ATRIAL SEPTAL DEFECT

ASD classiefied by their location:

1. Ostium secundum defect - in the region of fossa ovalis

2. Ostium primum defect - inferior portion of the septum; may be associated with other endocardial abnormalities (e.g. split anterior leaflet, VSD)

PATHOPHYSIOLOGY: the left-to-right shunt in the atria determined by the size of the defect and the relative compliance of RV - gradual enlargement of the right size of the heart and of pulmonary arteries - pulmonary hypertension and sometimes shunt reversal

CLINICAL FEATURES:

• patients often asymptomatic during childchood and early adulthood

dyspnoea, chest infections, cardiac failure, arrhythmias (e.g. FA) - modes of presentations

• the characteristic physical signs: wide fixed splitting of the second heart sound (wide-delay in right ventricular ejection, increased stroke volume and RBBB; fixed-ASD equalises left and right atrial pressures throughout the respiratory cycle)

• a systolic flow murmur over the pulmonary valve (the left and right atrial pressure are similar, and the flow across the defect does not directly contribute the murmur)

• a diastolic flow murmur over the tricuspid valve (in children with a larged shunt)

• CXR - enlargement of the heart, the pulmonary artery, and pulmonary plethora

• ECG - IRBB (RV depolarisation is delayed as a result of ventricular dilatation), with a left axis deviation in a primum ASD

• patients with ASD and pulmonary-to-systemic shunt rations greather than 1.5 are referred for surgical repair

Category: Cardiology Notes