Continuous wave Doppler in the evaluation of simple and complex congenital heart disease in infants and children.

Continuous wave Doppler assessment of systolic pressure gradients was performed using a digital maximal frequency estimator in 118 consecutive infants and children with suspected ventricular outflow obstruction who were undergoing cardiac catheterisation. There was satisfactory correlation with measured systolic pressure gradients in most patients with isolated pulmonary valve stenosis, aortic stenosis or aortic coarctation. Important under-estimation of gradients, however, occurred frequently in patients with more complex lesions. In many of these, the stenotic jet was posteriorly located or obstruction to flow occurred at more than one level. Continuous wave Doppler assessment of outflow tract gradients should be interpreted with caution in complex congenital heart lesions. A low predicted gradient should not be relied upon in isolation for clinical decision making. On the other hand, demonstration of a large gradient by continuous wave Doppler ultrasound provides additional information which may obviate the need for invasive investigation.