CHICAGO – Pregnancy-associated hemodynamic and physiologic changes can challenge hearts with diseased aortic valves. Understanding pregnancy’s toll on the body can help physicians take better care of pregnant women with aortic stenosis or aortic regurgitation, said Patrick T. O’Gara, MD. “This is a relatively infrequent condition, and it causes all of us a great deal of apprehension,” he said.
Dr. O’Gara, director of clinical cardiology at Brigham and Women’s Hospital, Boston, walked attendees through current recommendations for caring for pregnant women with aortic valve disease in a presentation at the annual Heart Valve Summit.
When talking to women with aortic valve disease, it’s important to let them know that a pregnancy during which they experience an adverse maternal cardiac event appears to increase their risk for later events as well, said Dr. O’Gara. One study of pregnancy in women with aortic valve disease, said Dr. O’Gara, found that the risk of later events for women who had had a cardiac event in pregnancy was 27% plus or minus 9 percentage points in the 5 years following pregnancy, while the risk was just 15% plus or minus 3 percentage points for women whose pregnancies were not complicated by cardiac adverse events (P = .02) (Heart. 2010 Oct;96(20):1656-61).
The World Health Organization classification of pregnancy risk, said Dr. O’Gara, provides some guidance. Patients who are WHO class III are considered to be high risk; pregnancy in these individuals calls for counseling and a multidisciplinary care team. Patients who fall into this class are those with mechanical heart valves, those with Marfan syndrome and aortic involvement with a valve diameter of 40-45 mm, and those with bicuspid aortic valve disease with a valve diameter of 45-50 mm.
WHO class IV patients, according to the guidelines, are at prohibitive risk. These patients should consider terminating a pregnancy if one occurs. Conditions that place women into WHO class IV include symptomatic severe aortic stenosis (AS), severe left ventricular dysfunction with an ejection fraction less than 40%, and severe coarctation of the aorta. Women with Marfan syndrome with aortic valve diameters greater than 45 mm and women with bicuspid aortic valves and a diameter over 50 mm also fall into this category of prohibitive risk.
If a physician is lucky enough to have a pre-conception relationship with a patient, then a host of considerations can come into play. In addition to cardiac risk stratification, obstetric and intrapartum risk to the mother as well as neonatal risk should be considered. Some factors to take into account are maternal life expectancy and potential long-term complications to the mother from pregnancy and childbirth.
Plasma volume increases rapidly through the first trimester, plateauing about halfway through pregnancy. With this normal dilutional anemia, “Most normal pregnancies are accompanied by a grade II systolic murmur, best heard at the upper left sternal border,” said Dr. O’Gara. Since stroke volume and heart rate both also increase through pregnancy, cardiac output goes up as well.
“Importantly, systemic vascular resistance is reduced throughout pregnancy,” said Dr. O’Gara. Consequently, “regurgitant heart valve problems are generally much better tolerated than stenotic lesions in pregnancy. That’s physiologic principle number one.”
In labor, abrupt hemodynamic changes include increases in cardiac output, heart rate, blood pressure, and venous return. “Labor and delivery are very stressful hemodynamic times for women,” said Dr. O’Gara.
In the immediate postpartum period, uterine contraction results in a return of a significant amount of blood to the maternal circulation. This effectively creates an autotransfusion, with resulting increased preload and cardiac output. The inferior vena cava is also freed from the pressure of a gravid uterus, increasing venous return further. Finally, there’s also a marked increase in systemic vascular resistance.
Aside from the risk of adverse cardiac events, other adverse outcomes for women can include an increased risk of premature rupture of membranes and postpartum hemorrhage. For the neonate, preterm birth and respiratory distress are more likely. Newborns are more likely to be small for gestational age, to suffer intraventricular hemorrhage, and to die. Depending on the parental genetic status, the infant may be at risk of congenital heart disease as well.
Neonatal risk may also be increased, said Dr. O’Gara. Some maternal conditions that can increase risk for the infant include a baseline New York Heart Association (NYHA) class of greater than II or having cyanosis; having a left heart obstruction; being a smoker; having a multiple gestation; having a mechanical heart valve; and taking an oral anticoagulant.
Ideally, a full discussion would include a genetic referral if indicated, as well as coordination with a gynecologist or primary care provider to provide contraception and to assist with planning for and optimizing outcomes of a pregnancy.
The American College of Cardiology and the American Heart Association have issued guidelines that include a class I recommendation regarding valve intervention before pregnancy for symptomatic patients with severe AS (those with aortic velocity of at least 4.0 m/sec, or mean pressure gradient greater than 41 mm Hg; stage D). For patients who meet the same hemodynamic criteria for severe AS but who are asymptomatic (stage C), the guidelines have a class IIa recommendation that pre-pregnancy valve intervention is “reasonable.” These recommendations have level C evidence supporting them.
However, another class IIa recommendation for patients with severe AS who are already pregnant advises valve intervention only in the case of hemodynamic deterioration, or the development of NYHA class III to IV heart failure symptoms. This is backed by grade B evidence, according to the associations.
For aortic regurgitation (AR), a level I recommendation advises valve repair or replacement before pregnancy if patients are symptomatic and have severe (stage D) regurgitation. Pregnant patients with severe regurgitation should only be considered for a valve operation if they have refractory NYHA class IV heart failure symptoms. These recommendations have level C evidence supporting them.
Since AR is better tolerated in pregnancy than AS, the nature of the valve disease is one of many factors to consider when deciding whether to perform intervention before the patient becomes pregnant. Plans for future pregnancy may also affect the choice of prosthesis, as anticoagulation management during pregnancy can be extremely tricky.
The recommendations overall make clear that, based on available evidence, “there should be a high threshold for intervention during pregnancy,” said Dr. O’Gara. And no one should go it alone when taking care of these complicated patients. “Care of pregnant women with heart disease requires coordination with a multidisciplinary team,” he said.
Dr. O’Gara reported no relevant disclosures.
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