Usefulness of echocardiographic assessment of right ventricular and pulmonary trunk size for estimating magnitude of left-to-right shunt in children with atrial septal defect

Abstract

M-mode and 2-dimensional echocardiographic studies were performed in 42 patients, aged 1 to 16 years (mean 6), with a secundum or sinus venosus type atrial septal defect (ASD) and normal pulmonary artery pressure. Twenty normal children served as a control group. In patients with ASD the echocardiographic variables were correlated with the magnitude of the left-to-right shunt (Qp/Qs) calculated by the Fick principle. Although M-mode echocardiograms showed increased right ventricular (RV) dimension in 69% of the patients, the correlation between RV dimension index (RV dimension/body surface area) and Qp/Qs was weak (r = 0.49). When RV dimension was related to left ventricular (LV) dimension and expressed by the RV/LV ratio, 90% of the patients were found to have an abnormally large right ventricle. The correlation between the RV/LV ratio and Qp/Qs was fairly good (r = 0.64). In 33 patients (78%), the pulmonary trunk (PT) was adequately visualized and measured on 2-dimensional echocardiograms. The dimension of the PT was related to the aortic root dimension and expressed by the PT dimension/aortic dimension ratio. This ratio was 0.99 ± 0.06 in normal children and 1.35 ± 0.23 in patients with ASD (p <0.001). The PT/aortic ratio exceeded the upper limit of normal (the normal mean value + 2 standard deviations) in each of the 27 patients with a Qp/Qs of 1.5 or greater. In 5 of the 6 patients with a Qp/Qs of less than 1.5 the PT/aortic ratio was close to 1 and within the normal range. An excellent correlation (r = 0.89) was found between the PT/aortic ratio and Qp/Qs. The echocardlographic determination of the RV/LV ratio and particularly the PT/aortic ratio is therefore useful in the noninvasive estimation of the left-to-right shunt in ASD.