Congenital Heart Disease

Maternal Congenital Heart Disease in Pregnancy

1. What every clinician should know

Congenital heart disease (CHD) is the most common birth defect, affecting 8 out of 1,000 live births. Advances in surgical techniques and medical therapies have resulted in approximately 85% of children born with structural heart defects surviving to childbearing age.

Today CHD comprises more than 50% of all cardiac disease observed in pregnancy. Women with CHD are at risk of cardiac complications in pregnancy but these risks vary depending on the lesion and functional status. The hemodynamic changes of pregnancy can unmask or overwhelm a previously well-compensated defect. Significant arrhythmias, heart failure, myocardial infarction, stroke and death are more common during pregnancy in women with CHD than in the general population. Despite these significant risks, there has been a decline in maternal mortality from CHD which, in part, is attributed to improvements in multidisciplinary cardiac care.

2. Diagnosis and differential diagnosis

In the past, almost all women with CHD were advised to avoid pregnancy. However, recent literature has shown that pregnancy can be successful with acceptable maternal and neonatal outcomes. Preconception counseling provides an opportunity to review all available data to estimate the maternal and fetal risks related to the patient’s specific cardiac condition, which in turn can determine whether acceptable outcomes can be expected and what management strategies may improve the prognosis. An assessment of the patient’s clinical status and ventricular function are necessary in order to best predict the outcome for pregnancy. The New York Heart Association (NYHA) classification system remains the standard tool to describe a patient’s functional status.

NYHA Class I: asymptomatic

NYHA Class II: symptoms with greater than normal activity

3. Management

Antepartum

Once pregnancy is achieved, the expected increases in preload, cardiac output and oxygen consumption coupled with the normal decrease in afterload in pregnancy may unmask or worsen cardiac status. Echocardiography is the primary imaging modality used in pregnancy, as both cardiac structure and function can be evaluated without risk to the patient or her developing fetus. Frequent office visits to assess functional status and serial evaluations of cardiac performance are necessary for the early recognition of complications.

Appreciation of deterioration can be delayed as complaints of shortness of breath, decreased exercise tolerance and peripheral edema are attributed to normal pregnancy. Women with moderate and complex disease should be referred to specialized centers and a coordinated plan for delivery timing and mode, analgesia plus monitoring during delivery and the post partum period needs to be agreed upon and in place by the third trimester.

With respect to increased risk of congenital heart disease in the offspring, all women should be offered genetic counseling and dedicated fetal echocardiographic evaluation between 18-22 weeks of pregnancy.

Intrapartum

Physiologic demands of normal peripartum events make this a critical time for patients with heart disease. During labor, the combination of pain, anxiety and contractions results in further increases in maternal heart rate, stroke volume, cardiac output and blood pressure. Patient position should be considered as the gravid uterus can compress the inferior vena cava and significantly decrease venous return. The second stage of labor is a time of increased hemodynamic and oxidative cardiac stress.

The majority of patients can safely undergo a trial of labor and experience a vaginal birth. However, in certain circumstances, an operative vaginal delivery may be performed to shorten and limit the stress associated with pushing in the second stage of labor. This is referred to as a ‘cardiac’ vaginal delivery, whereby the hemodynamic limitations of the heart are accommodated with avoidance of maternal Valsalva efforts. Early deep regional anesthesia is also used.

Anesthesia considerations during labor and delivery require particular attention. It is important to understand the parturient’s cardiovascular anatomy, particularly in the setting of lesions that have been uniquely repaired or palliated, resulting in complex cardiovascular physiology. Early epidural placement can decrease the sympathetic stimulation and myocardial oxygen consumption associated with labor and is recommended for most women with heart disease. In patients with fixed cardiac output, the initiation of epidural analgesia must be done slowly (incremental dosing), with careful attention to fluid balance and clinical status. Preload and blood pressure should be monitored carefully and fluid balance strictly adhered to, with avoidance of fluid overload or excessive blood loss.

There is a lack of consensus regarding the use of invasive monitoring during labor and delivery. While many centers have decreased the use of pulmonary artery catheters, peripheral arterial lines and central venous lines are often used to assess a patient’s cardiovascular status during the peripartum period. In general, invasive monitoring is indicated in lesions where large or rapid fluid shifts are poorly tolerated, such as left sided obstructive lesions.

Ideally, cesarean delivery is reserved for normal obstetric indications; however, despite the increased risks of hemorrhage, infection and large fluid shifts, there are a few conditions in which labor is avoided and cesarean delivery is recommended, such as:

Dilated aortic root (greater than 4 cm) or thoracic aortic aneurysm.
Severe symptomatic aortic stenosis (aortic valve gradient greater than 30mmHg).
Need for emergency valve replacement immediately after delivery.
Significant coarctation of the aorta (greater than 20mmHg).

Maternal congenital heart disease is not an automatic indication for routine endocarditis prophylaxis but when indicated, antibiotics should be given 30-60 minutes before delivery.

ACOG recommends prophylaxis in CHD that meets one of the following conditions:

Unrepaired cyanotic defect, including palliative shunts and conduits.
Completely repaired defects with prosthetic material or device, whether placed by surgery or catheter intervention, during the first 6 months after procedure.
Repaired defect with residual defects at the site or adjacent to the site of a prosthetic patch or prosthetic device.

Postpartum

For patients with limited cardiac reserve, the 500 ml autotransfusion that occurs after delivery of the placenta may not be tolerated. As a result, immediate postpartum management warrants close observation for congestive heart failure and measurement of the patient’s fluid balance and in some cases may require admission to an intensive care unit for telemetry or more invasive monitoring and therapy. Postpartum hemorrhage should be avoided and low dose oxytocin infusion is the optimal uterotonic agent. Ergometrine should be avoided as it can cause acute hypertension.

Close surveillance of cardiac patients after birth is necessary as the early postpartum period is often a time of acute decompensation. In patients with moderate-to-complex CHD, close postpartum observation is recommended for 2-3 days, and this period should be increased to 7-14 days in patients with pulmonary hypertension.

4. Complications

Approximately 13% of pregnancies are complicated by a cardiac event, most commonly pulmonary edema, arrhythmia, stroke or cardiac death. As a result, it is paramount that there is a multidisciplinary team approach in the care of pregnant patients with heart disease. Team members should include high risk obstetricians, cardiologists, anesthetists, geneticists and neonatologists who have expertise and experience with the implications of pregnancy and congenital heart disease.

A systematic plan for the management of each individual pregnancy should include optimal antenatal and postnatal surveillance, mode of delivery and analgesia. The classification of a patient’s lesion into low, moderate or high-risk pregnancy categories with respect to the probability of maternal or neonatal morbidity and/or mortality can aid management.

Different types of lesions are classified with respect to functional status and risk of complications during pregnancy.

( Figure 1)

The potential complications of commonly encountered lesions are summarized below.

Small left-to-right lesions

In pregnancy, increased cardiac output and blood volume are counterbalanced by a decrease in peripheral vascular resistance. Left-to-right shunting in women with ASDs, VSDs and PDA is therefore, reduced. In the absence of pulmonary hypertension, pregnancy, labor and delivery are well-tolerated. Avoid acute blood loss or vasodilation from rapid regional anesthesia in labor as both can impact the degree and direction of shunting, thereby reducing left ventricular output.

As a woman gets older, otherwise uncomplicated secundum defects are accompanied with an increased incidence of supraventricular arrhythmias, especially atrial fibrillation or flutter that may cause right ventricular failure and increase the probability of venous stasis and thromboembolism, specifically paradoxical emboli. Therefore, there should be a low threshold for heparin prophylaxis and meticulous leg care is advised.

Post-repair of tetralogy of Fallot

Tetralogy of Fallot is the most common form of cyanotic cardiac lesion and long-term survival is rare without surgical correction. This lesion consists of severe pulmonary stenosis, a non-restrictive ventricular septal defect, right ventricular hypertrophy and an overriding aorta. Pregnancy with uncorrected tetralogy of Fallot is not advised because the maternal mortality rate is as high as 15%, with a 30% fetal loss rate. Ectopic ventricular contractions are common after complete repair, and ventricular tachyarrhythmias, syncope and sudden death are late complications in 1-3% of patients. Recurrent syncopal episodes are indicative of high risk status.

Residual pulmonary regurgitation, right ventricular outflow obstruction and right ventricular dilation and dysfunction with tricuspid regurgitation may also follow successful repairs. Severe pulmonary regurgitation should be addressed prior to pregnancy. Left ventricular dysfunction may be present due to previous volume overload, thus increasing the likelihood of complications during pregnancy. During the course of pregnancy, the subaortic ventricle of a normal heart increases by 6%, in comparison to the 20% increase in the size of the right atrium and subpulmonary ventricle.

An already compromised subpulmonary ventricle may be particularly susceptible to pregnancy-induced volume overloading. Therefore, excessive fluid administration should be avoided in labor, as right ventricular volume overload may impair left ventricular diastolic compliance through ventricular-ventricular interactions which in turn may predispose to left heart failure. Additional right-sided volume load also may predispose to arrhythmias.

Post-atrial switch repair of complete transposition of the great arteries

In complete transposition of the great arteries, the aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle, so early survival is dependent on the presence of additional lesions to allow for the mixing of venous and arterial blood. A large ventricular septal defect may provide a natural shunt, or an urgent balloon atrial septostomy may be needed in the newborn period. In the past, complete transposition was managed with an interatrial repair such as the Mustard or Senning procedure, which redirects systemic venous return to the left ventricle and pulmonary venous return to the right ventricle. With these palliative procedures, the morphologic right ventricle supports the systemic circulation, which increases the risk of systolic dysfunction during pregnancy.

Although most women post-atrial switch repairs have favorable pregnancy outcomes, significant arrhythmias, heart failure and death have been reported. Supraventricular tachyarrhythmias are common after atrial switch procedures, affecting more than 20% of patients, and women with this history are at highest risk of atrial arrhythmias during pregnancy. Even asymptomatic women with good functional status may experience heart failure if their systemic right ventricle falters in response to the volume loading of normal pregnancy.

Given these risks – a reported 31% prematurity rate and up to a 10% perinatal mortality rate – pregnancy after atrial repair should only be undertaken with considerable caution. Deterioration of functional class occurs in a third of patients during pregnancy and can last beyond a year in up to 10% of cases.

Post-arterial switch repair of complete transposition of the great arteries (TGA)

The arterial switch, or Jatene operation, has become the standard surgical approach for complete TGA. This anatomic repair establishes the left ventricle as the systemic ventricle, a significant advantage over the atrial palliative procedures. The 15-year survival rate for patients with the arterial switch operation is over 85%. The early survivors of this procedure are now adults but pregnancy-related data is scant. Although fewer complications are anticipated with the arterial switch operation, aortic valve dysfunction, coronary artery obstruction and right ventricular outflow obstruction have been observed. The development of tachyarrhythmias with impaired systolic function also seems to be a common cardiac complication in pregnancy.

Post-Fontan palliation

The Fontan procedure is a palliative measure for a broad range of anatomic abnormalities that lack suitability for a two-ventricle repair. In cases of single ventricle physiology, the ventricle is chronically overloaded and at risk for failure. The basic Fontan procedure results in systemic venous blood bypassing the single ventricle to directly enter the pulmonary artery. The physiology of this repair is paradoxical, reducing volume load to the single ventricle while causing elevated systemic venous and right atrial pressures that place the patient at risk for peripheral edema, ascites and arrhythmias.

Various modifications of the procedure have led to progressive improvements in outcomes, with the 10-year survival rate after Fontan palliation now reaching over 85%. Patients with single ventricles have a limited ability to increase cardiac output and may not tolerate the hemodynamic changes of pregnancy. Although there are reports that pregnancy is tolerated in asymptomatic patients with good ventricular function, no pulmonary hypertension and oxygen saturation greater than 85%, there is still up to a 2% risk of maternal death. Women are at risk for systemic venous congestion, atrial flutter and fibrillation, deterioration of ventricular function and preterm birth.

Cyanotic heart disease without pulmonary hypertension

Cyanotic heart disease without pulmonary hypertension is caused by uncorrected transposition of the great arteries, uncorrected tetralogy of Fallot, truncus arteriosus and Ebstein anomaly with atrial septal defect. During pregnancy the fall in systemic vascular resistance and rise in cardiac output exacerbates any right-to-left shunting, worsening pre-existing cyanosis and hypoxia. Maternal complications depend mainly on ventricular function and include hemorrhage, paradoxical embolism and heart failure.

The effects on the fetus are marked, with a high incidence of spontaneous miscarriage and a 30-50% risk of premature delivery and low birth weight. The degree of hypoxemia is the most important predictor of neonatal outcome. It has been shown that a successful pregnancy is unlikely if the maternal hemoglobin is greater than 20g/dl or if the maternal arterial oxygen saturation was less than 85%. Admission for bed rest and oxygen therapy is an effective method of maintaining maternal oxygenation towards term, which in turn improves fetal oxygenation and growth.

Pulmonary hypertension

Pulmonary hypertension is defined as a systolic pulmonary artery pressure greater than 30 mmHg or a mean pulmonary artery pressure greater than 25 mmHg and can be primary or secondary. In cases secondary to congenital heart disease, reversal of flow through left-to-right shunts can occur, resulting in the development of Eisenmenger syndrome.

The most common cause of Eisenmenger syndrome is a large ventricular septal defect, which over time results in increased pulmonary vascular blood flow and increased pulmonary resistance that eventually exceeds systemic vascular resistance so that right-to-left shunting occurs with marked cyanosis. Once cyanosis has developed, surgical correction of the shunt no longer improves long-term prognosis. Fixed pulmonary vascular resistance prevents any increase in pulmonary flow in response to the increased cardiac output of pregnancy.

Despite advances in medical therapy and improvements in peripartum management, pulmonary hypertension related to congenital heart disease has a significant risk of maternal death. The postpartum period is the most dangerous for hypoxemia, cardiac dysrhythmias and thromboembolic events, which result in the majority of maternal deaths occurring in the first week after delivery, usually from right heart failure.

Maternal mortality depends on the underlying cause, with approximately 35% mortality in Eisenmenger syndrome, 30% in primary pulmonary hypertension and 56% in secondary pulmonary hypertension. As a result, pregnancy is contraindicated in cases of pulmonary hypertension; however, some patients are diagnosed late or refuse termination earlier in gestation, challenging the medical team to do what they can to optimize outcome. Perinatal risks are also high in ongoing pregnancies with spontaneous loss, poor fetal growth and complications of prematurity affecting up to 30% of cases.

Such patients should always be managed in tertiary centers by an experienced multi-disciplinary team. Medical therapy for ongoing pregnancies with pulmonary hypertension is focused on avoiding further increases in pulmonary vascular resistance, maintaining right ventricular preload and ventricular contractility. Newer agents such as intravenous epoprostenol and aerosolized iloprost have also been observed to reduce pulmonary vascular resistance in these patients and may improve survival. Drugs include calcium antagonists, inotropic agents, diuretics and inhaled nitric oxide. Bed rest for continuous cardiovascular monitoring is advisable in the third trimester and up to 14 days postpartum. Anticoagulation is also recommended due to the risk of pulmonary arterial thrombosis.

Marfan syndrome

The majority of women with significant aortic root dilation during pregnancy have Marfan syndrome, an autosomal dominant connective tissue disorder associated with regurgitant valvular disease and cystic medial degeneration of the aorta due to mutations in the fibrillin gene on chromosome 15q21. Given that there is a 50% risk of Marfan syndrome in the offspring, patients should be offered genetic counseling prior to conception and prenatal diagnosis in early pregnancy.

For non-pregnant patients who are symptomatic or have an aortic root dimension greater than or equal to 5.0 cm or a rapidly dilating aorta at a rate greater than or equal to ≥0.5 cm per year, surgical repair is recommended. In the event of unplanned pregnancy the option of termination should be discussed. Prophylactic beta-blockade has become the standard medical approach for pregnant women with Marfan syndrome, as it reduces hemodynamic stress on the ascending aorta and slows the rate of dilation.

Pregnancy seems to accelerate the pathologic changes in the aorta, perhaps in response to hormonal and hemodynamic influences. Without routine beta-blockade, aortic complications including dilation and dissection increase five-fold in pregnancy. Serial maternal transthoracic echocardiograms are recommended throughout gestation to help the multidisciplinary team determine the safest management plan. Vaginal delivery with regional analgesia and an assisted second stage seems safe for women with an aortic root diameter less than 4 cm.

When the aortic root measures 4 cm or greater, elective cesarean delivery is recommended with consideration of postpartum replacement of the proximal aorta, but advice varies with 4-4.9 cm dilation. Another indication of cesarean delivery is the presence of severe aortic regurgitation or heart failure. With respect to analgesia, if general anesthesia is required, there is potential for temperomandibular joint laxity and dislocation, resulting in difficult endotracheal intubation.

Overall, the maternal mortality associated with Marfan syndrome is about 1% but increases to more than 20% in cases of aortic dissection. A high level of suspicion is warranted when a patient presents with chest or back pain and urgent computed tomography or magnetic resonance imaging should be obtained to exclude the diagnosis of aortic dissection. Aortic rupture or dissection can occur at any root size.

Left-sided obstructive lesions

Conditions such as aortic stenosis or hypertrophic cardiomyopathy can lead to obstruction of output from the systemic left ventricle with devastating consequences. Valvular aortic stenosis can be congenital as a primary lesion or secondary to a bicuspid valve. Asymptomatic women with unremarkable resting electrocardiograms, a normal exercise test, good left ventricular function and a pre-pregnancy aortic valve peak pressure drop less than 80 mm Hg measured by Doppler echocardiography can expect a favorable pregnancy outcome.

Affected individuals are generally asymptomatic until the valve area decreases to less than a third of its original size or less than 1 cm ². While mild aortic stenosis is well tolerated, patients with severe aortic stenosis are at risk for angina, myocardial infarction, syncope and sudden death. Severe aortic stenosis, defined as a peak gradient greater than 50 mm Hg, warrants repair, and elective repair should be considered in women with gradients greater than or equal to 30 mm Hg or left ventricular ejection fractions below 30% who are contemplating childbearing.

Longstanding obstruction of outflow results in left ventricular hypertrophy, diastolic dysfunction and eventually a fixed cardiac output. The inability to increase output in response to increases in preload and heart rate can be life-threatening as the fixed flow can compromise coronary and carotid artery perfusion.

Bed rest and beta-blockers are used to decrease heart rate, which increases time for left ventricular ejection and coronary filling. Maintaining adequate cardiac output across a constricted aortic valve can be challenging during pregnancy. The fixed cardiac output also can compromise uteroplacental perfusion and fetal growth in these pregnancies. During pregnancy, balloon valvuloplasty can be considered in cases of severe aortic stenosis that require intervention prior to delivery. While this temporary measure may be used early in pregnancy, preterm delivery and postpartum repair is often the preferred approach in cases of critical aortic stenosis beyond 28-32 weeks gestation.

The demands of labor and volume shifts associated with delivery are significant stressors to patients with fixed cardiac outputs, and management of anesthesia is critical during this time. Hypovolemia is not well tolerated, so maintaining a positive fluid balance is recommended. Minimizing pain to avoid the associated increase in catecholamines and avoidance of Valsalva is optimal. Vasodilators should also be avoided. Overall, 10% of women with congenital aortic stenosis experience cardiac complications during pregnancy.

Coarctation of the aorta

Coarctation of the aorta occurs in 6-8% of patients with congenital heart disease. The majority are diagnosed in infancy and childhood and are either surgically corrected or treated by balloon dilatation or stent implantation. Pregnancy is usually well-tolerated in women with adequate repairs; however, the rate of miscarriage and preeclampsia are higher than the general population. In both repaired and native coarctation, pregnancy poses the risk of aortic dissection and resistant hypertension due to the hemodynamic and aortic medial changes of pregnancy.

It is essential to exclude and appropriately manage complications such as re-coarctation, aneurysm at the site of repair, an associated bicuspid aortic valve or systemic hypertension, prior to contemplating pregnancy. MRI to exclude the presence of an aortic aneurysm is generally recommended prior to the onset of pregnancy.

If blood pressure is not well controlled during pregnancy, intervention is recommended to correct the increased coarctation gradient. Both surgery and stent placement to alleviate obstruction should be considered. For stent placement, potential teratogenic exposure from radiation can be limited by performing the procedure after the second trimester with abdominal shielding.

5. Prognosis and outcome

The risk of pregnancy to the mother ranges from very low, similar to the general population, for example, in mild pulmonic or tricuspid valve disease or repaired atrial septal defect, versus up to a 50% risk of a life-threatening cardiovascular event in pulmonary hypertension.

Although the emphasis has understandably been on quantifying and reducing maternal cardiac risk, obstetrical complications are also substantial. There are reports that more than one third of pregnancies are associated with adverse obstetrical events such as preterm delivery, postpartum hemorrhage, premature rupture of membranes, pregnancy-induced hypertension or pre-eclampsia, placental abruption and intra-uterine fetal demise. Pregnancy-induced hypertensive disorders are more common in patients with aortic stenosis, aortic coarctation and transposition of the great arteries. These potential complications highlight the importance of a high-risk obstetrical team in the multidisciplinary management of women with congenital heart disease.

Adverse fetal and neonatal outcomes complicate 15-39% of pregnancies. Frequent complications include preterm birth, small-for-gestational-age low birth weight, respiratory distress and intraventricular hemorrhage. Intrauterine demise and neonatal death have been reported in most CHD series, but predominantly occur in women with complex lesions. Reported independent cardiac risk factors include maternal cyanosis at the baseline visit, poor functional class (NYHA class greater than II) or left heart obstruction.

For women with congenital heart disease, there is also the risk of recurrence of cardiac anomalies in their offspring. While the background risk for congenital heart defects is 8 per 1,000 live births, the risk for babies born to affected mothers is about 5%, representing a 10-fold increase in the background rate of these malformations in the general population. Disease-specific recurrence risks are available and consultation with a geneticist specializing in prenatal counseling and diagnosis can be particularly useful. For example, recurrence is as high as 50% in single gene disorders such as Marfan syndrome.

Women with CHD are also at risk for late cardiac events beyond 6 months postpartum. Late events affect more than 10% of women, particularly those with low functional status, cyanosis, ventricular dysfunction, left heart obstruction and a history of prior cardiac complications. There is a dearth of literature with respect to longer term effects; therefore, the ultimate effect of pregnancy on future cardiac wellbeing is largely unknown.

6. What is the evidence for specific management and treatment recommendations

Warnes, CA, Williams, RG, Bashore, TM. “ACC/AHA 2008 Guidelines for the Management of Adults with Congenital Heart Disease: Executive Summary”. J Am Coll Cardiol. vol. 52. 2008. pp. 1890-947. (These American College of Cardiology/American Heart Association guidelines discuss recommended care settings for the management and delivery of women with congenital heart disease.)

Simpson, LL. “Maternal Cardiac Disease”. Obstet Gynecol. vol. 119. 2012. pp. 345-59. (A comprehensive up-to-date review of both congenital and acquired heart disease in pregnancy with specific detail on commonly seen complex defects.)

Bowater, SE, Thorne, SA. “Management of pregnancy in women with acquired and congenital heart disease”. Postgrad Med J. vol. 86. 2010. pp. 100-5.

Siu, SC, Sermer, M, Colman, JM, Alvarez, AN, Mercier, LA. “Prospective multicenter study of pregnancy outcomes in women with heart disease”. Circulation. vol. 104. 2001. pp. 515-21. (Prospective multicenter study [CARPREG] of pregnancy in women with various forms of congenital and non-congenital heart disease that proposed a clinically applicable risk index.)

Fernandes, SM, Arendt, KW, Landzberg, MJ, Economy, KE, Khairy, P. “Pregnant women with congenital heart disease: cardiac, anesthetic and obstetrical implications”. Expert Rev. Cardiovasc Ther. vol. 8. 2010. pp. 439-48.

Thorne, SA. “Congenital heart disease: pregnancy in heart disease”. Heart. vol. 90. 2004. pp. 450-6.

Harris, IS. “Management of pregnancy in patients with congenital heart disease”. Progress in Cardiovascular Diseases. vol. 53. 2011. pp. 305-11.

Khairy, P, Ouyang, DW, Fernandes, SM, Lee-Parritz, A, Economy, KE. “Pregnancy outcomes in women with congenital heart disease”. Circulation. vol. 113. 2006. pp. 517-24. (Prospective cohort study of pregnant women exclusively with congenital heart disease.)

Drenthen, W, Boersma, E, Balci, A, Moons, P, Roos-Hesselink, JW. “Predictors of pregnancy complications in women with congenital heart disease”. Eur Heart J. vol. 31. 2010. pp. 2124-32.

Gelson, E, Johnson, M, Gatzoulis, M, Uebling, A. “Cardiac disease in pregnancy. Part 1: congenital heart disease”. The Obstetrician & Gynaecologist. vol. 9. 2007. pp. 15-20.

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