[Value and limitations of pulsed Doppler echocardiography in the determination of pressure gradients in children].

The aim of this study was to evaluate the results of pulsed Doppler echocardiography in assessing pressure gradients in children despite the theoretical limitations of this technique in the measurement of high velocity blood flow (due mainly to the phenomenon of "aliasing"). 20 patients with an average age of 6.7 years (range 3 months to 19 years) were studied by 2D echocardiography and pulsed Doppler within 48 hours of cardiac catheterisation. Valvular stenosis was present in 14 cases (aortic, 7, pulmonary, 7). There were 3 cases of infundibular obstruction and 2 vascular stenosis (coarctation of the aorta and stenosis of a branch of the pulmonary artery). One patient had stenosis at the origin of a prosthetic tube graft. The gradient was estimated from the Doppler flow curves using simplified Bernoulli formula (P = 4 X maximal jet velocity). In 17 patients (gradients of 20 to 90 mmHg) an excellent correlation was observed between the pulsed Doppler and haemodynamic results (r = 0.90). In 3 cases with gradients over 80 mmHg it was not possible to quantify the gradient but pulsed Doppler fixed an inferior limit of 80 mmHg. Therefore, using a 3 or 2.25 MHz probe at the low depths of investigation encountered in childhood, pulsed Doppler gave a reliable indication of pressure gradients less than or equal to 80 mmHg. These results and the non-invasive nature of the method make pulsed Doppler a particularly interesting complementary examination in children or babies with stenotic cardiac lesions.