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Indian Pediatr 2019;56: 917-922 |
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Electrocardiographic Parameters in Indian
Newborns
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SK Md Habibulla1,
Arijit Bhowmik2,
Jayanta Saha3,
Avijit Hazra4,
Sanjay K Halder3
and Rakesh Mondal5
From Departments of 1Pediatrics, 2Neonatology,
3Cardiology, and 4Pediatric Medicine, Medical
College Kolkata, and 5Department of Pharmacology, IPGMER and
SSKM Hospital; Kolkata, West Bengal, India.
Correspondence to: Dr Rakesh Mondal, Premises no 50,
Shibrampur Bye Lane, Sarsuna, Kolkata 700061,
West Bengal, India.
Email: [email protected]
Received: August 22, 2018;
Initial review: December 27, 2018;
Accepted: September 03, 2019.
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Objective: To generate data of
electrocardiogram (ECG) parameters according to gestational age in
Indian newborns. Methods: An observational study was carried out
over 7 months in neonatology unit of a tertiary care teaching hospital.
Following auscultation, ECG parameters were recorded simultaneously in
12 leads, on third day of life, in hemodynamically stable neonates. Data
from 364 babies were analyzed, keeping at least 30 records for each
gestational age between 30 to 42 weeks. Results: There was no
difference in mean heart rate recorded through auscultation and ECG
traces. The mean (SD) values recorded were: P wave duration 0.04 (0.01)
s, P wave amplitude 1.3 (0.4) mm, T wave duration 0.07 (0.02) s, T wave
amplitude 1.1 (0.6) mm, PR interval 0.09 (0.02) s, QRS duration 0.04
(0.01) s, QT interval 0.26 (0.02) s, QTc 0.4 (0.03) s and QRS axis 127
(22) degree. Gestation age-wise percentile charts of different ECG
parameters were generated. Conclusion: These gestational age-wise
percentile charts of different ECG parameters for Indian newborns can be
used as reference for neonatal ECG.
Keywords: Characteristics, Charts,
Gestational age, Percentiles.
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P
rominent anatomical and
physiological changes
occur in the cardiovascular system from birth to
adolescence [1]. Both term and preterm infants
experience cardiorespiratory changes at birth, that coincide with
termination of the placental circulation and improved lung compliance.
The changes taking place in fetal cardiac physiology during the last
part of gestation and perinatal transition are reflected in the
evolution of electrocardiographic (ECG) parameters during the neonatal
period [1]. In the newborn, ECG recording is necessary for diagnosis of
different cardiac ailments, hemodynamic monitoring during intensive care
stay and during resuscitation. Survival of even preterm babies has
improved because of increasing availability of specialized neonatal care
with SpO2 monitors, cardiac
monitors etc. The different ECG parameters reflecting cardiac
electrophysiological changes need to be compared with gestational age
appropriate data for interpretation. Unfortunately, there is a paucity
of data on ECG measurements in term and preterm neonates and such data
is nonexistent for Indian babies. We therefore conducted a descriptive
observational study to generate gestational age wise data of ECG
parameters of the newborn from the Indian perspective.
Methods
The study was conducted between March and September
2017 in the neonatology unit of a tertiary-care teaching hospital in
Kolkata, India. The research protocol was approved by the institutional
ethics committee and written informed consent was obtained.
Healthy term or preterm newborns, admitted for
establishment of feeding or observation for neonatal jaundice, or babies
kept in the maternity ward with mothers requiring postpartum hospital
stay were enrolled. Babies with critical illness, birth asphyxia, major
congenital anomaly including cardiac abnormality or with maternal
antenatal history of serious illness or maternal medication use, were
excluded. Gestational age was estimated from the date of last menstrual
period, from antenatal ultrasound or new Ballard score [2] as
appropriate. If any discrepancy occurred, the gestational age estimated
through new Ballard score was accepted.
ECG was recorded on the third day after birth. A
twelve lead simultaneous acquisition ECG machine (ClarityMed ECG 100C;
CMRR > 90 dB, dynamic range ± 4.25 mV, frequency response 0.05-150Hz
(-3dB), time constant 3.2 sec, input impedance >10 M W
on each electrode) was used to record ECG. The American Heart
Association (AHA) recommendations for pediatric ECG of 150 Hz as minimum
bandwidth cut off and 500 Hz as minimum sampling rate were followed [3].
Disposable electrodes were used. Electrode placement and removal were
done cautiously in order to avoid injury to the delicate skin,
especially in preterm babies. If needed, the electrodes were trimmed to
make them smaller in size without damaging the metal panel. Standard
electrode sites were carefully identified and placement done according
to AHA recommendations [4]. The recording team comprised one ECG
technician who operated the ECG machine using a standardized protocol,
one junior resident (pediatric postgraduate student) who placed the
electrode following guidelines and maintaining asepsis protocol, and one
supervising pediatrician. The team was trained beforehand by a pediatric
cardiologist and a neonatologist. The same machine and the same team
recorded all the ECGs.
Data were captured on a structured case report form.
Weight, gender and heart rate determined by auscultation, were recorded.
Data extracted from the ECG traces were heart rate (bpm), P wave
duration (s), P wave amplitude (mm), R wave amplitude in lead V1 (mm), S
wave in V1 (mm), R wave in V6 (mm), S wave in V6 (mm), T wave duration
(s), T wave amplitude (mm), PR segment interval (s), QRS complex
duration (s), QT segment interval (s), QTc (s), and QRS complex axis
(degree)
No formal sample size calculation was done beforehand
but the target was to recruit at least 30 babies born in each
gestational week between weeks 28 to 42. Sampling was purposive and
consecutive babies were recruited as far as possible, provided informed
consent was available.
Statistical analysis: Descriptive statistics,
namely mean, standard deviation (SD), 95% confidence interval (CI), and
10th, 25th, 50th, 75th and 90th percentile values were calculated for
the whole cohort and gestational age based weekly subcohorts. Numerical
variables were compared between male and female subgroups by
Mann-Whitney U test with two-sided P<0.05 as the cut-off for
statistical significance. Significance of change across gestational age
was assessed by Kruskal-Wallis analysis of variance (ANOVA). Correlation
between variables was quantified by calculating Spearman’s rank
correlation coefficient rho, after verifying from scatter plots that an
approximately linear relationship exists. Statistica version 6 (Tulsa,
Oklahoma: StatSoft Inc., 2001) and MedCalc version 11.6 (Mariakreke,
Belgium: MedCalc Software, 2011) software were used for statistical
analyses.
Results
Although 511 babies were screened, 364 ECG traces
could be analyzed. The exclusions occurred stepwise – 27 babies were
excluded at screening (19 failed exclusion criteria; 8 refused consent),
26 were excluded due to difficulties in lead placement, 39 excluded due
to poor ECG recording and finally, 55 traces were discarded because the
preset criterion of at least 30 records for each gestational week were
not met. The babies included were healthy and those born preterm were
all ensured to be hemodynamically stable. There were 212 babies (58.2%)
in the analyzed cohort who were born before 37 completed weeks. Male
babies numbered 191 (52.5%). The mean (SD) birth weight of the whole
cohort was 2.11 (0.73 kg) (95% CI 2.03-2.18 kg) and for preterm cohort (n=212)
was 1.60 (0.13) kg (95% CI 1.55-1.66 kg).
The mean (SD) values were: P duration, 0.04 (0.01) s;
P amplitude, 1.3 (0.4) mm; T duration 0.07 (0.02) s; T amplitude, 1.1
(0.6) mm; PR interval, 0.09 (0.02) s, QRS duration, 0.04 (0.01) s; QT
interval, 0.26 (0.02) s, QTc interval, 0.4 (0.03) s; and QRS axis, 127
(22) degree. There were no statistically significant gender differences
in birthweight, heart rate and ECG parameters.
The gestation age-wise (30 weeks to 41 weeks) summary
of the ECG measurements (mean with SD), has been presented in
Table I. Detailed percentile values as per gestation are
available in Web Table I. Among the ECG parameters, heart
rate, R and S wave amplitudes and QT interval and QTc showed significant
variation with gestational age (P<0.001), but the overall range
was narrow, as can be seen from the 10th and 90th percentile values,
other than for heart rate.
TABLE I Descriptive Statistics of ECG Parameters in the Newborn Stratified by Gestational Age in Weeks
|
Gestation |
Heart
|
P dura- |
P ampli- |
R ampli- |
S ampli- |
R ampli- |
S ampli- |
T dura- |
T ampli- |
PR inter- |
QRS dura- |
QT inter- |
QTc |
QRS axis
|
|
Rate
|
tion |
tude |
tude in |
tude in
|
tude in |
tude in
|
tion
|
tude
|
val
|
tion (sec) |
val (sec) |
|
(degree) |
|
(bpm) |
(sec) |
(mm) |
V1 (mm) |
V1 (mm) |
V6 (mm) |
V6 (mm) |
(sec) |
(mm) |
(sec) |
|
|
|
|
|
30 weeks |
|
Mean |
159
|
0.04
|
1.2
|
7.1
|
5.1
|
8.3
|
9.8
|
0.05
|
1.1
|
0.09
|
0.04
|
0.25
|
0.41
|
129
|
|
(SD) |
(17) |
(0.01) |
(0.3) |
(2.8) |
(2.3) |
(2.7) |
(3.8) |
(0.01) |
(0.2) |
(0.01) |
(0.01) |
(0.02) |
(0.03) |
(26) |
|
Median |
159 |
0.04 |
1.0 |
6.8 |
4.8 |
7.8 |
9.0 |
0.04 |
1.0 |
0.08 |
0.04 |
0.25 |
0.40 |
130 |
|
31 weeks |
|
Mean |
144
|
0.04
|
1.2
|
7.5
|
5.3
|
7.5
|
8.9
|
0.06
|
1.2
|
0.09
|
0.04
|
0.26
|
0.4
|
127
|
|
(SD) |
(17) |
(0.01) |
(0.3) |
(3.0) |
(2.6) |
(3.1) |
(3.2) |
(0.02) |
(0.2) |
(0.01) |
(0.01) |
(0.02) |
(0.03) |
(24) |
|
Median |
147 |
0.04 |
1.0 |
7.0 |
5.0 |
7.0 |
8.8 |
0.06 |
1.0 |
0.08 |
0.04 |
0.26 |
0.40 |
127 |
|
32 weeks |
|
Mean |
137
|
0.04
|
1.2
|
7.6
|
5.1
|
7.5
|
7.8
|
0.06
|
1.1
|
0.09
|
0.04
|
0.26
|
0.4
|
125
|
|
(SD) |
(16) |
(0.01) |
(0.3) |
(3.3) |
(2.8) |
(2.9) |
(3.1) |
(0.02) |
(0.2) |
(0.02) |
(0.01) |
(0.02) |
(0.04) |
(23) |
|
Median |
139 |
0.04 |
1.0 |
7.5 |
4.5 |
7.0 |
8.3 |
0.06 |
1.0 |
0.08 |
0.04 |
0.26 |
0.39 |
125 |
|
33 weeks |
|
Mean |
148
|
0.04
|
1.3
|
7.5
|
5.9
|
7.9
|
9.4
|
0.06
|
1.0
|
0.09
|
0.04
|
0.25
|
0.38
|
119
|
|
(SD) |
(20) |
(0.01) |
(0.4) |
(3.3) |
(2.5) |
(2.5) |
(3.5) |
(0.01) |
(0.2) |
(0.01) |
(0.01) |
(0.02) |
(0.03) |
(23) |
|
Median |
145 |
0.04 |
1.0 |
6.8 |
5.5 |
7.0 |
8.0 |
0.06 |
1.0 |
0.08 |
0.04 |
0.24 |
0.39 |
120 |
|
34 weeks |
|
Mean |
144
|
0.05
|
1.3
|
7.3
|
5.3
|
7.6
|
8.9
|
0.06
|
1.1
|
0.09
|
0.04
|
0.26
|
0.4
|
123
|
|
(SD) |
(15) |
(0.01) |
(0.4) |
(3.1) |
(1.7) |
(2.4) |
(3.4) |
(0.01) |
(0.3) |
(0.01) |
(0.01) |
(0.02) |
(0.02) |
(23) |
|
Median |
143 |
0.04 |
1.0 |
6.5 |
5.3 |
7.0 |
8.3 |
0.06 |
1.0 |
0.08 |
0.04 |
0.26 |
0.40 |
125 |
|
35 weeks |
|
Mean |
139
|
0.04
|
1.4
|
8.3
|
5.9
|
5.5
|
5.9
|
0.07
|
1.2
|
0.09
|
0.04
|
0.27
|
0.41
|
125
|
|
(SD) |
(15) |
(0.01) |
(0.4) |
(3.5) |
(1.9) |
(1.7) |
(2.0) |
(0.01) |
(0.3) |
(0.01) |
(0.01) |
(0.02) |
(0.03) |
(23) |
|
Median |
136 |
0.04 |
1.5 |
7.8 |
6.0 |
5.5 |
5.5 |
0.07 |
1.0 |
0.08 |
0.04 |
0.27 |
0.41 |
125 |
|
36 weeks |
|
Mean |
138
|
0.04
|
1.23
|
10.1
|
7.2
|
4.4
|
2.9
|
0.07
|
1.2
|
0.09
|
0.04
|
0.26
|
0.39
|
127
|
|
(SD) |
(15) |
(0.01) |
(0.3) |
(3.9) |
(2.7) |
(1.4) |
(1.2) |
(0.01) |
(0.2) |
(0.01) |
(0.01) |
(0.02) |
(0.03) |
(19) |
|
Median |
137 |
0.04 |
1.0 |
9.3 |
6.5 |
4.0 |
3.0 |
0.06 |
1.0 |
0.08 |
0.04 |
0.26 |
0.39 |
125 |
|
37 weeks |
|
Mean |
135
|
0.05
|
1.3
|
11.5
|
7.8
|
4.9
|
3.3
|
0.07
|
1.1
|
0.09
|
0.04
|
0.27
|
0.41
|
128
|
|
(SD) |
(14) |
(0.01) |
(0.4) |
(3.7) |
(2.6) |
(1.6) |
(1.3) |
(0.01) |
(0.3) |
(0.01) |
(0.01) |
(0.02) |
(0.03) |
(19) |
|
Median |
136 |
0.04 |
1.0 |
11.3 |
8.0 |
5.0 |
3.0 |
0.06 |
1.0 |
0.08 |
0.04 |
0.28 |
0.40 |
130 |
|
38 weeks |
|
Mean |
132
|
0.04
|
1.3
|
12.2
|
7.8
|
4.5
|
3.1
|
0.07
|
1.1
|
0.09
|
0.04
|
0.27
|
0.4
|
131
|
|
(SD) |
(16) |
(0.01) |
(0.4) |
(4.8) |
(2.6) |
(1.5) |
(1.3) |
(0.01) |
(0.3) |
(0.02) |
(0.01) |
(0.02) |
(0.03) |
(19) |
|
Median |
133 |
0.04 |
1.0 |
12.0 |
8.3 |
4.5 |
3.0 |
0.08 |
1.0 |
0.08 |
0.04 |
0.28 |
0.40 |
130 |
|
39 weeks |
|
Mean |
134
|
0.05
|
1.4
|
12.1
|
8.4
|
4.6
|
3.3
|
0.08
|
1.1
|
0.1
|
0.04
|
0.27
|
0.39
|
130
|
|
(SD) |
(18) |
(0.01) |
(0.4) |
(4.8) |
(2.4) |
(1.8) |
(1.5) |
(0.02) |
(0.3) |
(0.02) |
(0.01) |
(0.02) |
(0.03) |
(23) |
|
Median |
133 |
0.04 |
1.5 |
11.8 |
8.5 |
4.8 |
3.5 |
0.08 |
1.0 |
0.10 |
0.04 |
0.27 |
0.39 |
130 |
|
40 weeks |
|
Mean |
122
|
0.04
|
1.2
|
12
|
8.5
|
4.5
|
3.4
|
0.07
|
1.1
|
0.09
|
0.04
|
0.28
|
0.4
|
131
|
|
(SD) |
(15) |
(0.01) |
(0.5) |
(5.1) |
(2.6) |
(1.9) |
(1.3) |
(0.01) |
(0.2) |
(0.01) |
(0.01) |
(0.02) |
(0.02) |
(23) |
|
Median |
123 |
0.04 |
1.0 |
12.3 |
8.3 |
4.3 |
3.5 |
0.07 |
1.0 |
0.08 |
0.04 |
0.28 |
0.40 |
130 |
|
41 weeks |
|
Mean |
131
|
0.05
|
1.2
|
12.3
|
8.8
|
4.9
|
3.3
|
0.07
|
1.1
|
0.09
|
0.04
|
0.27
|
0.4
|
130
|
|
(SD) |
(14) |
(0.01) |
(0.4) |
(4.5) |
(2.4) |
(1.8) |
(1.4) |
(0.01) |
(0.2) |
(0.02) |
(0.01) |
(0.02) |
(0.03) |
(20) |
|
Median |
134 |
0.04 |
1.0 |
12.0 |
9.0 |
5.0 |
3.3 |
0.06 |
1.0 |
0.08 |
0.04 |
0.26 |
0.40 |
130 |
|
(Note: n = 32 for gestational age of 40 weeks, 31 for weeks
32 and 33 and 30 for all other weeks) |
Gestational age showed moderate inverse correlation
with heart rate (–0.40) and strong inverse correlation with S wave
amplitude in Lead V6 (–0.71). The QT interval showed good inverse
correlation with heart rate (–0.55). Birth weight also showed good
inverse correlation with S wave amplitude in V6 (–0.68). Correlation was
near perfect (0.99) between auscultated heart rate and that derived from
ECG.
Discussion
The gestation age-wise (30 to 41 weeks) summary of
the ECG measurements, including percentile values were generated. Heart
rate, R and S wave amplitudes and QT interval and QTc showed significant
variation with gestational age (P<0.001).
This study has limitations, including the relatively
small sample size and lack of prospective follow-up of ECG and clinical
data. Our analysis does not include ECG data of babies below 30 weeks
and over 41 weeks as we did not get sufficient numbers. Logistic
limitations prevented us from generating gestation-wise ECG data from
babies in the community rather than in hospital. Difficulties were
encountered in adhering to chest lead placement following AHA guidelines
in babies with small chests and a sizeable number of ECG records had to
be discarded owing to lead loosening artefacts caused by movement in the
babies.
Most studies on neonatal ECGs done in the 1970s [5,6]
do not provide gestation-wise data. Gestational age-specific ECG data is
lacking in literature, including from India. Until recently, the most
comprehensive study of ECG variability in children was that of Davignon,
et al. [5] based on measurements made from 2141 White children in
Quebec, Canada. Normal limits were presented for few parameters and
there were no gestational age-wise stratification attempted. For
available parameters, percentile values of ECG parameters in our study
are quite comparable to that study [5]. This applies to heart rate, mean
QRS axis, QRS duration, R and V amplitude in leads V1 and V6. However,
our result differ, to some extent, with respect to P wave duration, QRS
duration and QRS axis from figures reported in the study by Rijnbeek,
et al. [7], where the study population comprised children aged 11
days to 16 years.
The most recent guidelines for interpretation of
normal ECG in newborns have been provided by the Task Force for
Interpretation of the Neonatal Electro-cardiogram of the European
Society of Cardiology in 2002 [8]. However, these do not provide
gestational age-wise stratification of data. Except the mean P amplitude
value, S in V1, R in V6, S in V6, other ECG parameters in our study are
comparable with these guidelines. It suggests that Western data may not
be appropriate to interpret ECG in Indian babies. Heart rate assessment
at birth by ECG may be reasonable according to the 2015 guidelines on
neonatal resuscitation from American Heart Association (AHA) [9] and
European Resuscitation Council (ERC) [10] since clinical and pulse
oximetry assessment are sometimes found to be both inaccurate and
unreliable [11-14] in the newborn. Therefore availability of data on
heart rate by ECG, stratified by gestational age, will be useful in
following the resuscitation protocol. The influence of gender on some
electrocardiographic variables has been noted in some reports [15,16],
unlike the results of our study.
Notwithstanding the above limitations, in conclusion,
we have provided normative data of ECG parameters according to
gestational age in Indian scenario. This data need to be validated at
other centers and in the community. These values, validated through
additional studies, can serve as reference for interpretation of
neonatal ECG, both in term and preterm babies.
Contributors: MHSk: primary investigator, data
collection, manuscript drafting and review; AB: data collection, patient
management, literature search; JS: study design, patient management,
data interpretation; AH: literature search, statistical analysis,
manuscript review; SKH: technical inputs in data Collection, data
interpretation; RM: study conception and design, literature search,
manuscript review and corresponding author. MHS,RM: shall act as
guarantor of the study.
Funding: None; Competing Interest: None
stated.
|
What This Study Adds?
•
Gestational age-wise percentile
charts of different electrocardiographic parameters have been
derived for Indian newborn babies.
|
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