What is the blood supply to the ventricular septum?

Blood Supply to the Ventricular Septum

The ventricular septum receives dual blood supply: the anterior two-thirds is supplied by septal perforator branches from the left anterior descending (LAD) coronary artery, while the posterior one-third is supplied by the posterior descending artery (PDA), which typically arises from the right coronary artery in right-dominant circulation (90% of individuals). 1, 2, 3

Anterior Septal Blood Supply

The anterior two-thirds of the interventricular septum is predominantly supplied by:

• 4 to 10 septal perforator branches arising from the LAD coronary artery 3
• One or two long septal arteries (present in 94% of cases) that also originate from the LAD 3
• The first septal perforator is typically the largest and its location can be predicted relative to the medial papillary muscle 4
• The bulk of the anterior septum depends on these LAD septal branches, making proximal LAD occlusions particularly devastating for septal perfusion 5

Posterior Septal Blood Supply

The posterior one-third of the septum receives blood from:

• The posterior descending artery (PDA), which runs in the posterior interventricular groove and gives off septal perforator branches 1
• In right-dominant circulation (approximately 90% of people), the PDA arises from the RCA 1
• The cephalic (upper) portion of the posterior septum is supplied by the PDA 3
• The caudal (lower) portion may receive supply from the LAD when it wraps around the apex (wrapped LAD configuration) 2, 3

Additional Vascular Contributions

• In approximately 85% of individuals, the right coronary artery or its conus branch provides an interventricular septal branch that pierces the anterior wall of the right ventricle, runs subendocardially on the supraventricular crest, and anastomoses with anterior perforators from the LAD 3
• The remaining 15% who lack this septal branch are at higher risk for larger infarctions if the LAD becomes occluded 3
• The conduction tissues at the base of the ventricles (AV node, bundle of His, and branching bundle) tend to receive blood supply from arteries arising from the posterior descending artery 4

Clinical Implications

Wrapped LAD anatomy (where the LAD extends beyond the apex to the inferior wall) creates a situation where the apical septum receives blood supply only from the LAD, significantly increasing the risk of ventricular septal rupture (VSR) with anterior MI 2:

• VSR occurs in 1-2% of all myocardial infarctions 6
• ST-segment elevation in all three inferior leads (II, III, aVF) in addition to anterior leads suggests wrapped LAD anatomy and predicts VSR risk (odds ratio 16.93) 2
• Without surgery, VSR mortality is 54% within the first week and 92% within the first year 6

The crista supraventricularis shares muscle fibers with the interventricular septum and serves important contractile functions during systole 6

Anatomical Variations and Surgical Considerations

• The triangular area bordered by the margin of any ventricular septal defect, the muscular outlet septum, and the medial papillary muscle is free of major perforating arteries 4
• This anatomical relationship provides surgeons with a predictable safe zone during septal operations 4
• Septal perforator arteries are the target vessels during alcohol septal ablation for hypertrophic cardiomyopathy, where 1-3 cc of ethanol is injected to create a controlled septal infarction 6