AXIAL DEVELOPMENT OF VELOCITY-FIELDS IN THE PORCINE MAIN PULMONARY-ARTERY SYSTEM

The aim of this study was to provide detailed data on velocity profile development in the normal porcine main pulmonary artery and its main branches. Under spontaneous hemodynamic conditions in twelve open-ches t 90kg pigs, perivascular pulsed Doppler ultrasound was used for blood velocity measurements in the entire cross-sectional area in three axi al locations in the main pulmonary artery and along one diameter in th e main branches. Computerized three-dimensional visualizations of the spatial and temporal development of velocity profiles were made throug hout the heart cycle. The results were similar one and two diameters d ownstream of the pulmonary valve. In the early systolic acceleration p hase, the velocity profile became skewed, with the highest velocities (132.7 +/- 19.4cm.sec(-1)) towards the inferior to right superior vess el wall, and rotated counterclockwise 45 degrees-90 degrees during the late acceleration to early deceleration phase in 9 out of 11 pigs. Ma ximum retrograde velocities (31.4 +/- 14.9cm.sec(-1)) were observed at the inferior to the right superior vessel wall in the late systolic d eceleration phase and in early diastole. During diastole, low retrogra de to insignificant antegrade velocities were observed. Immediately up stream of the pulmonary bifurcation, the velocity profile disclosed tw o peaks at locations corresponding to the two main branches. A confine d area with retrograde velocities was seen at the right vessel wall in late systole. Low-scale antegrade velocities were observed throughout diastole in the entire cross-sectional area. In the left main branch, the velocity profiles were found to be somewhat skewed towards the le ft vessel wall, corresponding to the smaller curvature of the left mai n branch, while the velocity profile in the right main branch was skew ed against the superior vessel wall throughout systole. This study thu s disclosed that the blood velocity profiles in the main pulmonary art ery system were skewed and that mean velocity varied 26%-50% between m easuring points, exhibiting an as yet unexplained rotational phenomeno n. The skewed velocity profile in the porcine pulmonary trunk indicate s that single-point blood velocity measurements can only serve as a ba sis for cardiac output estimations when used with considerable caution .