A multitude of physiologic adaptations of the cardiovascular system to pregnancy influence the impact of heart disease in the pregnant woman. The most notable changes are the increases in intravascular volume and cardiac output. Early estimates obtained via invasive cardiac testing suggest that cardiac output increases from 3.5 to 6.0 L/min at rest, a rise of close to 40% [3]. These changes begin as early as the first trimester of pregnancy. Several noninvasive studies suggest that cardiac output may decrease in the latter portion of the third trimester [4–7]. The changes in cardiac output are related to increases in maternal heart rate as well as stroke volume [8]. As blood pressure typically decreases during early pregnancy, the rise in cardiac output is accompanied by a dramatic fall in peripheral vascular resistance. Interestingly, the fall in peripheral vascular resistance contributes minimally to the overall rise in cardiac output [9,10]. Various mediators, including estrogens, prostaglandins, and nitric oxide, likely contribute to these changes [11– 13]. During labor and delivery, uterine contractions result in an additional increase of cardiac output and blood pressure, the increase in cardiac output approaching 20% [14,15]. Following delivery, relief of vena caval compression and autotransfusion from the emptied and contracted uterus cause additional rises in cardiac output. Most hemodynamic alterations resolve rapidly post partum and are near normal by 6 weeks though structural cardiac changes may not return completely to normal until 6 months.

The key to safe pregnancy care in the context of cardiac disease is prenatal assessment. The initial approach to obstetric patients should include an appropriate obstetric and cardiac history, as well as physical examination. Appendix 5.1, at the end of this chapter, provides a review of the basics of the cardiac examination. Laboratory investigations will include hemoglobin and platelet count. Specific cardiac testing will generally include electrocardiography and echocardiography. Where appropriate, oxygen saturation, Holter monitoring, exercise stress testing, chest X-ray, CT scanning, and cardiac catheterization can and should be performed. Should this assessment reveal that the cardiac condition can be optimized by medical or surgical means, then these measures should be performed, ideally prior to conception. It has been demonstrated that corrective surgery, or even palliative surgery, when appropriate, improves both maternal and fetal outcome [16,17].

Although most diagnostic radiation is associated with minimal exposure and hence risk to the developing fetus, it is preferable to perform such examinations prior to conception and, for reasons more cultural than scientific, to avoid the first trimester. However, most cardiac diagnostic tests can be safely carried out in pregnancy when indicated (see Chapter 32). No increase in the congenital abnormality rate has been documented with radiation exposure of less than 10 rads (0.1 Gy) [18,19]. A chest X-ray delivers less than 0.005 rads (0.00005 Gy) to the pelvis, while cardiac catheterization delivers about 1–2 rads (0.01–0.02 Gy) to the pelvis. Thus these tests should not be withheld during pregnancy if the benefit is deemed to outweigh the potential risk [20]. Echocardiography has proven to be a very useful and safe diagnostic test, regardless of pregnancy state, and it should be used liberally when indicated. Magnetic resonance imaging has not been linked to unfavorable fetal effects, and recent reports suggest minimal fetal risks associated with gadolinium exposure, commonly utilized to enhance diagnostic capability [21].

Following review and discussion of the assessment with the patient and her family, the risks to mother and fetus require careful consideration. Occasionally, the risks are so great that pregnancy may be discouraged. In such cases, other options such as gestational carriers can be discussed. However, in the majority of cases, the likelihood of unfavorable outcome is relatively low. Thus patients and their families can be cautioned yet reassured. Box 5.1 summarizes the high-, intermediate- and low-risk conditions [22].

In the prediction of adverse maternal and fetal outcome, it is helpful to focus on maternal functional status (Box 5.2) in addition to:

• the type of cardiac abnormality
  
• whether the patient has undergone corrective surgery or procedure to correct the underlying condition
  
• whether other risk factors are present
  
• assessment of maternal prognosis and expected survival, and the maternal ability to engage in childrearing
  
• the heredity of the cardiac lesion in the offspring, if applicable.

Maternal and fetal outcome can be linked to functional status. Maternal mortality may be as high as 7% when class III and IV patients are combined. In contrast, classes I and II combined yield a mortality of 0.5%. Similarly, fetal mortality may be as a high as 30% in class III and IV patients, in contrast to 2% for classes I and II [17]. In situations where maternal mortality risks are considerable, appropriate counseling and social support for the pregnant woman and her family are critical, including frank discussions about who will be involved in the care of the child should maternal demise occur. The context of the birth must also be taken into consideration, for example, if the child is born prematurely or in the setting of perimortem cesarean delivery.

Prenatal diagnosis and genetic counseling are important components of pre-pregnancy and early pregnancy management. The incidence of congenital heart disease in the offspring of women with congenital heart disease is increased. Autosomal dominant conditions such as Marfan’s syndrome carry a 50% recurrence rate. The association between maternal and fetal congenital and inherited heart disease is discussed below in the section on fetal considerations.

Maternal considerations

In cases where continuing the pregnancy poses significant risk to the pregnant woman with cardiac disease, termination of pregnancy should be discussed. If the woman opts to continue, as is the case in most situations when the risks are deemed acceptable, a management plan is formulated and discussed. Antepartum surveillance seeks to prevent, identify and treat maternal complications including congestive heart failure, arrhythmias, and thromboembolism.

Certain complications, such as congestive heart failure, may be avoidable despite the potential for the physiologic changes of pregnancy to overwhelm the compromised heart’s ability to adapt. In such cases, reduction in physical activity, such as work and exercise cessation, may be indicated. It may also be advisable for the pregnant patient to seek methods of stress reduction, avoid excessive atmospheric heat and humidity, and decrease consumption of salt and large meals. In order to avoid unnecessary Valsalva maneuver, constipation should be avoided by increasing dietary fiber intake and the use of stool softeners. Patients belonging to class III–IV as well as those with significant pulmonary hypertension often require inpatient admission during the mid-second trimester for the duration of the pregnancy. Patients should be counseled to watch for signs and symptoms of arrhythmias (particularly palpitations, presyncope or syncope), as tachyarrhythmias commonly occur in pregnant women with congenital heart disease, and may lead to congestive heart failure. Common third-trimester pregnancy complications can pose significant risks to the gravida with heart disease, including conditions such as gestational hypertension, infection, and anemia. Assessment of hemoglobin and urine cultures in each trimester are reasonable approaches to surveillance for these conditions.

Healthy pregnant women often experience fatigue, chest discomfort, dyspnea, palpitations and even syncope. However, in the setting of cardiac disease, these symptoms may represent signs of decompensation. Careful evaluation in normal pregnancies may reveal any of the following: peripheral edema, prominent neck vein pulsations, a diffuse apical impulse, a systolic pulsation along the left sternal border, a split first heart sound, a third heart sound, a systolic murmur that is less than 3/6 in intensity, an accentuated second heart sound, a venous hum, and mammary arterial murmurs [24]. However, identification of severe or progressive dyspnea, orthopnea particularly with paroxysmal nocturnal dyspnea, hemoptysis, syncope with exertion, chest pain related to effort or emotion, development of cyanosis, persistent neck vein distension, systolic murmur grade 3/6 or more in intensity, any diastolic murmur, cardiomegaly, sustained arrhythmia, a fixed split second sound, and left parasternal lift or loud P2 suggestive of pulmonary hypertension should initiate further investigation as to the likely indicated underlying cardiac abnormalities [25].

Fetal considerations

Given the recurrence risk associated with maternal congenital heart disease, fetal assessment includes diagnosis and management of cardiac lesions, as well as detection of pregnancy complications such as intrauterine growth restriction and preterm birth. Infants of mothers with congenital heart disease are more likely to be growth restricted [26], be premature [26,27] and have congenital cardiac anomalies [28,29]. In the general population, the incidence of congenital heart disease (CHD) is 0.7–0.8%, but the incidence has been reported to be as high as 3.4–14.2% for patients with congenital heart conditions, depending on the particular cardiac lesion [17, 30–32]. In a recent literature review of 48 studies including 2491 pregnancies, the recurrence rate for CHD was lowest in patients with corrected transposition of the great arteries (0.6%) and highest in those with atrioventricular septal defects (8%) [33]. In one comprehensive study from the 1960s, the reported recurrence rate was 17.9–23% for women with uncorrected lesions, but this report was likely confounded by genetic syndromes [17].

Fetal cardiac anomalies are best assessed through echocardiography at 18–20 weeks gestation. Smoking cessation, correction of maternal anemia and rest may be employed to minimize the risks of intrauterine growth restriction and preterm birth [34–38]. Aggressive measures to reduce maternal activity, such as hospital admission, as well as continuous oxygen therapy, may lessen risks of fetal growth restriction and preterm birth in cases of cyanotic maternal heart disease or pulmonary hypertension. For the same reason, in-hospital management should be considered for patients who belong to New York Heart Association (NYHA) functional class III or IV. Fetal well-being, growth, and Amniotic Fluid Index can be assessed with serial fetal ultrasound and biophysical testing beginning as early as 24–26 weeks gestation. The frequency of testing depends on the patient’s presenting symptoms and underlying cardiac condition. Early preterm labor can be detected with fundal palpation for uterine contractions, pelvic exam to assess cervical dilation, and, in certain cases, cervical length measurement using vaginal ultrasound. Administration of antenatal corticosteroids for fetal lung maturity should be considered when preterm birth prior to 32–24 weeks is anticipated.

The interval between prenatal visits may need to be as frequent as every 2 weeks until 32 weeks, and weekly to delivery to ensure adequate surveillance of maternal and fetal status. Depending on the maternal cardiac status and fetal well-being, this surveillance may need to be increased or decreased accordingly.

Multidisciplinary approach

Managing pregnant patients with complex cardiac disease mandates participation from a multidisciplinary medical team. When potential exists for maternal compromise, the management is best delivered in a tertiary-level perinatal center with availability of obstetricians, cardiologists, pediatricians, anesthesiologists, and obstetric nursing. Early in the pregnancy, a patient care meeting is arranged to chart a course of management for the antepartum, peripartum and postpartum phases of care. Anticipation and contingency planning for obstetric, cardiac or pediatric emergencies are articulated in advance. Given the infrequent nature of these cases and that some or much of the care will be occurring on units that do not routinely care for cardiac patients, it is important that the plan be as specific and detailed as possible. Should the patient be on a cardiac monitor? What training should the nurse have who is caring for the patient? What medications might be needed for potential complications and how are these medications administered? These are all examples of the specific questions the care plan should address. A checklist of items to consider and/or carry out when caring for pregnant women with cardiac disease is given in Box 5.3. Such directives are placed in writing in the patient’s medical record and are communicated to medical and nursing staff in the maternity units as well as cardiology and intensive care units, so that everyone is familiar with the contingency planning. As nursing staff are most often the healthcare providers who first identify such emergency situations, it is imperative they be informed and incorporated into the multidisciplinary planning process.

Peripartum management

Labor and delivery management usually follows the standard obstetric indications for induction and mode of delivery. Rarely is a cesarean delivery indicated solely due to maternal cardiac disease. However, elective induction is often advocated to ensure that the necessary staff are readily available for management of peripartum complications. Furthermore, advanced delivery planning allows for the necessary adjuncts to care, such as insertion of monitoring lines and epidural anesthesia, both of which can be introduced in a controlled environment.

If the patient is receiving full therapeutic doses of anticoagulation, delivery may need to be timed such that anticoagulation can be stopped shortly prior to delivery. Unfractionated intravenous heparin (UFH) is usually stopped 4–6 hours prior to induction of labor, cesarean delivery and/or regional anesthesia to allow normalization of partial thrombin time (PTT). If the patient has received full-dose low molecular weight heparin (LMWH), the recommended waiting period extends to 24 hours [39]. This allows safe insertion of regional anesthesia and decreases potential for peripartum hemorrhage. If an anticoagulated patient goes into spontaneous labor, protamine can be given intravenously to reverse heparinization. Protamine can completely reverse UFH and partially reverse LMWH. Anticoagulation can usually be restarted 6–12 hours after the delivery depending on the patient’s condition and the amount of bleeding (see Chapters 3, 4 and 46).

The American Heart Association and the American College of Cardiology now recommend that infective endocarditis (IE) prophylaxis be given only for patients undergoing dental or respiratory procedures who have a cardiac lesion deemed to be at very high risk for IE. They no longer recommend IE prophylaxis for patients with congenital or valvular heart disease undergoing genitourinary procedures, including vaginal or cesarean deliveries [40]. IE prevention in obstetric patients with cardiac lesions should be restricted to antibiotic prophylaxis for dental and respiratory procedures and the prompt and consistent use of antibiotics to prevent and treat noncardiac infections just as would be done in obstetric patients without cardiac disease. This recommendation is based on both the lack of evidence of benefit of IE prophylaxis in uncomplicated vaginal and cesarean deliveries and the real but small possibility that IE prophyaxis will cause harm. However, many obstetric physicians and centers have been reluctant to adopt this recommendation. The widespread use of antibiotics in the delivery suite both to treat group B streptococcal colonization and prevent wound infections in cesarean deliveries makes many clinicians skeptical about the risks of IE prophylaxis and even in the absence of good evidence of their benefit, the practice continues.

Although present recommendations do not support its use, if the decision is made to give IE prophylaxis, it is increasingly clear that it should be reserved for those patients with cardiac lesions that are at a particularly high risk of IE. This does not include the majority of the cardiac lesions discussed in this chapter and is limited to patients with the following conditions:

• a prior history of IE
  
• unrepaired or incompletely repaired cyanotic congenital heart disease (including those with palliative shunts and conduits)
  
• completely repaired congenital heart defects with prosthetic material or devices during the first 6 months after insertion
  
• any residual defect near the site of a prosthetic patch or device
  
• cardiac transplant patients who have valvular regurgitation through structurally abnormal valves.

Patients with known arrhythmias or who are at risk for rate or rhythm disturbances are monitored with telemetry, or a bedside monitor and nurse when telemetry facilities are not available. The treatment for arrhythmias is similar to that in the nonpregnant state. Persons caring for such patients should be educated on the preparation and use of cardiac medications that may be required and ready access to these medications ensured.

For pregnant patients with intracardiac shunts, it is critical to avoid decreases in left-sided filling pressures. Reversal of left to right flow or exacerbation of existing right to left flow may lead to pulmonary thrombosis and/or cardiopulmonary collapse. Oxygen desaturation can be monitored with continuous pulse oximetry. Maternal expulsive efforts are minimized in the second stage of labor to avoid the Valsalva maneuver. Peripartum hemorrhage should be identified and managed promptly. In cases where mothers have previously experienced peripartum hemorrhage, are receiving anticoagulation or have Eisenmenger’s syndrome, cross-matching for blood products before labor and delivery admission is advisable. To prevent paradoxic air emboli in cyanotic patients with intracardiac shunts, an air filter is placed in all intravenous lines.

Congestive heart failure is another peripartum complication requiring immediate identification and treatment. When the laboring woman is in the supine position, uterine contractions increase the maternal cardiac output by 24% [41], due to the repeated autotransfusion of blood from the contracting uterus into the intravascular space, as well as catecholamine release and attendant increase in the arterial blood pressure [42,43]. Thus, laboring in the left lateral position is most appropriate, as the increase in cardiac output is closer to 10%, and there is a lesser increase in arterial blood pressure [41,44]. If ventricular function is known to be compromised on echocardiographic assessment, or if the patient has known class II– IV functional status, labor should take place with carefully titrated epidural anesthesia. The anesthesia will lessen the catecholamine release, attenuating the rise in arterial blood pressure. Uterine contractions, under epidural coverage, should be allowed to facilitate the descent of the presenting part in the early phase of the second stage of labor. This process often takes several hours and the second stage of labor may in fact be prolonged. Maternal expulsive efforts are then minimized in the latter portion of the second stage with the aid of assisted vaginal delivery, with either forceps or a vacuum device.

As there is further autotransfusion of blood from the contracting uterus and the vena caval compression is simultaneously relieved, the period immediately following delivery is when the largest increase in cardiac output may be anticipated [45]. These changes will occur irrespective of mode of delivery, so cesarean delivery is normally reserved for the usual obstetric indications rather than maternal cardiac status.

Complications such as pulmonary edema and congestive heart failure (CHF) are treated in the standard fashion. Features of CHF include tachypnea, tachycardia, elevations in jugular venous pulse, rales on lung examination, peripheral edema, hypoxia and chest X-ray changes which may include an enlarged heart, increased vascular markings in the upper lung fields, pleural effusion and bilateral fluffy interstitial infiltrates. Acute treatment includes oxygen, an intravenous diuretic such as furosemide with aggressive dosing to maintain a 1–2 liter/day negative fluid balance, and careful documentation of all fluid intake and output. Delivery is generally not expedited until the maternal hemodynamic status is stabilized, unless fetal compromise is detected. In some cases, precipitous delivery by cesarean section may actual destabilize the maternal status, by exacerbating cardiac output and thus cardiac work. If aggressive pharmacologic measures to treat pulmonary edema are not rapidly successful, noninvasive ventilation such as biphasic positive airway pressure (BiPAP) or intubation and mechanical ventilation are appropriate. In emergency situations where pulmonary edema occurs at cesarean delivery, following the delivery of the neonate, the obstetrician may perform manual compression of the vena cava to decrease the preload as a temporizing measure [22].

Invasive hemodynamic monitoring (through the use of pulmonary artery or Swan–Ganz catheters) is rarely needed for the intrapartum care of most cardiac patients. Increasing data have brought into question the use of these monitors for the management of nonpregnant surgical and intensive care patients (even in very experienced hands) and many experts (including the editors) believe the risk/benefit ratio is not favorable to their use in the obstetric setting. However, other experts would recommend the use of invasive monitoring for patients with conditions such as pulmonary hypertension, severe aortic or mitral stenosis, patients with uncorrected cyanotic lesions, patients with NYHA functional class III–IV status, and high-grade ventricular dysfunction. Therefore final decisions on the use of these devices in the peripartum period should be made on the basis of both the patient’s clinical condition and the quality and availability of local expertise and support.

Peri- or postmortem cesarean delivery should be discussed in advance with patients and the multidisciplinary team in circumstances of severe or complex congenital heart disease or other lesions associated with a high maternal mortality rate.

Contraceptive counseling

In cases where women of reproductive age have significant cardiac lesions or for those who develop life-threatening cardiac complications during pregnancy, it is critical that counseling regarding effective contraception occurs. Furthermore, as most pregnancies in the general population are unplanned, women with congenital or acquired heart disease require special attention. Options for contraception include barrier methods, hormonal contraception, and sterilization. The choice of method depends on the maternal cardiac status, associated risk factors and consideration of the consequences of unplanned pregnancies in life-threatening situations [46]. The reader is directed to Chapter 33 and Trussell [47] for further reading on contraceptive efficacy.

As most barrier methods are associated with a high failure rate (up to 26%), they cannot be recommended alone as ideal contraception. However, when used in conjunction with other methods, they may confer greater confidence in conception control. The standard combined oral contraceptive tablets are highly effective, with typical failure rates less than 1%. Vaginal rings and combined injectable forms of combined estrogen/progestin preparations are available in some areas, but have less established use in the setting of women with heart disease. All contraceptives containing estrogen carry risks of arterial and venous thrombosis and are generally to be avoided in women with significant valvular heart disease associated with the risk of valvular or mural thrombosis or in patients with cyanotic heart disease with the potential for paradoxic embolism. Although women taking coumadin for prothrombotic heart conditions have a relative contraindication to estrogen-containing contraceptives, the efficacy of these agents may justify their use when a patient is reliably protected by anticoagulation but desiring a reversible mode of contraception.

Progestin-only preparations are not contraindicated in cardiac disease as they carry minimal thrombotic risk [48,49]. The failure rates associated with progestin-only preparations are slightly higher than for combined oral contraceptives and are associated with higher vaginal breakthrough bleeding rates. However, with careful use and barrier method back-up, they may provide an ideal solution for women with complex heart disease. The long-acting injectable form, depot medroxyprogesterone, provides a high degree of protection, but may be a source of bleeding and/or hematoma formation at the site of injection in women who are anticoagulated.

Intrauterine devices (IUD), such as the copper device or progestin-containing intrauterine system (IUS), have very low failure rates, approaching the rates seen with sterilization procedures. Placement of these devices may theoretically predispose to bacterial endocarditis, but a similar situation applies here as to the role of IE prophylaxis as was previously discussed for vaginal and cesarean deliveries. The editors and the World Health Organization support their use in women with cardiac disease. At the time of insertion, clinicians should be aware that a vagal response may occur, and the resulting decrease in left-sided pressures may be undesirable in patients with intracardiac shunts. Arrhythmias at the time of IUD insertion have been reported as well [50]. Thus, in patients with shunts and those at higher risk of developing bacterial endocarditis (Eisenmenger’s syndrome, uncorrected tetralogy of Fallot, patent ductus arteriosus, coarctation of the aorta, and significant mitral and aortic valve disease), IUD should be inserted with caution or placed carefully (due to the risk of uterine perforation) in the immediate postpartum period [51].

For patients who have completed their families or where the medical condition cannot be repaired and is perceived to be associated with high maternal and fetal morbidity and mortality (severe pulmonary hypertension, left ventricular dysfunction, NYHA class III and IV), vasectomy or tubal ligation should be offered. As tubal ligations are typically performed via a laparoscopic approach, the effect of intraperitoneal carbon dioxide insufflation and general anesthesia on cardiac output, as well as the possibility of air embolism, must be considered in patients with cyanotic lesions or pulmonary hypertension. Laparoscopic procedures usually require general anesthesia, as insufflation of the abdomen and pressure on the diaphragm is poorly tolerated by awake patients under neuraxial anesthesia. It may be a safer approach to consider a mini-laparotomy as the preferred approach, under slowly titrated neuraxial anesthesia.

With continued advances in the early diagnosis and definitive treatment of CHD, women with a variety of heart defects now live longer, into their childbearing years. Furthermore, as women delay childbearing, there are more women with acquired heart disease who choose to become pregnant. Although the cardiac effects and outcome of pregnancy in these women and their offspring have improved, the risk of pregnancy remains significant. The care and management of patients with heart disease require a clear understanding of how each type of defect responds to the known physiologic alterations of pregnancy. Both maternal and neonatal morbidity and mortality can be predicted using a risk index derived from a prospective study of 562 women with a broad range of congenital and acquired heart disease. Complications of pulmonary edema, arrhythmias, stroke and cardiac death were increased in women with prior cardiac events, poor functional class, left ventricular dysfunction and left heart obstruction [52].

The normal hemodynamic adaptations to pregnancy are well defined, with a marked increase in blood volume, vascular compliance, heart rate and cardiac output. The impact of these physiologic changes on the pathologic cardiovascular system can be anticipated. Therefore, it is helpful to group the different acquired and congenital heart defects by pathophysiologic characteristics into categories that have similar treatments, outcomes, and labor and delivery options. The three categories are lesions that produce volume overload, lesions that produce pressure overload, and lesions that produce cyanosis. Other cardiac conditions which have their own unique issues are cardiomyopathy, coronary artery disease and Marfan’s syndrome.

The congenital volume overload lesions are due to left-to-right shunts and include atrial septal defects (ASD), ventricular septal defects (VSD), and patent ductus arteriosus. Uncorrected lesions are generally well tolerated in pregnancy. However, in rare cases, chronic volume overload of the right heart from the shunted blood leads to increased right-sided heart pressures and pulmonary hypertension. If right heart and pulmonary pressures begin to approach the pressures of the left side of the heart, right-to-left shunting of blood can occur, resulting in systemic desaturation (cyanosis). This is Eisenmenger’s syndrome physiology with a very different and elevated risk and is discussed separately below [33,52]. Acquired volume overload lesions are due to valvular insufficiency.

Stenotic lesions produce pressure load on the preceding chamber. They include aortic stenosis, mitral stenosis, coarctation of the aorta, and pulmonary valve stenosis. They are generally moderately well tolerated in pregnancy unless the obstruction is severe. The obstructive lesion idiopathic hypertrophic subaortic stenosis (IHSS, a type of hypertrophic cardiomyopathy or HCM) may actually experience some lessening of obstruction in pregnancy due to the fact that increased blood volume in this particular lesion leads to lessening of outflow tract obstruction.

Cyanotic heart disease results from right-to-left shunts because shunt flow is increased. These patients are usually corrected or palliated at a young age, and uncorrected patients rarely survive to adulthood and childbearing years. These diseases include tetralogy of Fallot, more severe degrees of Ebstein’s anomaly, tricuspid atresia, transposition of the great vessels (TGV), truncus arteriosus, and univentricles. Maternal and fetal morbidity and mortality correlate with the degree of cyanosis as expressed by the maternal hematocrit and arterial PO2. Patients with severe pulmonary hypertension or Eisenmenger’s syndrome have a maternal mortality rate approaching 50% [53].

Volume overload lesions

Atrial septal defects

The most common congenital lesions in adults are atrial septal defects and they may be first diagnosed during pregnancy. There are three types of ASD classified by their location and embryology; the most common, accounting for approximately 80%, is the secundum type. The secundum ASD (located in the central portion of the atrial septum) is associated with myxomatous mitral valve disease and prolapse in 20–30% of cases. The more unusual types are primum, or endocardial cushion, defects (located in the lower portion of the atrial septum), which are most commonly associated with Down’s syndrome, and sinus venosus defects (located in the upper portion of the atrial septum) in which the right upper pulmonary vein is usually emptying into the superior vena cava and right atrium. The uncorrected left-to-right shunt produces a volume load on the right side with enlargement of the right atrium and ventricle.

The flow across an ASD is not very turbulent and runs down a low gradient and hence does not directly cause an audible murmur; however, increased flow across the pulmonary valve may cause a 2/6 systolic ejection flow murmur. Classically, an ASD causes a wide fixed split second heart sound with the patient in the sitting/standing position. Signs of right ventricular hypertrophy and pulmonary hypertension can be present in advanced and severe cases. ASD are typically asymptomatic but may be associated with atrial arrhythmias, stroke from paradoxic emboli, migraine and right heart failure. The diagnosis can usually be made on transthoracic echocardiography but may require transesophageal echocardiography to detect some smaller shunts and sinus venosus defects.

The expected 50% increase in blood volume during pregnancy causes further volume loading, although usually without a concomitant increase in pulmonary artery pressures. Most patients with an isolated ASD tolerate pregnancy well; good left ventricular ejection fraction and NYHA functional status are predictive of uncomplicated and successful outcomes [52,54]. With larger defects and shunts, there is risk for congestive heart failure, atrial arrhythmias, peripheral venous thrombosis or embolism, cerebral vascular accidents, and shunt reversal with cyanosis from sudden systemic hypotension [52, 54–56]. Congestive heart failure can be treated medically with digoxin and diuretics. Atrial arrhythmias can worsen or precipitate heart failure and should be treated with beta-blockers and digoxin. Due to the relative hypercoagulable state of pregnancy, empiric use of low-dose aspirin after the first trimester is advocated to reduce the risk of venous thrombosis and hence paradoxic emboli. Systemic hypotension, which can occur during parturition and epidural anesthesia, should be anticipated and rapidly corrected with pressors and volume to prevent possible shunt reversal and oxygen desaturation. Preconception closure of the defect is recommended for women with symptoms, arrhythmias or significant right-to-left shunts where the ratio of pulmonary to systemic blood flow (the Qp to Qs ratio, which is normally 1:1) is >1.5:1). For moderate-sized, secundum ASD, surgical patch or transcatheter devices have been shown to have equivalent short- and long-term success [57,58].

Ventricular septal defects

Ventricular septal defects (VSD) are common at birth (0.3–3 per 1000 livebirths) but many close spontaneously in childhood [59]. The size and location of the defect affect the clinical course. The most common type of defect occurs in the membranous septum or left ventricular outflow tract; they may be associated with aortic insufficiency due to prolapse of the adjacent aortic cusp.

The flow across a VSD produces a loud (typically 4–6/6) systolic ejection murmur and hence most VSD in the developed world are identified and repaired in infancy or childhood. Those that are left unrepaired in adulthood are small, without significant volume of shunting; these are often asymptomatic unless the patient develops IE or the effects of chronic volume overload and secondary pulmonary hypertension begin to manifest as exercise intolerance, dyspnea or congestive heart failure. Clinical sequelae and symptoms are most likely to happen if the VSD is large in size and therefore exerts a hemodynamic effect. Infective endocarditis, however, can occur with any size of VSD. Similarly to ASD, VSD should be repaired if symptomatic, large (a Qp:QS ratio of >1.5:1) or associated with an elevation in pulmonary artery pressure.

Isolated VSD are usually well tolerated in pregnancy unless the size is large and degree of shunting places a large volume burden on the system; peripartum risks are determined by parameters which reflect the degree of shunting: left ventricular size and function, pulmonary artery pressures, and the patient’s functional class [52,60,61]. In hemodynamically significant shunts, complications include congestive heart failure, atrial arrhythmias, worsening pulmonary artery hypertension, and shunt reversal with cyanosis due to systemic hypotension. In a study from Connecticut, USA, in the 1970s, there were no maternal deaths reported in 98 pregnancies resulting in 78 liveborn infants in 50 women with VSD [17]. In women with corrected lesions, no increased risks are associated with gestation.

Patent ductus arteriosus

Patent ductus arteriosus is the persistence after birth of the direct connection between the pulmonary and arterial circulation that is an essential part of the normal fetal circulation. Isolated, persistent patent ductus arteriosus may be found in approximately 1:2000 newborns, but rarely in adults. The residual embryonic shunt is from the descending aorta at the isthmus to the proximal left pulmonary artery. Similar to above, the risks of pregnancy are related to shunt size and degree of pulmonary hypertension. Clinical symptoms and complications are also similar to those associated with VSD. Physical examination classically reveals a grade 4–6/6 continuous (diastolic and systolic), “machinery” (i.e rumbling) murmur that is best heard at the upper left sternal border or infraclavicular area. In asymptomatic women with normal pulmonary artery pressures and small shunts, maternal and fetal outcomes are not altered. As with other left-to-right shunts, there is still a theoretical risk of shunt reversal and cyanosis from sudden, systemic hypotension. Patients with large shunts have enlargement of the pulmonary artery and left-sided chambers and can develop high-output heart failure. In corrected or uncorrected patent ductus arteriosus, pulmonary hypertension significantly increases maternal and fetal morbidity and mortality rates [56].

Mitral and aortic regurgitation (insufficiency)

Valvular regurgitation may be due to rheumatic disease, prolapse or endocarditis. It can also occur in relation to ischemic heart disease and dilated cardiomyopathies. Trivial or physiologic regurgitation of the mitral valve is present in up to 70% of normal patients on echocardiography; it is not audible and is of no clinical signficance. Complications occur from valvular regurgitation as a result of chronic volume overload and related atrial or ventricular strain and can include arrhythmias (especially atrial fibrillation in the setting of mitral regurgitation), pulmonary hypertension (particularly from chronic severe mitral insufficiency or congestive heart failure. Mitral regurgitation typically causes a blowing or high-pitched holosystolic murmur (2–4/6) heard best at the apex of the heart and radiating to the left axilla. S1 may be diminished and S2 may have a fixed split as can be seen with both a VSD and an ASD (see Appendix 5.1 at the end of this chapter). Surgical valve repair or replacement is typically done if the patient is symptomatic, has left ventricular enlargement or dysfunction or pulmonary hypertension.

Aortic regurgitation typically causes a blowing diastolic (1–4/4) murmur heard best at the right upper sternal border at end expiration with the patient leaning forward. Severe, chronic insufficiency is most classically characterized by the many manifestations of high cardiac output with bounding pulses and a widened pulse pressure (a large difference between systolic and diastolic blood pressure).