[Quantification of atrial septal defects of the secundum type by subcostal 2-dimensional echocardiography].

Visualization of the interatrial septum (IAS) was most consistently achieved by subcostal 2-dimensional echocardiography (s2-DE) as compared with the apical and parasternal view. This approach also enabled a quantitative assessment of isolated atrial septal defects of secundum type (ASD II). The study group consisted of 33 children aged 5-14, mean 8 years, with ASD II (2 patent foramina ovale) and normal pulmonary vascular resistance. A good correlation was demonstrated between the end-diastolic diameter of the defect measured by s2-DE and left-to-right shunt determined by the Fick principle (r = 0.89). With respect to the endsystolic diameter of the defect, the correlation was less favourable (r = 0.76). This may be explained by the greater variability of the maximal defect in size in end-systole determined frame-by-frame. In conclusion, the size of an ASD II can be evaluated with accuracy by s2-DE. School children with isolated ASD II and diameters larger than 15 mm, corresponding to a 40% left-to-right shunt, will need surgical closure. However, surgery is not indicated in defects less than 11 mm and shunts smaller than 30%. In questionable cases we would be in favour of surgical closure.