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  Atrial Septal Defect (ASD)

It is the most common congenital heart disease presenting with symptoms in adults. There are four types of ASD; of which the first three are most common. ASD is more common in females.

1. Ostium secundum (90%)

2. Ostium primum (5%)

3. Sinus venosus (5%).

4. Coronary sinus type –very rare 

Ostium primum type of ASD is commonly associated with either Down’s syndrome or with endocardial cushion defects (MR, TR).

Ostium secundum type of ASD can be sporadic or transmitted as autosomal dominant condition.

PFO (Persistent foramen ovale) – there is only anatomical patency.

In ostium secundum ASD there is both anatomical and functional patency.

Syndromes with ASD 

1. Holt-Oram syndrome (Ostium secundum ASD) Triphalangeal (fingerised) thumb, sometimes abrachia or phocomelia, autosomal dominant inheritance. 

2. Trisomy 13 (Patau syndrome) Polydactyly, flexion deformity of fingers, simiancrease, microcephaly, holoprosencephaly, cleft lip and palate and low set malformed ears (ASD, VSD, PDA).

3. Trisomy 18 (Edward syndrome) Prominent occiput, low set malformed ears and micrognathia together with clenched fists and rocker bottom feet (ASD, VSD, PDA).

4. Others: Ellis van Creveld (polydactyly, nail dysplasia, chondrodystrophic dwarfism), TAR (thrombocytopenia and absent radius), trisomy 21 and rubella. 

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ASD can be associated with 

a. MVP

b. Acquired MS (Lutembacher’s syndrome). 

Sinus venosus type of ASD occurs high in the septum near the SVC entrance. It is sometimes associated with partial anomalous pulmonary venous connection. 

• AF is common in ASD.

• Infective endocarditis is uncommon in ASD, except in ostium primum type, due to associated MR or TR. 

Clinical Features of ASD

a. One-third of patients with ASD have a systolic thrill. If thrill is prominent, associated PS should be thought of.

b. Wide, the fixed split of S2 is the characteristic auscultatory finding of ASD.

c. S2 split is narrowed with the development of PHT.

d. Split is variable with development of AF.

e. Flow ESM across pulmonary valve.

f. Flow MDM across the tricuspid valve.

Differential Diagnosis 

1. Partial anomalous pulmonary venous connection can simulate ASD (Acyanotic).

2. Total anomalous pulmonary venous connection with a large interatrial communication without pulmonary hypertension or pulmonary venous obstruction can also simulate ASD (Cyanotic).

3. MS with pulmonary hypertension. 

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ECG

a. Ostium secundum: RAD with RV dominance and incomplete RBBB

b. Ostium primum: LAD with incomplete RBBB

c. Sinus venosus: Inverted P-wave in inferior leads. Junctional rhythm may be present.

 Rarely ostium primum defects may be associated with complete heart block. 

Chest X-ray

Dilated right atrium, right ventricle and pulmonary arteries, with a less prominent aortic knuckle gives a characteristic ‘Jug handle appearance’. Dilatation of SVC is in favour of sinus venosus type of ASD. The lung fields are plethoric. 

Treatment of ASD

Surgical closure (ideal age 3–6 years). Indication for surgery—significant shunt with pulmonary to systemic flow > 1.5 : 1.

A new non-invasive surgical procedure is closure of the defect using an umbrella (Fig. 3.94). However, ASDs can close spontaneously upto 2 years of age.

Prosthetic closure of ASD using pericardial graft can be done.