Knowledge of the cardiovascular changes of pregnancy is necessary to distinguish between normal and pathologic signs and symptoms in the pregnant patient (Table 42). During a normal pregnancy, patients develop a relative anemia due to increases in plasma volume and, to a lesser degree, erythrocyte mass. Mean arterial pressure slightly decreases in the setting of reduced systemic vascular resistance and increased heart rate and cardiac output. By the 32nd week of pregnancy, maternal cardiac output peaks at approximately 40% above the prepregnancy level. During delivery, the cardiac output may increase to as much as 80% above the prepregnancy level owing to increased heart rate and blood pressure.
All women with cardiovascular disease who are anticipating pregnancy should undergo specialized prepregnancy cardiovascular evaluation, high-risk obstetrics consultation, obstetric anesthesia consultation, and, if appropriate, genetic counseling to evaluate the risks of pregnancy and develop a management plan for labor and the postpartum period. Prepregnancy risk assessment tools include the CARPREG index (Table 43), ZAHARA risk score (Table 44), and the modified World Health Organization pregnancy risk classification (Table 45). All of these tools are used to estimate risk for complications during pregnancy in women with cardiovascular disease.
Pregnancy is contraindicated in patients with ventricular outflow tract obstruction (for example, aortic stenosis or coarctation of aorta) and those with left ventricular systolic dysfunction (ejection fraction <40%) accompanied by New York Heart Association functional class III or IV heart failure symptoms because these conditions confer a high risk for maternal and fetal complications. Women with severe pulmonary hypertension are at high risk for maternal death, with a mortality rate of up to 30%.
Women with obstructive valvular lesions may experience symptoms during pregnancy as a result of the increases in blood volume and cardiac output. These patients should be evaluated to determine whether cardiac intervention should be considered before pregnancy. Women with regurgitant valve lesions tend to tolerate pregnancy well. Women with symptomatic hypertrophic cardiomyopathy should be treated with nonvasodilating β-blockers (metoprolol, bisoprolol, labetalol, pindolol, propranolol), with monitoring of fetal growth.
Vaginal delivery is generally preferred for patients with cardiovascular disease because it results in less blood loss, quicker recovery, and lower risk for thrombosis than does cesarean delivery. Cesarean delivery is recommended for obstetric reasons in women with severe decompensated cardiovascular disease or a markedly dilated aorta. In women receiving warfarin therapy, cesarean delivery is indicated to reduce the risk for fetal intracranial hemorrhage because the fetus is fully anticoagulated.
Peripartum cardiomyopathy is left ventricular systolic dysfunction recognized toward the end of pregnancy or in the months following delivery in the absence of another identifiable cause. Risk factors for peripartum cardiomyopathy include multiparity, age older than 30 years, African descent, multifetal pregnancy, gestational hypertension, preeclampsia, a previous episode of peripartum cardiomyopathy, and therapy with a tocolytic agent.
Death in women with peripartum cardiomyopathy is caused by heart failure, thromboembolic events, and arrhythmias. Most women who develop peripartum cardiomyopathy recover fully, as measured by improvement in ejection fraction; however, 13% have major cardiovascular events or persistent severe cardiomyopathy. Studies suggest that the time frame for recovery is 6 months. Prognostic factors that portend a worse outcome include severe left ventricular dysfunction/dilatation or Black race.
Women with peripartum cardiomyopathy should be promptly treated with medical therapy, which may include β-blockers, digoxin, hydralazine, nitrates, or diuretics. ACE inhibitors, angiotensin receptor blockers, and aldosterone antagonists are teratogenic and should be avoided until after delivery. Owing to the risk for thromboembolism associated with peripartum cardiomyopathy, anticoagulation is recommended for women with left ventricular ejection fraction below 35%. The choice of anticoagulant (heparin or warfarin) depends on whether the patient is still pregnant and the time since delivery; the decision should be made in consultation with a cardiologist. Duration of anticoagulation is at least 8 weeks, although therapy can be discontinued sooner if the ejection fraction normalizes.
Women with severe refractory heart failure due to peripartum cardiomyopathy should be referred for further evaluation and treatment, including ventricular assist device placement or heart transplantation. Limited evidence from small studies suggests that bromocriptine, which blocks prolactin secretion, improves left ventricular ejection fraction and clinical outcomes when added to peripartum-related heart failure therapy; however, its use is considered investigational.
Because subsequent pregnancy is often associated with recurrent or further reduction of left ventricular function, potentially resulting in clinical deterioration or death, women with a previous episode of peripartum cardiomyopathy with persistent left ventricular dysfunction should be advised to avoid future pregnancy.
Women with Marfan syndrome have an increased risk for pregnancy-related aortic dissection. Aortic repair is recommended before pregnancy in women with Marfan syndrome and an aortic diameter of 4.5 cm or greater. Risk factors for dissection during pregnancy in patients with Marfan syndrome with an aortic diameter of less than 4.5 cm include rapid dilatation of the aorta or a personal or family history of aortic dissection. These patients should be counseled to have aortic replacement before pregnancy.
Spontaneous coronary artery dissections may occur during pregnancy or in the postpartum period. Conservative, noninterventional therapy is preferred for most patients. A high index of suspicion is required, as patients presenting with spontaneous coronary artery dissection are generally considered at low risk for acute coronary syndromes.
Guidelines for the use of select cardiovascular drugs during pregnancy are outlined in Table 46. The FDA formerly used a letter system to categorize drugs by their fetal effects during pregnancy; however, with the implementation of a new pregnancy and lactation labeling rule in 2015, more information is now provided on drug effects in pregnant women, lactating women, and women and men of reproductive potential (see MKSAP 18 General Internal Medicine). Most cardiovascular drugs are not FDA approved for use during pregnancy because of limited safety data. Cardiovascular medications should be used only when needed and at the lowest possible dosage, and the desired therapeutic effect should outweigh the risk.
β-Blocker use during pregnancy or lactation requires periodic fetal and newborn heart rate monitoring because β-blockers cross the placenta and are present in human breast milk. Labetalol is the preferred β-blocker in this setting. Atenolol has been linked to premature delivery and small-for-gestational-age babies; therefore, it is usually avoided during pregnancy.
Adenosine is the drug of choice for treatment of acute symptomatic supraventricular tachycardia during pregnancy. Recurrent episodes of tachycardia are often treated with β-blockers and digoxin; sotalol and flecainide have also been safely used. Because of toxicity concerns, amiodarone is rarely used.
ACE inhibitors, angiotensin receptor blockers, and aldosterone antagonists should be avoided during pregnancy because of their associated teratogenicity, although some ACE inhibitors are safe to use while breastfeeding. There is inconclusive evidence on the safety of angiotensin receptor blockers while breastfeeding; thus, these drugs are generally avoided during lactation. Spironolactone is considered compatible with breastfeeding.
The LactMed database (https://toxnet.nlm.nih.gov/newtoxnet/lactmed.htm) provides information on drugs to which breastfeeding mothers may be exposed, including potential adverse effects and suggested therapeutic alternatives.
Pregnancy is associated with hypercoagulability, and anticoagulation is often indicated in pregnant patients. Table 47 lists the indications, recommended regimens, and monitoring parameters for therapy. Prepregnancy counseling is recommended for all women requiring long-term anticoagulation to enable them to make informed decisions regarding anticoagulant preference and to understand the maternal and fetal risks.
Warfarin, unfractionated heparin, and low-molecular-weight heparin can all be used during pregnancy. Careful monitoring and dosage adjustment are indicated for all anticoagulation regimens. It is important to note that warfarin use during the first trimester can cause warfarin embryopathy when the daily dose is greater than 5 mg. Warfarin is stopped before delivery owing to the risk for fetal intracranial hemorrhage if spontaneous labor and vaginal delivery occur while the mother (and thus the fetus) is anticoagulated with warfarin.
Pregnant women with a mechanical valve prosthesis represent a high-risk subset of patients; concerns include valve thrombosis with its associated maternal risks, bleeding, and fetal morbidity and mortality. Warfarin appears to be the safest agent to prevent maternal prosthetic valve thrombosis; however, warfarin poses an increased fetal risk, with possible teratogenicity, miscarriage, and fetal loss due to intracranial hemorrhage. Data suggest that low-molecular-weight heparin and unfractionated heparin are safer for the fetus than warfarin is, but these therapies appear to increase the risk for maternal prosthetic valve thrombosis.
Guidelines from the American College of Cardiology/American Heart Association on the management of anticoagulation during pregnancy in the setting of mechanical valve prosthesis recommend warfarin during the first trimester if the daily dose is 5 mg or less at the time of conception. Intravenous unfractionated heparin or dose-adjusted low-molecular-weight heparin is preferred if the warfarin dose is more than 5 mg daily. During the second and early third trimesters, warfarin therapy is preferred. Intravenous unfractionated heparin is preferred for anticoagulation around the time of delivery in patients with a mechanical valve prosthesis. Weekly monitoring of the anticoagulation level is recommended during pregnancy irrespective of the regimen used, with dosage adjustment as indicated.
Limited data do not suggest a high risk for embryopathy or neonatal complications with exposure to non–vitamin K antagonist oral anticoagulants. However, owing to small case numbers, it is recommended that pregnancy and lactation be avoided in patients receiving non–vitamin K antagonist oral anticoagulants.