Tetralogy of Fallot With Pulmonary Stenosis Treatment & Management

The prognosis of patients with unrepaired tetralogy of Fallot (TOF) is inferior to the life expectancy of those undergoing repair. Therefore, whether to repair tetralogy of Fallot is not often debated.

The timing of surgery and the initial surgical procedure performed in the patient with symptomatic tetralogy of Fallot remain controversial. The nature of the right ventricular (RV) outflow tract obstruction (RVOTO) often dictates the symptoms. In cyanotic tetralogy of Fallot, hypercyanotic episodes (tetralogy of Fallot spells) may occur with agitation or irritability. If the episode is profound, the child develops severe cyanosis, often with hypotension, hemodynamic instability, and altered consciousness.

Medical management of tetralogy of Fallot spells often includes use of mechanical ventilation, inotropes, and an alpha-agonist such as phenylephrine hydrochloride (Neo-Synephrine) to increase pulmonary blood flow. In neonates with spells, prostaglandins may be used to reestablish ductal patency; however, this approach is not always successful.

Patients whose condition is refractory to medical management and stabilization require urgent surgical intervention. In some centers, these patients are treated with initial surgical palliation with a systemic-to-pulmonary artery shunt and subsequent complete repair, whereas, in other centers, these children are treated with urgent primary complete repair.

Controversy also surrounds the timing of surgery in children with asymptomatic tetralogy of Fallot. In asymptomatic patients, some centers advocate that elective repair be performed from the neonatal period, whereas other centers wait until age 1 year. Most surgeons repair the infant with asymptomatic tetralogy of Fallot between ages 4 and 6 months.

In cyanotic patients with tetralogy of Fallot (TOF), conservative management includes the following:

• Knee-to-chest positioning

• Administration of supplemental oxygen

• Sedation

• Volume expansion

• Correction of anemia, if present

• Additional measures that increase cardiac preload and systemic vascular resistance

• Beta-blockade to decrease infundibular spasm

In acyanotic patients, medical management is similar to management of a patient with a ventricular septal defect (VSD) and may include diuretics (furosemide [Lasix]), digoxin, and afterload reduction (captopril).

The role of transcatheter interventions for tetralogy of Fallot (TOF) is controversial. Most centers do not use transcatheter interventions for tetralogy of Fallot and instead perform surgical palliation and repair.

Some centers advocate balloon dilation of the right ventricular outflow tract (RVOT) for infundibular and pulmonary valvar stenosis. The balloon dilation for pulmonary valvar stenosis is more likely to be successful than dilation for infundibular stenosis.

Patients who undergo transcatheter balloon dilation for recurrent RVOT after valve-sparing repair of tetralogy of Fallot appear to demonstrate acute reduction in the RVOT gradient, with more favorable outcomes in those with stenosis solely at the level of the valve. ^[11] However, balloon dilation often leads to an increase in pulmonary regurgitation and has a high rate of reintervention.

Cutting-balloon angioplasty of pulmonary artery stenosis in tetralogy of Fallot has been investigated but is not commonly performed. In certain high-risk infants, stenting of the RVOT has been performed. Elective surgical repair and stent removal can be performed later without longer cardiopulmonary bypass times or recognizable complications compared with shunted patients. ^{[12, 13]}

Transcatheter interventions do play a major role in the rehabilitation of the distal pulmonary arteries in the setting of tetralogy of Fallot with pulmonary atresia.

A systemic-to-pulmonary artery shunt is indicated in patients in whom the risk in complete repair is considered to be higher than the cumulative risk in 2-stage repair.

The timing and type of surgical intervention in tetralogy of Fallot (TOF) is controversial. In asymptomatic patients, elective repair has been advocated from the neonatal period up until age 1 year. Most surgeons perform repair in infants with asymptomatic tetralogy of Fallot between ages 4 and 6 months. In symptomatic or cyanotic patients, depending on institutional preferences, complete repair can be performed as a primary single-stage procedure or as a 2-stage approach, with initial systemic-to–pulmonary artery shunting.

The preoperative evaluation for tetralogy of Fallot (TOF) repair includes an assessment of functional status and pulmonary evaluation. Chest radiographic findings may depict the classic boot-shaped heart. Echocardiography is diagnostic, and associated anomalies can be excluded. Cardiac catheterization is indicated before repair of tetralogy of Fallot in patients with previous palliation and when aortopulmonary collaterals and pulmonary artery branching abnormalities are suspected (see Workup).

Preoperative diagnostic studies must provide the surgeon with the following data:

• The number, size, and location of all ventricular septal defects (VSDs)

• The severity and location of right ventricular (RV) outflow tract (RVOT) obstructions (RVOTOs)

• The size and distribution of the pulmonary artery

• The origins and branching pattern of the coronary arteries

• The origin and distribution of all sources of pulmonary blood flow, including major aortopulmonary collateral arteries (MAPCAs)

The role of palliative surgery for tetralogy of Fallot (TOF) is controversial. Patients whose conditions are refractory to medical management and stabilization require urgent surgical intervention. In some centers, these patients are treated with initial surgical palliation with a systemic-to–pulmonary artery shunt and subsequent complete repair. In other centers, these children are treated with urgent primary complete repair. ^{[14, 15]}

Creation of a systemic-to–pulmonary artery shunt can be performed from the midline by means of a sternotomy or thoracotomy. Advantages of the sternotomy approach include the simple use of cardiopulmonary bypass if necessary. Advantages of the thoracotomy approach include the preservation of a virgin sternotomy approach with a simplified sternotomy for the eventual complete repair with minimal adhesions.

A modified Blalock-Taussig (BT) shunt procedure is most commonly performed by using a polytetrafluoroethylene (Gore-Tex) tube graft anastomosed end-to-side to the right subclavian artery and end-to-side to the right pulmonary artery. The modified BT shunt is most commonly created on the side opposite the aortic arch. Therefore, with a left aortic arch, a right modified BT shunt is typically created. With a right aortic arch, a left modified BT shunt is typically created.

Complete intracardiac repair of tetralogy of Fallot (TOF) can be performed as a single-stage procedure or as a 2-stage approach, with initial systemic-to–pulmonary artery shunting.

Complete surgical repair involves closure of the ventricular septal defect (VSD) and relief of the right ventricular (RV) outflow tract obstruction (RVOTO). A median sternotomy approach is used with cardiopulmonary bypass.

Complete surgical repair goals

The goals of complete repair are relief of all obstruction to blood flow from the RV to the pulmonary artery and closure of the VSD. The relief of RVOTO may involve resection of obstructing RVOT muscle bundles, creation of an RVOT patch, creation of a transannular RVOT patch, pulmonary valvotomy or valvectomy, and pulmonary arterioplasty of the main and branch pulmonary arteries. ^[3] The VSD is usually closed with a patch taking great care to avoid damage to the conduction system.

Transventricular vs transatrial approach

Two potential surgical approaches are the transventricular approach and the transatrial approach. Transventricular repair with a right ventriculotomy in the infundibulum allows for exposure of the VSD and patch closure of the infundibular incision. With the transatrial approach, the VSD and subpulmonary obstruction can be approached from a transatrial direction. Muscle resection is performed to relieve the RVOTO.

Transannular patching

Assessment of the pulmonary annulus using predicted mean-normal diameters of the pulmonary valve annulus corrected for body surface area provides some guidance for enlarging the pulmonary annulus (transannular patching). A conduit connection from the RV to the pulmonary arteries may be necessary in patients with pulmonary atresia, anomalies of the coronary arteries, or severe multilevel obstruction and hypoplasia. Distal pulmonary arteries and branch pulmonary artery stenosis can be managed at the time of surgery by using autologous pericardial patch enlargement. Additional work on the branch pulmonary arteries can be accomplished preoperatively and postoperatively by means of the transcatheter approach.

In neonates and young infants, use of a transannular patch is most likely, and extensive RVOT muscle resection is not usually necessary. In select patients, intraoperative pulmonary balloon valvuloplasty can be used as an adjunctive therapy to relieve obstruction while preserving pulmonary valve integrity and function. ^[13] In older children, use of a transannular patch is relatively unlikely, and extensive RVOT muscle resection is common.

After surgery, various residual abnormalities may be encountered, ranging from a nearly normal-appearing heart to one in which substantial right ventricular (RV) dysfunction and residual RV outflow tract obstruction (RVOTO). ^[16]

Two-dimensional (2-D) echocardiography and Doppler ultrasonographic techniques can be the definitive means for monitoring patients with respect to the recovery of RV function and the development of complications, such as recurrent RVOTO and residual or recurrent ventricular septal defect (VSD) (see Workup).

Postoperative pulmonary insufficiency can be associated with late RV dysfunction and may necessitate intervention.

Clinical, electrocardiographic (ECG), and echocardiographic follow-up monitoring is indicated. Echocardiography is the diagnostic modality of choice for follow-up.

Further in/outpatient care

Some children, especially those repaired at a younger age, may require prolonged hospitalization. Causes are multifactorial but may include sepsis, residual left-to-right shunts through ventricular septal defects (VSDs), low cardiac output syndrome, ventricular dysfunction, or cardiac arrhythmias. Associated noncardiac problems, including feeding difficulties, renal insufficiency, or pulmonary insufficiency, may require ongoing management and delayed discharge.

Patients who are status post repair of tetralogy of Fallot deserve lifelong outpatient follow-up with a focus on early detection of signs of congestive heart failure or functional impairment, as well as ongoing surveillance for cardiac arrhythmias.

Two areas of controversy are briefly discussed in this section: the differentiation between tetralogy of Fallot (TOF) and double-outlet right ventricle (DORV) and the management of late pulmonary insufficiency.

Tetralogy of Fallot versus double-outlet right ventricle

The tetralogy of Fallot manuscript of The International Congenital Heart Surgery Nomenclature and Database Project clearly stated that the distinction between tetralogy of Fallot and DORV is controversial. ^[17] Some authors use the term DORV when the pulmonary artery arises from the right ventricle (RV) and when more than 50% of the aorta arises from the RV. Other authors use this term only when the pulmonary artery arises from the RV and when 90% or more of the aorta arises from the RV. Still others use the term only when fibrous continuity is absent between the aortic and mitral valves.

In the DORV manuscript of The International Congenital Heart Surgery Nomenclature and Database Project, DORV is defined as a type of ventriculoarterial connection in which both great vessels arise predominantly from the RV. ^[18] In the tetralogy of Fallot manuscript of The International Congenital Heart Surgery Nomenclature and Database Project, Marshall Jacobs stated, "It is inescapable that some hearts will be called tetralogy of Fallot at some centers and DORV at other centers."

Management of late pulmonary insufficiency

After repair of tetralogy of Fallot, many patients present in need of reoperative surgical reconstruction of the RV outflow tract (RVOT). The predominant physiologic lesion is often pulmonary insufficiency, but varying degrees of RVOT may also be present. In the past, patients were thought to tolerate pulmonary insufficiency reasonably well. However, in some, the long-term effects of pulmonary insufficiency and subsequent RV dilatation and dysfunction are associated with poor exercise tolerance and increased incidences of arrhythmias and sudden death.

Pulmonary valve insertion or replacement can be performed as treatment for pulmonary insufficiency to improve performance status, optimize hemodynamics, and improve control of arrhythmias. Indications for RVOT reconstruction in this setting and the surgical strategy continue to evolve. Several surgical options for pulmonary valve replacement are available, including the use of aortic and pulmonary homografts, stented and stentless porcine valves, porcine valve conduits, bovine jugular vein conduits, man-made polytetrafluoroethylene pulmonary valves, and even mechanical valves and mechanical valve conduits.

Over the last several years, concerns regarding postoperative pulmonary insufficiency or combined insufficiency and stenosis have increasingly emerged. The belief about patients' tolerance of pulmonary insufficiency after valvectomy and/or transannular patching during repair of tetralogy of Fallot is no longer simply accepted. The sequence of pulmonary insufficiency that causes volume overload leading to RV dilatation and dysfunction has been demonstrated with echocardiography and magnetic resonance imaging (MRI). ^{[19, 20]} Exertional symptoms often follow these objective changes in ventricular function and size and can be documented with exercise testing.

Further, peak oxygen consumption (VO₂), ventilation-carbon dioxide (VE/CO₂) slope, and heart rate reserve during exercise testing prediction have been shown to be predictive of early mortality. ^[21] Finally, life-threatening ventricular arrhythmias seem to be associated with relatively severe cases of pulmonary insufficiency and ventricular changes.

RV dilatation and dysfunction are reversible after pulmonary valve replacement. Therefore, as the population of children with repaired congenital heart disease ages, an increasing number of patients will benefit from pulmonary valve insertion. However, data suggest a lack of notable recovery of RV indices after pulmonary valve replacement in adults with long-standing pulmonary insufficiency. Therefore, the timing of pulmonary valve replacement is of major importance in the overall maintenance of ventricular function and optimal long-term outcomes. In addition, a program of aggressive pulmonary valve replacement in conjunction with intraoperative cryoablation is effective in decreasing QRS duration and in controlling ventricular arrhythmias in patients with tetralogy of Fallot and severe pulmonary insufficiency.

In general, indications for pulmonary valve replacement are evolving but currently include patients with moderate to severe pulmonary insufficiency and/or stenosis and any of the following: exertional symptoms of New York Heart Association (NYHA) class II or worse, RV dysfunction (RV ejection fraction <47%<ref>22</ref>, RV dilatation (RV end-diastolic volume index >150mL/m² or Z score >4 ^[22] ), decreased performance capacity on exercise testing, ventricular arrhythmias, and/or QRS duration of more than 160 ms.