Anatomy
This can occur as secundum defects (80%) , primum defects (10%), or sinus venosus ASD.
Frequency
1/1500 need closure. 10-20% of adults have some sort of inter-atrial communication.
Physiology
Holes between the atria are usually remnants of the foramen ovale, in which the flap valve does not fit across the foramen well. These are in the middle part of the septum and are termed secundum. Primum defects are caused by abnormal growth of the septum and are in the inferior part of the septum, near the AV node. These form part of an AVSD and are associated with conduction defects.
Flow across the defect is left to right, but because pressures are similar on both sides of a defect, there is no murmur from the defect itself, and signs of heart failure are rare. Frequently there is a pulmonary flow murmur because of an excess of flow into the lungs.
Management
The majority of isolated secundum ASDs <6 mm diameter close spontaneously by two years, and some as late as 5 years of age. Thus, in the absence of associated symptoms, early closure is not indicated for these defects. Many question the value of closing all but the largest defects.
The generally accepted indication for isolated secundum ASD is to repair those with a large left-to-right shunt resulting in symptoms or significant right heart enlargement, usually associated with a ratio of pulmonary to systemic flow (Qp/Qs) exceeding 2:1 .
Transcatheter closure – percutaneous closure of secundum ASDs, however not suitable for defects greater than 18 mm. A decent rim of septal tissue is needed all around the defect for the device to engage with.
Surgical closure – Sinus venosus defects, coronary sinus defects, primum ASDs, and complex congenital lesions.
Clinical
Asymtomatic
Soft systolic murmur at upper left sternal edge (due to increased flow across pulmonary valve)
Fixed split S2 due to overload of right ventricle with prolonged ejection into the pulmonary artery circulation)
Mid-diastolic murmur at left lower sternal border (increased volume passing across tricuspid valve)
Investigations
ECG – Normal. Partial right bundle branch block, Right ventricle hypertrophy, Right Axis Deviation (Secundum ASD), Left Axis Deviation (Primum ASD)
CXR – (rarely) Increased pulmonary markings
Exam vignette
I examined Jane, a 7-year-old girl who looks well-grown for her age and I would like to plot her height and weight on a growth chart.
She is pink and not in respiratory distress. There are no dysmorphic features or finger clubbing. There is a median sternotomy scar on her chest. She has no murmur.
The findings is consistent with repaired congenital heart condition, for example, ASD.
