Continuous measurement of canine coronary blood volume change with alterations of heart rate.
OBJECTIVE
The aim was to examine the effects of heart rate on total coronary blood volume with pressure-type plethysmography in isolated and vasodilated canine hearts.


METHODS
Nine hearts were excised from anaesthetised mongrel dogs (13.1-15.2 kg) and perfused with arterial blood of other dogs (17.0-29.0 kg). The venous blood returning to the right atrium and both ventricles was drained under constant negative pressure (-10 mm Hg). A thin latex balloon filled with water was inserted into the left ventricle to keep the intraventricular volume constant. The pressure difference between the cylinder into which the heart was placed and a compensation chamber was measured as a change in coronary blood volume while heart rate was altered from 120 beats.min-1 (control heart rate) to a target level (60, 90, 150, or 180 beats.min-1).


RESULTS
The mean coronary blood volume change compared with that at control heart rate was 1.65(SEM 0.32) ml x 100 g-1 at 60 beats.min-1 (p < 0.005) and -0.74(0.20) ml x 100 g-1 at 180 beats.min-1 (p < 0.005) under the perfusion pressure of 70 mm Hg. The mean volume decreased with the increase in heart rate. Diastolic-systolic variations in coronary blood volume also decreased with an increase in heart rate, from 0.61(0.06) ml x 100 g-1 (60 beats.min-1) (p < 0.005) to 0.12 ml.100 g-1 (180 beats.min-1). Both mean change and variation were almost linear functions of R-R interval (r = 0.88 and r = 0.83). Lowering the perfusion pressure from 70 to 40 mm Hg diminished the changes in both mean and variation of the coronary blood volume.


CONCLUSIONS
Tachycardia reduces the mean coronary blood volume and the diastolic-systolic variations in isolated vasodilated canine hearts.
Hangai
K
K
First Department of Internal Medicine, Tohoku University School of Medicine, Sendai, Japan.
Satoh
S
S
Sato
F
F
Watanabe
J
J
Maruyama
Y
Y
Takishima
T
T
D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D003326:Coronary Circulation / Q000502:physiology*; D003331:Coronary Vessels / Q000502:physiology; D004285:Dogs; D006339:Heart Rate / Q000502:physiology*; D006439:Hemodynamics / Q000502:physiology; D010991:Plethysmography