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Departments of Obstetrics, Internal Medicine (Cardiology), Physiology, and Pharmacology and Heart Research Center, Oregon Health Sciences University, Portland, Oregon 97201-3098
We measured maximal coronary
artery conductance in near-term fetal sheep before and after chronic
infusion with adenosine to determine whether an increase in coronary
flow without hypoxemia results in increased coronary vascular growth.
Adenosine was infused into the circumflex coronary artery for 12 h
each day for 4 days. Coronary flow was maintained at double the resting
level by regulating the infusion of adenosine via a computerized
servocontrol device signaled by a Doppler flow-velocity sensor. Total
arterial hemoglobin, oxygen content, and hemodynamics were unchanged.
Resting circumflex coronary blood flow increased from control of
250 ± 111 to 530 ± 216 ml · min
1 · 100 g left
ventricle
1 with adenosine on day 1 and from
194 ± 74 to 878 ± 210 ml · min
1 · 100 g left
ventricle
1 with adenosine on the last day
(P < 0.01). Coronary conductance, determined during
maximal vasodilation, increased from 14.0 ± 5.0 to 26.9 ± 3.9 ml · min
1 · 100 g
1 · mmHg
1 over the 4 days
(P < 0.001). Coronary flow reserve, the difference between resting and maximal myocardial blood flow interpolated at 40 mmHg, increased from 299 ± 196 to 672 ± 266 ml · min
1 · 100 g
1
(P < 0.001). Maximal coronary conductance was
unchanged in control saline-infused fetuses (18.5 ± 5.1 vs.
18.5 ± 8.7 ml · min
1 · 100 g
1 · mmHg
1). We conclude that
chronic intracoronary adenosine administration to the fetal myocardium
modulates coronary vascular growth, even in the absence of tissue hypoxia.
fetal; coronary conductance; vascular growth
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