Electrocardiography in normal pregnancy

P Karsini; R Niruby; Nidhi Sharma

doi:10.4103/JCDM.JCDM_4_20

ORIGINAL ARTICLE

Year : 2021 | Volume : 1 | Issue : 1 | Page : 12-17

Electrocardiography in normal pregnancy

P Karsini¹, R Niruby², Nidhi Sharma²
¹ MBBS Student, Saveetha Medical College, Saveetha University, Chennai, Tamil Nadu, India
² Department of Obstetrics and Gynecology, Saveetha Medical College, Saveetha University, Chennai, Tamil Nadu, India

Date of Submission	15-Oct-2020
Date of Decision	14-Jan-2021
Date of Acceptance	02-Apr-2021
Date of Web Publication	18-May-2021

Correspondence Address:
Dr. Nidhi Sharma
Department of Obstetrics and Gynecology, Saveetha Medical College, Saveetha University, Chennai 602 105, Tamil Nadu
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/JCDM.JCDM_4_20

Abstract

Aim: The primary objective was to study the electrocardiogram (ECG) findings of normal pregnant women in their third trimester. The secondary objective was to compare the ECG findings of pregnant women in their third trimester with the ECG findings during the postpartum period. Materials and Methods: An Electrocardiography recording was done for 60 pregnant women during their third trimester and on postpartum day 7. Results: The common ECG findings during pregnancy found in our study were sinus tachycardia, and conspicuous Q wave (LV dilation) and an inverted P wave (nonspecific) in lead II. We also found left axis deviation of a mean of 15° (QRS axis) when compared with the QRS axis of the same patient postpartum (P < 0.05). Conclusion: There are physiological changes in an ECG during pregnancy. A routine antenatal ECG is safe, feasible, economic, and possibly advantageous to lower maternal mortality and morbidity. The ECG findings must be interpreted carefully during pregnancy.

Keywords: Antenatal care, electrocardiography, pregnancy

How to cite this article:
Karsini P, Niruby R, Sharma N. Electrocardiography in normal pregnancy. J Cardio Diabetes Metab Disord 2021;1:12-7

How to cite this URL:
Karsini P, Niruby R, Sharma N. Electrocardiography in normal pregnancy. J Cardio Diabetes Metab Disord [serial online] 2021 [cited 2023 Jun 6];1:12-7. Available from: http://www.cardiodiabetic.org/text.asp?2021/1/1/12/316097

Introduction

Human pregnancy is the physiological adaptation of all biological systems. Pregnancy is a physiological challenge that influences all the elements of the maternal body. Different physiological changes, particularly changes in the cardiovascular system, happen during a normal pregnancy. Pregnancy is a stress on the cardiovascular system. At times, the challenge on the cardiovascular system imposed by pregnancy may not be adequately met and a normal well-compensated cardiovascular system may be required to decompensate.

The physiology of pregnancy influences all the systems of the maternal body and achieves unique modification in the cardiovascular system. These cardiovascular adaptations and changes in electrophysiological pulse wave transmission in a normal pregnancy modify the biophysical, chemical, and radiological findings.^[1],[2] The physiological changes during pregnancy are depicted as different changes in the ECG, and these changes may be confused with coronary illness.

A large number of the physiological adjustments of typical pregnancy modify the electro-physical findings; therefore, the diagnosis with an ECG during pregnancy becomes confusing. The most common reason for referral of the pregnant patient from the obstetrician to the cardiologist is the assessment of a systolic murmur heard over the precordium. The cardiologist invariably requests an ECG. However, interpretation of ECG changes in pregnancy becomes a challenge to both obstetricians and cardiologists.

It is prudent not to diagnose coronary illness when none exists and simultaneously not to neglect to identify and properly treat coronary illness when it exists.^[3] The impact of an ordinary pregnancy on the ECG has been a subject of extraordinary enthusiasm since the beginning of electrocardiography. The ECG reflects the condition of the heart, which, in turn, is regulated by hemodynamic alterations during a normal pregnancy. The present study attempted to determine electrocardiographic changes in a normal pregnancy. This study was conducted to feature the impact of a typical pregnancy on the sinus rhythm, QRS hub, Q wave, and T-wave of the ECG.^[4]

Materials and Methods

Sixty apparently healthy pregnant women in the age group of 20 to 35 years in their third trimester were recruited by consecutive enumerative sampling in the outpatient and inpatient wards of the Department of Obstetrics and Gynecology of Saveetha Medical College and Hospital. The participants were included after obtaining written informed consent in the local language. A detailed explanation was given to all the pregnant women before the ECG recording in the local language.

A detailed obstetrical history of parity, gestational age, cough, breathlessness, edema, and past history of heart diseases such as rheumatic fever or congenital heart diseases was provided. A detailed obstetrical and cardiovascular systemic examination was done in all participants. Physical examination of all the subjects included pulse rate, pallor, jugular venous pressure, pedal edema, hepatomegaly, thyroid, and body mass index (BMI). A detailed clinical examination of the cardiovascular system and respiratory system was conducted. Women with cardiovascular disease, thyroid disease, renal disease, anemia, and comorbidities were excluded from the study.

A 12-lead ECG was recorded in the subjects during the resting state. The instrument used was manufactured by Philips Electronics Ltd. The ECG was assessed for pivot deviation, Q wave, and T-wave and results were obtained. The ECG was performed on four occasions at the first antenatal visit (8–12 weeks), 24–28 weeks, and 38–40 weeks and again during the postpartum puerperal state on postnatal day 7. The same two cardiologists interpreted ECG films. Clinical details were shared with the cardiologist, and an ECHO was performed if advised.

Descriptive and inferential statistics were performed for maternal demographic variables. Angle of QRS axis was calculated by automated ECG equipment and expressed as mean + standard deviation. One-way analysis of variance (ANOVA) was used to analyze variables by using MEDCALC. This online calculator was used to generate a complete ANOVA table for the groups, including sums of squares, degrees of freedom, mean squares, F and P-values, the mean, and standard deviation. Differences were considered significant when P < 0.01(CI 95%). Statistical analysis was done by using MEDCALC version 18 (Medcalc is a statistical software designed for biomedical science at Acalcialaan 22, 8400, Ostend, Belgium).

Results

Postpartum ECG was done in 58 out of 60 women. Two women were lost to follow-up. The heart rate during the third trimester was 92 ± 8.76, whereas the heart rate during the postpartum period was 80 ± 7.86 (P < 0.05).

In 47 out of 60 women, there was a prominent Q wave in lead II, III, and avF in the third trimester. Only 23 out of 58 women experienced a prominent Q wave in these leads during the postpartum period (P < 0.05). There were also nonspecific ST segment and T-wave anomalies (32/60) in lead III, VI–V3 as compared with postpartum status (6/58) (P < 0.05) [Figure 1]A and [Figure 1]B. Atrial and ventricular premature contractions were relatively frequent during the third trimester (11/60) as compared with during the postpartum period (3/58).

Figure 1: (A and B) Third-trimester pregnant women (38 weeks 2 days). Lead I (A) and avF (B), showing sinus tachycardia and nonspecific ST changes

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In electrocardiography, the mean of QRS axis was 58 ± 6.88degree whereas during the postpartum period the mean of QRS axis was 78 ± 8.44. The left axis deviation during the third trimester was significant as compared with during the postpartum period (P < 0.05). This finding can be explained due to the uplifting of cardiac chambers [Figure 2]A, [Figure 2]B and [Figure 3]A, [Figure 3]B. The uplifting and levorotation of the heart can also explain the mild ST changes that were seen in the inferior leads. Atrial and ventricular premature contractions were relatively frequent, and the increased end diastolic volume can explain them during the third trimester. We have not done a chest X-ray in our set of patients, though a literature search has shown that the heart silhouette is usually larger during pregnancy; however, gross cardiomegaly can be excluded.

Figure 2: (A and B) Third-trimester pregnant women (39 weeks 1 day). Lead I (A) and avF (B), showing P axis at 47°, QRS axis at 71°, and T axis at 41°

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Figure 3: (A and B) Same patient in nonpregnant postpartum day 7 showing Lead I (A) and avF (B), showing P axis at 48°, QRS axis at 88°, and T axis at 70°

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The four main concepts that affect management have been emphasized by the American College of Obstetrics and Gynecology (ACOG). The first consideration is a 50% increase in blood volume and cardiac output by the early third trimester. The second important consideration is an exaggerated fluctuation in volume and cardiac output during the peripartum period. The third important point is that there is a decline in systemic vascular resistance, reaching a nadir during the second trimester, and then rising to 20% below normal by late pregnancy. The fourth consideration is the risk of hypercoagulability in women requiring anticoagulation in the nonpregnant state.

Discussion

Multiple changes take place during pregnancy; among these, cardiovascular changes are highlighted in this study. We have enumerated several causes for these clinical changes in the cardiovascular system. The enlarging uterus elevates the diaphragm; the heart is displaced upward. There is hypertrophy of the left ventricle due to the cardiac overload by the increased blood volume during late pregnancy. There is an increase of about 75mL in cardiac volume.^[5],[6] The left ventricular mass increases due to increased stroke volume. The end diastolic pressures are increased due to the increased preload. The cardiac output increases by about five to six liters during the third trimester.

Cardiac problems are relatively common in women of childbearing age, and they are the causes for complications in about 1% of pregnancies. Maternal mortality related to heart disease has decreased remarkably over the past 50 years (from 5.6 to 0.3/100 000 live birth). However, heart diseases are still the second most common non-obstetrical cause of maternal mortality.

There is an increase in blood volume by 40% after 20 weeks of pregnancy. This can result in severe hypertension in a nonpregnant individual but still blood pressure decreases during the second trimester of pregnancy. This happens because of decreased peripheral vascular resistance and increased venous capacitance. If the vascular system is nonresilient and the vessel walls still maintain their stiffness and elastic recoil pregnancy, these can result in induced hypertension.

Rheumatic heart disease is the most common cardiac disease during pregnancy. Congenital heart disease is the second most common cause. Other problems affecting the heart are hypertensive heart disease, coronary disease, and thyroid disease during pregnancy. Rarely syphilitic and kyphoscoliotic cardiac disease may be present.^[7]

Further, there are cases of idiopathic cardiomyopathy manifesting during the peripartum and postpartum periods. Cor pulmonale and constrictive pericarditis are rare serious problems during pregnancy. Heart block and isolated myocarditis are also occasionally seen during pregnancy.^[8],[9]

The physiology of pregnancy has a profound effect on the cardiovascular system. The most important changes in cardiac function occur during the first eight weeks of pregnancy, with maximum changes at 28 weeks After 20 weeks as the pregnancy progresses, there is a decrease in vascular resistance and a reduction in blood pressure. There is an increase in heart rate and stroke volume, leading to an increased cardiac output (cardiac output = blood pressure × heart rate). The blood volume increases by 30–50%.^[10] Increased maternal weight and basal metabolic rate further increase the cardiac output. Later in pregnancy, the cardiac output is higher when women are in the lateral recumbent position than when they are in the supine position. During labor, cardiac output increases moderately during the first stage of labor and appreciably greater during the second stage.^[11],[12] Cardiac output also increases during the immediate postpartum period due to increased preload.

During pregnancy, the heart is displaced upward and to the left with lateral rotation on its long axis; this may result in ECG changes. The resting pulse increases by about 10 beats per minute. There is an exaggerated splitting of the first heart sound, with an increased loudness of both first and second heart sounds.

There are no definite changes in the aortic and pulmonary elements of the second sound, and the easily heard third sound. Systolic murmur is heard in 90% of cases. Soft diastolic murmur is transiently heard in 20% of cases. Continuous murmur arising from the breast vasculature is audible in 10% of cases. In echocardiography, normal changes of pregnancy include tricuspid regurgitation, significantly increased left atrial size, and left ventricular outflow cross-sectional area.^[13]

The ECG is an essential and a simple test to predict chamber size and arrhythmias. Previous studies have shown various changes in ECG, even in normal pregnant patients. These changes have to be correlated with the history, symptoms, clinical findings, and ECHO.

Conclusion

This study concludes that there are changes ECG during a normal pregnancy, such as sinus tachycardia and leftward hub deviation of QRS axis. There are prominent Q waves in lead II, Ill, and aVF and nonspecific T-wave variations during the postpartum period. Changes in the level of VI–V3 were seen more during the third trimester of pregnancy, as compared with during the postpartum period. The reference range of the normal electrical activity of the heart. Q wave and T-wave are altered during pregnancy. Therefore, there is a requirement for the methodical assessment of hemodynamic and ECG changes during pregnancy.

To conclude, routine ECG is a reasonable tool to assess heart diseases in pregnancy and it may be adopted routinely in antenatal care. An ECG is safe, feasible, economic, and possibly advantageous to lower the risks of maternal mortality and morbidity. To ensure the best possible outcome, pregnancy should involve a multidisciplinary approach comprising the obstetrician, cardiologist, and anesthesiologist. All women should be explained about the risks of heart failure, subacute bacterial endocarditis, and thromboembolic disease. Doubtful ECG findings during pregnancy can be confirmed with 2D Echography or cardiac magnetic resonance imaging (MRI).

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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