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Interventricular septal branch S2

The interventricular septal branch S2 is the second septal perforator artery, arising from the proximal segment of the left anterior descending (LAD) artery). Septal branches descend perpendicularly from the LAD into the interventricular septum, supplying both myocardium and the cardiac conduction system.

The S2 branch specifically penetrates the upper anterior interventricular septum, providing arterial supply to the bundle branches of the conduction system and the adjacent myocardium. This makes it clinically significant: obstruction or infarction involving the S2 branch can impair ventricular conduction pathways, leading to bundle branch blocks or arrhythmias.

Anatomically, septal branches show variability in number and size; S1 and S2 are usually the dominant feeders of the anterior septum. In coronary artery bypass grafting or interventional cardiology, the septal perforators are landmarks and can be inadvertently compromised.

Synonyms

  • Septal perforator artery S2

  • Second septal branch of LAD

  • Interventricular septal perforator (proximal)

Function

  • Provides arterial blood to the upper anterior interventricular septum

  • Supplies the bundle branches of the conduction system

  • Supports contractility of the anteroseptal myocardium

  • Plays a role in maintaining synchronous ventricular contraction

MRI Appearance

T1-weighted images:

  • Lumen not directly visible without angiographic sequences; appears as a signal void

  • Indirect visualization possible from adjacent myocardium

T2-weighted images:

  • Lumen remains a signal void

  • Ischemia or edema in the supplied territory (anteroseptal myocardium) appears hyperintense

STIR (Short Tau Inversion Recovery):

  • Suppresses fat, highlighting edema in the septal myocardium after ischemic injury

  • Useful for identifying acute septal infarction involving S2 territory

T1 Post-Contrast (Gadolinium-enhanced):

  • Septal myocardium supplied by S2 enhances in normal states

  • Infarcted or fibrotic tissue shows late gadolinium enhancement (LGE) in an anteroseptal distribution

MRI Non-Contrast Cardiac-Gated 3D Coronary MRA:

  • Depicts the S2 septal branch as a bright linear structure arising from proximal LAD

  • Visualizes origin, course, and penetration into the interventricular septum

  • Best for evaluating congenital anomalies or proximal LAD-septal anatomy

CT Appearance

Non-contrast CT (Calcium Scoring):

  • Not suitable for direct visualization of S2 branch

  • Proximal LAD calcification may suggest involvement of septal perforators

CT Coronary Angiography (CCTA):

  • High-resolution imaging of septal perforators, including S2

  • Depicts origin, angulation, and penetration into the septum

  • Identifies stenosis, occlusion, anomalous origin, or small aneurysms

  • Useful for planning PCI, assessing ischemia in septal territory, and arrhythmia correlation

CT images

Interventricular septal branch S2 anantomy CT axial image -img-00000-00000