Underlying anatomy and common variations in nature of intervention for surgical repair of tetralogy of Fallot. Image (a) depicts the underlying anatomical substrate of tetralogy of Fallot. Anterocephalad deviation of the outlet septum (arrow) is the key anatomical feature leading to subpulmonary stenosis, ventricular septal defect, aortic override and right ventricular hypertrophy. Image (b) depicts a right-sided modified Blalock-Taussig shunt (arrow) from the right subclavian artery to the right pulmonary artery. Image (c) depicts the use of a transannular patch (block arrow) to augment the right ventricular outflow tract and main pulmonary artery (pulmonary valve annulus level dotted line; dashed arrow). This is associated with pulmonary regurgitation in follow-up. Image (d) depicts the use of a pulmonary artery patch (solid arrow) and a right ventricular outflow tract patch (dashed arrow) allowing augmentation of the pulmonary artery and right ventricular outflow tract whilst sparing the pulmonary valve (pulmonary valve annulus level marked by dotted line). If outflow tract patching is avoidable, the patient can be spared right ventriculotomy (Adapted from Babu-Narayan PhD thesis, University of London, Imperial College, 2010. Pathophysiology and management of adults with repaired tetralogy of Fallot studied using cardiovascular magnetic resonance)
7.1.3 Repaired Tetralogy of Fallot with Significant Pulmonary Regurgitation
Pulmonary regurgitation is a common consequence of repair of tetralogy of Fallot in particular where more extensive right ventricular outflow and pulmonary artery reconstruction were needed to relieve the original obstruction. It is generally well tolerated by patients and may be asymptomatic from the cardiac viewpoint for several decades. However, with time, pulmonary regurgitation results in right ventricular dilatation, right heart dysfunction, arrhythmia, heart failure and death. In the last 15 years, a lot of progress has been made regarding the timing of reoperation or transcatheter intervention to replace the pulmonary valve. This is now more commonly offered at an earlier stage, based on investigations and before patients become symptomatic. The status of the right ventricle is a more important arbiter of pregnancy-related risk than the degree of pulmonary regurgitation (Fig. 7.2). If both right and left ventricular functions are preserved, pregnancy is likely to be well tolerated despite severe pulmonary regurgitation. However, the risks of pregnancy are increased in the setting of pulmonary regurgitation with right ventricular dilatation and dysfunction and associated clinical symptoms (New York Heart Association class II or higher) . As pregnancy results in an increased circulating volume, this further compounds the right ventricle volume overload. In some cases, irreversible cardiac remodelling can develop especially during the late stage of pregnancy.
Cardiovascular magnetic resonance still frames in diastole (a) and systole (b) from a four-chamber steady-state free precession cine showing severe right ventricular dilatation consequent to severe pulmonary regurgitation late after repair of tetralogy of Fallot with functional moderate tricuspid regurgitation and impaired systolic function. There is right atrial dilatation and history of sustained clinical atrial arrhythmia. Using cardiovascular magnetic resonance imaging, accurate assessment of right as well as left ventricular volumes can be made without geometric assumptions which can be particularly misleading in the context of the postoperative right ventricle. In this case, the RV is dramatically dilated with indexed RV volume above 200 mL/m2 and impaired right ventricular ejection fraction of 41 %
When planning pregnancy, a full assessment of the impact of any pulmonary regurgitation should be made. If criteria are met for elective pulmonary valve replacement, this may be preferable prior to embarking on pregnancy. The decision regarding indications for elective pulmonary valve replacement to treat asymptomatic pulmonary regurgitation is individualised as for the patient not planning pregnancy. Echocardiography is the routine test of choice for screening patients with significant pulmonary regurgitation and right heart dilatation and for assessing ventricular function (Figs. 7.3, 7.4). Cardiovascular magnetic resonance imaging is used for accurate right ventricular volume and function assessment and cardiopulmonary exercise testing for objective measure of exercise capacity, and heart assessment also includes 12-lead electrocardiogram and chest x-ray for cardiothoracic ratio. Pregnancy planning may bring forward detailed heart assessment that culminates in recommendation that there are sufficient criteria to warrant haemodynamic intervention prior to pregnancy. In the author’s institution, a recovery period of 6 months post-operatively is recommended before then attempting to conceive.
Echocardiography images are from a 28-year-old woman born with tetralogy of Fallot and aortopulmonary window who underwent repair of aortopulmonary window at 8 weeks after birth and repair of tetralogy of Fallot at age 4 years. She also had a history of transcatheter stent insertion to the right pulmonary artery at 19 years old. Echocardiography images at 6 months after delivery are shown. (a) Apical four-chamber view showing severely dilated and hypertrophied right ventricle (RV) and dilated right atrium (RA). (b) Parasternal short axis view of the right ventricular outflow tract (RVOT). Stent seen in RPA (arrow). (c) Colour Doppler showing a narrow jet and turbulent flow in the stented right pulmonary artery (RPA). (d) Continuous wave Doppler recording of flow across RPA with peak flow velocity 4.2 m/s and calculated peak gradient of 69 mmHg, suggesting severe RPA stenosis
Echo images of a 36-year-old patient at 13 weeks gestation. (a) Parasternal short axis view showing aneurysmal dilatation of RVOT with mild infundibular narrowing and thickened pulmonary valve. (b) Colour Doppler of RVOT showing a broad jet of regurgitation suggesting severe pulmonary regurgitation (PR). (c) Apical four-chamber view showing severely dilated RV and dilated RA. (d) Continuous wave Doppler recording of flow in the RVOT. The very short pulmonary regurgitation duration suggests free PR
7.1.4 Repaired Tetralogy of Fallot with Significant Residual Pulmonary Stenosis
In general stenotic lesions are less well tolerated than regurgitant lesions. Doppler flow velocity, hence calculated pressure gradient across the stenotic RVOT, will increase to double, or even triple baseline during pregnancy as the circulating volume increases. Moderate stenosis before pregnancy is very likely to become severe with pregnancy judged by pressure gradient on Doppler. Although patients with mild to moderate right ventricular outflow tract obstruction may go through pregnancy without major cardiovascular or obstetric complications, relief of right ventricular outflow tract obstruction is indicated by a peak-to-peak gradient of more than 50 mmHg or a peak-right ventricular pressure more than 75 mmHg and should be performed prior to pregnancy. If pregnancy is already embarked on and right ventricular function remains preserved, even severe right ventricular outflow tract obstruction may be tolerated , but it may also be complicated by right heart failure and the onset of atrial arrhythmia. If early right heart failure is precipitated by pregnancy, balloon valvuloplasty may need to be considered as part of maternal care.
7.1.5 Repaired Tetralogy of Fallot with Aortic Dilatation and Other Risk Factors
Aortic dilatation is prevalent in tetralogy of Fallot . For those patients with Caesarean section or more marked aortic dilatation, for example, with aortic dilatation exceeding 50 mm, early epidural and assisted delivery may be advisable. Current guidelines do not suggest intervention for aortic dilatation in the setting or repaired tetralogy of Fallot below diameters of 55 mm . Though aortopathy could potentially complicate pregnancy management in repaired tetralogy of Fallot, acute aortic dissection in the setting of repaired tetralogy of Fallot is extremely rare. To date aortic dissection has only been described in four men all with significantly dilated aortas greater than or equal to 55 mm.
Left ventricular dysfunction as for all patients considering pregnancy confers additional risk. During pregnancy, mild LV dilatation and reduced ejection fraction is a common finding for repaired congenital heart disease including repaired tetralogy of Fallot. Pulmonary hypertension also confers additional risk. This can be secondary to historic use of Waterston surgical shunt though this will become increasingly rare in women with repaired tetralogy of Fallot of childbearing age; it may rarely occur due to small pulmonary arteries in repaired tetralogy of Fallot. Women with the native diagnosis for pulmonary atresia with ventricular septal defect who had pulmonary blood supply via aortopulmonary collateral arteries are discussed below.
For patients with co-morbidity due to coronary artery disease, obesity or diabetes or for those requiring anticoagulation, specific recommendations for these should be followed.
7.1.6 Tetralogy of Fallot with MAPCAs and Other More Complex Situations
Pulmonary atresia with ventricular septal defect and MAPCAs may be regarded as an extreme variant of tetralogy of Fallot. There is absence of any direct connection between the heart and the pulmonary arterial tree, a large VSD and two ventricles. Blood reaches the pulmonary bed via a patent ductus arteriosus and or major aortopulmonary collateral arteries. Those patients that have successfully undergone a biventricular repair surgical strategy with closure of the ventricular septal defect and right ventricular outflow tract reconstruction with a conduit are acyanotic. However, biventricular dysfunction especially diastolic dysfunction is more prevalent than in patients with simple Fallot variant. Those repaired patients that embark on pregnancy may be regarded similarly to other repaired tetralogy of Fallot patients but with precise risks depending on the status of the repair including the conduit function. However, remaining patients that have more complex anatomy may remain cyanotic. The risks depend on severity of cyanosis and degree of pulmonary hypertension (which can be subsegmental). In general, resting oxygen saturations less than 85 % are unlikely to result in successful pregnancy.
7.1.7 Unrepaired Tetralogy of Fallot
Clinical presentation with pregnancy and unrepaired tetralogy of Fallot is rare but described . Patients may present to specialist adult congenital heart disease services already pregnant with less favourable haemodynamics. Late repair in adulthood of tetralogy of Fallot prior to embarking on pregnancy is preferable.
7.2 Pregnancy Outcome
Most pregnancy outcome studies are small or single centre or retrospective. However, such data as exist suggest that for tetralogy of Fallot patients, most can have successful uneventful pregnancies, but maternal cardiac complications occur in 7–10 % , most commonly atrial arrhythmia (6–7 %)  and symptomatic right heart failure (2–5 %) . Adverse maternal cardiac events are associated with severe pulmonary regurgitation combined with right ventricular dysfunction, particularly when these occur in combination with left ventricular dysfunction or pulmonary hypertension . In a study of pregnancy in women with repaired tetralogy of Fallot which included 123 completed pregnancies in two centres, the use of cardiac medications prior to pregnancy was the most important predictor of both maternal cardiac events and of small-for-gestational-age babies .
Atrial arrhythmia is the most common pregnancy-related cardiac event in patients with repaired tetralogy of Fallot [12, 14]. This is due to the increased circulating volume, which exacerbates the risk of arrhythmia related to scarring caused by atriotomy at previous reparative surgery and by worsening existing chamber dilatation and right ventricular dysfunction. Not surprisingly, a history of arrhythmia increases the chance of recurrence [12, 15, 16].
Ventricular function and cyanosis during pregnancy are the major determinants of outcome for patients with Fallot and pulmonary atresia , and careful surveillance of both throughout pregnancy is needed. For the mother, cyanosis may progressively worsen in pregnancy with increasing right to left shunting further reducing pulmonary blood flow and oxygenation. Furthermore, maternal complications related to cyanosis include thrombosis, bleeding diathesis, arrhythmia and heart failure . The risks of fetal complications are high and include fetal loss, low birth weight and prematurity. For sicker patients, bed rest, oxygen therapy and low molecular weight heparin may be required to address maternal oxygen consumption and prevent thromboembolic complications.