Ultrasound Doppler methods for calculating cardiac volume flows, cardiac output, and cardiac shunts.

The variety of volume flow calculation methods described for determination of cardiac output by Doppler and the controversy surrounding their relative accuracy is to some extent a result of how difficult they are to use and the fact that they break down in patients whose anatomic and physiologic flow cross sections do not match, in patients who may have flow in vessels with flow profiles that are not flat, and in patients who are difficult to examine in one view or another or who do not give clean Doppler waveforms. Nonetheless, most of the methods work to some extent in most patients. Discovering those patients who do not fit the assumptions in these methods and whose cardiac output can therefore not be accurately calculated will probably be a major contribution of the new flow mapping Doppler technologies. We believe these new technologies may provide more sophisticated methods for calculating volume flows, cardiac outputs, regurgitant fractions, and shunt volumes.