26. Pregnancy and heart disease
- Introduction. Pregnancy produces a number of alterations in cardiovascular function. The end result of these alterations is increased cardiac work. The patient with heart disease who becomes pregnant, therefore, places two stresses on her heart: the demands of pregnancy and the demands of heart disease. To understand the effect of pregnancy on forms of heart disease, it is necessary to understand the cardiovascular alterations imposed by pregnancy.
- Cardiac and circulatory changes with normal pregnancy. Pregnancy results in increased cardiac output, heart rate, blood volume, peripheral venous pressure, and right-sided heart pressures (Table 26-1).
- Cardiac output rises progressively during pregnancy. By 32 weeks of pregnancy, resting cardiac output and blood volume are increased by approximately 50%.
- Increases in cardiac output are the result of increases in both stroke volume and heart rate.
- Increases in resting heart rate during pregnancy average approximately 10 beats per minute at term.
- Blood volume rises approximately 40% to 50% during normal pregnancy. Most of this increase represents an augmentation of plasma volume. Hemoglobin concentration therefore diminishes during pregnancy.
- Peripheral vascular resistance decreases during pregnancy, but arterial blood pressure changes relatively little because cardiac output increases.
- Peripheral venous pressure increases during pregnancy, particularly in the legs, because of pressure from the enlarging uterus on the inferior vena cava.
- Greater peripheral venous pressure commonly results in peripheral edema, hemorrhoids, and varicose veins even in healthy pregnant women.
- Total body water increases during pregnancy.
- Right-sided heart pressures are modestly elevated at rest in healthy pregnant women. Left-sided heart pressures are unaffected by pregnancy.
- Labor with attendant anxiety, exertion, and recurrent Valsalva maneuvers produces marked increases in systemic arterial and venous pressures, right ventricular pressure, heart rate, and cardiac output. All these alterations disappear after delivery. Blood volume and venous pressure return to normal almost immediately after delivery. Other parameters return to normal within hours to days after delivery.
- Alterations in clinically observable phenomena. During pregnancy, the physiologic alterations just noted produce a number of changes in the physical examination, ECG, chest x-ray film, and echocardiogram of the healthy pregnant woman.
- Physical examination. Systolic murmurs and continuous venous flow murmurs of no clinical significance are often heard during pregnancy. Diastolic murmurs occur rarely and usually signify the presence of heart disease. The intensity of P2 is increased, and a physiologic third heart sound also may be present. Peripheral edema is a common concomitant of normal pregnancies. Physical findings that may be observed in healthy pregnant women are recorded in Table 26-2.
- ECG. The ECG remains normal during pregnancy, but some modest changes occur: increased heart rate, shift of the frontal plane axis to the left, and minor T wave changes. Occasional atrial or ventricular premature beats do not imply that organic heart disease is present (Table 26-3).
- Chest x-ray examination. Radiographic studies should be kept to a minimum in pregnant women to protect the fetus from radiation. Chest x-ray pictures remain normal in healthy pregnant women with clear lung fields and normal heart size. Pulmonary blood vessels become more prominent secondary to increased blood volume (Table 26-3).
- Echocardiogram. Modest changes within the range of normal are noted in the echocardiograms of healthy pregnant women. Thus, heart rate increases, and left and right ventricular end-diastolic dimensions and left ventricular mass increase (Table 26-3).
- Effect of pregnancy on patients with heart disease. The circulatory changes that occur in healthy pregnant women (Table 26-1) represent an additional strain on the cardiovascular system of women with preexisting heart disease. Symptoms and signs of heart disease usually increase during pregnancy. In general, patients with heart disease can expect worsening by one clinical class during pregnancy. Thus, patients who are New York Heart Association (NYHA) class I before pregnancy develop class II symptoms during pregnancy. Individuals who are class II before pregnancy move into class III during pregnancy, and so forth. Specific forms of heart disease may require medical or even surgical therapy during pregnancy.
- Valvular heart disease. Valvular heart disease is the most common cardiovascular condition in pregnant women, with mitral stenosis predominant. Murmurs of valvular heart disease increase in intensity during pregnancy and are sometimes first noticed at this time. Risk to the fetus and mother increases with increasing clinical class, being in an acceptable range only for patients who are class I or II before pregnancy. Potential complications in pregnant patients with valvular heart disease include pulmonary edema, infectious endocarditis, pulmonary embolism, and supraventricular arrhythmias. A number of women with prosthetic heart valves have had successful pregnancies. Problems in these individuals usually revolve around managing their anticoagulation during pregnancy, delivery, and postpartum (see Section V.A.3.).
- Congenital heart disease. Women with repaired congential heart defects usually have no difficulty with pregnancy; however, women with pulmonary hypertension are at high risk for sudden death during pregnancy. For these women, pregnancy should be avoided or terminated. Patients with Eisenmenger's syndrome can expect a mortality of approximately 25% from pregnancy, regardless of the underlying congenital defect. Very few of such individuals carry a fetus successfully to term. Women with unrepaired asymptomatic or minimally symptomatic congenital heart disease usually do well during pregnancy. Patients with cyanotic congenital heart disease are at increased risk for fetal and/or maternal morbidity and mortality.
Women with coarctation of the aorta and Marfan's syndrome have an increased risk of aortic rupture or dissection during pregnancy.
- Pulmonary embolism. Pregnancy increases the risk of women with or without heart disease to develop venous thrombosis and pulmonary embolism. Anticoagulation is often difficult to manage in such patients (see Section V.A.3.).
- Perinatal cardiomyopathy. An unusual entity is primary myocardial disease occurring late in pregnancy or in the early postpartum period (postpartum or perinatal cardiomyopathy; see Chapter 18). This entity occurs more often in multiparous malnourished women, especially if the pregnancy has been complicated by toxemia. Arterial and venous embolism and left ventricular failure are common in these women, with resultant high mortality.
- Hypertension. Elevated arterial blood pressure deserves careful attention during pregnancy because toxemia may develop with resultant high risk for the patient and her fetus. Blood pressure, urinalysis, and even serum blood urea nitrogen or creatinine should be monitored regularly. If acceleration in hypertension occurs (toxemia) with attendant edema, albuminuria, or retinal changes, the patient should be admitted to the hospital for urgent therapy (see Section V.A.5.).
- Management of pregnant women with heart disease
- Medical treatment
- Heart failure. Signs and symptoms of heart failure in the pregnant patient with heart disease should be managed by decreased activity (or even a brief period of bed rest), decreased salt intake, digitalization, and diuresis (see Chapter 4). Afterload reduction may be administered in the form of oral hydralazine. Angiotensin-converting enzyme inhibitors should not be given because they increase the incidence of stillbirths. Interruption of the pregnancy should be considered and discussed with the obstetrician if heart failure is refractory to medical therapy or difficult to manage. Patients with stabilized heart failure often fare best if hospitalized during the final 2 to 3 weeks of their pregnancy.
- Cardiac arrhythmias. Pregnant patients with heart disease are prone to develop supraventricular and ventricular arrhythmias. Arrhythmias are usually best managed in the hospital with conventional therapies (see Chapter 3). Electrical cardioversion and pacemakers can be used as required, with the same indications and precautions as in nonpregnant patients. Amiodarone is contraindicated, but beta-blockers or verapamil may be administered.
- Anticoagulation. Pregnant patients with deep venous thrombosis, pulmonary or arterial embolism, or prosthetic heart valves should be treated with anticoagulants. Heparin is the drug of choice: Because the molecule is too large to cross the placenta, the fetus is protected from simultaneous anticoagulation. Anticoagulation therapy should be discontinued for 1 to 3 days before delivery. Subcutaneous low-molecular-weight heparin is particularly useful in pregnant patients because of ease of administration and efficacy.
Long-term (greater than 1 to 2 months) heparin therapy results in osteoporosis. Therefore, patients with prosthetic heart valves or those in whom anticoagulation must continue for more than 2 months should receive oral anticoagulants (warfarin).
- Because warfarin crosses the placenta, it should be avoided during the first trimester, when it predisposes to hemorrhage and fetal developmental abnormalities. The drug should be stopped again during the last 3 weeks before term to allow fetal clotting mechanisms to return to normal before delivery. Heparin (usually subcutaneous low-molecular-weight heparin) is substituted for warfarin during periods when the latter is discontinued.
- Oral anticoagulants can be restarted after delivery, but patients should not breast-feed because warfarin is excreted in the milk.
- Antibiotic prophylaxis. Patients with valvular and congenital heart disease (except atrial septal defect) and an infection involving the reproductive organs or vagina should receive 600,000 U of procaine penicillin twice a day, starting with the onset of labor, together with 1 g of intramuscular streptomycin daily, beginning immediately after delivery. Both antibiotics are continued for 3 days. Alternative antibiotic regimens for penicillin-sensitive individuals are listed in Chapter 16. Patients who do not have vaginal or reproductive organ infections do not require endocarditis prophylaxis.
- Antihypertensive therapy. Patients who are hypertensive during pregnancy should be treated in an effort to prevent toxemia. The drug regimens used usually involve some combination of alpha-methyl-dopa, beta-blockers, diuretics, verapamil, and/or hydralazine (see Chapter 12).
Patients with toxemia should be admitted to the hospital and treated vigorously (antihypertensive or anti–heart failure regimens or both). Renal function should be monitored closely (see Chapter 13).
- Interruption of pregnancy. Therapeutic abortion should be considered for patients with pulmonary hypertension or symptoms of NYHA class III (moderately severe) or IV (severe) heart failure or angina during the first trimester.
- Delivery. Cesarean section or forceps-assisted delivery is usually not necessary, even for symptomatic patients. Vaginal delivery is usually preferred, with caesarian section reserved for patients with obstetrical indications for this intervention.
- A number of drugs commonly used during labor are relatively contraindicated in patients with heart disease (e.g., atropine, scopolamine, and ergot derivatives).
- Early ambulation is encouraged after delivery to decrease the risk of deep venous thrombosis and pulmonary embolism.
- Cardiac surgery. Cardiac surgical intervention during pregnancy carries an increased risk for both mother and fetus. Fortunately, it is rarely necessary.
Mitral valvuloplasty or replacement is the most common cardiac surgical procedure considered during pregnancy. Surgery should be performed only in women with severe disabling signs and symptoms of pulmonary congestion despite intensive medical therapy. Balloon valvuloplasty can usually be performed safely during pregnancy in patients who become markedly symptomatic.
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