9

Cardiovascular Disorders*

*See also Chapter 19: Hypertensive States of Pregnancy. Cardiovascular Changes in Normal Pregnancy The major cardiocirculatory changes that occur during normal pregnancy include an increase in cardiac output and blood volume and a decrease in peripheral resistance (Table 22–1). During normal pregnancy, 6–8.5 L of fluid and 500–900 mmol of sodium are retained because of the action of progesterone, renin, aldosterone, and prolactin. A dilutional anemia occurs as a result of the greater increase in plasma volume relative to red cell mass. Renal blood flow increases by 30%, the glomerular filtration rate increases by 50%, and uterine blood flow reaches 500 mL/min at term. Hormonal changes include a rise in levels of estrogen and progesterone, renin, angiotensinogen, angiotensin II, and aldosterone and a decreased sensitivity to infused angiotensin II. Myocardial contractility increases as do heart rate and atrial and ventricle chamber size (Table 22–1). Late in pregnancy, a decrease in cardiac output has been reported when measurements are made with the patient in the supine rather than the lateral recumbent position. This apparent decrease is due to interference with venous return resulting from compression of the inferior vena cava by the gravid uterus. If the drop is dramatic enough, the patient may experience supine hypotensive syndrome, which is characterized by dizziness and even syncope on recumbency. However, the profound hypotension may represent a failure of the normal baroreceptor-mediated reflex adaptation to a fall in pressure, inadequate collateral venous circulation, and exaggerated parasympathetic response. Additional hemodynamic changes occur during the various stages of labor and delivery and depend on the patient's position, the degree of sedation, and the type of anesthesia used. Cardiac output increases by about 20% with each uterine contraction as 300–500 mL of blood is expelled from the contracting uterus. Systolic blood pressure also rises with each contraction, increasing the load on the left ventricle by 10%, while the heart rate falls. Pain, fear, and anxiety contribute further to an increase in cardiac output. These changes are less marked if the patient is in the lateral decubitus position during labor or receiving epidural anesthesia. Following delivery, depending on the amount of blood lost—usually 500 mL during vaginal delivery and 1000 mL or more with cesarean section—the cardiac output and plasma volume increase by 20–60% because of a shift of blood from the uterus and placenta into the vascular space as well as resorption of interstitial fluid. Oxytocic drugs can produce further hemodynamic changes. The hemodynamic changes of pregnancy begin to regress shortly after delivery, and pre-pregnancy levels are usually reached within 2 weeks postpartum, but may take longer. The hemodynamic changes of normal pregnancy can result in symptoms and signs that mimic those of heart disease, often making it difficult to differentiate the two (Table 22–2). It is the severity and persistence of symptoms that suggest underlying organic heart disease (Table 22–3). Heart Disease Cardiovascular disease is the most important nonobstetric cause of disability and death in pregnant women, occurring in 0.4–4% of pregnancies. The reported maternal mortality rate ranges from 0.4% in patients with New York Heart Association classifications I and II to 6.8% or higher among patients with class III and IV severity. It is not surprising that the added hemodynamic burden of pregnancy, labor, and delivery can aggravate symptoms and precipitate complications in a woman with preexisting cardiac disease. However, even a previously healthy woman may develop cardiovascular problems specifically related to pregnancy, such as preeclampsia, varicose veins, thromboembolic complications such as pulmonary emboli, aortic dissection, or shock due to hemorrhage, amniotic fluid emboli, disseminated intravascular coagulation, or sepsis. Furthermore, any woman in the childbearing years may develop incidental myocarditis, pericarditis, or infective endocarditis while she is pregnant. Drugs used for obstetric complications such as preterm labor may have adverse effects on the woman with heart disease, and drugs used for the treatment of maternal heart disease may have adverse effects on the fetus. Heart disease can be classified as congenital (operated or unoperated) or acquired. Acquired diseases can be infectious, autoimmune, degenerative, malignant, or idiopathic. Ideally, the patient with known heart disease should consult her physician before becoming pregnant in order to determine the advisability and optimum timing for pregnancy, the need for and timing of diagnostic procedures, the prospects for corrective or palliative cardiac surgery, the type of prosthetic valve to be used, and the need for discontinuing certain drugs during pregnancy. If a woman with heart disease presents for medical care after she has become pregnant, the obstetrician must be able to recognize the presence of preexisting cardiac disease, assess the degree of disability, and understand the impact of the added hemodynamic changes of pregnancy. Pre-pregnancy planning might, for instance, include performance of an exercise tolerance test to determine if the woman with severe heart disease can tolerate the added hemodynamic burden of pregnancy as well as a 3D echocardiogram to evaluate potential structural defects and the ejection fraction. The obstetrician must also be able to anticipate, prevent, diagnose, and treat complications such as arrhythmias or congestive heart failure when they arise, and advise the patient regarding discontinuation or continuation of the pregnancy and the risk of future pregnancies. Management of an obstetric patient with heart disease should be carried out by a team consisting of an obstetrician, cardiologist, and anesthesiologist. Rheumatic heart disease has historically been the most common type of heart disease in pregnant women. However, in countries where infectious causes of heart disease are generally less common, congenital heart disease now represents a larger percentage of diseases encountered. It is therefore especially important that obstetricians understand the late complications of surgically corrected or uncorrected congenital heart disease that are likely to occur during pregnancy, labor, delivery, and lactation. In addition, degenerative diseases such as ischemic heart disease are encountered more frequently due to the longer survival of patients with diabetes mellitus and chronic renal disease, the prevalence of tobacco addiction, cocaine use, and delayed childbearing. In patients with limited ability to increase cardiac output due to valvular or intrinsic myocardial disease, the added hemodynamic burden leads to symptoms early in pregnancy when blood volume has increased considerably. The normal increase in blood flow to the uterus is limited, resulting in increased incidence of spontaneous abortion, prematurity, and intrauterine growth restriction. In women with cyanotic heart disease, the incidence of spontaneous abortion may be as high as 60%, and preterm delivery and fetal growth restriction are common. Maternal risks increase with increasing age and parity and are greatest after 30 weeks' gestation. Evaluation of the Patient with Heart Disease Evaluation of the pregnant woman in whom heart disease is suspected should include a careful medical history, complete physical examination, and noninvasive laboratory tests in order to establish a diagnosis and to determine the severity of the disease in order to facilitate planning the patient's management. The degree of functional disability is graded according to the following New York Heart Association classification:   Class I: No symptoms limiting ordinary physical activity.   Class II: Slight limitation with mild to moderate activity but no symptoms at rest.   Class III: Marked limitation with less than ordinary activity; dyspnea or pain on minimal activity.   Class IV: Symptoms at rest or with minimal activity and symptoms of frank congestive heart failure. A classification such as this one that is based on symptoms is only a rough guideline and may not accurately reflect the severity of disease, and sudden and unpredictable changes in classification can occur during pregnancy. Medical History In patients with a previous diagnosis of heart disease or hypertension, the following information should be obtained: age at diagnosis and circumstances of diagnosis; previous symptoms and complications; previous diagnostic procedures, including cardiac catheterization, exercise testing, and echocardiography; prior drug treatment; timing and exact nature of operative procedures and degree of improvement achieved; residual defects, symptoms, and limitations; current medications and diet; and previously imposed prohibitions regarding activity. Medical records from previous physicians regarding previous hospitalizations, diagnostic and therapeutic procedures, and complications should also be obtained. In patients without an established diagnosis of heart disease, the intake health provider should routinely inquire about a history of rheumatic fever and other illnesses that may be related to heart disease, such as scarlet fever, systemic lupus erythematosus, pulmonary disease, renal disease, diphtheria, or pneumonia, as well as prior hospitalizations, accidents, and major operations. The physician should elicit a history of signs and symptoms such as cyanosis at birth or with exertion, squatting in childhood, multiple respiratory infections in childhood, prior arrhythmias, dyspnea at rest or on exertion, chronic cough, hemoptysis, asthma, exercise intolerance, headache, dizziness, effort syncope, chest pain, and peripheral edema. Activities or events precipitating these symptoms should be assessed. Finally, the family history of cardiovascular disease or other congenital anomalies should be ascertained, together with a history of prior fetal abnormalities. In patients from developing countries, a history of exposure to tuberculosis, hepatitis, and rickettsial and parasitic infections should also be obtained. Physical Examination On physical examination, note should be made of height, weight, and body build; any facial, digital, or skeletal abnormalities that suggest congenital anomalies; and skin changes such as cyanosis, pallor, angiomas, pigmentation, xanthelasmas, and xanthomas. The blood pressure should be carefully measured with an appropriately sized cuff and, if elevated, repeated measurements should be made in both arms and in several positions. The radial pulses should be carefully palpated. A collapsing pulse of aortic insufficiency, a diminished pulse of low cardiac output, or the absence of a pulse due to prior surgery or thrombosis should be noted. Inspection of the head should focus on congenital abnormalities such as low hairline or low-set ears, nasal deformities, and high-arched palate, as well as gingival overgrowth, dental caries, or cyanosis. The jugular venous pressure and venous waves in the neck should be inspected with the patient's head elevated at a 30-degree angle above the table, and the carotid pulse and thyroid gland should be palpated. A venous hum should be differentiated from a cardiac murmur or bruit. Inspection and palpation of the chest should identify the presence of scars and skeletal abnormalities such as pectus excavatum deformity, precordial bulge, left or right ventricular heave, or thrill. The cardiac rhythm (regular or irregular, fast or slow) should be assessed. The first heart sound is often widely split in pregnant women, when listening with the diaphragm. Increased intensity of the first heart sound is the hallmark of mitral stenosis, and decreased intensity suggests first-degree heart block. Fixed splitting of the second heart sound suggests atrial septal defect or right bundle branch block, while paradoxic splitting suggests advanced left ventricular hypertrophy or left bundle branch block. A third heart sound is commonly heard, especially late in pregnancy. However, a fourth heart sound, an opening snap, an ejection click, or a mid- or late systolic click should suggest heart disease. In patients with prosthetic valves, the opening and closing of the valve may produce characteristic metallic clicking sounds. The systolic murmurs of normal pregnancy must be differentiated from those of underlying heart disease. The murmurs of right or left ventricular outflow tract obstruction may be initiated by an ejection click and are characteristically crescendo-decrescendo, ending before the closing sound of the valve involved, and are usually grade III or IV/VI in intensity, as opposed to the grade II murmurs heard in normal pregnancy. Regurgitant murmurs of the semilunar valves (aortic and pulmonary) are diastolic and decrescendo and are well heard along the left sternal edge when the patient is sitting with held expiration. Diastolic murmurs are not heard in normal pregnancy. The diastolic murmur of mitral stenosis is characteristically associated with a loud first heart sound and an opening snap, a high-frequency sound that follows the aortic valve closure by 0.07–0.12 second. This low-frequency diastolic rumble of mitral stenosis is best heard when the patient is positioned in the left lateral decubitus position, with the bell of the stethoscope lightly placed upon the skin. The mitral regurgitation murmur is a long holosystolic murmur, which is best heard at the apex radiating into the left axilla, whereas the tricuspid regurgitation murmur is best heard at the lower left sternal edge and increases markedly with inspiration. The murmur of mitral valve prolapse may be musical, and both murmur and click are often inaudible late in pregnancy unless the patient is sitting up or standing. Patients with atrial septal defect have a pulmonary systolic ejection murmur, often a low-frequency diastolic rumble, which represents a tricuspid flow murmur, and a characteristic widely split second heart sound, which remains widely split even in expiration. Those with a ventricular septal defect have a pansystolic, loud, harsh murmur resembling that of mitral regurgitation, which is heard best along the lower left sternal edge. The systolic murmur of coarctation of the aorta is best heard in the left second interspace and between the scapulae. Patients with an extracardiac shunt (patent ductus arteriosus) usually have a continuous systolic and diastolic murmur. Examination should continue with percussion and auscultation of the lungs and palpation and auscultation of the abdomen to ascertain the presence of hepatosplenomegaly, aortic aneurysm, masses, or bruits. The peripheral pulses should be carefully palpated and the extremities examined for the presence of varices, cyanosis, edema, stasis changes, clubbing, "splinter" hemorrhages, joint deformities, muscle wasting, or skeletal deformities such as arachnodactyly or brachydactyly, which suggest multiple congenital anomalies. Funduscopic examination should be performed in patients with hypertension to determine the presence of arteriolar narrowing, sclerosis, and arteriovenous compression; these imply long-standing hypertension. The presence of retinal edema, cotton-wool patches, and papilledema suggest preeclampsia or accelerated hypertension. A brief neurologic examination, including examination of the cranial nerves, muscle strength, sensation, and reflexes, should be performed when indicated. Laboratory Tests In addition to routine laboratory tests, patients with suspected cardiac disease may need the following noninvasive diagnostic procedures: Electrocardiogram The electrocardiogram (ECG) is useful for determining abnormalities of rhythm and the presence of conduction defects, evidence of chamber enlargement, and signs of myocardial or pericardial disease, ischemia, or infarction. The Holter monitor (24-hour continuous ECG) is occasionally useful for documenting the presence and nature of recurring arrhythmias or heart blocks and for correlating symptoms of palpitations, near syncope, or syncope with concurrent cardiac rhythm. Echocardiogram The transthoracic echocardiography (TTE) echocardiogram (both M mode and 2-dimensional sector scan) is a rapid, safe, and reliable tool for differentiating the physiologic murmurs resulting from the increased cardiac output of a normal pregnancy from the murmurs of congenital or acquired heart disease. The echocardiogram can provide information about abnormalities of anatomy and function of the chambers, valves, and pericardium. By inspection of the collapsibility of the inferior vena cava, the echocardiogram can provide information about the patient's volume status and differentiate cardiac from noncardiac causes of pulmonary edema that are important for diagnosis and treatment. The presence, location, and magnitude of intracardiac left-to-right and right-to-left shunts can be approximated by injecting 1–2 mL of normal saline shaken with 1 cc of air into a peripheral vein to produce microbubbles. The microbubbles magnify the reflected echo signal, and the presence of bubbles on the left side or an area of "negative contrast" in the right atrium or ventricle suggest an intracardiac shunt. Echocardiography can also be used to diagnose aortic dissection and coarctation. transesophageal echocardiography (TEE) has added a new dimension to the evaluation, especially of posterior structures such as the left atrium and the mitral valve. Because of its better resolution, TEE is particularly useful for the detection of left atrial thrombi and evaluation of prosthetic valves, and has been used in place of fluoroscopy for insertion of a pacemaker or even for performing valvuloplasty. TEE is also useful in the operating room and intensive care unit when TTE does not provide adequate resolution. Doppler Echocardiography Pulsed, continuous-wave, and color Doppler echocardiography is combined with 2-dimensional echocardiography for determination of blood flow and velocity, quantitation of pressure gradients and the degree of regurgitation, as well as for measuring intracardiac shunts and estimation of pulmonary pressure. Exercise Tolerance Test Exercise studies such as the treadmill test are normally not used during pregnancy, since pregnancy itself is a form of stress test. However, they may be useful in a woman contemplating pregnancy or in early pregnancy if the degree of compensation and ability to carry a pregnancy to term are in doubt, or to investigate the cause of chest pain and certain arrhythmias. In a woman with a prior myocardial infarct who is contemplating becoming pregnant, an exercise study with radionuclide myocardial perfusion would be a useful test to perform to determine the amount of fixed myocardial damage and the presence of reversible ischemia. Miscellaneous Additional studies for specific conditions include a throat culture to diagnose the presence of beta-hemolytic streptococcal infection and a C-reactive protein and antistreptolysin titer if antecedent streptococcal infection is suspected. Serial blood cultures are indicated if infective endocarditis is suspected. Chest x-rays, cardiac catheterization, and radionuclide scans are generally avoided during pregnancy, since the radiation can be harmful to the fetus, especially early in gestation. However, these tests can be performed with careful shielding of the abdomen and pelvis, if the mother's condition requires it. Rheumatic Heart Disease In developed countries, the incidence and the severity of rheumatic fever have declined progressively since the 1960s because of the widespread, prompt use of penicillin in the treatment of group A beta-hemolytic streptococcal upper respiratory tract infections and because of an apparent decrease in virulence of the organism. However, in Asia and Central and South America, rheumatic heart disease is still prevalent, and valvular abnormalities are common in women of childbearing age. Active rheumatic carditis, although rare during pregnancy, can be a serious and potentially fatal complication. The diagnosis is based on the Jones criteria: evidence of a preceding group A streptococcal infection (positive throat culture, scarlet fever, or elevated antistreptolysin titer), carditis, chorea, subcutaneous nodules, erythema marginatum, and polyarthritis. The minor criteria included fever, arthralgias, elevated sedimentation rate, and first-degree heart block. Carditis may result in acute congestive heart failure or may aggravate established rheumatic valvular disease. Treatment should consist of specific antistreptococcal antibiotics as well as salicylates and corticosteroids when indicated. Sodium restriction and bed rest are general nonspecific measures. Continuous prophylaxis against recurring rheumatic fever (secondary prevention) is advised until at least age 30 years in any patient with a history of rheumatic fever or rheumatic heart disease. In areas where rheumatic fever is prevalent, prophylaxis probably should be continued for patients with rheumatic heart disease, especially if they have small or school-aged children. The American Heart Association regimen is as follows:   Benzathine penicillin G, 1.2 million units intramuscularly at monthly intervals; or   Penicillin V, 250 mg orally twice daily for compliant patients; or   Sulfadiazine, 0.5–1 g orally once a day (contraindicated late in pregnancy because of transplacental passage); or   Erythromycin, 250 mg orally twice daily. Mitral Valve Disease Mitral stenosis is the most common lesion in young women with rheumatic heart disease, although mitral stenosis can result from Libman-Sacks endocarditis in patients with lupus and can be congenital, especially in association with atrial septal defect (Lutembacher's syndrome). Most patients with mild to moderate stenosis who are in sinus rhythm tolerate pregnancy well, although the risk for superimposed infective endocarditis is ever present even in hemodynamically mild disease. Those with moderate to severe disease are more likely to develop complications such as pulmonary venous congestion or frank pulmonary edema, right ventricular failure, pulmonary vascular hypertension, hemoptysis, atrial fibrillation, and systemic or pulmonary emboli. However, sudden and unexpected deterioration can occasionally occur during pregnancy in patients with any degree of mitral stenosis. New onset of atrial fibrillation in a previously asymptomatic woman can precipitate acute pulmonary edema, which occasionally requires emergency commissurotomy. The normal hemodynamic changes of pregnancy put patients with mitral stenosis at special risk for developing pulmonary congestion. The increased heart rate with consequent shortening of the diastolic filling period, augmented cardiac output and blood volume, and increased pulmonary venous pressure all contribute to raising left atrial pressure. The increased atrial irritability and increased sympathetic tone predispose to the onset of atrial fibrillation. The pregnant cardiac patient is also at risk for the development of thromboembolic complications, because of the hypercoagulable state of the blood during pregnancy as well as venous stasis in the legs. When right ventricular failure is associated with increased pulmonary vascular resistance, fluctuations in venous return can result in decreased cardiac output, and even syncope. The risk for developing heart failure increases progressively throughout pregnancy and is further increased during labor and delivery and immediately postpartum. Symptoms can also be aggravated by associated anemia, thyrotoxicosis, fever, respiratory infections, and tachycardia resulting from anxiety, stress, and unusual physical exertion, as well as a hot, humid environment. The risk of infective endocarditis remains throughout pregnancy, delivery, and the early puerperium. Labor imposes an additional load on the pregnant cardiac patient, but congestive failure rarely occurs for the first time during labor in a previously well-controlled patient with mitral stenosis. Postpartum pulmonary edema occurs more frequently, however, because of the abrupt redistribution of blood volume. The mortality rate in women with rheumatic mitral valve disease is 1% overall and reaches 3–4% in women with class III and class IV severity. Clinical Findings The symptoms of mitral valve disease are those of pulmonary venous congestion; dyspnea on exertion, and later at rest; right ventricular failure; atrial arrhythmias; and occasionally, hemoptysis. Fatigue and decrease in exercise tolerance are more often manifestations of mitral insufficiency. The characteristic findings on physical examination include a right ventricular lift, a loud first heart sound (S-1), accentuated pulmonic component of the second heart sound (P-2), an opening snap (OS), and a low-frequency diastolic rumble at the apex with presystolic accentuation (if the patient is in sinus rhythm). The murmur is best heard with the bell and should be carefully listened for when the characteristic cadence of S-1, P-2, OS is appreciated. The electrocardiogram is often normal but may indicate left atrial enlargement, right axis deviation, or even right ventricular hypertrophy. The echocardiogram is particularly useful for defining the anatomy of the valve and intravalvular structures, quantitating the degree of stenosis and associated regurgitation, and identifying the presence of abnormalities in other valves and pulmonary artery pressure. Treatment The goals of treatment for the patient with mitral stenosis should be to prevent or treat tachycardia and atrial fibrillation, to avoid fluid overload, and to avoid unnecessary increases in oxygen demand such as occur with anxiety or physical activity. Digitalis, quinidine, occasionally beta adrenergic blocking agents, sodium restriction, and diuretics may be necessary for treating congestive failure and atrial arrhythmias. Patients with chronic atrial fibrillation should be anticoagulated with subcutaneous heparin. Anemia, intercurrent infection, and thyrotoxicosis should be corrected. Large fluctuations in hemodynamics due to venous pooling in the legs should be avoided by the use of elastic support hose, especially late in pregnancy. Cardiac surgery or balloon valvuloplasty, although rarely necessary as an adjunct to careful medical management of patients with chronic rheumatic heart disease, occasionally becomes necessary as a lifesaving maneuver. In patients with severe mitral stenosis, especially if manifested in childhood, mitral valvotomy has often been performed for relief of symptoms before the patient becomes pregnant. Closed surgical mitral commissurotomy can be performed at any time during pregnancy but is rarely necessary as a lifesaving procedure until cardiac output has increased significantly in the late second or early third trimester. Balloon valvuloplasty has become a preferred, less invasive procedure, especially for patients with a noncalcified, pliable valve. In an occasional patient, mitral valve replacement may be necessary as an emergency procedure during pregnancy, as, for instance, in a patient with prior valve replacement whose valve becomes obstructed by pannus or thrombus. Recent reports indicate a low mortality rate for both mother and fetus with cardiopulmonary bypass. However, open heart surgery should be deferred until after the first trimester, if possible. Patients who have had a valve replaced with a prosthetic valve require anticoagulation and need to be switched from coumadin to heparin during the pregnancy. The teratogenic and fetotoxic effects of warfarin and the risks of bleeding for the mother and fetus during labor and delivery must be balanced against the risks of thromboembolic episodes, especially in patients with earlier-model prosthetic valves. The use of tissue valves obviates the need for anticoagulants, but the life span of bioprosthetic valves is only 8–10 years, and if the patient is in atrial fibrillation, anticoagulation is still required. Patients with rheumatic valvular disease should be delivered vaginally at term unless cesarean section is indicated for obstetric reasons. Appropriate analgesia should be given during labor, and epidural anesthesia without epinephrine should be used for delivery. Fluid loading for epidural anesthesia must be done gradually. To avoid the added exertion of bearing down during the third stage of labor, outlet forceps may be used. Careful hemodynamic monitoring during labor and delivery is indicated in patients with compromised circulation. Postpartum oxytocics should be given cautiously and blood loss carefully monitored. Redistribution of fluid from the interstitial to the intravascular space immediately postpartum can precipitate pulmonary edema in compromised patients. Mitral Regurgitation Patients with isolated or predominant mitral regurgitation tolerate the physiologic consequences of pregnancy better than do patients with predominant mitral stenosis. The fall in systemic vascular resistance decreases the left ventricular afterload and actually reduces the regurgitant fraction, thus reducing the risk of pulmonary congestion. The risk of atrial fibrillation and of endocarditis, however, is no less in patients with predominant mitral insufficiency. Although mitral regurgitation is frequently the result of rheumatic disease, other causes include: genetic defects in collagen synthesis (such as occur in Marfan's syndrome and Ehlers-Danlos syndrome) or following endocarditis on a previously abnormal valve, late complication of mitral valve prolapse, or papillary muscle infarction or rupture. The clinical course and findings are similar to those of rheumatic mitral insufficiency. The characteristic finding on physical examination is a long systolic murmur that ends with the second heart sound and is best heard at the apex with radiation into the axilla. An associated third heart sound is often present, and with associated mitral valve stenosis an opening snap may be present. Rheumatic Disease in Other Valves The aortic, pulmonary, and tricuspid valves may also be involved by the rheumatic process, usually in association with mitral valve disease. Involvement of multiple valves compounds the problems of management in these patients. In patients with aortic or pulmonary stenosis who have fixed ventricular outflow obstruction, the gradient across the valve increases with progressive increase in cardiac output during pregnancy, leading to an increased systolic pressure load on the ventricle. Although left ventricular failure is rare, postexertion syncope and angina due to inadequate cardiac output reserve may develop for the first time during pregnancy, especially in the last trimester, when venous return may be abruptly reduced due to compression of the inferior vena cava by the uterus. Patients with severe aortic stenosis should be advised to undergo surgical correction before becoming pregnant. Because patients with high-grade aortic stenosis are unable to maintain normal cardiac output, hypotension, hypertension, and increased cardiac work must be avoided by restricting physical activity and carefully replacing intrapartum blood loss. Patients with aortic insufficiency—like those with mitral regurgitation—tolerate pregnancy well, since the fall in peripheral resistance favors blood flow and decreases the regurgitant fraction. The risk of endocarditis is present in both stenotic and insufficient valves regardless of severity, and antibiotic prophylaxis during delivery is recommended. Patients with elevated left ventricular end-diastolic pressure, however, are more likely to develop left ventricular failure during pregnancy. Corrective surgical procedures for rheumatic valve disease include balloon valvuloplasty, surgical commissurotomy, and valve replacement. Two types of valves are available. Heterograft or homograft tissue valves do not require systemic anticoagulation but tend to deteriorate in 8–10 years. Prosthetic valves such as the tilting disc or caged ball valves may last 20 years or longer but always require anticoagulation, complicating the management of pregnancy. Infective Endocarditis Endocarditis is an acute or subacute inflammatory process resulting from blood-borne infection with Streptococcus viridans or other streptococci such as enterococcus (eg, Streptococcus faecalis), staphylococci, gram-negative organisms, or fungi. Abnormal heart valves and the endocardium in the proximity of congenital anatomic defects are preferential sites for involvement by blood-borne infections. Progressive involvement of the valve leaflets may result in acute aortic, mitral, or tricuspid valvular regurgitation, which may precipitate cardiac failure. Infected material from vegetations can embolize from right-sided lesions such as the tricuspid valve to the lungs, and from left-sided lesions to the systemic circulation. A focal embolic or immune complex glomerulonephritis may also develop. Untreated endocarditis carries a high mortality rate. Patients with endocarditis often give a history of recent extensive dental work, intravascular or urologic procedures, cardiac surgery, or intravenous illicit drug abuse. Intravenous drug users are at particular risk for developing acute endocarditis, often due to unusual pathogens and often on previously normal valves. Aseptic endocarditis occasionally occurs with rheumatoid arthritis, systemic lupus erythematosus (Libman-Sacks disease), and hypereosinophilic states (Löffler's endocarditis). Clinical Findings The diagnosis is based on symptoms such as persistent fever, malaise, chills, sweats, weakness, and embolic phenomena, both to the lungs and to the periphery in an individual with risk factors for endocarditis. Physical findings include petechial hemorrhages, clubbing of the fingers and toes, splenomegaly, Osler's nodes, (septic emboli to the fingertips), the appearance of new murmurs or change in existing murmurs, and manifestations of congestive heart failure. The diagnosis is confirmed by the finding of a positive blood culture or demonstration of vegetations on the valves by echocardiography. Prevention Patients at risk for developing infective endocarditis include those with underlying congenital or acquired valvular heart disease and intravenous drug abusers (Table 22–4). Table 22–5 lists the types of procedures for which endocarditis prophylaxis is recommended or discretionary. The currently recommended antibiotic regimens for genitourinary and gastrointestinal procedures are listed in Table 22–6. Patients with underlying heart disease should be advised to maintain good oral hygiene and attend promptly to any infections. Pericardial Disease Pericardial disease, which is rare during pregnancy, occurs in various forms: as an acute infective process, usually due to a virus; as tamponade due to hemorrhage from trauma, aortic dissection, tumor, or effusion complicating collagen vascular disease, acquired immune deficiency syndrome (AIDS), or uremia; or as chronic pericardial constriction secondary to infection, irradiation, or infiltrative process. The symptoms and physical findings, diagnostic approach, and management are the same in the pregnant as in the nonpregnant patient and are well described in standard texts. However, the peripheral edema and increased jugular venous pulsations of normal pregnancy may mask the signs of both tamponade and chronic constrictive pericarditis, leading to frequent delays in diagnosis. Diagnosis can be suspected from the presence of a friction rub, a positive Kussmaul sign (increased jugular venous pressure with inspiration), or a pulsus paradoxus (decreased systolic pressure with inspiration), and confirmed by electrocardiography, echocardiography, and pericardiocentesis. Acute tamponade is a medical emergency requiring rapid pericardiocentesis or surgical decompression. Symptomatic treatment with salicylates and corticosteroids may be indicated for acute viral infections. In chronic constrictive pericarditis, surgical decortication may be indicated, but is rarely necessary during pregnancy. Myocardial Disease Myocarditis Acute inflammation of the myocardium may be due to rheumatic fever, diphtheria, or viral diseases such as infection with group B coxsackieviruses or protozoal diseases such as toxoplasmosis. Other infectious causes include many other viruses, including the human immunodeficiency virus (HIV), rickettsia (Q fever, Rocky Mountain spotted fever, and scrub typhus), trichinosis, and spirochetal infections (leptospirosis, Lyme disease). In South America, Chagas' disease due to Trypanosoma cruzi is common. The myocarditis may be acute or subacute, may be associated with symptoms of systemic illness, and may occur at any time during pregnancy. The clinical manifestations are those of chest pain, fever, pulmonary rales, tachycardia, edema, and systolic murmurs and gallops on physical examination; as well as cardiomegaly, reduced ventricular function, conduction defects, and arrhythmias on electrocardiography and echocardiography. Specific serologic and bacteriologic tests may reveal the identity of the initiating organism. The clinical course is variable, depending on the severity of the infection and the extent of myocardial inflammation. The acute phase of the disease may be subclinical and hence is probably often not recognized as such. The disease may run an acute, subacute, or chronic course; be self-limited with complete recovery; or lead to progressive myocardial fibrosis and eventually to cardiomyopathy. The relationship to peripartum cardiomyopathy is unknown. Treatment consists of bed rest, digitalis, diuretics, antiarrhythmic agents, and appropriate antibiotics if a specific organism has been identified. Salicylates and corticosteroids are effective in patients with active rheumatic carditis. The incidence of spontaneous abortions in patients with persistent infection is high. Cardiomyopathy Cardiomyopathy is a rare primary disease of cardiac muscle that presents clinically as heart failure and myocardial dysfunction that probably represent the end stage of various processes that affect the myocardium. Cardiomyopathy is classified broadly as dilated, restrictive/infiltrative, or hypertrophic. Restrictive cardiomyopathy is seen as the end stage of amyloidosis, scleroderma, sarcoid, hemochromatosis, or endomyocardial fibroelastosis. Dilated cardiomyopathy may result from excess alcohol consumption (beriberi), thyrotoxicosis, excessive catecholamine levels (pheochromocytoma), cocaine use, and cytotoxic drugs such as doxorubicin. Infectious causes for cardiomyopathy include rheumatic fever, diphtheria, rickettsia (scrub typhus), protozoa (Chagas' disease), spirochetes (Lyme disease), toxoplasmosis, and viral diseases. Lupus erythematosus, hypereosinophilia (Löffler's), ischemia, multiple infarction, and sickle cell disease can also cause a diffuse myocardial process that can lead to congestive heart failure. Peripartum Cardiomyopathy Peripartum cardiomyopathy is used to describe this form of cardiac failure when the onset occurs in the last months of pregnancy or within 6 months postpartum, and no specific etiology or prior heart disease is identified. The assumption is that the pregnant condition has somehow predisposed the woman to develop myocardial disease, but the mechanism remains unexplained. It is not understood why the symptoms usually appear following parturition rather than during the late second and third trimesters, when the hemodynamic burden is greatest. It may also be that symptoms of congestive failure are overlooked or misinterpreted as complaints commonly seen late in a normal pregnancy. The incidence appears to be higher in women of African descent, perhaps due to the high prevalence of hypertension, and in women living in warm climates, in twin gestations, and in women with preeclampsia. Cardiomegaly and heart failure may persist or regress postpartum and recur in subsequent pregnancies. The incidence varies from one in 1300 to one in 4000 deliveries, although among the Hausa people in Zaria in northern Nigeria, the incidence may be as high as one in 100–400 deliveries, probably because of the traditional high postpartum salt intake among these women. Clinical Findings The clinical manifestations are those of right and left ventricular failure with pulmonary congestion, hepatomegaly, low cardiac output, chest pain, hemoptysis and cough, fatigue, dyspnea, decreased exercise tolerance, edema, systolic murmurs, third heart sound, elevated jugular venous pressure, pulmonary rales, and cardiomegaly. Arrhythmias and pulmonary as well as systemic emboli are common. The electrocardiographic changes are nonspecific but include arrhythmias, low in electrocardiography, the complex consisting of q, r, s waves, corresponding to the depolarization of ventricles [complex] (QRS) voltage, left ventricular hypertrophy, abnormal Q waves, nonspecific ST-T wave changes, and conduction defects. On echocardiography, there is evidence of enlargement of all chambers, generalized decrease in wall motion, reduced ejection fraction, and often mural thrombi. Treatment & Prognosis The prognosis depends on the degree to which the cardiomegaly is reversible with standard treatment for congestive heart failure, such as digitalis, diuretics, salt restriction, and prolonged bed rest. Afterload reduction with vasodilators, but not converting enzyme inhibitors that are contraindicated in pregnancy, and use of anticoagulants are indicated for patients with intractable heart failure and repeated embolic episodes. Mortality rates of 25–50% have been reported. Patients with persistent cardiomegaly following standard therapy or 6 months after the onset of symptoms have a high incidence of recurrence, progression, and even mortality with subsequent pregnancies and should be cautioned not to become pregnant again. Hypertrophic Cardiomyopathy Hypertrophic cardiomyopathy with or without left ventricular outflow tract obstruction (subaortic stenosis) is a developmental abnormality of cardiac muscle that is usually inherited as an autosomal dominant abnormality, although it may occur sporadically. It may result in symptoms within the first 3 decades of life. The asymmetrically hypertrophied septum encroaches on the left ventricular outflow tract, producing an intraventricular pressure gradient and outflow tract obstruction, as well as systolic anterior motion that creates distortion of the mitral valve and mitral insufficiency. The thickened, distorted, abnormally developed, noncompliant muscle causes impaired left ventricular diastolic filling. Decreased cardiac output, atrial and ventricular arrhythmias, and postexertion syncope are common complications. The diagnosis is suspected on physical examination and must be differentiated from valvular aortic stenosis. Physical findings include a left ventricular heave, an aortic systolic murmur along the lower left sternal edge, and a mitral insufficiency murmur at the apex. A fourth heart sound is common. With increased sympathetic stimulation, the left ventricular outflow gradient, and hence the murmur, increase. A definitive diagnosis is made by echocardiography. The electrocardiogram usually shows left ventricular hypertrophy with septal hypertrophy. The axis and prominent Q waves are often suggestive of prior infarction, but may reflect the electrophysiologic properties of the hypertrophied septum. Management includes use of beta-adrenergic blockers and calcium entry blockers to decrease the vigor of ventricular contraction as well as to manage tachyarrhythmias. Care must be taken to avoid volume depletion. Sympathomimetics should not be used. Careful hemodynamic monitoring during labor and delivery is indicated in symptomatic patients. Ischemic Coronary Artery Disease The diagnosis of myocardial ischemia due to occlusive coronary artery disease is rarely made in women of childbearing age and is even less frequently made during pregnancy. Nonatherosclerotic causes, such as congenital malformations, Kawasaki disease, vasculitis, endocarditis, emboli and coronary artery spasm as may occur with cocaine use, excessive levels of catecholamines, or bromocriptine used for postpartum suppression of lactation, predominate in young women. However, the presence of risk factors for accelerated arteriosclerosis such as diabetes mellitus, hyperlipidemia, cigarette smoking, chronic hypertension, and a family history of premature coronary artery disease may combine with delayed childbearing to produce atherosclerotic coronary artery disease even in relatively young pregnant women. In addition, angina pectoris can occur in women with high-grade aortic stenosis, hypertrophic cardiomyopathy, thyrotoxicosis, profound anemia, and increased levels of circulating catecholamines. Myocardial ischemia or reversible ischemia, manifested by chest pain and transient electrocardiographic changes, may also occur during tocolytic therapy for premature labor and in a patient with high levels of circulating catecholamines. The increases in myocardial oxygen consumption, heart rate, cardiac output, and total blood volume of pregnancy are poorly tolerated by patients with limited coronary artery reserve. Symptoms of ischemia occur at lower levels of exertion than in nonpregnant patients, especially as pregnancy advances. In patients with infarction during pregnancy, the outcome for both mother and fetus depends on the size of the infarct and the presence of complications. Risk to the mother and therefore to the fetus increases near term and especially with the stress of labor and delivery. In addition to controlling precipitating or aggravating factors, the principles of management of angina pectoris and of myocardial infarction in pregnant women do not differ from those in nonpregnant patients. Patients with angina pectoris should be treated with restriction of activity, avoidance of stress (to reduce oxygen demand), and coronary vasodilators to improve oxygen supply. Nitrates, beta-adrenergic blocking drugs, and calcium channel antagonists should be given. Smoking should be forbidden and other risk factors meticulously controlled. Acute myocardial infarction can be a catastrophic event during pregnancy, especially near term when the hemodynamic load is maximal. Standard therapy to reduce oxygen demands and to improve myocardial perfusion include bed rest, oxygen by nasal cannula, control of hypertension, treatment of hypotension, cautious afterload reduction, intravenous nitroglycerin or other coronary vasodilators, beta receptor antagonists for treatment of tachycardia, and, when indicated, thrombolysis and angioplasty. Women who have had a myocardial infarction before or during pregnancy should be delivered vaginally, if possible, with epidural anesthesia and outlet forceps to shorten the second stage of labor. Careful intrapartum hemodynamic monitoring may be indicated, especially if infarction has occurred in the third trimester. Aortic Dissection Aortic dissection is a rare catastrophic event that occurs occasionally during the third trimester of pregnancy or postpartum. It is rare in normotensive patients under age 40. However, chronic hypertension and the effects of estrogen and relaxin may cause degeneration of the arterial media and disruption of elastic tissue in the aorta, thus contributing to the risk of dissection, especially late in pregnancy. Aortic dissection is a much feared potential complication in patients with Marfan's syndrome, unoperated coarctation of the aorta, aortic aneurysm, Ehlers-Danlos syndrome, and myxomatous degeneration and dilatation of the ascending aorta or aortic root. The diagnosis should be suspected in a woman who has a sudden cardiovascular catastrophe in the third trimester, typically with severe crushing or searing pain in the chest or back, pulmonary edema, neurologic symptoms, evidence of cardiac tamponade, acute aortic insufficiency, and shock. Diagnostic radiologic and echocardiographic studies should be initiated immediately. In patients with a proximal intimal tear (type A), immediate operative intervention, occasionally with aortic valve replacement, can be lifesaving. In patients with a more distal intimal tear (type B), if aortic rupture is not imminent, medical treatment is indicated. This consists of rapid and sustained reduction of blood pressure with intravenous nitroprusside and reduction of the shearing forces on the aortic wall with beta-adrenergic blocking agents. The risk to the fetus is unavoidably high in either case. Pregnant patients with Marfan's syndrome (a hereditary connective tissue disorder) are at an especially increased risk for aortic dissection. Because of the high risk, many obstetricians counsel these women not to become pregnant. However, in women without aortic root dilatation (less than 4 cm in diameter measured just above the aortic valve by echocardiography), the risk of aortic rupture or dissection is acceptably low. Congenital Heart Disease Patients with congenital heart disease are surviving to childbearing age in increasing numbers because of the early recognition and treatment of complications that develop in infancy and the availability of palliative and curative operative procedures. Congenital heart disease occurs in approximately 0.9% of liveborn infants in the United States. The prevalence in the population of bicuspid aortic valve, mitral valve prolapse, hypertrophic cardiomyopathy, and ventricular preexcitation (Wolff-Parkinson-White syndrome)—all congenital lesions that usually do not become manifest until later in life—is unknown but may be as high as 2%. Congenital cardiac defects may occur as isolated lesions, as part of a syndrome, associated with other congenital anomalies, and possibly inherited as mendelian dominant or recessive characteristics. The common congenital cardiac anomalies can be broadly grouped under various categories such as cyanotic or acyanotic, simple or complex, mild or severe, and compatible with a normal pregnancy or a contraindication for pregnancy. The following is a simplified classification:   (1) Obstructive lesions of the right or left ventricular outflow tract that result in pressure overload of the ventricle, such as pulmonary stenosis, aortic stenosis, hypertrophic subaortic stenosis, or coarctation of the aorta.   (2) Left-to-right shunts resulting in ventricular volume overload and increased pulmonary blood flow, such as atrial septal defect, atrioventricular canal, ventricular septal defect, endocardial cushion defect, patent ductus arteriosus, and truncus arteriosus.   (3) Cyanotic or hypoxic congenital heart disease in which unoxygenated venous blood enters the systemic circulation, such as tetralogy of Fallot, Eisenmenger's complex, tricuspid atresia, pulmonary atresia, single ventricle, transposition of the great arteries, and Ebstein's anomaly. Complex lesions may combine several of these features. Operative procedures for correction or palliation are now available for almost all of these defects and are performed even in small infants. However, problems persist in most patients because of residual inoperable lesions, conduction defects, arrhythmias, irreversible pulmonary hypertension, valvular incompetence, ventricular failure, deterioration of prosthetic materials such as valves and conduits, and the need for anticoagulation (Table 22–7). Susceptibility to infective endocarditis persists in all patients except those with corrected uncomplicated secundum atrial septal defects, completely closed ventricular septal defects, and patent ductus arteriosus. Patients with acyanotic congenital heart disease tolerate pregnancy well, whether the heart disease has been surgically corrected or not, and have a low incidence of spontaneous abortions and premature labor. Induced abortion is rarely indicated for cardiac causes in patients with class I or class II severity. However, patients with class III or class IV severity at the onset of pregnancy have a high incidence of spontaneous abortions and stillbirths, and interruption of pregnancy or postponement until a corrective or palliative procedure can be performed for cardiac indications may be required. In patients with congestive heart failure or large intracardiac shunts, pregnancy is not well tolerated. Atrial Septal Defect Ostium secundum atrial septal defect, one of the most common forms of congenital heart disease, is well tolerated by most women, although secondary pulmonary hypertension and right ventricular failure can develop, especially in women with large left-to-right shunts. The characteristic findings on physical examination include a right ventricular lift; a widely split and accentuated second heart sound that does not change with respiration; and a pulmonic systolic ejection murmur, usually considerably louder than the systolic murmur of normal pregnancy. A diastolic tricuspid rumble is often present with large shunts. The electrocardiogram shows an incomplete right bundle branch block and right-axis deviation. The presence, location, and size of the shunt can be identified by echocardiography and color flow Doppler studies. If significant pulmonary hypertension has developed, patients are characterized as having Eisenmenger's syndrome, and the risk of pregnancy rises steeply (see later). Atrial arrhythmias are more likely to occur with advancing age. The risk of infectious endocarditis is low, and paradoxic emboli occur rarely. Patients with ostium primum atrial septum defects (one end of the spectrum of atrioventricular canal defect), who have associated cleft mitral or tricuspid valves with insufficiency, tolerate pregnancy less well because of the increased risk of both left or right ventricular failure. If the mitral insufficiency is severe, a mitral prosthesis may have been previously implanted, raising the issue of anticoagulation for a mechanical valve and the risk of deterioration of a tissue valve. Due to the presence of mitral regurgitation, the risk for endocarditis is correspondingly higher, as is the risk for developing atrial arrhythmias. In ostium primum septal defect, the clinical findings include a right ventricular lift and often a left ventricular heave as well, a widely split second heart sound, and a pulmonic ejection murmur as well as the long pansystolic murmur of mitral insufficiency at the apex and occasionally of tricuspid insufficiency at the lower end of the sternum. The electrocardiogram is more likely to show left ventricular hypertrophy, and characteristically left axis deviation, although the incomplete right bundle branch block may be present as well. The echocardiogram and color flow Doppler studies are used to define the location of the atrial septal defect and the degree of involvement of the mitral and tricuspid valves. Transesophageal echocardiography may be needed to evaluate a prosthetic valve. Ventricular Septal Defect Isolated ventricular septal defect, although common in infancy, is seen less frequently among pregnant women because the ventricular septal defect tends to close spontaneously before the woman reaches adulthood. Women with small to moderate-sized ventricular septal defects tolerate pregnancy well, although they are at risk for developing secondary infectious endocarditis and heart failure. With large ventricular septal defects, the risk of secondary pulmonary hypertension (Eisenmenger's syndrome) increases progressively (see later). Ventricular septal defects are often associated with other intracardiac defects, but large, complicated ones are likely to have been surgically corrected before puberty. Important late complications of ventricular septal defect, operated or unoperated, include ventricular arrhythmias and aortic valve insufficiency. The characteristic findings on examination include a palpable systolic thrill along the left sternal border and a loud pansystolic murmur best heard at the same location. There may be both a left and right ventricular heave or lift. When aortic insufficiency has developed, the presence of a systolic and diastolic murmur can be mistaken for a patent ductus arteriosus. Small ventricular septal defects, such as maladie de Roger may be very noisy but hemodynamically unimportant. The electrocardiogram may appear normal or show biventricular hypertrophy. The echocardiogram and Doppler studies readily identify the location and size of the defect, as well as associated lesions. Patent ductus arteriosus is now rarely seen in adults because the condition is so readily diagnosed in childhood. Small defects are well tolerated, although patients are at risk for endocarditis, but with large defects, the risk of secondary pulmonary hypertension with shunt reversal and left ventricular failure increases. Patients with a patent ductus characteristically have a palpable left ventricular heave, a loud pulmonic component of the second heart sound, and a systolic/diastolic murm [ 打印 ] [ 加入书签 ] [ 编辑 ] [ 删除 ] -=选择论坛=- 房地产经 妙手家园 文城往事 海外原创 书画艺廊 财经频道 网上谈兵 时事述评 我的中国 两岸交流 想唱就唱 移民论坛 难得一笑 脑筋急转 体育看台 大千股坛 奇闻怪谈 星相卜卦 婚姻生活 私房小菜 亲亲宝贝 宠物乐园 健康养生 流行时尚 爱的星空 爱车一族 我爱我家 世界风情 职场生涯 几曾回首 大学春秋 闲趣谜语 文化走廊 品茶小轩 音乐快递 武侠军事 跨国婚姻 影视人生 回国发展 生于70's 法律咨询 人在北美 人在澳新 人在欧洲 人在日本 人在狮城 人在英国 人在法国 人在德国 人在香港 人在韩国 中南美洲 实用电脑 电玩高手 摄影沙龙 子女教育 诗词欣赏 百家杂谈 美语世界 AI 潮流社 投资理财 人到中年 书香世家 唯美贴贴 运动健身 科学天文 常青人生 阅读 () ┆ 评论 (13) 评论 目前还没有任何评论 登录后才可评论.