Pregnancy and Cardiovascular Disease
Amanda R. Vest
Brian P. Griffin
Russell E. Raymond
I. INTRODUCTION.
Maternal cardiac disease is a major risk factor for nonobstetric mortality and morbidity in pregnant women. Substantial progress in the management of congenital heart disease has occurred over recent decades, so the majority of females born with heart defects now survive into their reproductive years. Advances in obstetrics have also enabled pregnancy in older mothers in whom hypertension and acquired heart disease are more prevalent and can pose challenges for the pregnancy. Rheumatic heart disease is less common than in the past, but is still encountered, especially in immigrant populations in the United States, and may manifest clinically for the first time in pregnancy. Cardiac disease has significant bearing on both maternal and fetal outcomes, and it is therefore essential that cardiologists and internists have a working knowledge of the impact of pregnancy on various cardiac diseases on pregnancy and can tailor management appropriately. In most cases, the presence of maternal heart disease does not preclude successful pregnancy, although thorough discussion and planning regarding risks and management strategies should begin prior to conception wherever possible.
II. NORMAL PHYSIOLOGIC CHANGES DURING PREGNANCY.
A series of cardiocirculatory changes occur in pregnancy and peripartum. These changes usually begin during the early first trimester (5 to 8 weeks), peak in the late second trimester, and tend to plateau thereafter until the postpartum period. This second trimester peak in hemodynamic adaptations tends to correlate with the onset of clinical manifestations of cardiac complications during pregnancy.
A. The increase in blood volume during pregnancy is attributed to estrogen-mediated stimulation of the renin—aldosterone system, leading to salt and water retention along with various other maternal and placental hormones. The plasma volume expansion varies from 20% to 100% and averages around 50%. The relatively greater increase in plasma volume as compared with red blood cell mass leads to the physiologic anemia of pregnancy, which usually manifests around 30 weeks.
B. Cardiac output, stroke volume, and heart rate. Table 38.1 summarizes the changes in heart rate, stroke volume, and cardiac output. The cardiac output is estimated to increase by approximately 30% to 50% above baseline. The increase is attributed to higher preload as a result of increased blood volume, decreased systemic vascular resistance, and an increase in maternal heart rate by 10 to 15 beats/min. During the third trimester, stroke volume and cardiac output are dependent on body position and increase in the lateral position (particularly left lateral) and decline in the supine position due to compression of the inferior vena cava by the gravid uterus.
C. Blood pressure and systemic vascular resistance. The decline in systemic vascular resistance causes blood pressure to begin to fall in the first trimester and reach a nadir of about 10 mm Hg below baseline by the end of the second trimester. The pulse pressure widens due to the greater fall in diastolic blood pressure than in systolic pressure. As many as 11% of women develop the uterocaval syndrome of pregnancy, with a significant and symptomatic drop in blood pressure when lying supine
due to vena caval compression. Weakening of the vascular walls of the medium and large muscular arteries occurs because of decreased collagen deposition due to estrogen release and the effects of circulating elastase and relaxin. This makes pregnant women more susceptible to aortic dissection, especially in individuals with abnormally weak aortic tissue such as in Marfan syndrome. The addition of low-resistance vessels in the uteroplacental bed also contributes to the decrease in afterload.
due to vena caval compression. Weakening of the vascular walls of the medium and large muscular arteries occurs because of decreased collagen deposition due to estrogen release and the effects of circulating elastase and relaxin. This makes pregnant women more susceptible to aortic dissection, especially in individuals with abnormally weak aortic tissue such as in Marfan syndrome. The addition of low-resistance vessels in the uteroplacental bed also contributes to the decrease in afterload.
TABLE 38.1 Normal Hemodynamic Changes during Pregnancy and Postpartum Period | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
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D. A hypercoagulable state with decreased protein S, increased stasis, and venous hypertension is also observed.
E. Hemodynamic changes during labor and delivery. Each uterine contraction displaces about 300 to 500 mL of blood into the maternal general circulation (autotransfusion). There is an increase in stroke volume and heart rate, with cardiac output increasing by approximately 75% above baseline during contractions. Blood pressure and oxygen consumption also rise. The magnitude of these changes will be influenced by the mode of delivery—vaginal versus cesarean section—and also by the method of anesthesia and analgesia.
F. Hemodynamic changes postpartum. Despite the blood loss during delivery (averaging 300 to 400 mL for vaginal delivery and 500 to 800 mL for cesarean section), there is a temporary increase in effective venous return due to the relief of caval compression and autotransfusion. This may lead to an increase in stroke volume and cardiac output, resulting in augmentation in renal blood flow and a brisk diuresis. In women with preexisting cardiac disease, these rapid hemodynamic shifts may cause profound clinical deterioration. The hemodynamic changes associated with pregnancy usually persist for a few weeks postpartum and it may take up to 12 to 24 weeks for the parameters to return to their prepregnancy baseline.
III. CARDIOVASCULAR EVALUATION IN PREGNANCY
A. History. Fatigue, dyspnea, ankle swelling, and reduced exertional capacity are common in normal pregnancy and can mimic cardiac disease. Chest pain, orthopnea, or paroxysmal nocturnal dyspnea may represent cardiac pathology.
B. Physical examination. Table 38.2 highlights the important cardiac findings in normal pregnancy. Signs of jugular venous distention, displaced point of maximal
impulse, and peripheral edema are common in normal pregnancy. Normal auscultatory findings in pregnancy include exaggerated physiologic splitting of S2, a physiologic S3, a physiologic systolic murmur in the pulmonic area, and the continuous murmurs of “mammary soufflé” or a cervical venous hum. Examination findings that are not physiologic include an S4, a loud systolic murmur, a purely diastolic murmur, and fixed splitting of S2 or pulmonary crackles.
impulse, and peripheral edema are common in normal pregnancy. Normal auscultatory findings in pregnancy include exaggerated physiologic splitting of S2, a physiologic S3, a physiologic systolic murmur in the pulmonic area, and the continuous murmurs of “mammary soufflé” or a cervical venous hum. Examination findings that are not physiologic include an S4, a loud systolic murmur, a purely diastolic murmur, and fixed splitting of S2 or pulmonary crackles.
C. Noninvasive testing with echocardiography is considered safe in pregnancy and findings are as given in Table 38.2. Chest radiography should be performed only when absolutely necessary and with shielding of the pelvic area with protective lead. Magnetic resonance imaging is sometimes used for the diagnosis of cardiac disorders; its safety profile in pregnancy is unknown, and it should be avoided if possible.
TABLE 38.2 Findings in Normal Pregnancy | |||||||||||||||||||||||||||||
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D. Invasive testing with pulmonary artery catheterization (without fluoroscopy) can be utilized during pregnancy, labor, delivery, and the postpartum period for invasive monitoring and can be very useful for patients who suffer hemodynamic deterioration. Cardiac catheterization during pregnancy is rarely needed, except in the setting of acute myocardial infarction (MI) or to permit balloon valvuloplasty. Fluoroscopy and cine time should be minimized and direct irradiation to the fetus avoided. Vascular access from the arm rather than the leg is preferred whenever feasible.
IV. RISK ASSESSMENT AND GENERAL PRINCIPLES OF MANAGEMENT.
One of the most important steps in managing a patient with heart disease who is considering pregnancy is to establish the level of maternal and fetal risk. This involves a multidisciplinary approach, with preconception counseling, contraception advice, and discussion of potential maternal and fetal acute and long-term morbidity and mortality. Baseline functional class, severity of cardiac disease, left ventricular function, and pulmonary pressures should guide the risk assessment. Table 38.3 delineates a stepwise approach for management of women with preexisting cardiac disease, and Table 38.4 lists highrisk predictors. Maternal New York Heart Association (NYHA) class II symptoms or higher, left ventricular ejection fraction < 40% or left-sided obstruction are factors known to be predictive of neonatal complications, including premature birth,
intrauterine growth restriction, respiratory distress syndrome, and death. Formal risk prediction scores include Cardiac Disease in Pregnancy (CARPREG), which is composed of four clinical features (prior arrhythmia or cardiac event, NYHA functional class > II or cyanosis, left heart obstruction, systemic left ventricular dysfunction with LVEF < 40%) with maternal cardiac event rates of 5%, 27%, and 75% for 0, 1, and > 1 of the features, respectively, and the more recent ZAHARA predictors derived from a large population of congenital heart disease patients.
intrauterine growth restriction, respiratory distress syndrome, and death. Formal risk prediction scores include Cardiac Disease in Pregnancy (CARPREG), which is composed of four clinical features (prior arrhythmia or cardiac event, NYHA functional class > II or cyanosis, left heart obstruction, systemic left ventricular dysfunction with LVEF < 40%) with maternal cardiac event rates of 5%, 27%, and 75% for 0, 1, and > 1 of the features, respectively, and the more recent ZAHARA predictors derived from a large population of congenital heart disease patients.
TABLE 38.3 Basic Management Principles for Pregnant Women with Valvular Heart Disease | ||||||||||||||||||||||||||||||||||||||||||||||||||||
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TABLE 38.4 Risk Predictors of Adverse Maternal and Fetal Outcomes | ||||||||||
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Management of the pregnant patient with heart disease is a team effort involving the patient’s primary care physician, high-risk obstetric team, and cardiologist, with active participation of the patients. Prophylactic intervention for cardiac lesions that significantly increase the risk of pregnancy should be performed where appropriate and feasible before pregnancy is contemplated. Most patients with relatively low-risk cardiac conditions are successfully managed throughout pregnancy, labor, and delivery with conservative medical measures designed to optimize intravascular volume and systemic
loading conditions. Simple measures help, such as bed rest and avoidance of the supine position. Medications should be used judiciously and only when absolutely required during pregnancy. Drugs that are contraindicated in pregnancy should be discontinued before conception if pregnancy is contemplated. In certain conditions such as cyanotic congenital heart disease, Eisenmenger syndrome, or severe pulmonary hypertension, pregnancy should be strongly discouraged, as patients with these conditions do not tolerate the hemodynamic changes of pregnancy.
loading conditions. Simple measures help, such as bed rest and avoidance of the supine position. Medications should be used judiciously and only when absolutely required during pregnancy. Drugs that are contraindicated in pregnancy should be discontinued before conception if pregnancy is contemplated. In certain conditions such as cyanotic congenital heart disease, Eisenmenger syndrome, or severe pulmonary hypertension, pregnancy should be strongly discouraged, as patients with these conditions do not tolerate the hemodynamic changes of pregnancy.
Specific lesions and their management in pregnancy are described later. The list, although extensive, is not complete, as a detailed description of every lesion is beyond the scope of this chapter.
V. PREGNANCY IN WOMEN WITH CONGENITAL HEART DISEASE.
In general, patients with noncyanotic congenital heart disease have a better outcome with pregnancy compared with patients with cyanotic disease. Where applicable, patients should be made aware of the potential inheritability of the congenital disease. The 2007 American Heart Association (AHA) endocarditis guidelines do not recommend the use of prophylactic antibiotics for vaginal delivery, even in high-risk patients, such as those with complex congenital heart disease or surgically constructed systemic—pulmonary shunts. However, owing to the difficulty in predicting complicated deliveries and the potential complications of endocarditis, some authors still suggest antibiotic prophylaxis as reasonable for all patients with congenital heart disease, except in isolated secundum atrial septal defects (ASDs) and corrected patent ductus arteriosus (PDA). The 2008 American College of Cardiology/AHA (ACC/AHA) guidelines on the management of adults with congenital heart disease do suggest antibiotics at the time of membrane rupture prior to vaginal delivery for patients with prosthetic cardiac material or unrepaired/palliated cyanotic defects.
A. ASD and patent foramen ovale (PFO).
Isolated ASD or PFO is usually well tolerated in pregnancy and considered low risk in general. Paradoxical pulmonary embolism during pregnancy has been reported. Ideally, an ASD with a significant shunt (> 1.5:1) should be corrected prior to pregnancy. Secundum ASD that is repaired prior to pregnancy is not associated with an increased risk of complications.
B. Ventricular septal defect (VSD).
Isolated VSD without pulmonary hypertension is usually well tolerated during pregnancy, and correction of VSD prior to pregnancy and before development of pulmonary hypertension eliminates the risk. In pregnant patients with VSD and pulmonary hypertension, a drop in blood pressure during or after delivery can result in transient shunt reversal. This may be prevented by close monitoring of blood pressure, volume replacement, and the use of vasopressors, if necessary. VSD is commonly inheritable.
C. Patent ductus arteriosus.
PDA without pulmonary hypertension usually has a favorable outcome. In patients with pulmonary hypertension, the management principles are similar to those with VSD.
D. Coarctation of aorta (COA).
Coarctation, although usually associated with favorable outcomes, has been associated with severe hypertension, congestive heart failure, or aortic dissection during pregnancy. There is an association with congenitally bicuspid aortic valves (AVs). It is also associated with circle of Willis aneurysms, and cerebral hemorrhage from rupture of an aneurysm during pregnancy is possible. Limiting physical activity and controlling blood pressure may prevent complications such as cerebral hemorrhage and dissection. β-Blockers are usually the antihypertensive drugs of choice, although care should be taken not to lower the blood pressure excessively as this may compromise uteroplacental circulation. Significant COA with evidence of systemic hypertension, heart failure, or a peak gradient > 20 mm Hg should be corrected prior to pregnancy. Women who underwent prior surgical repair of a coarctation remain at risk for dissection, as the aortic wall is still abnormally weak. Correction of COA during pregnancy is indicated in patients with severe uncontrollable hypertension or heart failure and may be performed percutaneously.
E. Congenital aortic stenosis (AS).
A congenitally bicuspid AV is one of the most common causes of AS. These patients should be screened for other cardiac malformations including COA. The details of management are described later in Section VI.
F. Pulmonic stenosis.
Isolated pulmonic stenosis is usually well tolerated in pregnancy. It should be corrected prior to pregnancy if severe (peak gradient > 60 mm Hg). Percutaneous balloon valvotomy during pregnancy may be required in patients with severe right ventricular failure.
G. Ebstein anomaly.
Noncyanotic Ebstein anomaly is usually well tolerated. Cyanotic patients are at very high risk for maternal heart failure and fetal prematurity or death. During labor and delivery, care should be taken to prevent a drop in blood pressure, and close hemodynamic monitoring is required along with rest, oxygen, and blood gas monitoring. It is sometimes associated with Wolff-Parkins on-White syndrome and pregnancy may precipitate supraventricular arrhythmias.
H. Tetralogy of Fallot (TOF).
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