Introducing Fetal ECG waveform analysis for Intrapartum Care

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Introducing Fetal ECG waveform analysis for
Intrapartum Care

• S Arulkumaran
• Professor Head Obstetrics Gynaecology
• St.Georges Hospital Medical School
• University of London

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Fetal Hypoxaemia gt Hypoxia gt Asphyxia

• How to prevent fetal hypoxia?
• Diagnose hypoxia
• Institute corrective measures
• Deliver

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Fetal response to hypoxemia

• more effective uptake of oxygen
• Reduced activity
• decrease in growth rate
• maintained energy balance

Oxygen saturation
Hypoxemia
Hypoxia
Asphyxia
Days and weeks
Hours
Minutes
Time
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The fetal response to hypoxia

• surge of stress hormones
• redistribution of blood flow
• anaerobic metabolism in the peripheral
  tissues
• maintained energy balance

Oxygen saturation
Hypoxemia
Hypoxia
Asphyxia
Days and weeks
Hours
Minutes
Time
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Fetal response to asphyxia

• Alarm reaction
• anaerobic metabolism in peripheral
  tissues
• brain and heart organ
• failure

Oxygen saturation
Hypoxemia
Hypoxia
Asphyxia
Days and weeks
Hours
Minutes
Time
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To prevent hypoxia we have to identify the fetus
likely to be affected

• The fetus untroubled by the events of labour.
• Troubled but able to fully compensate and is in
  no immediate danger.
• Troubled and utilising key resources in an
  attempt to compensate or unable to fully
  compensate.

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Hypoxia from reduced cord blood flow
Oxygen reduces and CO2 increases (respiratory
acidosis develops)
If cord flow is not improved then base excess
used up and bicarbonate reduces (metabolic
acidosis develops)
Major fetal organ damage
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Pathophysiology of hypoxia
Negative
Anaerobic metabolism
Glycogenolysis
Lactate
Change in membrane potential due to liberation of
potassium
ST segment elevation high T waves
Metabolic acidosis
DETECT by FBS
DETECT by fetal ECG
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The first observation 1971
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ECG waveform analysis
Fetal Scalp Electrode Maternal skin reference
electrode
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The ECG complex
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ST-wave forms
Normal ST

• aerobic myocardial metabolism
• positive energy balance
• Isoelectric line T wave
• Only Changes in these parameters will be detected
  hence the need to start analysis before changes
  take place

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Myocardial energy balance
Positive
Negative
Available oxygen Arterial saturation /
Haemoglobin Myocardial blood flow
Consumed oxygen (Myocardial work load) HR / BP /
contractility / adrenaline surge
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ST-wave forms
T-wave amplitude

• hypoxia
• adrenaline surge
• anaerobic metabolism

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Recording
30 accepted ECG complexes
Average ECG
T/QRS ratio biphasic ST
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Changes in the ST segment T wave
ST rise a fetus responding to hypoxia
Biphasic ST a fetus not fully capable of
responding or has not had time to respond
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ST-wave forms
Biphasic ST

• Caused by an inability of the myocardium to
  respond
• Prematurity,
• Infections,
• Increase in overall demand (mat fever),
• Myocardial dystrophy,
• Chronic hypoxia,
• Initial phase of acute hypoxia.

• grade 1
• grade 2
• grade 3

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STAN 21
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Presentation of ST
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FHR vs STAN A Swedish RCT

• Clinical management FHRST Group
• preterminal FHR immediate delivery
  (regardless of ST)
• normal FHR no intervention
  (regardless of ST)

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CTG vs. CTGST A Swedish RCT

• Clinical management FHR (CTG)ST Group
• FHR interpretation supported by the ST-log

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STAN simplified clinical guidelines
These guidelines are applicable to a term
pregnancy of 36 completed gestational weeks or
more. They indicate situations in which
intervention is required. This means delivery or
alleviation of a cause of fetal distress such as
over-stimulation or maternal hypotension. During
the second stage of labour with active pushing,
immediate delivery is recommended. If there is
an abnormal CTG and a normal ST during the second
stage of labour, you can wait 90 minutes before
intervention. The event log requires 20 minutes
before automatic ST analysis can begin. At
start-up and when there is a decrease in signal
quality with discontinuous T/QRS ratios, manual
data analysis is required.
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The outcome of two RCTs
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The Fetal ECG ProjectThe Derby Experience

• Mr Onnig Tamizian -
• Clinical Research Fellow, Mr.Ian Symonds - Senior
  Lecturer, S.Arulkumaran - Professor

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7.268/-0.074
7.195/-0.077
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6.65 mmol/l /-3.68
4.33 mmol/l /-3.01
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5.88 mmol/l /-2.39
4.07 mmol/l /-1.60
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• Cochrane collaboration
• Neilson JP. Fetal eleectrocardiogram (ECG) for
  fetal monitoring during labour. The Cochrane
  library, Issue 2, 2003. Oxford

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Neilson JP. Fetal eleectrocardiogram (ECG) for
fetal monitoring during labour. The Cochrane
library, Issue 2, 2003. Oxford

• The use of ST waveform analysis (7400 women) was
  associated with fewer babies with severe
  metabolic acidosis at birth (cord pH lt7.05 and
  BDgt12 mmol/L.
• RR 0.44, 95 CI 0.26-0.75
• This was achieved with fewer fetal scalp samples
  during labour (RR 0.86) and fewer operative
  deliveries (RR 0.89)

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Neilson JP. Fetal eleectrocardiogram (ECG) for
fetal monitoring during labour. The Cochrane
library, Issue 2, 2003. Oxford

• These findings support the use of ST waveform
  analysis when a decision is made to undertake
  continuous EFM in labour.
• A better approach might be to restrict fetal ST
  waveform analysis to those fetuses demonstrating
  disquieting features on CTG (opinion)

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• Ms L C
• 30 years old
• Primip
• PMSH - Nil
• Current Pregnancy - uneventful
• Admitted T12 for IOL
• Prostin 2mg x 2 on 11.01.01

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2200 hrs - 11.01.01 CTG after Prostin
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06.00 hrs
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0600 hours - CTG after SROM - Meconium stained
liquor 0630 hours -In view of meconium ? Augment
with Oxytocin ??
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9.00 hrs - persistent decelerations for FBS in
view of meconium
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1015 hours FBS pH 7.307 BE -4.2 Cx - 3cm
dilated?
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1450 hours Cx fully dilated ROT at spines
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1520 hours - NVD Apgar 9 at 1 10 at 5 Art -
pH 7.059, BE 8.17 Ven -pH 7.143, BE 8.71
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