June 18, 2014
Maternal cardiac disease complicating a pregnancy occurs in approximately 1 to 3 percent of pregnancies. The etiology of the cardiac disease includes congenital defects, rheumatic heart disease, cardiomyopathy and ischemic disease. The prevalence of these etiologies varies by region, with rheumatic heart disease still the most common concern in the developing world. However, in the United States, declining cases of rheumatic heart disease and improved survival of patients with congenital heart disease have resulted in congenital defects being the most common cause of maternal heart disease affecting pregnancy.
The cardiovascular changes during pregnancy superimposed on the altered physiology of many congenital defects can lead to maternal and fetal complications and require expert management and evaluation during the antepartum, peripartum and postpartum periods. A multidisciplinary team approach is optimal, with participation from congenital cardiology, cardiac surgery, maternal and fetal medicine, anesthesiology, and neonatology.
The hemodynamic changes during pregnancy are significant and begin early in gestation. Heart rate, stroke volume, afterload, preload and contractility are all affected, with heart rate increases occurring as early as two weeks after conception. Increases in heart rate, stroke volume, preload and contractility combined with a drop in afterload result in increased cardiac output throughout pregnancy. The most significant increase in cardiac output occurs during the first two trimesters.
Cardiac structure is also altered by pregnancy, with increased ventricular wall thickness and ventricular mass noted. Overall, blood volume increases by approximately 40 percent, and cardiac output by about 45 percent during gestation. Labor and delivery require additional alterations in cardiac physiology, including a further increase in cardiac output by 30 percent during contractions.
Maternal and fetal outcomes of a pregnancy complicated by maternal cardiac disease depend on the interaction of the physiology of the specific cardiac lesion with the altered cardiac physiology of pregnancy. While many women with cardiac disease can complete a pregnancy successfully, there are cardiac conditions that pose a high risk of maternal mortality, so pregnancy is contraindicated for these women. These conditions include:
- Pulmonary hypertension (pulmonary artery pressure > 75 percent systemic)
- Ventricular dysfunction with New York Heart Association (NYHA) Class III to IV heart failure symptoms
- Marfan syndrome with aortic enlargement > 40 mm
Many cardiac conditions, including those with outflow obstruction, cause increased risk to the mother and fetus but are not absolutely contraindicated. Therefore, a risk model has been developed by Canadian investigators to appropriately advise patients regarding risk of cardiac complication during pregnancy. It was published in Circulation in 2001.
Ideally, mothers should seek consultation prior to pregnancy to best understand their cardiac risk and develop a plan for care during gestation and delivery. Cardiac care during the pregnancy may include starting or adjusting cardiac medications, utilizing catheter-based procedures, or even undergoing cardiac surgery. A review of patients undergoing cardiopulmonary bypass during pregnancy at Mayo Clinic demonstrated a fetal loss rate of 21 percent. Fetal loss was associated with emergency cardiac surgery, early gestational age and maternal comorbidities.
The risk of pregnancy in patients with complex anatomy and single ventricle physiology is not easily assessed, but successful pregnancies are reported in this cohort of patients with the most severe congenital heart diseases.
Use of the Fontan procedure
The Fontan procedure, a surgical intervention that directs caval blood flow to the pulmonary arteries, is used to palliate patients with single ventricle physiology. The cardiac output after Fontan is determined by the central venous pressure (CVP), the left atrial pressure (LAP) and the pulmonary vascular resistance (PVR). Cardiac output = (CVP-LAP)/PVR.
Patients with Fontan physiology are preload dependent, and it can be difficult to significantly increase cardiac output. These patients have an increased incidence of atrial arrhythmias and intracardiac thrombi, impacting their ability to complete a pregnancy without complications.
A recent multicenter retrospective study of 71 pregnancies in patients after a Fontan, published in the Journal of the American College of Cardiology in 2013, demonstrated a 73 percent live birth rate, with a high rate of preterm delivery (average gestational age of 34 weeks). Maternal cardiac complications occurred in 37 percent and obstetrical complications in 52 percent of these pregnancies. There was no maternal mortality during pregnancy, but it was unclear from these data if long-term survival is affected.
There is an increased risk of fetal congenital cardiac disease in the offspring of a parent with a congenital heart defect. Therefore, pregnancy management should include evaluation of the fetus for cardiac abnormalities. Fetal echocardiography is an excellent tool that can be utilized optimally at 18 to 22 weeks gestation for delineation of fetal cardiac anatomy.
At Mayo Clinic, a 32-year-old woman presented at 11 weeks gestation for a second opinion on the risk of continued pregnancy. A murmur had been heard two weeks prior to the consultation during an office visit for an upper respiratory tract infection.
Further investigation with echocardiography demonstrated severe aortic valve stenosis with a bicuspid aortic valve. The ascending aortic dimension was normal, as was the left ventricular systolic function. The patient was active and asymptomatic, having delivered a healthy term infant 15 months prior. Termination of the current pregnancy had been advised at another institution.
Using the risk model, specialists felt that the patient had approximately a 30 percent risk of cardiac complication during pregnancy. It was emphasized to the patient that the risk of death was low. The patient elected to continue the pregnancy with close observation.
The patient was seen regularly by maternal-fetal medicine and congenital cardiology. At 20 weeks gestation, a fetal echocardiogram demonstrated fetal situs inversus without evidence of other structural heart disease. The patient was seen in consultation with pediatric cardiology and neonatology. The pregnancy progressed without symptoms. In the third trimester, the patient met with anesthesia and a delivery plan was developed.
The patient relocated to Rochester, Minnesota, at 37 weeks gestation to be near the delivery medical center. At 39 weeks gestation, spontaneous labor occurred and a healthy infant was delivered.
The case demonstrates the importance of cardiac consultation with a specialist in the care of pregnancy complicated by maternal cardiac disease to appropriately assess risk and develop a multidisciplinary approach to improve the odds of successful maternal and fetal outcomes.
For more information
Siu SC, et al. Prospective multicenter study of pregnancy outcomes in women with heart disease. Circulation. 2001;104:515.
Canobbio MM, et al. Pregnancy after Fontan operation: Early and late outcomes. Journal of the American College of Cardiology. 2013;61:e427.