This is a relatively infrequent question at consultation, as severe heart failure may itself impair ovarian function and depress libido and fertility. However, in those patients with preexisting heart disease who wish to become pregnant, the associated changes in cardiovascular physiology in particular, a 50% increase in cardiac output, a 40% increase in plasma volume, and peripheral vasodilation can increase maternal and fetal morbidity and mortality. The potential cardiovascular accidents comprise systemic or pulmonary hypertension, tachyarrhythmia, and bradyarrhythmia, embolism, infective endocarditis, aggravated heart failure, myocardial ischemia, and acute pulmonary edema, all of which may be associated with varying degrees of hemodynamic destabilization, up to and including sudden death. Although the overall risk obviously varies with the type of heart disease and its severity, risk awareness is the key to effective heart failure prevention.
Risk assessment in the prospective mother
Individual risk assessment presupposes a precise diagnosis, a careful estimate of cardiovascular reserve, and thorough understanding of the cardiovascular response to pregnancy. Risk is stratified according to the following factors:
• Type of heart disease (including surgical repair, postsurgical hemodynamic status, etc).
• Prepregnancy functional status (NYHA class, cyanosis, arrhythmia, cardiac events, etc).
• Probability of pregnancy-induced complications.
• Choice of drug therapy.
Fetal risk must also be considered, given that normal uterine blood flow and placental function are essential to fetal viability and growth. Maternal hypertension, for example, correlates with a higher risk of perinatal mortality, stillbirth, and intrauterine growth retardation. Only about 45% to 55% of hypoxemic mothers deliver a live baby; such babies are often underweight and/or premature. The high incidence of spontaneous abortion correlates directly with maternal hematocrit and hemoglobin levels. Mothers with heart disease, in particular aortic stenosis or another type of outflow obstruction, are at higher risk of giving birth to infants with noncardiac abnormalities (up to 14% of births). Genetic counseling will be required if the maternal heart disease is congenital. Advice also depends on a review of other systems (especially kidneys and liver) and obstetric referral. Clearly, if corrective treatment is indicated irrespective of an intended pregnancy, this should be performed in the first instance.
Pulmonary hypertension (systolic pulmonary artery pressure >50 mm Hg), assessed by Doppler echocardiography of the pulmonary and tricuspid valves and calculation of atrioventricular pressure gradient, is associated with maternal mortality of 50% and perinatal mortality only fractionally lower at 40% to 50%, irrespective of the underlying heart disease. The increase in cardiac output and decrease in systemic resistance are poorly tolerated, given the stability of high pulmonary resistance.
Cyanosis carries a much higher risk of heart failure than in noncyanotic patients (47% vs 4.3%). Chronic cyanosis lowers the probability of normal gestation, being associated with poor fetal growth, prematurity, dysmaturity, and high fetal loss related to the hematocrit. It also increases the risk of paradoxical embolism.
A history ofperipartum cardiomyopathy carries a high risk of a significant decrease in left ventricular function, causing clinical deterioration and even death.
New York Heart Association (NYHA) functional classes III and IV carry a 30% to 50% risk of cardiovascular morbidity, a 25% to 50% risk of maternal death, and a 30% risk of fetal death. Women in classes I and II, on the other hand, have a low risk of maternal mortality (<1%) and 0% fetal mortality.
Calculating cardiac reserve
Given the additional demands of pregnancy, estimation of a patient’s functional impairment at rest should be supplemented by that of their cardiac reserve, but the paucity of relevant clinical experience prevents this logical proposal from being presented as a recommendation. Ideally it should comprise cardiopulmonary testing, with measurement of the anaerobic threshold and 02 consumption, characterizing the patient’s physical performance, heart rate and blood pressure in response to dynamic stress, and their ability to increase cardiac output in response to physical effort. Dobutamine challenge provides an alternative approach. However, robust decision-guiding criteria are currently unavailable in either case.
Maternal risk index
The most recent maternal risk index, proposed by Siu et al, authors of the 2001 Canadian multicenter CAR-diac disease in PREGnancy (CARPREG) study, incorporates the following predictors:
Prior cardiac events (heart failure, transient ischemic attack, stroke) or arrhythmia.
pregnancy; risk assessment; cardiovascular event; cardiac reserve; contraindication; peripartum cardiomyopathy; contraceptive drug; prognosis