Relation between pulsed and continuous Doppler velocimetry of the anterior cerebral artery in newborn infants

Abstract

Continuous wave (cw) and pulsed wave (pw) Doppler velocimetry are both used to measure blood flow velocity in cerebral arteries. We examined whether data obtained with the two methods are interchangeable and equally useful for clinical application. We studied 20 infants at an age between 1 day and 2 1/2 months and a body weight between 1.2 and 3.4 kg. Cw Doppler measurements were performed using an Angiomatic (Medimatic) and pw measurements using a Mark 600 Duplex Scanner (ATL). We applied both methods within an interval as short as possible. For the data analysis the pulsatility index (PI) was used, a parameter fairly independent of the emission angle. PI was 0.66 +/- 0.06 (mean +/- SD) using the cw and 0.8 +/- 0.08 using the pw method. The linear correlation between the pulsatility indices obtained with the cw and the pw method respectively was statistically significant (r = 0.53, n = 20, p less than 0.0025), the variation around the regression line rather large. The slope of the regression line differed significantly from that of the identity line (y = 0.391x + 0.54). Therefore the PI values obtained with the two methods are not interchangable and require to be judged according to normal values. Both methods, however, yield PI values which correlate and can thus be equally used. The choice of the method rather depends on the goal to be achieved. The pw method seems to be more suitable for precise momentaneous descriptions and the cw method for continuous monitoring of cerebral blood flow.