At 20–25 weeks, a multidisciplinary team should evaluate the progress of each patient. The team should consist of at least a cardiologist, an obstetrician and an anaesthesiologist. Echocardiography or other examinations should be discussed. An individualised labour plan should be made, taking into account the WHO classification, as specified during preconception counselling. It should describe the planned method and timing of delivery, whether there is a need for primary caesarean section, induction, primary epidural anaesthesia and assisted vaginal delivery and the need for postpartum prolonged admission. The delivery plan should be documented electronically if possible and made easily available to all involved specialties.
5.3 Diagnostic Modalities
After taking a careful history and physical examination, an electrocardiogram should be performed as a part of standard care. Heart rate increases by approximately 10–20 % during normal pregnancy [7]. Deviation towards a left axis is observed, which can be explained by elevation of the diaphragm and increase in ventricular mass and/or blood volume. Prominent Q waves may evolve in the inferior leads in 50–68 %, and T-wave abnormalities have been described in 70–80 % of pregnant women. These changes are also thought to be related to a physical shift in the position of the heart. Alternatively, the increased workload of the pregnant heart or the hormonal and serum electrolyte changes have been suggested to cause Q- and T-wave deviations [8].
Echocardiography is the basis of the evaluation of cardiac status during pregnancy, both routinely and in the event of a clinical deterioration. In any patient with congenital heart disease, echocardiography should be performed at least once during pregnancy. Ventricular and valvular function as well as ascending aorta dimensions can be assessed and compared to pre-pregnancy values. Left ventricular diastolic dimensions are known to increase approximately 7–12 % throughout pregnancy and to return to preconception values 6–12 months after pregnancy in healthy women [9]. Systolic dimensions remain stable, allowing for the increment of stroke volume. Maximum haemodynamic adaptation takes place beyond 20 weeks up to the end of the second trimester [7], and routine echocardiographic follow-up during pregnancy can therefore be planned between 20 and 24 weeks of gestation. Transoesophageal echocardiography is relatively safe during pregnancy. It is in particular helpful in haemodynamically stable women with a mechanical valve prosthesis and suspected valve thrombosis to determine thrombus size and to guide therapy [10].
Exercise testing during pregnancy has been studied and showed no adverse consequences with regard to the fetal well-being measured by umbilical artery Doppler indices and fetal heart rate [11]. Safety of exercise testing in women with established congenital heart disease has not been studied. Therefore it is recommended to not exceed a heart rate of 80 % of predicted maximum heart rate and a respiratory exchange ratio of 1.0 in VO2max testing [3]. Dobutamine stress exercise should be avoided, because of limited experience during pregnancy.
MRI is the preferred imaging modality in women with aortic disease in whom aortic diameters need to be assessed during pregnancy and cannot be visualised using echocardiography. In these cases, it is recommended to have an MRI performed before pregnancy, for comparability of diameters. Gadolinium is not routinely used. It readily passes the placental border and thus may enter the fetal circulation and is excreted in the amniotic fluid through the fetal kidneys. The impact of the presence of gadolinium in the amniotic fluid on the fetus is unclear but should be considered harmful [12]. In individual cases, gadolinium use may be considered based on the estimated risk-benefit ratio in favour of the benefits for the mother.
A supine position compresses the inferior vena cava, but not the aorta. A left lateral position with a tilt of 30°, rather than 15°, relieves this compression at least partially [13]. Position should be consistent from early pregnancy to delivery, because of the large influence of position on cardiac haemodynamic parameters [14].
While survival of congenital heart disease patients has increased over the past decades, the imaging burden of this population has similarly grown. The number of tests per patients is partly associated with the disease complexity [15]. Also, utilisation rate of CT during pregnancy increased in the general population [16]. Cardiac catheterisation, chest CT or nuclear imaging leads to a fetal exposure to low-dose ionising radiation and should be avoided during pregnancy. But if a strong indication exists and chest CT is performed, the risks of fetal damage are low. Fetal radiation exposure below 50 mSv is associated with a negligible fetal risk. Chest CT leads to a fetal exposure of approximately 0.01–3 mSv, depending on the target diagnosis. Only abdominal CT and myocardial perfusion scans exceed 50 mSv [17]. CT imaging should be performed in left lateral position, and to further decrease the fetal radiation exposure rate, shielding may be considered, but decrease of exposure is limited and clinically hardly relevant [18, 19]. Iodinated contrast agents cross the placenta and are better avoided, although evidence of serious fetal harm is lacking [17].
Cardiac catheterisation may be needed in rare cases. In the case of fluoroscopy by trans-radial approach, shielding causes double exposure to the patient [20]. To avoid the use of fluoroscopy, an electroanatomical mapping system might be used to navigate and perform intracardiac pressure measurements [21]. Fluoroscopy might be considered in cases of suspected mechanical valve thrombosis, with short exposure times. All imaging modalities including clinical indications are summarised in Table 5.2.
Table 5.2
Imaging modalities and their implications during pregnancy in women with congenital heart disease
5.4 Incidence and Timing of Events
Most simple types of congenital heart disease are associated with a low risk of events during pregnancy, while women with complex lesions are at higher risk. In a comprehensive literature review, complicated pregnancies were most often seen in patients with a cyanotic heart disease, a Fontan circulation or a partial atrioventricular septal defect [22]. About 35–40 % of these pregnancies ended in a miscarriage, compared to approximately 10 % in the general population. The highest risk of heart failure, arrhythmia or cardiovascular mortality was found in patients with Eisenmenger’s syndrome, cyanotic disease, Fontan circulation and partial atrioventricular septal defect and patients with a transposition of the great arteries.
With a physiologic haemodynamic burden being present from the first weeks of gestation and increasing towards the end of the second trimester [7], cardiac events are likely to happen during the entire pregnancy. The contractions during labour are an additional load, and therefore patients are also at risk of events during the peripartum period.
5.4.1 Heart Failure
Indeed, in a prospective study, heart failure occurred throughout pregnancy, but most typically at the end of the second trimester and in the first week after delivery. In women with congenital heart disease, the incidence of heart failure was 8 %, which is much lower than the 19 % in pregnant women with valvular heart disease and 40 % in women with a cardiomyopathy. Women with signs or symptoms of heart failure before pregnancy and those with pulmonary hypertension are at highest risk [23].
5.4.2 Arrhythmia
In the absence of cardiac disease, pregnancy is very rarely complicated by arrhythmias [24]. In patients with congenital heart disease outside pregnancy, mainly those with multiple previous cardiac surgeries and those with a diminished ventricular function are at risk. During pregnancy, the risk of arrhythmias in women with congenital heart disease is generally low. The incidence of supraventricular arrhythmias is estimated at 0.4–0.7 % [25, 26]. Ventricular arrhythmias occur in approximately 0.4–1.6 % in the presence of structural congenital heart disease [27, 28]. However, the incidence is much higher in patients with inherited arrhythmic disease, up to 13 % in women with previously diagnosed arrhythmogenic right ventricular cardiomyopathy with an ICD, although this is not increased compared to outside pregnancy [29].
5.4.3 Valve Thrombosis
Hormonal changes cause a hypercoagulable state during pregnancy. Therefore, patients with an increased risk of thrombosis, based on their underlying cardiac disease, should receive adequate anticoagulation and be monitored intensively throughout pregnancy. For instance, women with a mechanical valve prosthesis deserve special attention, and close cooperation with a haematologist is advised. Mechanical valve thrombosis is a hazardous complication that may occur in approximately 5 % of pregnancies, with a mortality rate as high as 20 % [30]. Several anticoagulant strategies for the prevention of valve thrombosis have been proposed, but none have been proved to be superior. Specific time of risk is presumably when a patient is switched to a different anticoagulant agent. Other patients at risk are those with low flow mechanical valves such as a valve in the mitral position or in the case of ventricular dysfunction, although studies are too small to statistically substantiate these theories.
5.4.4 Aortic Dissection
In line with the haemodynamic changes in pregnancy, the vessel wall integrity is both influenced by different loading conditions and hormonal influences on the smooth muscle cells and reticular fibres of the tunica media of the aortic wall. In women with aortic disease such as Marfan syndrome, but presumably also in patients with Loeys-Dietz or vascular-type Ehlers-Danlos, these changes result in an increased risk of aortic dissection during pregnancy [31–34]. In Marfan syndrome, the incidence of aortic dissection is approximately 4.5 % during pregnancy. An aortic dissection may occur throughout the entire pregnancy and up to several weeks after delivery. Because of this elevated risk, women with aortic disease and a dilated aorta should be seen every 4–8 weeks with imaging of the aorta (either echocardiography or MRI).
5.5 Medication During Pregnancy
The treatment of symptoms during pregnancy is limited by the potential fetal toxicity of therapeutic agents. The Food and Drug Administration (FDA) controls a database of drugs and their potential harm to the fetus. Table 5.3 shows the FDA classification and an overview of cardiac medication. In each woman the balance between maternal benefit and fetal risk of these drugs needs to be taken into account.
Table 5.3
FDA classification for drugs in pregnancy
The physiologic haemodynamic changes of pregnancy alter the pharmacokinetics and pharmacodynamics of drugs. The volume of distribution increases warranting a higher dosage in some drugs to reach therapeutic levels, e.g. in the case of digoxin. Many more complex influences of pregnancy on pharmacokinetics exist [35]. Overall, the absorption is reduced, and drug elimination is increased during pregnancy, generally leading to a lower level of plasma concentration. Close monitoring of drug levels may be necessary during pregnancy, in particular for drugs with a low therapeutic index (therapeutic-toxic dose ratio).
5.5.1 Anticoagulation in Patients with a Mechanical Valve
Several guidelines advise on anticoagulation strategies that are based mainly on small cohort studies and expert opinion [3, 36]. None of the anticoagulation regimens used worldwide seem to be superior, with the use of vitamin K antagonists leading to more frequent fetal demise, while a higher rate of valve thrombosis may be encountered in patients switched to (low molecular weight) heparin [30]. Patients should be changed to low molecular weight or unfractionated heparin as soon as they become pregnant and continue at least up to the end of the first trimester [3]. Strict control of either through levels of anti-Xa (LMWH) [37–41] or APTT (unfractionated heparin) is warranted. The guidelines advise treating women with vitamin K antagonists in the second and third trimester. The period of switching to another anticoagulant agent might put the patient at an increased risk of valve thrombosis, although this is not supported by the evidence. It is recommended to use dual anticoagulation until the INR is at least >2.5 during two consecutive measurements. In the case of a planned vaginal delivery, they should be switched to a form of heparin again by 36 or 37 weeks. At 36 h before planned labour, unfractionated heparin is the first choice of treatment as it can be reversed more easily than LMWH. At 4–6 h before planned delivery, heparin should be stopped temporarily and restarted 4–6 h after delivery [3, 36].
5.6 Cardiac Interventions During Pregnancy
5.6.1 Interventions for Arrhythmia
When pharmacological treatment fails or the arrhythmia is associated with haemodynamic instability in women suffering from tachyarrhythmia, direct current cardioversion is the first choice therapy. It can be used safely in pregnancy, with facilities for emergency delivery readily available [42]. It has been suggested that direct current cardioversion might induce uterine contractions [43], although this was described in the era of monophasic shock protocols [44]. Cardioversion should be performed in left lateral position to relieve the inferior cava compression, and fetal monitoring is advised.
In drug-resistant or recurrent tachyarrhythmias with haemodynamic compromise, radio-frequency ablation can be considered. However, evidence on safety during pregnancy is based only on a few case reports. The use of fluoroscopy can be avoided in the presence of an electroanatomical mapping system, with a minimum of radiation exposure [45].
5.6.2 Device Implantation
The indication for ICD implantation is the same as outside pregnancy [46]. Fluoroscopic guidance should be avoided if possible, for instance, using transoesophageal echocardiography or with reconstructed 3D geometry [47, 48]. Also, temporary pacing or pacemaker implantation can be performed safely. Recently, the use of (3D) electroanatomical reconstruction was reported with subsequent successful pacemaker implantation in early pregnancy free of fluoroscopy [49].
5.6.3 Resuscitation
In principle, cardiopulmonary resuscitation is performed following the standard procedures, except for some adjustments [50]. Basic life support should be performed with manual left uterine displacement to relieve caval compression, specifically in the case of an obvious gravid uterus. Fetal monitors are better removed, as the first goal is to resuscitate the mother and monitoring of the fetus is less important. Intravenous access should be achieved quickly, preferably above the diaphragm level during advanced cardiovascular life support. After 4 min of resuscitation without return of spontaneous circulation, immediate emergency caesarean section should be strongly considered and ideally be performed within 5 min of onset. Table 5.4 presents possible contributing factors which are summarised in acronym ‘BEAUCHOPS’ [51]. Next to a direct cardiac cause, obstetric indirect causes of cardiac deterioration should be considered. Key knowledge in the further treatment of a pregnant woman in shock is the fact that the uterus, and thus the fetal circulation, is considered a nonvital organ during shock.
Table 5.4
Potential causes of cardiac arrest during pregnancy
BEAUCHOPS |
|---|
Bleeding/DIC |
Embolism: coronary, pulmonary, amniotic |
Anaesthetic complications |
Uterine atony |
Cardiac disease: MI, ischaemia, aortic dissection, cardiomyopathy |
Hypertension/preeclampsia/eclampsia
 Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
Get Clinical Tree app for offline access
|