LOSS OF CONTRAST INTENSITY DURING SYSTOLE IN THE LEFT-VENTRICULAR CAVITY WITH THE USE OF THE CONTRAST AGENT ALBUNEX - AN ANALYSIS OF ITS CORRELATION WITH PRESSURE AND VELOCITY

RATIONALE AND OBJECTIVES. Several investigators have observed a decrea se in video intensity in the left ventricular cavity during systole wh en using contrast echocardiography. It has been suggested that this ph enomenon is related to microbubble instability, The authors propose th at this phenomenon is, in part, related to the effects of pressure and velocity on the acoustic reflectance of ultrasound contrast agents, M ETHODS. Using an in vitro flow tube model and varying concentrations o f Albunex contrast agent, the effects of pressure and velocity on micr obubble video intensity were investigated. Velocity and pressure were varied independently and the imaging tube was scanned using three tran sducer frequencies at different concentrations of Albunex, Contrast vi deo intensity was analyzed using high and low velocities (at constant pressure) and high and low pressures (at constant velocity), In additi on, the fluid from the system was collected and imaged in a nonflowing reservoir tank to investigate the video intensity of the microbubbles when exposed to variable velocity and pressure, RESULTS. The video-in tensity measurements were inversely and irreversibly related to ambien t pressure changes (independent of velocity) in a tube model, However, video intensity varied inversely but reversibly with velocity (indepe ndent of pressure), This observation could not be explained simply by the ''laminar flow'' theory, by a change in transducer angulation, nor by a change in ultrasound imaging frame rate, This phenomenon was lim ited to Albunex microbubbles and was not observed with a contrast medi um (corn starch) devoid of the acoustic properties of Albunex.