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.
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 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.
Usually not needed, but may show:
- Oximetry: Complete mixing of blood at atrial level with mild systemic hypoxemia and cyanosis.
- High PA pressure is common.
- High pulmonary vascular resistance in some cases.
- 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.