Introducing Fetal ECG waveform analysis for Intrapartum Care S Arulkumaran Professor & Head – Obstetrics & Gynaecology St.George’s Hospital Medical School University of London

Fetal Hypoxaemia > Hypoxia > Asphyxia How to prevent fetal hypoxia? Diagnose hypoxia Institute corrective measures Deliver Fetal Hypoxaemia > Hypoxia > Asphyxia

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

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

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

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.

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

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

The first observation 1971

ECG waveform analysis Fetal Scalp Electrode & Maternal skin reference electrode

The ECG complex

ST-wave forms aerobic myocardial metabolism Normal ST 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

Myocardial energy balance Positive Available oxygen Arterial saturation / Haemoglobin Myocardial blood flow Negative Consumed oxygen (Myocardial work load) HR / BP / contractility / adrenaline surge

ST-wave forms T-wave amplitude hypoxia adrenaline surge anaerobic metabolism

Recording 30 accepted ECG complexes Average ECG T/QRS ratio biphasic ST

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

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

STAN 21

Presentation of ST

FHR vs STAN – A Swedish RCT Clinical management – FHR+ST Group preterminal FHR immediate delivery (regardless of ST) normal FHR no intervention (regardless of ST)

CTG vs. CTG+ST – A Swedish RCT Clinical management – FHR (CTG)+ST Group FHR interpretation supported by the ST-log

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.

The outcome of two RCTs

The Fetal ECG Project The Derby Experience Mr Onnig Tamizian - Clinical Research Fellow, Mr.Ian Symonds - Senior Lecturer, S.Arulkumaran - Professor

7.268+/-0.074 7.195+/-0.077

6.65 mmol/l +/-3.68 4.33 mmol/l +/-3.01

5.88 mmol/l +/-2.39 4.07 mmol/l +/-1.60

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

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 <7.05 and BD>12 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)

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)

Ms L C 30 years old Primip PMSH - Nil Current Pregnancy - uneventful Admitted T+12 for IOL Prostin 2mg x 2 on 11.01.01

2200 hrs - 11.01.01 CTG after Prostin

06.00 hrs

0600 hours - CTG after SROM - Meconium stained liquor 0630 hours -In view of meconium  Augment with Oxytocin ??

9.00 hrs - persistent decelerations for FBS in view of meconium

1015 hours FBS pH 7.307 BE -4.2 Cx - 3cm dilated?

1450 hours Cx fully dilated ROT at spines

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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