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Tuesday, February 22, 2011

ATRIAL SEPTAL DEFECT

Atrial septal defect is more common in female. Since the normal right ventricle is much more complaint than the left, a large volume of blood shunts through the defect from the left to right atrium and then to the right ventricle and pulmonary arteries.
 As a result there is gradual enlargement of the right side of the heart and of the pulmonary artery and its main branches. Pulmonary hypertension and shunt reversal sometimes complicate atrial septal defect, but are less common and tend to occur later in life than with other type of left-to-right shunt.

Clinical features
There may be no symptoms for many years and the condition is often detected after a routine chest radiograph. Dyspnoea, cardiac failure and arrhythmias such as atrial fibrillation are other  possible modes of presentation. The characteristic physical signs are:

1.Wide fixed splitting of the second heart sound- wide because of delay in right ventricular ejection, fixed because the septal defect equalities left and right atrial pressure throughout the respiratory cycle;

2. a systolic flow murmur over the pulmonary valve.

In children with a large shunt there may be a diastolic flow murmur over the tricuspid valve; unlike a mitral flow murmur, this is usually high-pitched.
The chest radiograph shows enlargement of the heart and of the pulmonary artery; increased pulsation of the vessels can be seen on screening. The ECG usually shows incomplete right bundle branch block because right ventricular depolarisation is delayed as a result of ventricular dilatation. Echocardiography is very useful, and cross-sectional echocardiography may directly demonstrate the defect.

Management
Atrial septal defect large enough to be clinically recognisable should be closed surgically, and the long term prognosis thereafter is excellent. pulmonary hypertension and shunt reversal are contraindications to surgery.

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