ECG in pregnancy: interpretation of indicators
Electrocardiography (cardiogram, ECG) is an additional research method that allows to evaluate the functioning of the electroconductive system of the heart. By the time the study takes no more than 5-10 minutes and has a minimum amount of contraindications.
For carrying out the ECG, a special medical device is used which, by imposing on the chest, arms and legs of the sensors, registers the electrical activity of the heart and shows the results on paper graphically or on a monitor in digital.
Throughout pregnancy, all women who are registered in the antenatal clinic, ECG is conducted twice. The first time - after the initial examination, which allows an overall assessment of the heart's work in a pregnant woman. The second time before the maternity leave. If necessary, if there are symptoms of heart disease, the ECG can be administered at any desired time.
Video: Decoding of the cardiogram: norm and pathology
Description of electrocardiography
The heart during the contraction generates electrical impulses that are captured by an electrocardiograph.
The first electrocardiogram was recorded by the French physicist Gabriel Lippmann, who used a mercury electrometer for this purpose. Later, the Netherlands physiologist Willem Einthoven created a string galvanometer and first determined the values of the ECG teeth.
ECG in the study of healthy hearts has certain characteristics. If the ECG is different from normal, it can indicate a heart problem. A physician can recommend an ECG in determining the risk of developing a heart disease. This is especially true when there is a hereditary predisposition to heart disease or another risk factor (smoking, overweight, diabetes, high cholesterol or high blood pressure).
The physician can also recommend an ECG in case of unfavorable symptoms: chest pain, dyspnoea, dizziness, fainting, fast or irregular heartbeat.
ECG is a safe and non-invasive procedure without any significant risks and side effects to the health of the pregnant and the child.
There is no need to limit yourself to eating food or liquids before doing research. Another thing is when you are taking any medications and you should always let the doctor know about it. Also, you should notify about the presence of any allergic reactions to adhesive tapes and substances, which are often used to attach electrodes.
Before the study you will need to remove the outer clothing so that the electrodes can be attached to the chest and limbs. (For women wearing a separate top with trousers or a skirt, you can provide easy access to the chest). In some cases, it is recommended that you even remove the bra so that the doctor can properly attach the electrodes.
To attach the electrodes to the chest, arms and legs, use a suction cup or sticky gel. With the installed sensors, electric currents generated by the heart are detected - they are measured and recorded by an electrocardiograph.
The three main types of ECG are:
- Standard ECG - the indicators are removed in a calm state, when the woman lies on the couch and for 1-2 minutes the doctor registers the ECG. During the procedure, movements are not allowed, since electrical impulses generated by other muscles can interfere with those that are created in the heart. This type of ECG usually takes 5 to 10 minutes.
- Outpatient ECG - It is sometimes recommended to carry a portable recording device for at least 24 hours. This type of diagnosis is also called holter monitoring. During the study, you can move freely, lead a normal lifestyle, while a connected monitor registers the electrical activity of the heart. This type of ECG is suitable in cases where unstable symptoms are detected that do not appear with a quiet ECG recording. Additionally, you need to register your symptoms in the diary and note when they occur, so that you can then compare it with the ECG
- Stress test (stress test ) - this diagnostic method is used to record ECG while riding a stationary bike or walking on a treadmill. Carrying out this type of ECG takes from 15 to 30 minutes.
- ECG in the fetus (CTG, cardiotocography) - is carried out in the third trimester of pregnancy, most often at the stage of preparation for childbirth. It shows the fetal activity and heart rate. If the test is done during labor, then the frequency of labor.
When the procedure is completed, all electrodes are removed. ECG is completely painless and non-invasive, as the skin does not get injured.
The doctor can interpret the results of the ECG on the basis of medical history, symptoms and clinical status immediately after the examination, or the conclusion is transmitted with a card of the pregnant woman a little later.Typically, the conclusion indicates the heart rate (heart rate), the position of the electrical axis of the heart (right, left, normal), correctness or deviation of the heart rate.
As an example, the following conclusion of the ECG (variant of the norm) can be given: Rhythm of the right sinus, HR of 85 beats / min, normal EOS.
Possible complications of ECG
ECG is a safe procedure without any known risks. The device does not transmit electric current to the chest. Some people may have an allergy or sensitivity to the electrodes, which can lead to redness of the skin, so you should inform your doctor before the procedure about such known reactions.
After the ECG, there is no need to observe any regimens. The ECG is non-invasive and does not include the use of medications (eg, anesthetics), so no recovery time is required.
ECG results allow the doctor to determine whether special treatment is needed or not.
Some of the various heart diseases that can be diagnosed with an ECG include:
- Cardiovascular heart defects associated with a conductive (electrical) system.
- Abnormal rhythm (arrhythmia) - fast, slow or irregular heartbeat.
- Heart damage, for example, when one of the cardiac arteries is blocked (coronary occlusion), there is a bad supply of blood to the heart department.
- Inflammation is pericarditis or myocarditis.
- Monitoring of cardiac disorders due to incorrect chemical reactions (electrolyte imbalance), which control cardiac activity.
- Previous heart attacks.
A woman with a heart disease can have a normal ECG result, if it does not cause a violation of the electrical activity of the heart. In such cases, other diagnostic methods may be recommended, especially if there are suspicions of a pathology of the heart.
Changes in the cardiovascular system during pregnancy
Deep changes begin to be determined already in the early stages of pregnancy, so that by the eight-week period the cardiac output increased by 20%. First of all, there is peripheral vasodilation. This is due to factors that depend on the endothelium, including synthesis of nitric oxide, increased release of estradiol, and possibly vasodilating prostaglandins (PGI2).
Peripheral vasodilation leads to a drop in systemic vascular resistance by 25-30%, and to compensate for this, cardiac output increases by about 40%. Therefore, during pregnancy, tachycardia (rapid heartbeat) is often determined.
Heart work is mainly complicated by increasing the stroke volume, and to a lesser extent - increasing the heart rate. The maximum cardiac output is detected approximately at 20-28 weeks of gestation.
The increase in the shock volume occurs against the background of an increase in the muscle mass of the ventricular wall and the final diastolic volume (but not the final diastolic pressure). The heart physiologically expands and the contractility of the myocardium increases. Although the shock volume at the end of pregnancy is somewhat reduced, the heart rhythm of the mother remains the same, which allows to maintain an increased cardiac output.
Arterial pressure decreases in the first and second trimesters, but increases to non-pregnant rates in the third trimester.
There is a certain influence of the position of the woman's body on the hemodynamic profile of both the mother and the fetus.
- In the supine position on the back, the uterus exerts pressure on the lower vena cava, which causes a decrease in the venous return to the heart and a subsequent drop in the stroke volume and cardiac output.
- Turning from a lateral position to the back can result in a 25% reduction in cardiac output. Therefore, if a woman still breastfeeds during pregnancy, then it is better to do it on the left or right side, if possible.
- If a woman should lie on her back, the pelvis should be rotated so that the uterus descends in the opposite direction from the inferior vena cava, and the cardiac output and uteroplacental blood flow are normal.
Reduction of cardiac output is associated with a decrease in blood flow in the uterus and, consequently, with perfusion of the placenta, which can lead to adverse effects on the fetus.
Despite the increase in blood volume and stroke volume during pregnancy, pulmonary capillary pressure and central venous pressure do not increase significantly. Nevertheless, pulmonary vascular resistance, like systemic vascular resistance, decreases significantly in normal pregnancy, so women in the position are more prone to pulmonary edema.
During childbirth, cardiac output is further increased (by 15% during the first stage of labor and by 50% in the second period). Reductions of the uterus lead to auto-transfusion of 300-500 ml of blood back into the mother's circulation. In this case, the emerging sympathetic reaction to pain and anxiety further increases the heart rate and blood pressure.The cardiac output increases between contractions, and even more during fights.
After delivery, there is an immediate increase in cardiac output due to a decrease in pressure in the inferior vena cava and contraction of the uterus, which redirects the blood to the systemic circulation. Cardiac output increases by 60-80%, and then rapidly decreases to its original level. The flow of fluid from the extravascular space increases the volume of venous return and stroke volume.
Cardiac output almost returns to the norm (values before pregnancy) two weeks after delivery, although some pathological changes (eg, hypertension during preeclampsia) may take much longer.
ECG parameters in pregnancy
The above-mentioned physiological changes in the body of a pregnant woman lead to changes in the cardiovascular system, which may be misconstrued as pathological. They may include a limiting or collapsing pulse and systolic murmur present in more than 90% of pregnant women. Noise can be loud and audible in all the precordial region, with the first tone of the heart sounding louder than the second tone. Additionally, ectopic beats and peripheral edema may be noted.
Normal ECG data for pregnancy, which may partially relate to changes in the position of the heart, include:
- Atrial and ventricular ectopic rhythms.
- Q-wave (small) and inverted T-wave in lead III.
- Depression of the ST segment.
- Shorter than normal, PR interval.
- Inversion of the T-wave in the lower and lateral directions.
- Shift to the left of the QRS.
- The electric axis of the heart is turned to the left.
- The heart rate is higher than normal.
Electrocardiography, like other methods of diagnosis, has certain drawbacks:
- Far from all the heart diseases can be determined with the help of ECG, therefore, with suspicion and normal ECG results, ultrasound of the heart and other methods of diagnostics are necessarily prescribed.
- The standard ECG is not able to "catch" signs of cardiac dysfunction, if they were not at the time of the study. The daily monitoring of ECG partly addresses this issue.
- The symptoms of ECG are often nonspecific, so it is often necessary to recheck the diagnosis by other methods of research.
However, the absolute safety of the ECG and the simplicity of the procedure make this type of diagnosis widely available, therefore it is used to study the condition of both seriously ill, children and pregnant women.
Video: Cardiotocogram (CTG): what is it like to interpret