to septal perforating arteries that enter and supply the interventricular septum

The artery is embedded in epicardial fat and surrounded by a capillary network, facilitating oxygen and nutrient exchange with the myocardium.

Function

The primary function of the posterior interventricular branch is to supply oxygenated blood to:

• The posterior third of the interventricular septum

• The inferior walls of the left and right ventricles

• Parts of the atrioventricular (AV) node and posterior part of the cardiac conduction system (in most cases)

It is essential for supporting coordinated ventricular contraction and conduction.

Physiological Role(s)

The posterior interventricular branch contributes to several critical physiological functions:

• Supports electrical conduction: Supplies the posterior part of the interventricular septum, which houses important parts of the bundle branches and AV node.

• Facilitates coordinated contraction: Supplies muscular walls of both ventricles, aiding synchronous cardiac contraction during systole.

• Perfusion during diastole: Like other coronary arteries, it primarily fills during ventricular diastole due to aortic recoil and closed aortic valve.

Clinical Significance

The posterior interventricular branch is clinically important due to its contribution to myocardial perfusion and its involvement in coronary artery disease:

• Myocardial Infarction (Inferior MI): Occlusion of the PDA leads to infarction of the inferior portion of the heart, typically producing ECG changes in leads II, III, and aVF.

• Conduction abnormalities: Ischemia or infarction in the PDA territory can affect the AV node or bundle branches, leading to heart blocks or arrhythmias.

• Coronary dominance: Assessment of whether the PDA originates from the RCA or LCx determines coronary dominance, which has surgical and interventional implications.

• Revascularization procedures: During coronary artery bypass grafting (CABG) or percutaneous coronary intervention (PCI), the PDA may be targeted if it is stenotic or occluded.

• Diagnostic Imaging: Coronary angiography and CT angiography are used to visualize the PDA and its role in perfusion, especially in planning cardiac interventions.

Knowledge of the posterior interventricular branch and coronary dominance is essential in cardiology, radiology, and cardiothoracic surgery for accurate diagnosis, risk assessment, and treatment planning.