Cardiac output measurements in congenital heart disease: validation of a simple, portable Doppler method

Noninvasive Doppler cardiac output measurements are clinical standards in adults and children. Presently, these standard Doppler methods generally require relatively expensive and large imaging equipment with complex signal-processing techniques. Thus, universal access to these important measurements has been limited. Simple, portable Doppler methods have been validated previously and applied to infants and children without cardiac disease. Nevertheless, these specific, inexpensive techniques have not been validated in children with complex congenital heart disease. Accordingly, we compared a noninvasive, suprasternal, non-image-guided, pulsed Doppler cardiac output with standard invasive Fick cardiac outputs in 20 patients (age range, 1 month to 15 years) with congenital heart disease. Doppler cardiac output was displayed by multiplying the mean velocity with an operator-selected angiographic or echographic estimate of the aortic diameter. The values from linear regression analysis were r = 0.96; Doppler cardiac output = 0.98 x Fick cardiac output - 0.08 L/min (range, 0.55-3.10 L/min). The 95% confidence limits were less than 35% of the mean of Doppler and Fick cardiac outputs across the range of measurements. We conclude that relatively linear and accurate measurements of cardiac output can be made by this simple, inexpensive, portable method in selected infants and children with various forms of congenital heart disease.