Maximal myocardial blood flow is enhanced by chronic hypoxemia in late gestation fetal sheep

M. D. Reller, M. J. Morton, G. D. Giraud, D. E. Wu, K. L. Thornburg

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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 μg · 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.

Original languageEnglish (US)
Pages (from-to)H1327-H1329
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume263
Issue number4 32-4
StatePublished - Jan 1 1992

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Keywords

  • adenosine
  • coronary flow
  • fetus

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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