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The mechanism of late deceleration of the heart rate and its relationship to oxygenation in normoxemic and chronically hypoxemic fetal lambs

  • Author Footnotes
    * National Institutes of Health, International Fellow (Grant No. TWO 2767) from Rambam Medical Center, Haifa, Israel.
    Joseph Itskovitz
    Correspondence
    Department of Obstetrics and Gynecology “A,” Rambam Medical Center, Haifa, Israel
    Footnotes
    * National Institutes of Health, International Fellow (Grant No. TWO 2767) from Rambam Medical Center, Haifa, Israel.
    Affiliations
    From the Cardiovascular Research Institute and the Departments of Pediatrics, Physiology, and Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, California
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  • Boyd W. Goetzman
    Affiliations
    From the Cardiovascular Research Institute and the Departments of Pediatrics, Physiology, and Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, California
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  • Abraham M. Rudolph
    Affiliations
    From the Cardiovascular Research Institute and the Departments of Pediatrics, Physiology, and Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, California
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  • Author Footnotes
    * National Institutes of Health, International Fellow (Grant No. TWO 2767) from Rambam Medical Center, Haifa, Israel.
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      The responses of fetal heart rate and blood pressure to a transient reduction in uterine blood flow were studied in normoxemic and chronically hypoxemic lambs. In normoxemic fetuses, a reduction in uterine blood flow, if prolonged sufficiently, produced reflex bradycardia mediated through chemoreceptors and was associated with a decrease in carotid arterial Po2 to below 20 torr. The bradycardia was associated with a marked decrease in left ventricular output as measured by electromagnetic flowmeter; both were abolished by atropine. In chronically hypoxemic fetuses, a reduction in uterine blood flow produced a delayed deceleration of the heart rate which consisted of three components: reflex bradycardia due to chemoreceptor stimulation; baroreceptor-mediated reflex bradycardia which involved the slow and late recovery of the heart rate; and nonreflex bradycardia which was probably secondary to hypoxic myocardial depression. Quantitative analysis revealed a relationship between the components of delayed deceleration and the status of fetal oxygenation prior to the reduction in uterine blood flow. The lower the carotid arterial Po2, the shorter was the delay in the onset of bradycardia, the greater the decrease in heart rate, and the more prolonged the duration of bradycardia. The conclusion is that the response of fetal heart rate to a transient reduction in uterine blood flow is related to the duration of the reduction and to the status of fetal oxygenation prior to the decrease in uterine blood flow.
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      REFERENCES

        • Schifrin B.S.
        • Dame L.
        Fetal heart rate patterns and prediction of Apgar score.
        J.A.M.A. 1972; 219: 1322
        • Hon E.H.
        Electronic evaluation of the fetal heart rate. VI. Fetal distress—a working hypothesis.
        Am. J. Obstet. Gynecol. 1962; 83: 333
        • Mendez-Bauer C.
        • Poseiro J.J.
        • Arellano-Hernandez G.
        • Zambrana M.A.
        • Caldeyro-Barcia R.
        Effects of atropine on the heart rate of the human fetus during labor.
        Am. J. Obstet. Gynecol. 1963; 115: 1033
        • Martin Jr., C.B.
        • de Haan J.
        • van der Wildt B.
        • Jomgsma H.W.
        • Dieleman A.
        • Arts T.H.M.
        Mechanisms of late decelerations in the fetal heart rate. A study with autonomic blocking agents in fetal lambs.
        Eur. J. Obstet. Gynaecol. Reprod. Biol. 1979; 9: 361
        • Parer J.T.
        • Krueger T.R.
        • Harris J.L.
        Fetal oxygen consumption and mechanisms of heart rate response during artifically produced late deceleration of fetal heart rate in sheep.
        Am. J. Obstet. Gynecol. 1980; 136: 478
        • Harris J.L.
        • Krueger T.R.
        • Parer J.T.
        Mechanisms of late decelerations of fetal heart rate during hypoxia.
        in: Scientific Abstracts, Twenty-seventh Annual Meeting of the Society for Gynecologic Investigation, Denver, Colorado, March 19-221980: 136
      1. Itskovitz, J., and Rudolph, A. M.: Denervation of arterial chemoreceptors and baroreceptors in chronically instrumented fetal lambs. In preparation.

        • Rudolph A.M.
        • Heymann M.A.
        Fetal and neonatal circulation and respiration.
        Annu. Rev. Physiol. 1974; 36: 187
        • Rudolph A.M.
        • Heymann M.A.
        Cardiac output in the fetal lamb: The effects of spontaneous and induced changes of heart rate on right and left ventricular output.
        Am. J. Obstet. Gynecol. 1976; 124: 183
        • Elsner R.
        • Franklin D.L.
        • Van Citters R.L.
        • Kenney D.W.
        Cardiovascular defense against asphyxia.
        Science. 1966; 153: 941
        • Zapol W.M.
        • Liggins G.C.
        • Schneider R.C.
        • Qvist J.
        • Snider M.T.
        • Creasy R.K.
        • Kochachka P.W.
        Regional blood flow during simulated diving in the conscious Weddell seal.
        J. Appl. Physiol. 1979; 47: 968
        • Linden R.J.
        • Snow H.M.
        The inotropic state of the heart.
        in: Linden R.J. Recent Advances in Physiology. Churchill Livingstone, Edinburgh1974: 148-190
        • Comline R.S.
        • Silver I.A.
        • Silver M.
        Factors responsible for the stimulation of the adrenal medulla during asphyxia in the foetal lamb.
        J. Physiol. (Lond.). 1965; 178: 211
        • Myers R.E.
        • Mueller-Heubach E.
        • Adamsons K.
        Predictability of the state of fetal oxygenation from a quantitative analysis of the components of late deceleration.
        Am. J. Obstet. Gynecol. 1973; 115: 1083
        • James L.S.
        • Morishima H.O.
        • Daniel S.S.
        • Bowe E.T.
        • Cohen H.
        • Niemann W.H.
        Mechanism of late deceleration of the fetal heart rate.
        Am. J. Obstet. Gynecol. 1972; 113: 578
        • Kunzel W.
        • Kastendieck E.
        • Kurz C.S.
        Heart rate and blood pressure response of the sheep fetus following the reduction of uterine blood flow.
        in: Abstracts of Scientific Papers, 26th Annual Meeting of the Society for Gynecologic Investigation, San Diego, California1979: 25
        • Kunzel W.
        • Kastendieck E.
        • Kurz C.S.
        The effect of total reduction of uterine blood flow on cardiovascular and metabolic parameters of the sheep fetus.
        in: Abstracts of Scientific Papers, 26th Annual Meeting of the Society for Gynecologic Investigation, San Diego, California1979: 61