Radionuclide angiographic and echocardiographic quantitation of left-to-right shunts in children with ventricular septal defect.

Pulmonary to systemic blood flow ratios (Qp:Qs) were estimated in 16 children with ventricular septal defects using simultaneous echocardiography and radionuclide angiography, and compared to Qp:Qs measured at cardiac catheterization by the Fick principle method (Fick). When ratios of echographic left atrial dimensions (LAD) to body surface area (LAD/M2), body length (LAD/ht), and aortic root diameter (LAD/Ao) were compared to the Qp:Qs determined by Fick, the correlation coefficients were r = 0.70 for LAD/M2, r = 0.66 for LAD/ht, and r = 0.54 for LAD/Ao. The correlation coefficients between Qp:Qs by Fick, and left ventricular dimensions/M2 and fractional shortening of the left ventricle were not significant. The correlation coefficients between Qp:Qs and the ratios estimated by gamma-variate and area-ratio analysis of radioisotope pulmonary dilution curves were r = 0.92 and r = 0.84, respectively. Thus, radionuclide angiography provided more accurate quantitation of left to right shunting through a ventricular septal defect than echocardiography. However, difficulty in obtaining adequate bolus injections of the radioisotope may result in technical failures whereas echocardiographic measurement is possible in almost all pediatric patients. Finally, the gamma-variate method cannot accurately quantitate shunt ratios greater than 3.5 to 1.