Atrial Septal Defect
Definition
An abnormal defect in the interatrial septum
Types
- Ostium secundum (70%): defect located in the mid-portion of the interatrial septum
- Ostium primum (20%): defect located at the inferior portion of the inter-atrial septum (associated with a cleft mitral valve)
- Sinus venosus (10%): defect located in the superior portion of the inter-atrial septum (associated with partial anomalous pulmonary venous return)
Shunt
- Predominantly left-to-right with a brief reversal of the shunt during atrial relaxation (early ventricular systole)
Cardiac Auscultation
- Increased flow across the pulmonary valve causes an ejection-type murmur
- Fixed splitting of S2 due to delayed emptying of the right ventricle
Electrocardiogram
- Incomplete right bundle branch block
- Right atrial enlargement
- Right axis deviation
Chest X-ray
- Cardiomegaly (enlargement of the right atrium, right ventricle, and main pulmonary artery)
Cardiac Catheterization
Should demonstrate an oxygen step-up in the right atrium, as compared with oxygen samples taken from the inferior and superior vena cava
Treatment
- Close with pericardial or Dacron patch if Qp/Qs is ≥ 1.5:1
M-Mode
- Right ventricular volume overload pattern (paradoxical septal motion with right ventricular enlargement)
2-D
- Subcostal approach is recommended to best visualize the interatrial septum (parasternal short-axis view of the aortic valve is also a thoughtful approach)
- Right ventricular volume overload pattern (paradoxical septal motion with right ventricular enlargement)
- Flattened interventricular septum ("pancaking") due to right ventricular volume overload
- Pulmonary artery enlargement
- T-artifact (increased echogenicity at the edge of the interatrial septum) as seen from the apical four-chamber view
- Cleft mitral valve (primum atrial septal defect)
- Mitral valve prolapse
Doppler
- Subcostal approach is recommended to best visualize the interatrial septum (parasternal short-axis view of the aortic valve and right parasternal view of the interatrial septum should also be attempted)
- PW and color flow Doppler demonstrate a left-to-right shunt across the defect
- Note turbulent flow in the pulmonary artery due to increased blood flow to the lungs
- Determine the presence and severity of tricuspid and pulmonary regurgitation due to annular stretching from increased right-sided volume
- Determine the presence and severity of mitral regurgitation if a cleft mitral valve is present
- Determine Qp/Qs
Contrast Technique
- An injection of agitated saline may be used to determine the presence of an atrial septal defect
- Look for contrast crossing the defect into the left atrium or the negative contrast effect due to the left-to-right shunt
Postoperative
- Flat or paradoxical septal motion may persist (a normal finding after cardiac surgery)
- Use Doppler to determine whether a residual shunt is present
Patent Foramen Ovale
- Approximately 30% of normal adults have a patent foramen ovale, which may be a site for a shunt and an explanation for an embolic event
- Perform contrast examination with either transthoracic or transesophageal echocardiography
- Instruct the patient to cough or release after a Valsalva to see if a shunt exists.
Atrial Septal Aneurysm
- Abnormal bulging (> 1.5 cm in length and excursion) from midline of the interatrial septum may be detected by 2-D echo.
- The aneurysm is a potential site for either
- a shunt
- a source of embolism