CARDIOTOCOGRAPHY

By

Osama M Warda , MD Professor of Obstetrics & Gynecology

Mansoura University- EGYPT

BACKGROUND

� Cardiotocography (CTG) is a test used in pregnancy to monitor both the fetal heart pattern as well as the uterine contractions.

� It should only used in the 3rd trimester when fetal neural reflexes are present.

� Its purpose is to monitor fetal well-being & allows early detection of fetal distress antenatal or intra-partum.

� An abnormal CTG indicates the need for further invasive investigation & ultimately may lead to emergency CS

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When to do CTG?

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Frequency of testing

- Usually every 7 days (i.e. weekly)

- Twice-weekly testing is advocated by some in :

� Post term pregnancy

� Diabetes mellitus

� Fetal growth restriction,

� Gestational hypertension

- Additional testing is performed for maternal or fetal deterioration regardless of time elapsed

- Others perform non-stress tests daily or even more frequently

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The Machine

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Application: external; antenatal

� The machine used is called cardio-tocograph.

� It involves the placement of 2 transducers on the abdomen of a pregnant woman: one transducer records the fetal heart rate using ultrasound beam , the other transducer records uterine contractions by measuring the tension of the maternal abdominal wall. This provides indirect indication of the intrauterine pressure.

� These recordings are blotted on a special paper.

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Application of the transducers

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FSE

Application: internal; intra-partum

� The machine used is called cardio-tocograph.

� It involves the placement of 2 transducers: a fetal scalp electrode( FSE): an internal fetal heart monitor , and intrauterine pressure catheter(IUPC): an internal uterine contraction monitor

� These recordings are shown on a screen and

may be blotted on a special paper.

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Setting the CTG machine

Horizontal Scale

Paper speed is set to 1,2,or 3 cm /minute.

Vertical Scale:

� Sensitivity displays are set to 20 or 30 beats per minute (bpm) /cm.

� FHR range displays of 30–240 bpm .

� Uterine Activity: Internal 0-100 mmHg

External 0-100 relative units

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Setting the CTG machine

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3cm / min 1cm / min

3 small vertical spaces / cm 10 beats / small space

F H R

Ut.

Cont.

Setting the CTG machine

� Fetal heart rate is commonly recorded with paper speed at 1 cm/ min compared with 3 cm/min chart recorder.

� 3 cm: is the more accurate for abnormalities

� 1cm: less paper but less accurate : Used for screening

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ACOUSTIC STIMULATION TESTS

� Provoking acceleration of FHR.

� The acoustic stimulator is positioned on the

maternal abdomen and a stimulus of 1 to 2 sec .

� It may be repeated up to three times.

� It shortened the average time for non-stress

testing from 24 to 15 minutes.

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Interpretation of CTG

� To interpret a CTG you need a structured method of assessing its various characteristics.

� The most popular method can be remembered using the acronym DR C BRAVADO

- DR=Define Risk . - C= Contractions

- Bra= Baseline Rate - V=Variability

- A= Accelerations - D= Decelerations

- O= Overall impression

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Define Risk

� You first need to assess if this pregnancy is high or low risk

� This is important as it gives more context to the CTG reading ;e.g. If the pregnancy is high risk, your threshold for intervening may be lowered.

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DR C BRAVADO

Define Risk

High-risk pregnancies:

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DR C BRAVADO

Contraction

� Record the number of contractions present in a 10 minute period - e.g. 3 in 10

� Each big square is equal to 1 minute, so you look how many contractions occurred in 10 squares

� Individual contractions are seen as peaks on the part of the CTG monitoring uterine activity

� You should assess contractions for the following:

� Duration – how long do the contractions last?

� Intensity – how strong are the contractions? (assessed using palpation)

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DR C BRAVADO

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In this example there are 2-3 contractions in a 10 minute period - e.g. 3 in 10

Contraction DR C BRAVADO

Baseline Rate of fetal heart

� The baseline rate is the average heart rate of the fetus in a 10 minute window.

� Look at the CTG & assess what the average heart rate has been over the last 10 minutes

� Ignore any Accelerations or Decelerations

� A normal fetal heart rate is between 120-160 bpm.

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DR C BRAVADO

Baseline Rate of fetal heart

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DR C BRAVADO

Baseline Rate of fetal heart

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DR C BRAVADO

If the causes of tachy-or-bradycardia cannot be identified and corrected, immediate delivery is recommended

Variability

� Baseline variability refers to the variation of fetal heart rate from one beat to the next.

� Variability occurs as a result of the interaction between the nervous system, chemoreceptors, barorecptors & cardiac responsiveness.

� Therefore it is a good indicator of how healthy the fetus is at that time.

� This is because a healthy fetus will constantly be adapting it’s heart rate to respond to changes in it’s environment.

� Normal variability is between 10-25 bpm

� To calculate variability you look at how much the peaks & troughs of the heart rate deviate from the baseline rate (in bpm)

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DR C BRAVADO

Variability

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DR C BRAVADO

Variability can be categorized as: • Reassuring – ≥ 5 bpm • Non-reassuring – < 5bpm for between 40-90 minutes

• Abnormal – < 5bpm for >90 minutes

Variability

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Reduced variability can be caused by: 1. Fetus sleeping - this should last no longer than 40 minutes – most common cause 2. Fetal acidosis (due to hypoxia) – more likely if late decelerations also present 3. Fetal tachycardia

4. Drugs – opiates, benzodiazipine’s, methyldopa, magnesium sulphate 5. Prematurity – variability is reduced at earlier gestation (<28 weeks) 6. Congenital heart abnormalities

DR C BRAVADO

Accelerations

� Accelerations are an abrupt increase in baseline heart rate of >15 bpm for >15 seconds. Its presence is reassuring

� Ante-natal there should be at least 2 accelerations every 15 minutes.

� Accelerations occurring alongside uterine contractions is a sign of a healthy fetus

� However the absence of accelerations with an otherwise normal CTG is of uncertain significance

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DR C BRAVADO

Decelerations

� Decelerations are an abrupt decrease in baseline heart rate of >15 bpm for >15 seconds

� There are a number of different types of decelerations, each with varying significance

1. Early decelerations

2. Variable decelerations

3. Late decelerations

4. Prolonged decelerations

5. Sinusoidal pattern

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DR C BRAVADO

Decelerations

1. Early deceleration

� Early decelerations start when uterine contraction begins & recover when uterine contraction stops

� This is due to increased fetal intracranial pressure causing increased vagal tone

� It therefore quickly resolves once the uterine contraction ends & intracranial pressure reduces

� This type of deceleration is therefore considered to be physiological .

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DR C BRAVADO

Decelerations

2. Variable Decelerations:

� Variable decelerations are seen as a rapid fall in baseline rate with a variable

recovery phase.

� They are variable in their duration & may not have any relationship to uterine

contractions

� They are most often seen during labor & in patients with reduced amniotic fluid

volume

� Variable decelerations are usually caused by umbilical cord compression.

� The umbilical vein is often occluded first causing an acceleration in response. Then the

umbilical artery is occluded causing a subsequent rapid deceleration.

� When pressure on the cord is reduced another acceleration occurs & then the baseline

rate returns.

� Accelerations before & after a variable deceleration are known as the “shoulders of

deceleration”. Their presence indicates the fetus is not yet hypoxic & is adapting to

the reduced blood flow.

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DR C BRAVADO

Decelerations

2. Variable Decelerations: (continued)

� Variable decelerations can sometimes resolve if the mother changes position

� The presence of persistent variable decelerations indicates the need for close monitoring

� Variable decelerations without the shoulders is more worrying as it suggests the fetus is hypoxic

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DR C BRAVADO

Decelerations

3. Late deceleration � Late decelerations begin at the peak of uterine contraction & recover after the

contraction ends.

� This type of deceleration indicates there is insufficient blood flow through the uterus

& placenta. As a result blood flow to the fetus is significantly reduced causing fetal

hypoxia & acidosis

Reduced utero-placental blood flow can be caused by:

� Maternal hypotension

� Pre-eclampsia

� Uterine hyper-stimulation

NOTE: The presence of late decelerations is

taken seriously & fetal blood sampling for pH

is indicated, If fetal blood pH is acidotic it

indicates significant foetal hypoxia & the

need for emergency C-section

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DR C BRAVADO

Decelerations

4.Prolonged deceleration

� A deceleration that last more than 2 minutes

� If it lasts between 2-3 minutes it is classed as Non-Reasurring

� If it lasts longer than 3 minutes it is immediately classed as Abnormal

� Action must be taken quickly – e.g. Fetal blood sampling / emergency C-section

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DR C BRAVADO

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Decelerations

5. Sinusoidal Pattern

� This type of pattern is rare, however if present it is very serious

� It is associated with high rates of fetal morbidity & mortality

� It is described as:

� A smooth, regular, wave-like pattern

� Frequency of around 2-5 cycles a minute

� Stable baseline rate around 120-160 bpm

� No beat to beat variability

A sinusoidal pattern indicates:

� Severe fetal hypoxia

� Severe fetal anaemia

� Fetal/Maternal Hemorrhage

Immediate C-section is indicated

for this kind of pattern. Outcome is usually poor

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DR C BRAVADO

Overall impression

- Once you have assessed all aspects of the CTG you need to give your overall impression. The overall impression can be described as either:

� Reassuring

� Suspicious

� Pathological

-The overall impression is determined by how many of the CTG features were

either reassuring, non-reassuring or abnormal. The NICE guideline

demonstrates how to decide which category a CTG falls into:

1- Normal CTG= All four features are classified as reassuring.

2-Suspicious CTG= One feature is classified as non-reassuring while the remaining features are reassuring

3- Pathological CTG= ≥ 2 features non-reassuring, or ≥ 1 feature classified as abnormal

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DR C BRAVADO

Overall impression

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DR C BRAVADO

INTRAPARTUM FETAL MONITORING

Monitoring uncomplicated pregnancy:

- For a woman who is healthy and has had an otherwise uncomplicated pregnancy, intermittent auscultation should be offered and recommended in labor to monitor fetal well-being using Doppler or Pinard.

- In the active stages of labor, intermittent auscultation should occur after a contraction, for a minimum of 60 seconds, and at least:

- Every 15 minutes in the first stage

- Every 5 minutes in the second stage

- The maternal pulse should be palpated if FHR abnormality detected to differentiate the 2 heart rates.

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NICE 2007

INTRAPARTUM FETAL MONITORING

Continuous EFM In Low-risk Women:

Indications:

1. Significant or light Meconium-stained liquor

2. Abnormal FHR detected by intermittent auscultation (< 110 bpm; or > 160 bpm, or any decelerations after a contraction.

3. Maternal pyrexia (defined as 38.0 °C once or 37.5 °C on two occasions 2 hours apart)

4. Fresh bleeding developing in labor

5. Oxytocin use for augmentation

6. The woman’s request.

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NICE 9- 2007

INTRAPARTUM FETAL MONITORING

Continuous EFM In Low-risk Women:

Evaluation :

� There was a borderline evidence that continuous EFM were more likely to have an instrumental birth compared with the auscultation group although there was no evidence of differences in:

� Augmentation

� Perinatal mortality

� Other neonatal morbidities

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NICE 9- 2007

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