Peripartum cardiomyopathy

HOW TO SUPPORT A WOMAN WHO DEVELOPS THIS UNCOMMON BUT POTENTIALLY DEADLY COMpLICATION OF PREGNaNCY

Eva Thomas, 29, is 37 weeks pregnant and in the past several weeks has developed increasing dyspnea at rest, paroxysmal nocturnal dyspnea, orthopnea, dry cough, peripheral edema, and an S3 heart sound. Concerned that she may have heart failure, you refer her to a cardiologist, who diagnoses periparturn cardiomyopathy, an uncommon but lifethreatening complication of pregnancy.

In this article, I'll describe how to recognize and manage this potentially fatal cardiac condition.

CARDIAC MYSTERY Peripartum cardiomyopathy is the development of heart failure in the last trimester of pregnancy or within the first 6 months following delivery when no specific cause of heart disease can be determined. This condition accounts for less than 1% of all pregnancyrelated cardiovascular problems.

Any pregnant woman can develop peripartum cardiomyopathy, but she's at particular risk if she's African-American, over age 30, or multiparous; if she has pregnancyinduced hypertension; or if she's carrying more than one fetus. The cause of peripartum cardiomyopathy is unknown, but evidence suggests it's a type of myocarditis resulting from a viral, autoimmune, or idiopathic process.

Women who develop peripartum cardiomyopathy may recover completely; those who don't are managed medically. Despite medical management, however, some women eventually will need heart transplantation. For patients who don't receive a transplant, the 5year mortality rate ranges from 15% to 35%. Women with persistent cardiomegaly (lasting more than 6 months after onset of symptoms) who become pregnant again have a 50% chance of recurrent cardiomyopathy, which is always fatal without a transplant.

RECOGNIZING TROUBLE

The signs and symptoms of peripartum cardiomyopathy are similar to those of heart failure (see Red Flags: When to Get Further Evaluation). Onset of symptoms may be rapid or insidious; early diagnosis is important because of the disease's progressive nature.

Clinical diagnosis of heart failure in the third trimester of pregnancy is difficult, as many healthy pregnant women experience fatigue, dyspnea, reduced exercise tolerance, edema, tachycardia, systolic murmurs, and an S3 heart sound. Peripartum cardiomyopathy is diagnosed by excluding other conditions.

If you suspect that your patient may have periparturn cardiomyopathy, she should be immediately referred to a cardiologist familiar with the condition. He'll obtain a thorough history and physical examination and may order lab studies, electrocardiography, chest X-ray, and two-dimensional Mmode Doppler echocardiography to support the diagnosis and rule out other causes of cardiomyopathy (see Findings That Support the Diagnosis). He may also order right-sided and left-sided heart catheterization to assess her hemodynamic status and rule out underlying cardiac disease and an endomyocardial biopsy to rule out a viral cause.

EASING THE RrS WORK

Drug therapy in peripartum cardiomyopathy, as in heart failure, is aimed at decreasing symptoms and maximizing function. Typically, the physician prescribes digoxin to increase myocardial contractility and diuretics and vasodilators to decrease preload and afterload, maximizing cardiac function. Intravenous (I.V) dobutamine, milrinone, or nitroprusside may also help maximize heart function, especially in patients with severe heart failure. The physician will also correct any electrolyte imbalances to prevent cardiac arrhythmias and may order an anticoagulant to prevent thrombus formation related to the enlarged heart, hypercoagulable state of pregnancy, and restricted physical activity.

SPECIAL CONSIDERATIONS FOR THE PREGNANT PATIENT

Because some drugs can't be given to pregnant women, the drug regimen will depend on whether your patient's symptoms begin before or after her child is born. Many medications used to treat heart failure cross the placenta and threaten the fetus, so the risks of therapy to the fetus must be weighed against the benefits to the mother. Although digoxin crosses the placenta and is excreted in small amounts in breast milk, its benefits far outweigh possible adverse reactions. Hydralazine also may be given as an alternative to angiotensin-converting enzyme inhibitors, although it may cause transient neonatal thrombocytopenia.

Heparin is the anticoagulant of choice during pregnancy because it doesn't cross the placenta, and bleeding during delivery can be controlled with protamine. Because heparin isn't excreted in breast milk, it also can be used after delivery, but most women are prescribed warfarin after delivery.

Several drugs that typically are given to patients with heart failure shouldn't be given to pregnant or nursing mothers: Loop diuretics such as furosemide (Lasix) can cause electrolyte imbalances and impair maternal or fetal cardiac circulation. They should be given only with close monitoring to prevent dehydration.

Thiazide diuretics can cause fetal thrombocytopenia. Angiotensin-converting enzyme inhibitors are absolutely contraindicated during pregnancy because they may cause fetal death. They aren't recommended for nursing mothers because the drug may be excreted in breast milk.

Beta-blockers may cause fetal bradycardia and hypoglycemia and have been linked to premature labor and low birth weight. Warfarin has been linked to fetal death and birth defects but can be used after delivery because it isn't excreted in breast milk.

CARE DURING LABOR AND DELIVERY

Because labor greatly increases the demands on the failing heart, patients with peripartum cardiomyopathy are at increased risk for developing heart failure and pulmonary edema and must be closely monitored.

Signs of pulmonary edema include sudden onset of agitation, fever, tachycardia, tachypnea, and increased blood pressure; cool, clammy skin; and use of accessory muscles for breathing. On auscultation, you may hear an S3 heart sound, crackles, and wheezing. Watch for weak, thready pulses and cyanosis in the extremities (signs of decreased perfusion).

If your patient develops pulmonary edema, the fetus must be delivered immediately. (The obstetrician and cardiologist will decide whether cesarean section or induction is needed, depending on the mother's condition.) Assess and monitor her airway, breathing, and circulation, positioning her for breathing comfort and administering oxygen via nasal cannula. Attach her to a pulse oximeter and obtain a blood sample for arterial blood gas analysis. Monitor her heart rate and rhythm and blood pressure.

Before delivery, the physician will insert a pulmonary artery catheter to allow close monitoring of the patient's left ventricular function and hemodynamic status. The patient's hemodynamic status will continue to be monitored after delivery because of the large fluid shifts that occur postpartum.

HELPING MRS. THOMAS

Let's return to Mrs. Thomas, the patient we met at the beginning of this article. She's hospitalized, and her hemodynamic status is stabilized with I.V. furosemide, digoxin, and dobutamine and S.C. heparin. A week after admission, labor is induced, and she delivers a healthy baby vaginally.

In the hospital, you'll monitor Mrs. Thomas' electrolytes and serum drug levels regularly. Monitor her weight and intake and output daily. After discharge, she'll be monitored by a home health care nurse and be closely followed by her cardiologist.

Mrs. Thomas chose not to breast-feed, and she's discharged on enalapril, low-dose metoprolol, digoxin, furosemide, and warfarin. Teach her about adverse reactions such as bleeding and bruising and potential interactions with foods and over-the-counter medications. Explain that the frequency of blood work and dosage adjustment will decrease once a therapeutic drug range is established.

Tell Mrs. Thomas to limit physical activity, avoid strenuous activity, and not lift anything heavier than 15 pounds (6.8 kg). She should limit fluids to 2 liters daily, avoid alcohol and products containing caffeine, and limit salt to 2 grams daily. If she smokes, encourage her to quit. She should also avoid heat and humidity, which can strain an already weakened heart.

Tell her she can hold her new baby when she's sitting, but others should lift and carry the baby whenever possible. Encourage her to begin a formal cardiac rehabilitation program after her obstetrician gives the okay.

Because hospitalization following delivery is prolonged, Mrs. Thomas needs additional support and care. Provide emotional support for Mrs. Thomas and her family as they adjust to the challenges of caring for the baby and mother.

By learning to recognize peripartum cardiomyopathy and how it's treated, you can provide the support and comprehensive care that patients like Mrs. Thomas need.

SELECTED REFERENCES

Brown, C., and Bertolet, B.: "Peripartum Cardiomyopathy: A Comprehensive Review," American Journal of Obstetrics and Gynecology: 178(2):409-414, February 1998.

Campbell, C.: "Primary Care for Women: Comprehensive Cardiovascular Assessment," Journal of Nurse Midwifery. 40(2):137-149, March 1995.

Lampert, M., and Lang, R.: "Peripartum Cardiomyopathy," American Heart Journal. 130(4): 860-870, October 1995. Morley, C., and Lim, B.: "The Risks of Delay in Diagnosis of Breathlessness in Pregnancy," British Medical Journal. 311(7012):1083-1084, October 1995.

Oakley, C.: "Pregnancy and Heart Disease," British Journal of Hospital Medicine. 55(7): 423-426, April 1996.

Anator at Hahnemann Marie G. McHugh was formerly heart failure research nurse coordinator at Hahnemann University in Philadelphia, Pa. She lives in Horsham, Pa.

Copyright Springhouse Corporation Mar 1999
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