INTRALUMINAL RECORDING OF CROSS-SECTIONAL BLOOD VELOCITY DISTRIBUTIONOF HUMAN ASCENDING AORTA BY ULTRASOUND DOPPLER TECHNIQUE

A pulsed Doppler ultrasound technique was used for mapping two-dimensi onal blood velocity profiles in the human ascending aorta during open- heart surgery. An electronic position-sensitive device was constructed and linked to an intraluminal 10 MHz Doppler ultrasound probe. From a plane perpendicular to the central direction of blood flow, velocity mapping was performed covering the entire cross-section of the ascendi ng aorta 6-7 cm above the valve. This method is based on a sequential sampling of velocity from continuously changing locations during a sta ble haemodynamic period; typically velocity points are recorded from 1 50-300 beats. Further processing transformed data to suit a previously developed velocity distribution model for normal blood flow in the hu man ascending aorta, based on mutli-regression analyses. In this model , the time series of data from consecutive beats were computed into an average two-dimensional profile described through one cardiac cycle. This method allows high spatial resolution (1.5 mm), in addition to th e high-frequency response (200 Hz) of the modified ultrasound Doppler meter. Together with the advantage of velocity directionality and mini mal time interventions, this makes the method well suited for studies on normal flow conditions as well as flow velocity distribution distal to different heart valve prostheses.