Maximal myocardial blood flow is enhanced by chronic hypoxemia in late gestation fetal sheep
Reller, M.D.; Morton, M.J.; Giraud, G.D.; Wu, D.E.; Thornburg, K.L.
American Journal of Physiology 263(4 Pt 2): H1327-H1329
1992
ISSN/ISBN: 0002-9513 PMID: 1415781 Document Number: 396393
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 mu-g cntdot kg-1 cntdot 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 P-CO-2 = 49.8 +- 4.2 Torr, arterial P-O-2 = 16.1 +- 1.3 Torr, and arterial concentration of O-2 = 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 P-CO-2 = 43.1 +- 3.8 Torr, arterial P-O-2 = 19.8 +- 2.0 Torr, and arterial concentration of O-2 = 7.9 +- 1.0 ml/dl) (P lt 0.05). At comparable arterial pressures, the maximal myocardial flow (ml cntdot min-1 cntdot 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 lt 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.