Atrioventricular septum

Dr Joachim Feger et al.

The atrioventricular (AV) septum or septal atrioventricular junction forms a central part of the heart, where the interatrial and interventricular septum crosses the atrioventricular annular plane and join with the septal tricuspid and anterior mitral leaflet attachments.

On a four-chamber view the conjunction of both septa, the tricuspid and mitral leaflets display a cruciate appearance, hence the name crux of the heart, cardiac crux or crux cordis.

A characteristic anatomic feature of the atrioventricular junction is the atrioventricular septum a septal component separating the right atrium from the left ventricle. It forms an offset of the atrioventricular annular anatomy with a length of up to 8 mm/m2 BSA between the more apically located septal tricuspid leaflet and the hinge of the anterior mitral leaflet 1-3. It consists of an anterior membranous and inferior muscular part evolving from the right atrial septal wall and an extension or the crest of the interventricular septum on the left with fibrous and adipose tissue from the inferior atrioventricular groove sandwiched in between the two muscular structures 1-5.

The atrioventricular septum separates the right atrium from the left ventricle and is located inferior to the aortic root and immediately above the inferior pyramidal space. Towards the cardiac apex, it connects to the muscular interventricular septum and the septal tricuspid leaflet whereas towards the atria it fuses with the vestibular spine of the interatrial septum and the hinge of the anterior mitral leaflet 1-6.

The atrioventricular septum is supplied by septal branches and the atrioventricular nodal artery 1.

The septal atrioventricular junction is the location of the atrioventricular conduction axis and its membranous part is beyond the apex of the triangle of Koch 4-6.

The atrioventricular septum can be easily depicted on a four-chamber view with echocardiography, cardiac CT and cardiac MRI. The visualization of the detailed anatomic ultrastructure is usually beyond the scope of all three imaging techniques but most likely feasible with cardiac MRI, which can demonstrate the three layers in the case of abundant adipose tissue 1.

The septal atrioventricular junction can be delineated on a four-chamber view and its cruciate appearance has been first described on echocardiography 7.

The atrioventricular septum can be best visualized on ECG-gated cardiac CT with a triphasic bolus injection technique suitable for additional opacification of the right-sided cardiac chambers 1,2.

The three-layered architecture of the atrioventricular septum can be best differentiated by cardiac MRI on a four-chamber view immediately below the aortic root 1-3.

The cruciate appearance of the atrioventricular septal area was already described by Norman H. Silverman and Nelson B. Schiller in 1978 7.

The atrioventricular node is located near the central fibrous body of the membranous atrioventricular septum just beneath the apex of Koch's triangle and is a significant landmark for electrophysiologists in the planning radiofrequency ablation.

Pathological conditions related to the atrioventricular septum include 1-3:

Article information

rID: 86291
System: Cardiac
Section: Anatomy
Tag: cases
Synonyms or Alternate Spellings:
  • Atrioventricular muscular septum
  • Atrioventricular membranous septum
  • Septal AV junction
  • AV septum
  • Crux cordis
  • Crux of the heart
  • Cardiac crux
  • Septal atrioventricular junction

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