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Heart Disorders in Pregnancy

by Lara A. Friel, MD, PhD

Heart disorders account for about 10% of maternal obstetric deaths. In the US, because incidence of rheumatic heart disease has markedly declined, most heart problems during pregnancy result from congenital heart disease. However, in Southeast Asia, Africa, India, the Middle East, and parts of Australia and New Zealand, rheumatic heart disease is still common.

Despite dramatic improvements in survival and quality of life for patients with severe congenital heart defects and other heart disorders, pregnancy remains inadvisable for women with certain high-risk disorders such as

  • Pulmonary hypertension

  • Eisenmenger syndrome

  • Coarctation of the aorta if uncorrected or if accompanied by an aneurysm

  • Marfan syndrome with aortic root diameter of > 4.5 cm

  • Severe symptomatic aortic stenosis

  • A single ventricle and impaired systolic function (whether treated with the Fontan procedure or not)

  • Prior postpartum cardiomyopathy

Pathophysiology

Pregnancy stresses the cardiovascular system, often worsening known heart disorders; mild heart disorders may first become evident during pregnancy. Stresses include decreased Hb and increased blood volume, stroke volume, and eventually heart rate. Cardiac output increases by 30 to 50%. These changes become maximal between 28 and 34 wk gestation. During labor, cardiac output increases about 20% with each uterine contraction; other stresses include straining during the 2nd stage of labor and the increase in venous blood returning to the heart from the contracting uterus. Cardiovascular stresses do not return to prepregnancy levels until several weeks after delivery.

Symptoms and Signs

Findings resembling heart failure (eg, mild dyspnea, systolic murmurs, jugular venous distention, tachycardia, dependent edema, mild cardiomegaly seen on chest x-ray—see Heart Failure) typically occur during normal pregnancy or may result from a heart disorder. Diastolic or presystolic murmurs are more specific for heart disorders.

Heart failure can cause premature labor or arrhythmias. Risk of maternal or fetal death correlates with New York Heart Association (NYHA) functional classification, which is based on the amount of physical activity that causes symptoms of heart failure.

Risk is not increased if symptoms

  • Do not occur during exertion (class I)

  • Occur only during significant exertion (class II)

Risk is increased if symptoms

  • Occur during mild exertion (class III)

  • Occur during minimal or no exertion (class IV)

Diagnosis

  • Clinical evaluation

  • Usually echocardiography

Diagnosis is usually based on clinical evaluation and echocardiography. Because genetics can contribute to the risk of heart disorders, genetic counseling and fetal echocardiography should be offered to women with congenital heart disease.

Treatment

  • Avoidance of warfarin, ACE inhibitors, aldosterone antagonists, thiazide diuretics, and certain antiarrhythmics (eg, amiodarone)

  • For NYHA class III or IV, activity restriction and possibly bed rest after 20 wk

  • Most other usual treatments for heart failure and arrhythmias

Frequent prenatal visits, ample rest, avoidance of excessive weight gain and stress, and treatment of anemia are required. An anesthesiologist familiar with heart disorders in pregnancy should attend the labor and ideally should be consulted prenatally. During labor, pain and anxiety are treated aggressively to minimize tachycardia. Women are closely monitored immediately postpartum and are followed for several weeks postpartum by a cardiologist.

Before women with NYHA class III or IV status conceive, the disorder should be optimally treated medically and, if indicated (eg, if due to a valvular heart disorder), treated surgically. Women with class IV heart failure may be advised to obtain an early therapeutic abortion.

Some women with a heart disorder and poor cardiac function require digoxin 0.25 mg po once/day plus bed rest, beginning at 20 wk. Cardiac glycosides (eg, digoxin, digitoxin) cross the placenta, but neonates (and children) are relatively resistant to their toxicity. ACE inhibitors are contraindicated because they may cause fetal renal damage. Aldosterone antagonists (spironolactone, eplerenone) should be avoided because they may cause feminization of a male fetus. Other treatments for heart failure (eg, nonthiazide diuretics, nitrates, inotropes) may be continued during pregnancy depending on disease severity and fetal risk, as determined by a cardiologist and a perinatologist.

Arrhythmias

Atrial fibrillation may accompany cardiomyopathy or valvular lesions. Rate control is usually similar to that in nonpregnant patients, with β-blockers, Ca channel blockers, or digoxin (see Overview of Arrhythmias : Drugs for Arrhythmias). Certain antiarrhythmics (eg, amiodarone) should be avoided. If pregnant patients have new-onset atrial fibrillation or hemodynamic instability or if drugs do not control ventricular rate, cardioversion may be used to restore sinus rhythm.

Anticoagulation may be required because the relative hypercoagulability during pregnancy makes atrial thrombi (and subsequent systemic or pulmonary embolization) more likely. Standard or low molecular weight heparin is used. Neither standard heparin nor low molecular weight heparins cross the placenta, but low molecular weight heparins may have less risk of thrombocytopenia. Warfarin crosses the placenta and may cause fetal abnormalities (see Table: Some Drugs With Adverse Effects During Pregnancy), particularly during the 1st trimester. However, risk is dose-dependent, and incidence is very low if the dose is ≤ 5 mg per day. Warfarin use during the last month of pregnancy has risks. Rapid reversal of warfarin’s anticoagulant effects may be difficult and may be required because of fetal or neonatal intracranial hemorrhage resulting from birth trauma or because of maternal bleeding (eg, resulting from trauma or emergency cesarean delivery).

Management of acute supraventricular or ventricular tachycardia is the same as for nonpregnant patients (see Reentrant Supraventricular Tachycardias (SVT, PSVT) and see Ventricular Tachycardia (VT) : Treatment).


Endocarditis prophylaxis

For pregnant patients with a structural heart disorder, indications and use of endocarditis prophylaxis for nonobstetric events are the same as those for nonpregnant patients (see Infective Endocarditis : Prevention). The 2008 American Heart Association guidelines do not recommend endocarditis prophylaxis for vaginal and cesarean deliveries because the rate of bacteremia is low. However, in the highest-risk patients (eg, those with prosthetic heart materials, a history of endocarditis, an unrepaired congenital cyanotic heart lesion, or a heart transplant with a valvulopathy), prophylaxis is often considered when the membranes rupture, even though no evidence indicates any benefit.

If patients with a structural heart disorder develop chorioamnionitis or another infection (eg, pyelonephritis) requiring hospital admission, the antibiotics used to treat the infection should cover the pathogens most likely to cause endocarditis.


Key Points

  • Pregnancy may not be advisable for women with certain high-risk heart disorders (eg, pulmonary hypertension, Eisenmenger syndrome, coarctation of the aorta if uncorrected or accompanied by an aneurysm, Marfan syndrome with aortic root diameter of > 4.5 cm, severe symptomatic aortic stenosis, a single ventricle with impaired systolic function, prior postpartum cardiomyopathy, NYHA class III or IV heart failure).

  • Treat heart failure and arrhythmias during pregnancy as for nonpregnant patients, except avoid certain drugs (eg, warfarin, ACE inhibitors, aldosterone antagonists, thiazide diuretics, certain antiarrhythmics such as amiodarone).

  • Treat most pregnant patients who have atrial fibrillation with standard or low molecular weight heparin.

  • Indications for endocarditis prophylaxis for pregnant patients with a structural heart disorder are the same as those for other patients.

Valvular Stenosis and Insufficiency in Pregnancy

During pregnancy, stenosis and regurgitation (insufficiency) most often affect the mitral and aortic valves. Mitral stenosis is the most common valvular disorder during pregnancy. Pregnancy amplifies the murmurs of mitral and aortic stenosis but diminishes those of mitral and aortic regurgitation. During pregnancy, mild mitral or aortic regurgitation is usually easy to tolerate; stenosis is more difficult to tolerate and predisposes to maternal and fetal complications. Mitral stenosis is especially dangerous; the tachycardia, increased blood volume, and increased cardiac output during pregnancy interact with this disorder to rapidly increase pulmonary capillary pressure, causing pulmonary edema. Atrial fibrillation is also common.

Treatment

  • For mitral stenosis, prevention of tachycardia, treatment of pulmonary edema and atrial fibrillation, and sometimes valvotomy

  • For aortic stenosis, surgical correction before pregnancy if possible

Ideally, valvular disorders are diagnosed and treated medically before conception; surgical correction is often recommended for severe disorders. Prophylactic antibiotics are required in certain situations (see Endocarditis prophylaxis).


Mitral stenosis

Patients must be closely observed throughout pregnancy because mitral stenosis may rapidly become more severe. If required, valvotomy is relatively safe during pregnancy; however, open heart surgery increases fetal risk. Tachycardia should be prevented so that diastolic flow through the stenotic mitral valve can be maximized.

If pulmonary edema occurs, loop diuretics can be used.

If atrial fibrillation occurs, anticoagulation and control of heart rate (see Arrhythmias) are necessary.

During labor, conduction anesthesia (eg, slow epidural infusion) is usually preferred.


Aortic stenosis

Aortic stenosis should be corrected before pregnancy if possible because surgical repair during pregnancy has more risks and catheter valvuloplasty is not very effective.

During labor, local anesthesia is preferred, but if necessary, general anesthesia is used. Conduction anesthesia should be avoided because it decreases filling pressures (preload), which may already be decreased by aortic stenosis.

Straining, which can suddenly reduce filling pressures and impair cardiac output, is discouraged during the 2nd stage of labor; operative vaginal delivery is preferred. Cesarean delivery is done if indicated for obstetric reasons (see Cesarean Delivery).


Other Heart Disorders in Pregnancy

Mitral valve prolapse

This disorder occurs more frequently in younger women and tends to be familial. Mitral valve prolapse is usually an isolated abnormality but may cause some degree of mitral regurgitation or be accompanied by Marfan syndrome or an atrial septal defect.

Women with mitral valve prolapse generally tolerate pregnancy well. The relative increase in ventricular size during normal pregnancy reduces the discrepancy between the disproportionately large mitral valve and the ventricle.

β-Blockers are indicated for recurrent arrhythmias. Rarely, thrombi and systemic emboli develop and require anticoagulation.


Congenital heart disease

For most asymptomatic patients, risk is not increased during pregnancy. However, patients with Eisenmenger syndrome (now rare), primary pulmonary hypertension, or perhaps isolated pulmonary stenosis are predisposed, for unknown reasons, to sudden death during labor, during the postpartum period (the 6 wk after delivery), or after abortion at > 20 wk gestation. Thus, pregnancy is inadvisable. If these patients become pregnant, they should be closely monitored with a pulmonary artery catheter and an arterial line during delivery.

For patients with intracardiac shunts, the goal is to prevent right-to-left shunting by maintaining peripheral vascular resistance and by minimizing pulmonary vascular resistance.

Patients with Marfan syndrome are at increased risk of aortic dissection and rupture of aortic aneurysms during pregnancy. Bed rest, β-blockers, avoidance of Valsalva maneuvers, and measurement of aortic diameter with echocardiography are required.


Peripartum cardiomyopathy

Heart failure with no identifiable cause (eg, MI, valvular disorder) can develop between the last month of pregnancy and 5 mo postpartum in patients without a previous heart disorder. Risk factors include

  • Multiparity

  • Age ≥ 30

  • Multifetal pregnancy

  • Preeclampsia

The 5-yr mortality rate is 50%. Recurrence is likely in subsequent pregnancies, particularly in patients with residual cardiac dysfunction; future pregnancies are therefore not recommended.

Treatment is as for heart failure (see Treatment). ACE inhibitors and aldosterone are relatively contraindicated but may be used when the expected benefit clearly exceeds the potential risks.


Drugs Mentioned In This Article

  • Drug Name
    Select Trade
  • LANOXIN
  • CORDARONE
  • COUMADIN
  • INSPRA
  • ALDACTONE
  • PANHEPRIN

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