Pregnancy with uncorrected tetralogy of Fallot (TOF), pulmonary atresia and major aorto-pulmonary collateral arteries (MAPCA)

Introduction

Uncorrected tetralogy of Fallot (TOF) is extremely rare; affected individuals usually undergo repair early in life. Pregnancy in affected women is associated with fetal loss, fetal growth restriction (FGR), congenital heart defects (CHDs), and maternal morbidity and mortality related to worsening right-to-left shunt, cyanosis, pulmonary artery hypertension (PAH), arrhythmia and thrombosis [1]. TOF typically presents with pulmonary stenosis, ventricular septal defect (VSD), overriding aorta (OAo) and right ventricular hypertrophy (RVH). A variant form presents with pulmonary atresia (instead of pulmonary stenosis); here, the blood supply to the lungs is provided by major aorto-pulmonary collateral arteries (MAPCA) [2].

Due to the sparsity of reported cases, the management of affected patients is done on a case-by-case basis. We present a patient with uncorrected TOF and MAPCA who achieved two successful term pregnancies and provide management recommendations.

Case report

A 21-year-old primigravida presented to our clinic at 6 weeks with cyanosis and a continuous cardiac murmur. She reported fatigue with strenuous activities. Her heart rate (HR) was 90 beats/min, oxygen saturation (SpO2) 90% at rest (74% during ambulation) and body mass index 16 kg/m²; hematocrit was 50.4%. An echocardiogram showed a large VSD, balanced biventricular chamber size, RVH, pulmonary atresia and OAo (Figure 1). MAPCA were seen from the descending aorta supplying both lungs (Figure 2). Upon diagnosis of TOF, cardiothoracic surgery considered the patient at significant risk for repair. After discussing maternal (worsening cardiac function, hypoxia, arrhythmia, death) and fetal risks (CHD, FGR and perinatal death), she declined termination. Maternal chromosomal analyses were normal.

Figure 1:

Maternal echocardiogram showing infundibular ventricular septal defect (VSD) and overriding aorta (OAo).

Figure 2:

Maternal echocardiogram showing right pulmonary atresia (RPA), aorta (Ao) and major aorto-pulmonary collateral arteries (MAPCA).

We started acetylsalicylic-acid (ASA) 81 mg due to polycythemia, and recommended heparin thromboprophylaxis (which she declined), metoprolol (for non-sustained ventricular tachycardia), oxygen supplementation and frequent hydration. Repeat echocardiograms reported stable findings with balanced biventricular chamber size, right-to-left shunt and no reported PAH. Of note, the patient did not have angiogram or magnetic resonance imaging (MRI).

The fetal echocardiogram was normal. We started growth scans and non-stress tests (NSTs) at 28 weeks. At 32 weeks, we diagnosed FGR and recommended antenatal corticosteroids and Doppler studies. At 38 weeks, we recommended delivery due to suboptimal fetal growth.

Upon admission for delivery, the HR was 76 beats/min, SpO2 86% at rest, and hematocrit 43%. We used intravenous lines with air-filters. We inserted an arterial line to monitor fluid shifts. Epidural was placed (bupivacaine and fentanyl infusion) before starting oxytocin. The cervix was dilated to 3 cm; simultaneously she became tachycardic, hypotensive, with fetal heart rate (FHR) decelerations. Although the FHR improved with maternal resuscitation, her symptoms recurred at repeat vaginal exams; therefore, we opted for cesarean. She received bacterial endocarditis prophylaxis (ampicillin). After delivery, we repaired the uterus without exteriorization. Phenylephrine was administered to maintain the systolic blood pressure (BP) above 100 mm Hg. We used methylergonovine for uterine atony. Apgar score was 9 (1 and 5 min) and birthweight 2300 g confirming FGR.

Post-operatively, we ordered telemetry and heparin thromboprophylaxis. Three days later, she was discharged with ASA and metoprolol. She declined contraception.

Three years later, she presented pregnant at 15 weeks. We continued ASA and metoprolol. Baseline echocardiogram was unchanged. The fetal echocardiogram was normal. At 31 weeks, we diagnosed FGR. We performed a cesarean at 37 weeks with permanent sterilization. We used a non-invasive monitor, Aesculon (Osypka Medical, Inc.; La Jolla, CA, USA) to assess BP, HR, systemic vascular resistance (SVR), cardiac output (CO) and SpO2 during cesarean (Table 1). CO, SVR and BP decreased after epidural which stabilized after intravenous phenylephrine. SVR and BP again decreased after placental removal and after oxytocin infusion (reversed with phenylephrine). During these episodes, SpO2 remained stable suggesting no worsening in the right-to-left shunting.

One year later, our patient remains stable; her two daughters are healthy and without CHD.

Discussion and review

Our patient presented with a variant form of TOF VSD-pulmonary atresia along with the presence of MAPCA. Her baseline and follow up echocardiograms did not report the presence of PAH; however, we cannot exclude that there is no PAH in certain areas of the lung as our patient did not have angiogram or MRI. Because her baseline SpO2 was 90% on room air we assume that she did not have PAH. Maternal karyotype is recommended because the rate of associated aneuploidy or 22q11 deletion is 20–30%; [3] our patient had normal chromosomal analyses.

Publications on pregnancy management in uncorrected TOF and women with cyanosis are scant [4]. Pregnancy is discouraged until the defect is repaired, and in those with unplanned pregnancy the counseling should involve termination [4]. Our patient decided to continue with the pregnancy and we co-managed her with cardiology and anesthesiology; we highlight some aspects of her management:

• Serial echocardiograms, antenatal testing and growth scans are warranted.

• Physiologic decrease in SVR, increase in pulmonary vascular resistance (PVR), and/or increase in HR induce/worsen right-to-left shunting leading to more pronounced hypoxemia, cyanosis and increased risk for maternal and fetal death [4], [5], [6], [7].

• We prevented tachycardia with metoprolol, adequate hydration, pain control (epidural) and minimizing blood loss during delivery.

• We minimized hypotension by monitoring strict fluid shifts and blood loss with an arterial line.

• Hypotension can be prevented by using methylergonovine instead of oxytocin; of note, our patient became hemodynamically unstable with oxytocin use.

• Cyanosis leads to tissue hypoxia, poor placental oxygen transfer, FGR and even fetal demise [5], [8]. Although betablockers have been linked to FGR, in this case FGR was an effect of cyanosis. Supplemental oxygen may ameliorate these risks and partially improve oxygen delivery to the placenta [4].

• Polycythemia is associated with hyperviscosity and thrombosis. The utility of anticoagulants in polycythemia without prior thrombosis is questionable [5]. Nonetheless, prophylactic anticoagulation should be considered for women who remain in bed rest [4]. We used ASA throughout the pregnancy and reserved heparin to the post-operative course.

• Epidural anesthesia with slow and controlled incremental doses is safe to use in women with uncorrected TOF [9] and is preferred to spinal or general anesthesia to avoid profound sympathetic block, hypotension, rapid decrease in SVR reduction or tachycardia which induce/worsen right-to-left shunt [4].

• Phenylephrine is preferred to ephedrine as a vasopressor because it does not induce tachycardia, has minimal impact in the CO, maintains the SVR at normal-to-high range, and allows a stable SpO2 preventing worsening of right-to-left shunting (Table 1).

• Non-invasive monitoring provides useful hemodynamic information at baseline, during epidural, labor, placental delivery and oxytocin infusion (Table 1).

• The rate of CHD in women with TOF is 5% [10]. Fetal echocardiograms were normal, and neonatal sonograms confirmed no CHD.

• Hematocrit >65% has been associated with stillbirth; [5], [11] our patient never reached that hematocrit concentration.

• There are no standard recommendations on the time or mode of delivery, but vaginal route with adequate pain relief (epidural) is preferred [4]. Because of stable maternal status and reactive NST, our patient was delivered at term. Because she became hemodynamically unstable during labor, we opted for cesarean.

• Patients with uncorrected TOF must receive endocarditis antibiotic prophylaxis before delivery [12].

• During cesarean avoid unnecessary fundal pressure to minimize inferior vena cava compression, and preferably repair the uterus without exteriorization to minimize the risk of a vagal reaction or venous air embolism [4], [13].

• Methylergonovine is preferred to control the uterine tone over oxytocin which decreases the SVR significantly (Table 1).

• Filtered intravenous lines must be used to avoid paradoxical air embolism [7].

Finally, this case underlines the importance of a multidisciplinary approach with a team composed of a maternal-fetal medicine obstetrician, cardiologist and anesthesiologist familiar with the physiologic cardiovascular changes during pregnancy.