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8. Heart Disease
8.1 Introduction
Cardiac disease complicating pregnancy is seen in about 1–4% women. Due to effective treatment during childhood, the incidence of women with heart disease presenting during pregnancy is increasing. In developing countries like India, rheumatic heart disease still predominates, accounting for 60–80% of cardiac lesions in pregnancy. Congenital heart diseases are by far the commonest conditions in the west forming over 75% of heart diseases seen in pregnancy [1]. Pregnancy poses additional problem in women with underlying cardiac disease. A normal heart can adapt well to the hemodynamic alterations of pregnancy, whereas a diseased heart may not be able to do so and decompensate leading to heart failure. Ideally counseling and management of women of childbearing age with cardiac disease should start before pregnancy occurs. High-risk patients should be managed in specialized centers where multidisciplinary care is available. Diagnostic procedures and interventions should ideally be performed prior to pregnancy. Unfortunately in India, many women still are diagnosed to be having cardiac disease for the first time during pregnancy. This increases the morbidity and mortality associated with these disorders.
8.2 Hemodynamic Alterations During Pregnancy
Pregnancy induces many changes in the cardiovascular system of the woman [1]. It is important to understand physiological changes in the cardiovascular system which occur during pregnancy and puerperium in order to be able to manage the patient during pregnancy and labor.
This includes increase in blood volume and cardiac output (CO) and reductions in systemic vascular resistance and blood pressure (BP). A 30–50% increase in CO occurs in normal pregnancy. It has been shown in various studies that the cardiac output rises early in first trimester and there is further rise during second trimester. In the third trimester, the cardiac output may rise, fall, or plateau [2]. In the postpartum period, there is rapid fall of cardiac output, and the maximum decrease is in the first 2 weeks after delivery [3].
Heart rate starts rising at 20 weeks and peaks at 32 weeks, there after it plateaus and falls to normal within 1 week of delivery. Plasma volume reaches a maximum of 40% above baseline at 24 weeks gestation. Blood pressure falls during first and second trimester due to vasodilatation. The diastolic blood pressure may rise in third trimester and normalizes during early postpartum period.
Pregnancy leads to increase in concentration of fibrinogen, platelet adhesiveness, and other coagulation factors, thus increasing the risk of thromboembolism in pregnancy. These physiological adaptations influence the evaluation and interpretation of cardiac function and clinical status.
There are additional changes in the hemodynamics during labor and postpartum period due to positioning of patient, pain, anxiety, and other complications of labor. Choice of analgesia and anesthesia is limited by these changes. SBP and DBP also increase, during uterine contractions. CO increases by 15% in early labor, by 25% during stage 1, and by 50% during expulsive effort [4]. These changes become more rapid and abrupt during labor and delivery. Major threat to the pregnant lady is during labor and delivery. Labor produces rapid and severe hemodynamic changes. Thus labor may become very complex, so these women should preferably be delivered in an institute where multidisciplinary care is available. The team should comprise of obstetrician trained in managing these cases, anesthetist, cardiologist, and neonatologist.
8.3 Diagnosis of Heart Disease
History of dyspnea is important in identifying the clinical status. As a general rule, asymptomatic patients will have a good pregnancy outcome. Many of the normal symptoms of pregnancy, such as dyspnea on exertion, orthopnea, palpitations, giddiness, and ankle edema, are also symptoms of cardiac decompensation. However, chest pain, dyspnea at rest, and paroxysmal nocturnal dyspnea are not commonly seen with pregnancy, and patient should be evaluated for heart disease [5]. However relatively asymptomatic patients with conditions like primary pulmonary hypertension, Eisenmenger’s syndrome, or stenotic lesions of valves may have an acute deterioration also in the form of varied symptoms. On examination, patient may have jugular venous distension, prominent apical impulses, and presence of third heart sound and murmurs. Diastolic murmurs are rare in normal pregnancy [6]. Detailed physical and cardiovascular examination is needed in case of systolic murmurs of more than 2/6 intensity or continuous murmurs. Presence of heart failure or cyanosis suggests a high-risk pregnancy. ECG and chest x-ray complement the diagnosis and can diagnose complications like heart blocks and heart failure. Echocardiography forms the mainstay of diagnosis and should be carried out in all pregnant women with suspected heart disease. Cardiac catheterization is usually avoided in pregnant women due to the risks associated with radiation exposure. However it may be carried out in patients with suspected coronary artery disease and as part of therapeutic procedures like balloon mitral valvotomy.
8.4 Prepregnancy Counseling
Prepregnancy counseling should be carried out by a joint obstetrics and cardiology team. The maternal risk depends on the underlying condition. According to the Task Force recommendations, maternal risk assessment should be carried out according to the modified World Health Organization (WHO) risk classification [7]. This risk classification is based on the underlying heart disease and any other comorbidity. It also includes contraindications for pregnancy where medical termination of pregnancy is advised. CARPREG and ZAHARA risk scores/predictors are also used by many physicians for predicting maternal cardiovascular complications during pregnancy and neonatal outcome [8, 9]. Conditions that are very high risk include primary pulmonary hypertension; Eisenmenger’s syndrome; dilated cardiomyopathy with left ventricular ejection fraction <40%; symptomatic obstructive lesions like aortic stenosis, mitral stenosis, pulmonary stenosis, and coarctation of the aorta; Marfan syndrome with aortic root diameter >40 mm; cyanotic lesions; and women with mechanical prosthetic valves [1]. In contrast, patients with regurgitant lesions like mitral and aortic regurgitation who have normal left ventricular functions, left to right shunt lesions like atrial and ventricular septal defects, hypertrophic cardiomyopathy, surgically corrected congenital heart disease, and mild stenotic lesions have relatively uncomplicated pregnancies [1, 10–15]. Diseases affecting the aorta like Takayasu arteritis are usually well tolerated unless there is severe aortic obstruction, coronary involvement, or aortic regurgitation [16]. Patients with heart block may need pacemaker implantation. In patients who already have an implanted pacemaker, interrogation of pacemaker should be carried out by the cardiologist to confirm the parameters [17]. Girls with congenital heart disease should be referred to a joint cardiac/obstetric/gynecological clinic for advice about contraception and need for preconception counseling once they decide to plan pregnancy [18].
8.5 Risk Classification in Pregnancy and Heart Disease
Various criteria for risk stratification have been described. Most commonly used is the modified World Health Organization (WHO) risk classification [7, 19]. This risk classification includes all maternal cardiovascular lesions. According to this, very low-risk patients fall in WHO class I and need only 1–2 cardiology visits during pregnancy. Low- and moderate-risk patients fall in WHO class II and cardiology consultation should be carried out in each trimester. High-risk women fall in WHO class III. Monthly or bimonthly cardiology visits are recommended. Women in WHO class IV are at very high risk and should be advised against pregnancy. In case they present early in pregnancy, medical termination of pregnancy should be advised.
The conditions which are considered high risk for the mother and fetus are mitral stenosis with NYHA class II, III, or IV symptoms; mitral regurgitation with NYHA class III or IV symptoms; severe aortic stenosis with or without symptoms; aortic valve disease, mitral valve disease, or both resulting in pulmonary hypertension; aortic valve disease, mitral valve disease, or both with left ventricular ejection fraction less than 40%; Eisenmenger’s syndrome; Marfan syndrome; primary pulmonary hypertension and maternal cyanosis.
Asymptomatic aortic stenosis; aortic regurgitation with NYHA class I or II symptoms and normal left ventricular systolic function; mitral regurgitation with NYHA class I or II symptoms and normal left ventricular systolic function; mitral valve prolapsed, with no regurgitation or with mild-to-moderate regurgitation and normal left ventricular systolic function; mild-to-moderate mitral stenosis; and mild-to-moderate pulmonary valve stenosis are better tolerated during pregnancy and are considered low risk [1].
8.6 Antenatal Care
Antenatal care should involve a multidisciplinary team including senior obstetrician, cardiologist, and anesthetist. High-risk patients should be identified by using different risk scores (WHO score is recommended) and all aspects of their management including optimization of drug therapy, anticoagulation, timing and mode of delivery, and use of analgesia during labor should be decided before she goes into labor. Every antenatal checkup should include a detailed maternal obstetric, cardiovascular, and fetal assessment. A plan of management for mode of delivery, timing of delivery, and intrapartum care including need for invasive monitoring, cutting short second stage of labor, and need of oxytocics should be made at 34–36 weeks of pregnancy. The plan should also include postpartum care including need for thrombosis prophylaxis wherever required [18].
8.7 Timing and Mode of Delivery
Labor may precipitate decompensation in any type of heart lesion. There is a standard cardiac care which must be provided to all patients. Generally the mode of delivery is based on obstetrical indications only. However there are a few indications for elective cesarean in women with heart disease. These are aortic root diameter >4.5 cm, severe aortic stenosis, aortic dissection, and recent myocardial infarction [1]. Timing of delivery depends upon primary heart lesion, associated comorbid conditions, and other complications of pregnancy. Induction of labor is not contraindicated. Use of PGE2, mechanical dilators, and PGE1 is not contraindicated but should be used with caution. We prefer to plan the delivery at around 39 weeks in uncomplicated pregnancies in order to ensure optimum perinatal and maternal outcome.
8.8 Care During Labor
Maintenance of hemodynamic stability should be the main aim. Each cardiac condition needs specific considerations to achieve this aim.
General principles: Propped-up position and oxygen supplementation help in women who are breathless. Fluid intake should be restricted and should not be more than 70 mL/h. Pain relief during labor is essential to prevent tachycardia, and drugs like morphine and tramadol can be administered. Epidural analgesia can be provided with special care to prevent hypotension.
Artificial rupture of membranes should be avoided to augment labor. Infective endocarditis prophylaxis is not recommended for any genitourinary procedure anymore. However, when endocarditis occurs during pregnancy, maternal and fetal mortality rates are 22 and 25%, and variable incidence of bacteremia has been reported by various authors. The incidence can vary from 5 to 19% [20–22].
The ACC/AHA guidelines recommend against prophylaxis in cesarean and vaginal deliveries, but due to paucity of data from India and as such high incidence of infection, individualized decision should be taken by the consultant in charge after assessing the need for it. However it is recommended during vaginal delivery/cesarean in women with prosthetic heart valves and cyanotic heart disease and in those with previous history of infective endocarditis [23, 24]. The cost of treatment, morbidity, and mortality of infective endocarditis to the patient is so high that routinely giving prophylaxis to every woman in labor is not that unjustified especially in our settings. Prophylaxis consists of antibiotics using the AHA guidelines of ampicillin 2.0 g IM or IV plus gentamicin 1.5 mg/kg (not to exceed 120 mg) given at initiation of labor or within 30 min of a cesarean delivery, followed by ampicillin 1 g IM or IV or amoxicillin 1 g orally 6 h later. Vancomycin 1.0 g IV over 1–2 h is recommended for penicillin-sensitive patients.
Second stage of labor puts additional stress on mother’s heart, so bearing down efforts should be avoided, and instrumental delivery to cut down second stage of labor is recommended. Active management of third stage of labor should be done. Ergotamine is contraindicated as it produces severe peripheral vasoconstriction. Oxytocin 10 U IM or 25 U in 500 mL of normal saline can be given. Blood pressure, pulse rate, and oxygen saturation should be continuously monitored. Chest auscultation for crepitations should be frequently carried out. This gives a quick idea of deterioration of cardiac status, blood loss, and overzealous use of diuretic and oxytocin.
8.9 Postpartum Care
Low-dose oxytocin infusion (10 U in 500 mL of normal saline) that avoids hypotension should be administered after placental delivery to prevent hemorrhage. Prostaglandin F analogues are useful to treat postpartum hemorrhage, unless an increase in pulmonary artery pressure is undesirable. Early ambulation and elastic stockings reduce the risk of deep vein thrombosis. Heart failure can develop in the first day after delivery due to rapid fluid shifts and hemodynamic stresses. Close monitoring should be continued for at least 24 h after delivery.
8.10 Special Situations
Mitral stenosis: Fluid overload should be prevented in mitral stenosis. Regular monitoring of respiratory rate, auscultation of chest, use of concentrated, titrated doses of Pitocin, and maintaining an input-output record are essential. Tachycardia can precipitate pulmonary edema and atrial fibrillation. Diuretic administration after delivery of the baby reduces the excess preload to the left atrium which it cannot handle in presence of mitral stenosis [10, 15]. In symptomatic patients with severe mitral stenosis, balloon mitral valvotomy or closed mitral valvotomy provides immediate relief [25]. It is however associated with risk of precipitating preterm labor.
Aortic and mitral regurgitant lesions: They are generally well tolerated and may not require aggressive monitoring unless there is left ventricular dysfunction or pulmonary hypertension.
Congenital heart disease: Patients with severe aortic stenosis, primary pulmonary hypertension, Eisenmenger’s syndrome, cyanotic congenital heart diseases like tetralogy of Fallot, and Ebstein’s anomaly are at high risk and should be closely monitored [26]. The main aim during labor is to prevent hypotension. Maternal and perinatal outcome is better in patients who have been successfully operated in childhood [13].Prosthetic heart valves: Patients with mechanical prosthetic heart valves are at risk for complications like valve thrombosis, thromboembolism, and bleeding due to anticoagulation. Bioprosthetic valves on the other hand are associated with the risk of valve failure during pregnancy. Both types of valves lead to increased risk of endocarditis. The major issue with prosthetic valves in pregnant women is the risk of thrombosis as pregnancy is a hypercoagulable state. Therefore pregnant women with prosthetic heart valves need careful planning and counseling about anticoagulant usage. The preferred treatment for adequate anticoagulation is in the form of vitamin K antagonists (e.g., warfarin) which are associated with risk of warfarin embryopathy when used in the first trimester. A reasonable option is to use unfractionated heparin/low molecular weight heparin in the first trimester and then switch over to warfarin till the 36th week [1, 27–29]. Warfarin should be switched back again to unfractionated heparin from the 36th week since the anticoagulant effect of heparin can be rapidly reversed. Unfractionated heparin should be discontinued 4–6 h before planned delivery and restarted 4–6 h after delivery if there are no bleeding complications. If urgent delivery is needed for a patient on unfractionated heparin, protamine may be used to reverse the anticoagulant effect. If urgent delivery is needed in a patient who is on warfarin; cesarean delivery is preferred to reduce risk of intracranial hemorrhage in an anticoagulated fetus. Fresh frozen plasma may be used prior to cesarean delivery to achieve a target INR of ≤2.4. The guidelines recommend use of low molecular weight heparin also instead of unfractionated heparin. With the use of low molecular weight heparin, it is mandatory to measure anti-factor Xa activity [1]. If this investigation is not available in our setting, low molecular weight heparin should not be used. In patients who develop stuck valve doe to thrombus formation, thrombolysis is a reasonable alternative to redo valve surgery [30].
Cardiomyopathies: Cardiomyopathies, though rare disorders, commonly affect young people and are thus encountered in pregnancy. Of these dilated, peripartum and restrictive cardiomyopathies may cause severe complications in pregnancy, while hypertrophic cardiomyopathy is usually well tolerated even in the presence of left ventricular outflow tract obstruction [14, 31, 32]. Peripartum cardiomyopathy is a unique cardiomyopathy that usually occurs in the last month of pregnancy or the early postpartum period. The mainstay of treatment of dilated and peripartum cardiomyopathies is drug therapy with beta-blockers, angiotensin-converting enzyme inhibitors, aldosterone antagonists, and loop diuretics. Out of these angiotensin-converting enzyme inhibitors and aldosterone antagonists are contraindicated during pregnancy and can only be started postpartum. In case of acute deterioration, these patients have to be managed on lines of acute heart failure with propped-up position, oxygen, loop diuretics, digoxin, inotropes in case of hypotension or low cardiac output, and in severe cases mechanical supportive therapy [15].
8.11 Contraception
Care of women with heart disease is incomplete without providing adequate contraception advice. Risks of contraceptive use should be weighed against the risk of pregnancy. Barrier contraceptive is the safest for the woman but is associated with high risk of failure. A copper-containing intrauterine device can be inserted either post-placentally or after 6 weeks. Under aseptic precautions, the risk of infective endocarditis is very low [33]. Risks of excessive bleeding during menstruation should be explained especially to women on anticoagulants [1].
Levonorgestrel releasing intrauterine device is the safest and most effective contraceptive in women with complex heart lesions including cyanotic congenital heart disease and pulmonary hypertension. Low-dose oral contraceptives containing 20 mg of ethinyl estradiol are safe in women with a low thrombotic risk, but not in women at high risk for thrombotic complications, and generally they should be avoided. Monthly injectables containing medroxyprogesterone acetate should not be used in women with heart failure. This is due to fluid retention that they may cause. Tubal ligation is usually safe, even in relatively high-risk women. Vasectomy should be discussed with patients who have completed their family [34].
8.12 Conclusion
Pregnant women with heart disease pose challenges in cardiac and maternal-fetal management. Successful pregnancies can be achieved with good prenatal counseling, adequate antenatal care, and intensive monitoring during labor by cardio-obstetric team. Close collaboration between the obstetrician and cardiologist is required for optimal management of women with heart disease.
8.13 Points to Ponder
Box 1: Care During Pregnancy
Refer the patient to an institute where cardiology services are available.
Supervision by obstetrician and cardiologist jointly as a team.
Early decision for MTP (if indicated).
Change of drugs to safer alternatives.
Regular at least two weekly visits in antenatal clinic (medical surgical unit).
Admission in case of any cardiac indication or pregnancy complication.
Low threshold for admission.
Make a plan in third trimester for timing and mode of delivery.
Anesthesia consultation for labor analgesia and anesthesia in case of cesarean section.
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