Cardiotocography
A cardiotocograph recording fetal heart rate and contractions
In medicine (obstetrics), cardiotocography (CTG) is a technical means of recording (-
graphy) the fetal heartbeat (cardio-) and the uterine contractions (-toco-) duringpregnancy,
typically in the third trimester. The machine used to perform the monitoring is called
a cardiotocograph, more commonly known as an electronic fetal monitor or external fetal
monitor (EFM). CTG can be used to identify signs of fetal distress.
The invasive fetal monitoring was invented by Doctors Orvan Hess and Edward Hon. A
refined (antepartal, non-invasive, beat-to-beat) version (cardiotocograph) was later developed
for Hewlett Packard by Dr. Konrad Hammacher.
Method
Schematic explanation of cardiotocography: heart rate (A) is calculated from fetal heart
sounds determined by ultrasound, and uterine contractions are measured by a pressure
transducer (B). These numbers are represented on a time scale with the help of a running
piece of paper, producing a graphical representation.
Simultaneous recordings are performed by two separatetransducers, one for the measurement
of the fetal heart rate and a second one for the uterine contractions. Each of the transducers
may be either external or internal.
External measurement means taping or strapping the two sensors to the abdominal wall.
The heart ultrasonic sensor, similar to aDoppler fetal monitor, overlays the fetal heart. The
pressure-sensitive contraction transducer, called a tocodynamometer (toco), measures the
tension of the maternal abdominal wall - an indirect measure of the intrauterine pressure.
Internal measurement requires a certain degree of cervicaldilatation, as it involves inserting a
pressure catheter into the uterine cavity, as well as attaching a scalp electrode to the child's
head to adequately measure the pulse. Internal measurement is more precise, and might be
preferable when a complicated childbirth is expected.
A typical CTG reading is printed on paper and/or stored on a computer for later reference.
Use of CTG and a computer network allows continual remote surveillance: a single nurse,
midwife, or physician can watch the CTG traces of multiple patients simultaneously, via a
computer station.
Interpretation
A typical CTG output for a woman not in labour. A: Fetal heartbeat; B: Indicator showing
movements felt by mother (caused by pressing a button); C: Fetal movement; D: Uterine
contractions
Cardiotocography is used to monitor several different measures: uterine contractions and four
fetal heart rate features - baseline heart rate, variability, accelerations, and decelerations.
[1]
Before interpreting a CTG, it is important to define the risk factors which will influence
decision-making, for example any factors why this might be a low- or high-risk pregnancy. In
a patient at high-risk for adverse outcome (for example, when the fetus already
has intrauterine growth retardation), treatment will probably need to be less expectant (in the
example, the decision to proceed to cesarean section might be taken more quickly).
Ranges
Measure Low High
Uterine contractions - time more than 5 contractions in 10
between contractions, which min representsuterine
[2]
reduces as childbirth tachysystole.
progresses; they are quantified
as the number of contractions
present in a 10 min window and
averaged over 30 min. Normal
are 5 or less contractions in 10
min. (It is also possible to
measure the cumulative
intensity of the contractions
withMontevideo units.)
110. 160. (PersistentTachycardia is
(PersistentBradycardia is when Fetal Heart rate is
Baseline heart rate - average
when Fetal Heart rate is less greater than 160 for more than
baseline fetal heart rate
than 110 for more than ten ten minutes. May
minutes.) indicatechorioamnionitis)
Variability - fetal heart rate
5 (may indicate a loss of 25 ("saltatory pattern"; may
variability from Baseline per
fetal autoregulation) indicatehypoxia)[3]
minute
Accelerations and decelerations
Accelerations - increases in fetal heart rate from the baseline by at least 15 beats per
minute, lasting for at least 15 seconds. Should be 2 every 20 minutes lasting no longer
than 2 minutes. They are normally present, indicating a Reactive Tracing. Evaluated in
nonstress test.
Decelerations (decels) - decreases in fetal heart rate from the baseline by at least 15
beats per minute, lasting for at least 15 seconds. They are normally minimal. There are
three types of decelerations, depending on their relationship with uterine contraction:
Categor
Description Cause
y
begin at start of uterine contraction and
increased vagal tone due to fetal head
Early end with conclusion of contraction (mirror
compression
image)
occur at any time irrespective of uterine umbilical cord compression (such as
Variable
contractions that due to anuchal cord)
begin at or after the peak of a contraction fetal hypoxia due to uteroplacental
Late and ends long after it, hence the "late" insufficiency - the most worrisome
when compared to early decels deceleration
Additionally decelerations can be recurrent or intermittent based on their frequency (more or
less than 50% of the time) within a 20 min window.[2]
Significance
The terminology of a three-tiered system replaces the older terms "reassuring" and
"nonreassuring".[2]
Category I (Normal): Tracings with all these findings present are strongly predictive
of normal fetal acid-base status and the fetus can be followed in a standard manner:
Baseline rate 110-160 bpm,
Moderate variability,
Absence of late, or variable decelerations,
Early decelerations and accelerations may or may not be present.
Category II (Indeterminate):Tracing is not predictive of abnormal fetal acid-base
status, but evaluation and continued surveillance and reevaluations are indicated:
Category III (Abnormal): Either tracing predicts abnormal fetal acid-base status;
this requires prompt evaluation and management:
Absence of baseline variability with recurrent late or variable decelerations or
bradycardia; or
Sinusoidal fetal heart rate.
These steps can be remembered with the mnemonic 'DR. C. BRaVADO': Define Risk,
Contractions, Baseline Rate, Variability, Accelerations, Decelerations and Outcome.[4][5]
Types of tests
Use of CTG during the third trimester to monitor fetal wellbeing is called a nonstress test. A
positive (good) result is indicated by a reactive non-stress test. This means that the fetal heart
rate increased (acceleration) by at least 15 beats per minute for at least 15 seconds at least
twice during a 20 minute interval.[6] Vibroacoustic stimulation can wake the fetus, and is
sometimes used to speed up the test or to facilitate further evaluation of a nonreactive
nonstress test.[7]
Use of this machine during labor is called a stress test. When introduced, this practice was
expected to reduce the incidence of fetal demise in labor and make for a reduction in cerebral
palsy (CP). Its use became almost universal for hospital births in the U.S. In recent years
there has been some controversy as to the utility of the cardiotocograph in low-risk
pregnancies, and the related belief that over-reliance on the test has led to increased
misdiagnoses of fetal distress and hence increased (and possibly unnecessary) cesarean
deliveries.[8]
Biophysical profile is another test associated with CTG. It is often done when the non stress
test is non reactive.
Effect on management
A Cochrane Collaboration review has shown that use of cardiotocography reduces the rate
of seizures in the newborn, but there is no clear benefit in the prevention of cerebral
palsy, perinatal death and other complications of labour. In contrast, labour monitored by
CTG is slightly more likely to result in instrumental delivery (forceps or vacuum extraction)
or caesarian section.[9] The false-positive rate of cardiotocography for cerebral palsy is given
as high as 99%, meaning that only 1-2 of one hundred babies with non-reassuring patterns
will develop cerebral palsy.[10] The introduction of additional methods of intrapartum
assessment has given mixed results.[11]
PEMERIKSAAN PASIEN
Anamnesis : tentang riwayat kehamilan yang lalu (bila ada), kehamilan saat ini, dan faktor
resiko
Pemeriksaan Fisik : status generalis dan Obstetri.
1. Tentukan punktum maksimum jantung dan tinggifundus uteri.
2. Pasien tidur dengan posisi setengah duduk, atau miring ke kiri, atau duduk.
3. Pemasangan peralatan Kardiotokografi : tokometer dipasang di fundus dan kardiometer
dipasang di tempatpunktum maksimum jantung
4. Ukur tekanan darah pada awal pemeriksaan dan 15 menit kemudian
Perekaman KTG dimulai
Pengawasan berkala kondisi ibu dan janin oleh petugas kesehatan
5. Lama perekaman minimal 20 menit. Bila variabilitas berkurang, lakukan perangsangan
bayi dengan rangsang suara atau bel (beri tahu ibu sebelumtindakan tersebut
dilakukan)
MELAKUKAN INTERPRETASI HASIL
Dalam kehamilan : NST, dalam persalinan atau OCT : CST
Data pasien dan KTG diisikan pada formulir KTG
Melaporkan hasil pemeriksaan kepada dokter
penanggung jawab (bila ada)
