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(Circulation. 1996;94:445-451.)
© 1996 American Heart Association, Inc.

Articles

Relation Between Air-Filled Albumin Microbubble and Red Blood Cell Rheology in the Human Myocardium

Influence of Echocardiographic Systems and Chest Wall Attenuation

Suad Ismail, MD; Ananda R. Jayaweera, PhD; Gustavo Camarano, MD; Lawrence W. Gimple, MD; Eric R. Powers, MD; Sanjiv Kaul, MD

the Cardiovascular Division, University of Virginia School of Medicine (Charlottesville).

Correspondence to Sanjiv Kaul, MD, Cardiovascular Division, Box 158, Medical Center, University of Virginia, Charlottesville, VA 22908.

Background We have previously shown that the intravascular rheology of sonicated air-filled albumin microbubbles is similar to that of red blood cells (RBCs) and that their myocardial transit rate is also similar to that of RBCs in the beating canine heart. In the present study, we tested the hypothesis that the myocardial transit rates of these microbubbles reflect those of RBCs in humans at different coronary flow rates.

Methods and Results RBC and microbubble transit rates were measured in 17 patients undergoing coronary angiography: in 8, measurements were made only at rest, whereas in 9, they were performed both at rest and during a pacing-induced increase in coronary blood flow. A -variate function was used to derive mean RBC and microbubble transit rates from the time-activity and time-intensity plots after the left main injection of RBCs and microbubbles, respectively. There was linear correlation between the myocardial transit rates with both tracers with the slope of the correlation determined by the specific echocardiographic system that was used. Microbubble transit rate consistently overestimated RBC transit rate due to artificial narrowing of the time-intensity curves caused by chest wall attenuation of the echocardiographic signal, which was confirmed through in vitro experiments.

Conclusions There is close correlation between air-filled albumin microbubbles and RBC rheology in the human myocardium. The use of these microbubbles in the cardiac catheterization laboratory could, therefore, provide further insights into myocardial blood flow/myocardial blood volume relations in humans.

Key Words: contrast media • echocardiography • blood flow

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