title: Maximal myocardial blood flow is enhanced by chronic hypoxemia in late gestation fetal sheep.
abstract: The measurement of maximal myocardial blood flow gives information about the total cross-sectional area of the coronary resistance vessels. During a continuous left atrial infusion of adenosine (60 micrograms.kg-1.min-1), maximal myocardial blood flow was measured in 4 fetuses hypoxemic for a minimum of 5-8 days (pH = 7.33 +/- 0.01, arterial PCO2 = 49.8 +/- 4.2 Torr, arterial PO2 = 16.1 +/- 1.3 Torr, and arterial concentration of O2 = 5.3 +/- 1.2 ml/dl). These data were compared with an identically instrumented group of normoxemic fetuses (n = 7) following the same study protocol (pH = 7.38 +/- 0.02, arterial PCO2 = 43.1 +/- 3.8 Torr, arterial PO2 = 19.8 +/- 2.0 Torr, and arterial concentration of O2 = 7.9 +/- 1.0 ml/dl) (P < 0.05). At comparable arterial pressures, the maximal myocardial flow (ml.min-1.100 g tissue-1) for hypoxemic vs. normoxemic fetuses was 974 +/- 273 and 630 +/- 181 for the total myocardium, 986 +/- 367 and 602 +/- 192 for the left ventricular free wall, 1,025 +/- 346 and 614 +/- 178 for the septum, and 1,231 +/- 274 and 757 +/- 269 for the right ventricular free wall, respectively (P < 0.01). These data suggest that hypoxemia in the fetus can significantly alter the coronary vascular bed, which, if confirmed, would represent an important adaptation in the developing fetus.
authors.affiliation: Department of Pediatrics (Cardiology), Oregon Health Sciences University, Portland 97201.
authors.forename: M D
authors.initials: MD
authors.lastname: Reller
authors.forename: M J
authors.initials: MJ
authors.lastname: Morton
authors.forename: G D
authors.initials: GD
authors.lastname: Giraud
authors.forename: D E
authors.initials: DE
authors.lastname: Wu
authors.forename: K L
authors.initials: KL
authors.lastname: Thornburg
mesh_terms: D000818:Animals; D002908:Chronic Disease; D003326:Coronary Circulation; D005315:Fetal Diseases / Q000503:physiopathology*; D005333:Fetus / Q000502:physiology*; D005865:Gestational Age; D000860:Hypoxia / Q000503:physiopathology*; D012756:Sheep / Q000196:embryology