Monday, September 6, 2010

Single Atrium


Single atrium is defined as: absent or very rudimentary atrial septum.
It is also called: Cor triloculare biventriculare.


  • Great vessels are usually normally related: aorta (AO) from left ventricle (LV) & pulmonary trunk from right ventricle (RV).
  • L-loop of the ventricles (RV & tricuspid valve to the left) may occur.
  • Ventricular septal defect (VSD) may be present.
  • Mitral regurgitation (MR) is commonly present.

Secondary pathological changes: Secondary cardiac changes are similar to those described for large ASD.

Clinical picture:

Similar to large ASD: Congestive heart failure (CHF) in the 1st year of life, with slow weight gain, cyanosis & clubbing, in most cases.

Chest x-ray:

Chest x-ray findings are similar to large ASD: with cardiomegaly, enlarged central pulmonary arteries & pulmonary plethora.


ECG is similar to that in primum ASD, with left axis deviation & right ventricular hypertrophy (RVH).


Echocardiography usually shows the characteristic features of atrioventricular septal defects (AVSD).

Top: Diastolic image. ATRIUM indicates single atrium; RV, right ventricle; and LV, left ventricle. 
Bottom: Systolic image. A indicates single atrium.

Cardiac Catheterization:

Usually not needed, but may show:
  • Oximetry: Complete mixing of blood at atrial level with mild systemic hypoxemia and cyanosis.
  • Pressures:
    • High PA pressure is common.
    • High pulmonary vascular resistance in some cases.
  • Angiography:
    • Injection into systemic & pulmonary veins: To establish the pattern of venous drainage.
    • LV injection: to assess: MR, VSD, Great arteries relationship, Goose-neck deformity of the LV outflow tract.


  • Surgery may be difficult, due to:
    • Anomalous pulmonary and/or systemic venous drainage.
    • Difficulty in avoiding injury to the conduction system, during placement of the intra-atrial patch.
  • Procedure: Pericardial patch is placed directing the blood flow as follows:
    • Pulmonary veins to LV.
    • Systemic & Hepatic veins to RV.
    • Coronary sinus to either side.