Echocardiographic prediction of left-to-right shunt with atrial septal defects

We investigated the ability of transthoracic echo-cardiography to predict a ratio of pulmonary to systemic flow (Qp/Qs) ≥1.5 in patients with secundum atrial septal defects. The 44 study patients included 31 patients undergoing catheterization for device closure of atrial septal defects and 13 additional control patients with normal echocardiograms (median age 7.8 years, mean age 15.9 years, range 1.5 to 69 years). Right atrial end-systolic area, right ventricular end-diastolic volume, and the ratio of pulmonary annulus diameter to aortic annulus diameter were determined from standard transthoracic echocardiographic views. The 26 subjects in the shunt group had Qp/Qs between 1.5 and 3.0. The control subjects included the 5 catheterization patients with Qp/Qs between 0.9 and 1.2 and the 13 patients that did not undergo catheterization with assumed Qp/Qs = 1. The shunt patients had significantly increased median-indexed right atrial area (13.8 versus 8.5 cm²/M², P < .0001), median-indexed right ventricular-volume (85 versus 39 mL/M², P < .0001), and median ratio of pulmonary valve annulus to aortic valve annulus (1.26 versus 1.13, P = .008) compared with controls. Indexed right ventricular volume was the best predictor of significant shunt. A combination of right ventricular volume and right atrial area identified subjects with Qp/Qs ≥1.5 with 96% sensitivity, 94% specificity, and 96% positive and 94% negative predictive value. We conclude that quantitative transthoracic echocardiography can be used to screen for a significant shunt in patients with atrial septal defects.