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Preconception Care: Optimization of Cardiac Risk

Mary M. Canobbio

Introduction

The number of reproductive age women who are born with or develop heart disease is steadily growing, and with each decade the numbers continue to increase. While the exact numbers are unknown, advances in both medical and surgical arenas have created a larger pool of women of childbearing age with heart disease. Consequently, questions regarding pregnancy become an important issue for all providers who care for patients with heart disease, including congenital heart disease (CHD), acquired cardiac disorders, and those following cardiac transplant. In order to ensure their safety, it is imperative these patients undergo preconception counseling regardless of their desire to become pregnant; that they understand the actual or potential risk to them and to their fetus and the importance of avoiding an unplanned pregnancy. For cardiac and obstetrical providers, a number of risk scoring scales have been developed to help guide management. The importance of using risk assessment models to advise patients on the risk of pregnancy is reviewed.

Scope of the Problem

In the developed world, while prevalence rates are low, cardiovascular disease is the most common cause of maternal mortality [1–5]. CHD, which affects 0.8%–1.5% of the population, is the most frequently encountered cardiac disorder in obstetrics [6]. While the majority of women with simple CHD will tolerate pregnancy well, those with moderate to complex lesions that have been surgically repaired in childhood may present with residual effects of their surgical procedure as they grow older. It is therefore difficult to categorize these patients based solely on their primary defect, because many may be at risk for developing complications such as ventricular dysfunction, arrhythmias, or thromboembolic events. For women with complex CHD who have undergone surgical repair, such as univentricular circulation (Fontan palliation) or transposition of great arteries (Mustard, Senning), or those with cyanotic heart disease, the risk of developing complications during and after delivery is higher [7–13]. For women who remain cyanotic (O2 saturation ≤85%), with or without pulmonary hypertension, or those with critical left ventricular outflow tract obstruction (gradients >60 mmHg) or severe ventricular function pregnancy is not advisable [7].

While CHD is more prevalent, those with acquired heart disease carry a higher risk of mortality during childbirth [7,14]. These include women with ischemic heart disease, aortopathies, various cardiomyopathies, hypertensive disorders, and valvular heart disease, particularly requiring anticoagulation. In addition, over the past 2–3 decades, the number of children undergoing heart transplant has risen and consequently the number of these young women now and in future will be seeking to become pregnant. Today, transplanted female patients represent approximately 20% of overall cardiac transplants population, 25% of which are reported to be between the ages of 18–39 years [15,16]. While successful pregnancies have been reported, the majority experience complications such as hypertensive disorders of pregnancy, prematurity, graft rejection, and/or infection [17,18].

Preconception Counseling

The task of advising females regarding the safety of pregnancy has been challenging until recently. After almost three decades, the body of literature in this field has moved from expert opinion and case reporting to cumulative data reported from multicenter studies and international registries [8,19]. As result, we now have growing evidence-based data that permits us to advise patients regarding the safety of carrying a pregnancy. Less clear is the potential risk pregnancy poses to long-term survival of patients with complex cardiac lesions. Reports regarding long-term outcomes in patients with CHD indicate that for the majority of patients, the effects of pregnancy resolve within the first year after delivery, while for others it may be longer, but may not have a lasting effect on long-term survival [7,9].

Estimating Maternal and Fetal Risk

While the information regarding pregnancy outcomes across the spectrum of various cardiac disorder is growing, it remains a challenge to assign risk solely on the basis of their cardiac lesion. Therefore, in order to determine maternal risk, the patients must be evaluated against a number of parameters (Table 4.1) that include not only maternal primary disorder, but also any residual effects associated with the primary defect, such as diminished ventricular function, history of arrhythmias, and any prior surgical or procedural interventions [47]. A thorough review of the past medical history should also include the presence of any noncardiac comorbidities that may influence pregnancy, such as thyroid disease, diabetes, and history of use of recreational drugs, alcohol, and cannabis products, particularly those with tetrahydrocannabinol (THC), which passes through the placenta [20]. The history must also take into account a number of social factors such as history of medical compliance, geographical distance to doctor’s office and hospital as well the patient’s spousal and extended family support. The latter is of particular concern for the patient considered high risk in the event that post-delivery clinical problems arise making it difficult for the patient to care for her infant.

Maternal Risk Assessment

Maternal risk assessment is based on several factors as outlined above. Several predictors have been described and more recently various risk assessment models have been validated for use in pregnancy.

1.Functional capacity: Maternal functional capacity using the New York Heart Association (NYHA) classification has traditionally been used as a predictor of maternal and fetal prognosis. Thus women who enter the pregnancy in NYHA class I and II were reported to have a maternal mortality rate of less than 1% (0.4%) while class III–IV patients could have a rate that ranged from 5%–15%. A major limitation of this system, however, is that assessments are based upon subjective assessment rather than clinical data.

2.Risk scoring scales: Over the last two decades, a number of pregnancy risk scoring scales have been developed to better predict the likelihood of developing cardiac complications during pregnancy.

a.CARPREG: The first risk scoring system for women with various forms of heart disease was the Cardiac Disease in Pregnancy risk index (CARPREG), a population-based study that assesses the risk of an adverse maternal event on the basis of four specific indicators (Table 4.2) [19]. Each indicator is awarded one point each for poor functional status (NYHA >II), cyanosis (<90%), left ventricular (LV) systolic dysfunction, left heart obstruction, and history of cardiac events prior to pregnancy including arrhythmias, stroke, or pulmonary edema [19]. Thus a risk index score of 0 is estimated at a 5% risk, but a risk index of 1 rises to 27%, and at a risk index of >1, the likelihood of adverse event is 75%. For the past two decades this has been the most widely used index despite reported limitations, including that it was event-directed versus lesion-specific, thus excluding patients born with congenital heart disease, with pulmonary hypertension, and prosthetic valves [21].

b.ZAHARA: The ZAHARA (Zwangerschap bij vrouwen met een Aangeboredn HARtAfwijking-II) classification, a second retrospective study, was designed for patients with CHD, but also included patients with mechanical prosthetic valves. In addition, it identified additional predictors, such as use of cardiac medications before pregnancy, and unrepaired cyanotic heart disease, to develop a pregnancy risk score [22] (Table 4.2).

While both CARPREG I and ZAHARA, have been recognized as important risk assessment systems, they each are limited to their study population, and the retrospective and small sample size nature of the study, but have identified significant predictors for maternal and fetal risk that can impact pregnancy outcomes. These include prior cardiac events, left heart obstruction (mitral valve area <2 cm2, aortic valve area <1.5 cm2, peak left ventricular outflow tract gradient >30 mmHg), and reduced systemic ventricular systolic function and baseline NYHA functional class >II [14,23].

c.Modified World Health Organization (WHO) risk classification: The modified WHO risk classification is the more widely used and simplest risk scoring scale being used. A large validated prospective study, it integrates all known maternal cardiovascular risk predictors plus varying forms of heart disease, and takes into account medical history that includes comorbidities as well as functional class [25]. Recommended by the European Society of Cardiology (ESC) as the most reliable method of risk assessment to determine pregnancy risk of women with heart disease, it is made up of four categories, the WHO class I, which indicates low risk, WHO class II, intermediate risk, WHO class III, high risk, and WHO class IV, indicates pregnancy is contraindicated because of extreme high risk (Table 4.3) [6,7,21,24,26].

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