Rheumatic fever is uncommon in the United States because of less crowded living conditions, availability of penicillin, and evolution of nonrheumatogenic streptococcal strains. Still, it remains the chief cause of serious mitral valvular disease (Roeder, 2011).
Rheumatic endocarditis causes most mitral stenosis lesions. The normal mitral valve surface area is 4.0 cm2, and when stenosis narrows this to < 2.5 cm2, symptoms usually develop (Desai, 2000). The contracted valve impedes blood flow from the left atrium to the ventricle. The most prominent complaint is dyspnea due to pulmonary venous hypertension and edema. Fatigue, palpitations, cough, and hemoptysis are also common.
With more severe stenosis, the left atrium dilates, left atrial pressure is chronically elevated, and significant passive pulmonary hypertension develops (Table 49-7). These women have a relatively fixed cardiac output, and thus the increased preload of normal pregnancy, as well as other factors that increase cardiac output, may cause ventricular failure and pulmonary edema. Indeed, a fourth of women with mitral stenosis have cardiac failure for the first time during pregnancy (Caulin-Glaser, 1999). Because the murmur may not be heard in some women, this clinical picture at term may be confused with idiopathic peripartum cardiomyopathy (Cunningham, 1986, 2012).
TABLE 49-7Major Cardiac Valve Disorders ||Download (.pdf) TABLE 49-7 Major Cardiac Valve Disorders
|Type ||Cause ||Pathophysiology ||Pregnancy |
|Mitral stenosis ||Rheumatic valvulitis ||LA dilation and passive pulmonary hypertension ||Heart failure from fluid overload, tachycardia |
| || ||Atrial fibrillation || |
|Mitral insufficiency ||Rheumatic valvulitis |
|LV dilatation and eccentric hypertrophy ||Ventricular function improves with afterload decrease |
|Aortic stenosis ||Congenital bicuspid valve ||LV concentric hypertrophy, decreased cardiac output ||Moderate stenosis is tolerated; severe is life-threatening with decreased preload, e.g., obstetrical hemorrhage or regional analgesia |
|Aortic insufficiency ||Rheumatic valvulitis |
|LV hypertrophy and dilatation ||Ventricular function improves with afterload decrease |
|Pulmonary stenosis ||Rheumatic valvulitis |
|Severe stenosis associated with RA and RV enlargement ||Mild stenosis usually well tolerated; severe stenosis associated with right heart failure and atrial arrhythmias |
Also with significant stenosis, tachycardia shortens ventricular diastolic filling time and increases the mitral gradient. This raises left atrial as well as pulmonary venous and capillary pressures and may result in pulmonary edema. Thus, sinus tachycardia is often treated prophylactically with β-blocking agents. Atrial tachyarrhythmias, including fibrillation, are common in mitral stenosis and are treated aggressively. Atrial fibrillation also predisposes to mural thrombus formation and cerebrovascular embolization that can cause stroke (Chap. 60, Preeclampsia Syndrome). Atrial thrombosis can develop despite a sinus rhythm, and Hameed (2005) reported three such women. One suffered an embolic stroke, and another had pulmonary edema causing maternal hypoxemia leading to fetal encephalopathy.
In general, complications are directly associated with the degree of valvular stenosis. Recall that investigators from the large Canadian study found that women with a mitral-valve area < 2 cm2 were at greatest risk. In another study, Hameed (2001) described 46 pregnant women with mitral stenosis—43 percent developed heart failure and 20 percent developed arrhythmias. Fetal-growth restriction was more common in those women with a mitral valve area < 1.0 cm2.
Prognosis is also related to maternal functional capacity. Among 486 pregnancies complicated by rheumatic heart disease—predominantly mitral stenosis—Sawhney (2003) reported that eight of 10 maternal deaths were in women in NYHA classes III or IV.
Limited physical activity is generally recommended in women with mitral stenosis. If symptoms of pulmonary congestion develop, activity is further reduced, dietary sodium is restricted, and diuretics are given (Siva, 2005). A β-blocker drug is usually given to slow the ventricular response to activity (Maxwell, 2010). If new-onset atrial fibrillation develops, intravenous verapamil, 5 to 10 mg, is given, or electrocardioversion is performed. For chronic fibrillation, digoxin, a β-blocker, or a calcium-channel blocker is given to slow ventricular response. Therapeutic anticoagulation with heparin is indicated with persistent fibrillation. Some recommend heparin anticoagulation for those with severe stenosis even if there is a sinus rhythm (Hameed, 2005).
Labor and delivery are particularly stressful for women with symptomatic mitral stenosis. Uterine contractions increase cardiac output by increasing circulating blood volume. Pain, exertion, and anxiety cause tachycardia with possible rate-related heart failure. Epidural analgesia for labor is ideal, but with strict attention to avoid fluid overload. Abrupt increases in preload may increase pulmonary capillary wedge pressure and cause pulmonary edema. The effects of labor on pulmonary pressures in women with mitral stenosis are shown in Figure 49-3. Wedge pressures increase most immediately postpartum. Clark and colleagues (1985) hypothesize that this is likely due to loss of the low-resistance placental circulation along with the venous “autotransfusion” from a now-empty uterus and from the lower extremities and pelvis.
Mean pulmonary capillary wedge pressure measurements (red graph line) in eight women with mitral valve stenosis. Shaded yellow and blue boxes are mean (± 1 SD) pressures in nonlaboring normal women at term. A. First-stage labor. B. Second-stage labor 15 to 30 minutes before delivery. C. Postpartum 5 to 15 minutes. D. Postpartum 4 to 6 hours. E. Postpartum 18 to 24 hours. (Data from Clark, 1985, 1989.)
Most consider vaginal delivery to be preferable in women with mitral stenosis. Elective induction is reasonable so that labor and delivery are attended by a scheduled, experienced team. With severe stenosis and chronic heart failure, insertion of a pulmonary artery catheter may help guide management.
A trivial degree of mitral insufficiency is found in most normal patients (Maxwell, 2010). But if there is improper coaptation of mitral valve leaflets during systole, abnormal degrees of mitral regurgitation may develop. This is eventually followed by left ventricular dilatation and eccentric hypertrophy (see Table 49-7). Chronic mitral regurgitation has a number of causes, including rheumatic fever, mitral valve prolapse, or left ventricular dilatation of any etiology—for example, dilated cardiomyopathy. Less common causes include a calcified mitral annulus, possibly some appetite suppressants, and in older women, ischemic heart disease. Mitral valve vegetations—Libman-Sacks endocarditis—are relatively common in women with antiphospholipid antibodies (Roldan, 1996; Shroff, 2012). These sometimes coexist with systemic lupus erythematosus (Chap. 59, Lupus and Pregnancy). In contrast, acute mitral insufficiency is caused by chordae tendineae rupture, papillary muscle infarction, or leaflet perforation from infective endocarditis.
In nonpregnant patients, symptoms from mitral valve incompetence are rare, and valve replacement is seldom indicated unless infective endocarditis develops. Likewise, mitral regurgitation is well tolerated during pregnancy, probably because decreased systemic vascular resistance results in less regurgitation. Heart failure only rarely develops during pregnancy, and occasionally tachyarrhythmias require treatment.
This diagnosis implies the presence of a pathological connective tissue disorder—often termed myxomatous degeneration—which may involve the valve leaflets themselves, the annulus, or the chordae tendineae. Mitral insufficiency may develop. Most women with mitral valve prolapse are asymptomatic and are diagnosed by routine examination or while undergoing echocardiography. The small percentage of women with symptoms have anxiety, palpitations, atypical chest pain, dyspnea with exertion, and syncope (Guy, 2012).
Pregnant women with mitral valve prolapse rarely have cardiac complications. Hypervolemia may even improve alignment of the mitral valve, and women without pathological myxomatous change generally have excellent pregnancy outcomes (Leśniak-Sobelga, 2004; Rayburn, 1987). In a study of 3100 women in the Taiwanese Birth Registry with mitral valve prolapse, however, the preterm birth rate was 1.2 times higher than among controls (Chen, 2011).
For women who are symptomatic, β-blocking drugs are given to decrease sympathetic tone, relieve chest pain and palpitations, and reduce the risk of life-threatening arrhythmias. According to the American College of Obstetricians and Gynecologists (2011a), mitral valve prolapse is not considered an indication for infective endocarditis prophylaxis.
Usually a disease of aging, aortic stenosis in women younger than 30 years is most likely due to a congenital lesion. This stenosis is less common since the decline in incidences of rheumatic diseases, and the most frequent cause in this country is a bicuspid valve (Friedman, 2008). A normal aortic valve has an area of 3 to 4 cm2, with a pressure gradient of less than 5 mm Hg. If the valve area is < 1 cm2, there is severe obstruction to flow and a progressive pressure overload on the left ventricle (Carabello, 2002; Roeder, 2011). Concentric left ventricular hypertrophy follows, and if severe, end-diastolic pressures become elevated, ejection fraction declines, and cardiac output is reduced (see Table 49-7). Characteristic clinical manifestations develop late and include chest pain, syncope, heart failure, and sudden death from arrhythmias. Life expectancy averages only 5 years after exertional chest pain develops, and valve replacement is indicated for symptomatic patients.
Clinically significant aortic stenosis is infrequent during pregnancy. Mild to moderate degrees of stenosis are well tolerated, however, severe disease is life threatening. The principal underlying hemodynamic problem is the fixed cardiac output associated with severe stenosis. During pregnancy, a number of events acutely decrease preload further and thus aggravate the fixed cardiac output. These include vena caval occlusion, regional analgesia, and hemorrhage. Importantly, these also decrease cardiac, cerebral, and uterine perfusion. It follows that severe aortic stenosis may be extremely dangerous during pregnancy. From the large Canadian multicenter study cited above, there were increased complications if the aortic valve area was < 1.5 cm2 (Siu, 2001b). And in the report by Hameed and associates (2001) described earlier, the maternal mortality rate with aortic stenosis was 8 percent. Women with valve gradients exceeding 100 mm Hg appear to be at greatest risk.
For the asymptomatic woman with aortic stenosis, no treatment except close observation is required. Management of the symptomatic woman includes strict limitation of activity and prompt treatment of infections. If symptoms persist despite bed rest, valve replacement or valvotomy using cardiopulmonary bypass must be considered. In general, balloon valvotomy for aortic valve disease is avoided because of serious complications, which exceed 10 percent. These include stroke, aortic rupture, aortic valve insufficiency, and death (Reich, 2004). In rare cases, it may be preferable to perform valve replacement during pregnancy (Datt, 2010).
For women with critical aortic stenosis, intensive monitoring during labor is important. Pulmonary artery catheterization may be helpful because of the narrow margin separating fluid overload from hypovolemia. Women with aortic stenosis are dependent on adequate end-diastolic ventricular filling pressures to maintain cardiac output and systemic perfusion. Abrupt decreases in end-diastolic volume may result in hypotension, syncope, myocardial infarction, and sudden death. Thus, the management key is avoidance of decreased ventricular preload and the maintenance of cardiac output. During labor and delivery, such women should be managed on the “wet” side, maintaining a margin of safety in intravascular volume in anticipation of possible hemorrhage. In women with a competent mitral valve, pulmonary edema is rare, even with moderate volume overload.
During labor, narcotic epidural analgesia seems ideal, thus avoiding potentially hazardous hypotension, which may be encountered with standard conduction analgesia techniques. Easterling and coworkers (1988) studied the effects of epidural analgesia in five women with severe stenosis and demonstrated immediate and profound effects of decreased filling pressures. Xia and associates (2006) emphasize slow administration of dilute local anesthetic agents into the epidural space. Forceps or vacuum delivery is used for standard obstetrical indications in hemodynamically stable women. Late cardiac events include pulmonary edema, arrhythmias, cardiac interventions, and death, which were identified within 1 year of delivery in 70 pregnancies (Tzemos, 2009).
Aortic valve regurgitation or insufficiency allows diastolic flow of blood from the aorta back into the left ventricle. Frequent causes of abnormal insufficiency are rheumatic fever, connective-tissue abnormalities, and congenital lesions. With Marfan syndrome, the aortic root may dilate, resulting in regurgitation. Acute insufficiency may develop with bacterial endocarditis or aortic dissection. Aortic and mitral valve insufficiency have been linked to the appetite suppressants fenfluramine and dexfenfluramine and to the ergot-derived dopamine agonists cabergoline and pergolide (Gardin, 2000; Schade, 2007; Zanettini, 2007). With chronic insufficiency, left ventricular hypertrophy and dilatation develop and are followed by slow-onset fatigue, dyspnea, and edema, although rapid deterioration usually follows (see Table 49-7).
Aortic insufficiency is generally well tolerated during pregnancy. Like mitral valve incompetence, diminished vascular resistance is thought to improve hemodynamic function. If symptoms of heart failure develop, diuretics are given and bed rest is encouraged.
The pulmonary valve is affected by rheumatic fever far less often than the other valves. Instead, pulmonic stenosis is usually congenital and also may be associated with Fallot tetralogy or Noonan syndrome. The clinical diagnosis is typically identified by auscultating a systolic ejection murmur over the pulmonary area that is louder during inspiration.
Increased hemodynamic burdens of pregnancy can precipitate right-sided heart failure or atrial arrhythmias in women with severe stenosis. Surgical correction ideally is done before pregnancy, but if symptoms progress, a balloon angioplasty may be necessary antepartum (Maxwell, 2010; Siu, 2001a). In a study of 81 pregnancies in 51 Dutch women with pulmonic stenosis, cardiac complications were infrequent (Drenthen, 2006). NYHA classification worsened in two women, and nine experienced palpitations or arrhythmias. No changes in pulmonary valvular function or other adverse cardiac events were reported. However, noncardiac complications were increased—17 percent had preterm delivery; 15 percent had hypertension; and 4 percent developed thromboembolism. Interestingly, two of the offspring were diagnosed with pulmonic stenosis, and another had complete transposition and anencephaly.