[Doppler effect in cardiology. Continuous Doppler, pulsed Doppler, Doppler color]

Abstract

Echocardiography has contributed to the exploration of the heart by providing much information, and it has even given rise to new semiological concepts. However, abnormalities of intracardial blood flow, notably shunts and regurgitations, could only be diagnosed indirectly from their effects on cardiac cavities. A new step forward was the advent of pulsed and continuous doppler ultrasound, since from that moment it has been possible to demonstrate abnormal blood flows, to measure their velocity and to determine, albeit with some reservation, such crucial values as pressure gradients. Yet even when these two techniques were combined in the doppler-echotomography systems blind areas persisted, and a blood flow of strongly abnormal direction could in fact escape doppler velocimetry. This is where another development came to the rescue, for it enabled both normal and abnormal flows to be visualized in colours. Owing to this visualization, and provided all possible projections are used, it has become exceptional to "miss" an abnormal blood flow. The diagnosis is now easier and more accurate, and in a second stage the flow can be quantified by pulsed or continuous doppler ultrasound. The colour-coded doppler technique therefore has not superseded the previous one: one may say that it has merely increased diagnostic reliability, but is this not a decisive improvement?