Heart rate variability and electrocardiogram changes in the fetal lamb during hypoxia and beta-adrenoceptor stimulation

Lilja, Håkan; Karlsson, K.; Kjellmer, Ingemar; Lindecrantz, Kaj; Olsson, Torsten; Rosén, Karl G.

doi:10.1515/jpme.1984.12.3.115

Cited by 11 publications

(5 citation statements)

References 21 publications

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“…The initial increase in fetal heart rate variation with the onset of frequent episodes of fetal asphyxia observed in this study is consistent with previous experimental studies of inhalational hypoxia in fetal sheep 12,13,24–26 and monkeys 27 , placental embolisation in fetal sheep 9,28 , and cord occlusion in the fetal rat 29 . The mechanisms which underlie this rise, and indeed those which control normal variation, are not fully understood, but are likely to involve a combination of activation of the carotid chemoreflex 13 , and sympathetic stimulation 30–33 .…”

Section: Discussionsupporting

confidence: 86%

“…In one early study, nearly all mothers whose fetuses had reduced fetal heart rate variation had received diazepam 1 . However, a number of experimental studies have documented a progressive fall in fetal heart rate variation following the acute rise when inhalational hypoxia was continued and fetal acidaemia occurred 12,24,37,38 .In a recent study in the fetal sheep, acute placental embolisation, in which fetal pH fell to 6.97 after 6 h, was accompanied by a significant fall in MMR 28 . In the present study, a few fetuses showed an initial fall in fetal heart rate variation but were neither hypotensive nor acidotic.…”

Section: Discussionmentioning

confidence: 44%

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Fetal heart rate variability changes during brief repeated umbilical cord occlusion in near term fetal sheep

Westgate

Bennet

Gunn

1999

BJOG

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Objective To determine whether changes in fetal heart rate variation during repeated umbilical cord occlusions reflect evolving cardiovascular compromise in near term fetal sheep.Design Fetal heart rate variation, fetal mean arterial pressure, electroencephalogram (EEG) and acid-base status were measured during one minute umbilical cord occlusions, repeated either every five minutes (1 :5 group) or every 2.5 minutes (1 :2-5 group) for four hours or until mean arterial pressure fell below 20 mmHg for two successive occlusions.Sample Fourteen chronically instrumented fetal sheep, mean gestation 126.3 (2.6) days.Results Cord occlusion caused variable decelerations with initial sustained hypertension. In the 1 :5 occlusion group mean arterial pressure remained elevated throughout, with little change in acid-base status (pH = 7.34 (0.07), base deficit = 1.3 (3.9) after 4 hours) and no significant change in fetal heart rate variation. In contrast, in the 1:2.5 group from the third occlusion there was progressive hypotension during occlusions, severe progressive metabolic acidaemia (pH 6.92 (0. l), base deficit 17.0 mmol/L (4.7) after the last occlusion) and marked EEG suppression (P c 0.01). Fetal heart rate variation increased with the onset of occlusions (P c 0.05) and then progressively fell with continued occlusions. During the last 30 minutes of occlusions, fetal heart rate variation was severely suppressed in four, but increased in two fetuses, while all six fetuses developed overshoot-instability of fetal heart rate and mean arterial pressure following each occlusion.Conclusions Acute progressive asphyxia was typically associated with an immediate, transient increase in fetal heart rate variation. Subsequently variation became suppressed in only two-thirds of fetuses during terminal acidaemia and hypotension. Fetal heart rate overshoot-instability may be a useful marker of fetal decompensation following variable decelerations.

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Section: Discussionsupporting

confidence: 86%

Section: Discussionmentioning

confidence: 44%

Fetal heart rate variability changes during brief repeated umbilical cord occlusion in near term fetal sheep

Westgate

Bennet

Gunn

1999

BJOG

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“…Our laboratory has been interested in the study fetal cardiac maturation and in particular the adverse effects of elevated maternal cortisol on the fetal heart (13,23,44,47) As we have found an increase in peripartum stillbirth in our model of late gestation maternal stress, with transcriptomic effects indicative of altered cardiac metabolism, we wanted to develop a refinement in the methods for assessing fetal cardiac function, and in particular ECG, during labor, delivery, and the immediate perinatal period. Many previous studies have documented the late gestation changes in fetal blood pressure and heart rate (HR), as well as responses of fetal HR and ECG to manipulations such as hypoxia, cord occlusion, or chronic growth restriction (14,27,30,36,62,64). Fetal ECG (fECG) is suggested as a good measure for assessing fetal brain ischemia, and this has been widely studied in that context as an index of acute fetal stress (38,51).…”

mentioning

confidence: 99%

Use of radiotelemetry to assess perinatal cardiac function in the ovine fetus and newborn

Antolic

Wood

Keller‐Wood

2017

American Journal of Physiology-Regulatory, Integrative and Comp

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The late gestation fetal ECG (fECG) has traditionally been difficult to characterize due to the low fECG signal relative to high maternal noise. Although new technologies have improved the feasibility of its acquisition and separation, little is known about its development in late gestation, a period in which the fetal heart undergoes extensive maturational changes. Here, we describe a method for the chronic implantation of radiotelemetry devices into late gestation ovine fetuses to characterize parameters of the fECG following surgery, throughout late gestation, and in the perinatal period. We found no significant changes in mean aortic pressure (MAP), heart rate (HR), or ECG in the 5 days following implantation; however, HR decreased in the first 24 h following the end of surgery, with associated increases in RR, PR, and QRS intervals. Over the last 14 days of fetal life, fetal MAP significantly increased, and HR significantly decreased, as expected. MAP and HR increased as labor progressed. Although there were no significant changes over time in the ECG during late gestation, the duration of the PR interval initially decreased and then increased as birth approached. These results indicate that although critical maturational changes occur in the late gestation fetal myocardium, the mechanisms that control the cardiac conduction are relatively mature in late gestation. The study demonstrates that radiotelemetry can be successfully used to assess fetal cardiac function, in particular conduction, through the process of labor and delivery, and may therefore be a useful tool for study of peripartum cardiac events.

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“…Waveform changes in the ST segment of the ovine fetal electrocardiogram are considered to be a sensitive parameter of hypoxic stress, where the dominant response is a progressive increase in the T wave amplitude, and where the changes can be quantified as the T/QRS ratio [ 7 , 20 ]. Although clinical guidelines for STAN were defined for term infants, preterm and term ovine fetuses showed hypoxia-induced ST waveform changes which were comparable to that of the human term infant [ 14 , 15 ].…”

Section: Discussionmentioning

confidence: 99%

ST waveform analysis for monitoring hypoxic distress in fetal sheep after prolonged umbilical cord occlusion

et al. 2018

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IntroductionThe inconclusive clinical results for ST-waveform analysis (STAN) in detecting fetal hypoxemia may be caused by the signal processing of the STAN-device itself. We assessed the performance of a clinical STAN device in signal processing and in detecting hypoxemia in a fetal sheep model exposed to prolonged umbilical cord occlusion (UCO).MethodsEight fetal lambs were exposed to 25 minutes of UCO. ECG recordings were analyzed during a baseline period and during UCO. STAN-event rates and timing of episodic T/QRS rise, baseline T/QRS rise and the occurrence of biphasic ST-waveforms, as well as signal loss, were assessed.ResultsDuring baseline conditions of normoxemia, a median of 40 (IQR, 25–70) STAN-events per minute were detected, compared to 10 (IQR, 2–22) during UCO. During UCO STAN-events were detected in five subjects within 10 minutes and in six subjects after 18 minutes, respectively. Two subjects did not generate any STAN-event during UCO. Biphasic ST event rate was reduced during UCO (median 0, IQR 0–5), compared to baseline (median 32, IQR, 6–55). ST-waveforms could not be assessed in 62% of the recording time during UCO, despite a good quality of the ECG signal.ConclusionsThe STAN device showed limitations in detecting hypoxemia in fetal sheep after prolonged UCO. The STAN device produced high false positive event rates during baseline and did not detect T/QRS changes adequately after prolonged fetal hypoxemia. During 14% of baseline and 62% of the UCO period, the STAN-device could not process the ECG signal, despite its good quality. Resolving these issues may improve the clinical performance of the STAN device.

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Heart rate variability and electrocardiogram changes in the fetal lamb during hypoxia and beta-adrenoceptor stimulation

Cited by 11 publications

References 21 publications

Fetal heart rate variability changes during brief repeated umbilical cord occlusion in near term fetal sheep

Fetal heart rate variability changes during brief repeated umbilical cord occlusion in near term fetal sheep

Use of radiotelemetry to assess perinatal cardiac function in the ovine fetus and newborn

ST waveform analysis for monitoring hypoxic distress in fetal sheep after prolonged umbilical cord occlusion

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