Interventricular septum

Interventricular
septum • Parasternal short axis view - normal (transthoracic echocardiography) - Ganzer Fall bei Radiopaedia
Carroll D, Parasternal short axis view - normal (transthoracic echocardiography). Case study, Radiopaedia.org (Accessed on 03 Feb 2023) https://doi.org/10.53347/rID-62654 • CC by-nc-sa 3.0 (modified)
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The interventricular septum divides the right and left ventricles, running in the plane of the anterior and posterior interventicular grooves. Septation of the ventricles occurs in the fetus within 7 weeks of gestation, achieved by the formation of this embryologically heterogenous structure .

Gross anatomy

Roughly triangular in shape, the septum extends in three planes; anteriorly (in an antero-superior direction), inferiorly (rightward and inferolateral direction) and apically (toward the left ventricular apex). The apical two-thirds of the ventricular septum is heavily trabeculated, with a smooth walled basal one-third .

The interventricular septum is composed of a muscular and membranous portion, the former subdivided into the following constituent parts:

  • inlet septum
    • extends posteriorly to the cardiac crux, separating the atrioventricular valves
  • trabecular septum
    • primary structure dividing the anatomic bodies of the left and right ventricles
  • infundibular septum
    • directly inferior to the junction between the pulmonic commissure and the commissure between the right and left coronary cusps of the aortic valve
    • distinct from the rest of the septum both in orientation and perfusion
      • invests the right coronary sinus 
      • often derives its blood supply from the descending septal artery, a branch of the conus artery or proximal right coronary artery 

The comparatively diminutive membranous component is found between the outflow tracts of the left and right ventricles, anterior to the right fibrous trigone, posterior to the right coronary sinus, and continuous with the muscular septum . It is further sub-divided by the septal leaflet of the tricuspid valve: superior to the tricuspid valve attachment, the septum is inter-atrial whereas the portion inferior to the tricuspid valve is the true interventricular (ventricular) portion.

Relations
  • location:
    • membranous interventricular septum
      • continuous with the right fibrous trigone and the annuli of the mitral, tricuspid, and aortic valves
        • mediates the fusion between the tricuspid (commissure between the septal and anterior leaflets) and aortic (commissure between the right and non-coronary cusps
        • further subdivided by the septal leaflet of the tricuspid valve into atrioventricular and interventricular components
      • muscular interventricular septum
        • continuous with the membranous septum, the heavily trabeculated muscular septum courses toward the apex
  • blood supply:
  • relations:
    • forms the medial wall of the right ventricle and the left ventricle

Radiographic features

Echocardiography

Interventricular septal thickness at end-diastole is often measured in the parasternal long axis with transthoracic echocardiography, normal values often cited as between 0.6 cm and 1.0 cm .

Development

  • muscular septum
    • arises from the endocardial surface of the common ventricle
      • interventricular foramen persists at the superior portion, which will be occluded by the membranous septum
    • membranous septum
      • derived from the bulbar ridges and septum intermedium

Related pathology