© 1997 by European Society of Cardiology
Copyright © 1997, European Society of Cardiology
Red cell flux during the cardiac cycle in the rabbit myocardial microcirculation
aDepartment of Medicine, Halifax, N.S., Canada
bDepartment of Physiology and Biophysics, Halifax, N.S., Canada
cDepartment of Physics, Dalhousie University, Halifax, N.S., Canada
* Corresponding author. Department of Medicine, Division of Cardiology, Queen Elizabeth II Health Sciences Centre, New Halifax Infirmary, Room #2111, 1796 Summer Street, Halifax, N.S. B3H 3A7, Canada. Tel.: +1 (902) 473-6815; fax: +1 (902) 473-2434.
Objective: (1) To measure regional phasic myocardial red cell flux during a cardiac cycle using a laser Doppler velocimeter. (2) To test the responses of regional red cell flux to a vasodilator (adenosine), a vasoconstrictor (angiotensin II), and an inotrope (isoproterenol). Methods: Using an anaesthetised open-chest rabbit with the pericardium intact a 140-µm-tip fibre optic probe was placed in the left ventricular myocardium in various locations. With the fibre in place drugs were given to alter myocardial loading conditions while red cell flux was registered. Results: Phasic red cell flux was similar in the epicardium to endocardium giving an average endo/epi ratio of 1.14 in the rabbit heart. At least two peaks of increased red cell flux within a single cardiac cycle were observed. Some unique patterns for red cell flux were observed in specialised myocardial structures. Adenosine increased red cell flux but minimally changed the pattern of phasic flux throughout the cycle. Conclusions: Laser Doppler velocimetry permits the recording of phasic red cell flux during the cardiac cycle in the myocardial microcirculation. Its pattern is determined by both coronary arterial inflow and venous outflow. The pattern of red cell flux may be characteristic for a region—probably determined by difference in tissue pressure (attributable to the pattern of muscle fibre shortening and collagen tethering) and changes in capillary length and density.
KEYWORDS Myocardial red cell flux; Laser Doppler velocimetry; Adenosine; Angiotensin II; Isoproterenol; Rabbit, anesthetized