Tetralogy of Fallot

Please list the 4 abnormalities of Tetralogy of Fallot.

• Malalignment ventricular septal defect

• Right ventricular outflow tract obstruction or pulmonary stenosis

• Right ventricular hypertrophy

• Overriding aorta

Where does the malalignment VSD extend in Tetralogy of Fallot?

It is a subaortic outlet VSD that extends into the membranous septum.

Please list the 5 possible levels or forms of pulmonary stenosis in Tetralogy of Fallot.

• Valvar

• Subvalvar

• Supravalvar

• Atretic

• A combination of these levels

How do the pulmonary valve and pulmonary artery usually appear in Tetralogy of Fallot?

The pulmonary valve and pulmonary artery are usually small and dysplastic.

How common is the usual coronary artery arrangement in Tetralogy of Fallot, and what is that arrangement?

The usual coronary arrangement occurs in approximately 65% of patients:

• The RCA arises from the right aortic sinus.

• The LAD and circumflex arteries arise from the left aortic sinus.

What is the most common coronary artery anomaly in Tetralogy of Fallot?

The LAD arises from the RCA.

What is the primary embryologic error that causes Tetralogy of Fallot?

Anterior and superior deviation of the infundibular septum.

How does deviation of the infundibular septum cause pulmonary stenosis?

The deviated septum physically narrows the pathway leading to the pulmonary valve, producing pulmonary stenosis or RV outflow tract obstruction.

How does deviation of the infundibular septum cause the VSD?

The shifted septum fails to fuse with the rest of the ventricular wall, resulting in a large, unrestrictive VSD.

Why does the aorta override the VSD in Tetralogy of Fallot?

The shifted infundibular septum causes the aortic root to be positioned directly over the VSD, allowing the aorta to receive blood from both ventricles.

How common is Tetralogy of Fallot, and which sex is affected more often?

• It accounts for approximately 7%–10% of all congenital heart disease.

• It is the most common cyanotic heart defect.

• It affects males and females equally.

Please list the 6 syndromes associated with Tetralogy of Fallot.

• DiGeorge syndrome — approximately 35%

• Trisomy 21

• Alagille syndrome

• Cat-eye syndrome

• CHARGE syndrome

• VACTERL

Please list the 5 environmental or maternal factors associated with Tetralogy of Fallot.

• Maternal rubella

• Maternal diabetes

• Maternal phenylketonuria

• Retinoic acid exposure

• Trimethadione exposure

What 2 factors determine the hemodynamics of Tetralogy of Fallot?

• Severity of the pulmonary stenosis

• Size of the VSD

What is a “blue Tet”?

A blue Tet has a right-to-left shunt across the VSD. Deoxygenated blood moves from the RV through the VSD and enters the systemic circulation, causing cyanosis

What is a “pink Tet”?

A pink Tet has mild RV outflow tract obstruction, so a left-to-right shunt may predominate. The patient may not have cyanosis at rest.

What symptoms can occur in a pink Tet, and how may the condition progress?

The infant may develop pulmonary overcirculation from the VSD. The RV outflow obstruction may worsen over time, eventually causing cyanosis.

What are Tet spells?

Tet spells, or hypoxic spells, are acute episodes of:

1. Increased cyanosis

2. Hyperpnea or rapid breathing

3. Irritability

What determines the clinical presentation of Tetralogy of Fallot?

The clinical presentation depends on the severity of the RV outflow tract obstruction. Patients most commonly present as cyanotic newborns.

Why does cyanosis occur in Tetralogy of Fallot, and when may it appear?

Oxygen-poor blood bypasses the lungs and enters the systemic circulation. Cyanosis may be present at birth or may progressively develop during the first few months of life.

What findings are associated with failure to thrive in Tetralogy of Fallot?

• Feeding difficulties

• Excessive fatigue

• Poor weight gain

What murmur is associated with Tetralogy of Fallot, and what causes it?

A harsh systolic ejection murmur is heard at the left upper sternal border because of pulmonary stenosis.

What commonly triggers a Tet spell?

• Crying

• Feeding

• Defecating

What can happen during a severe Tet spell?

• Extreme hypoxia

• Worsening cyanosis

• Limpness

• Loss of consciousness

• The patient may become inconsolable

Why do older children with mild Tetralogy of Fallot squat when they become short of breath?

Squatting increases systemic vascular resistance, which forces more blood toward the lungs.

What are the typical chest X-ray findings of Tetralogy of Fallot?

• Normal-sized cardiac silhouette

• Upturned cardiac apex

• Concave main pulmonary artery segment

• Boot-shaped heart appearance

What long-term complications may result from chronic untreated hypoxemia in Tetralogy of Fallot?

• Clubbing of the fingers and toes

• Polycythemia from overproduction of red blood cells

• Lifelong risk of endocarditis

What should be evaluated by sweeping from the subcostal 4-chamber view toward the outflow tracts?

• Normal segmental anatomy of S, D, S

• Overriding aorta

• Malalignment VSD

What should be assessed from the subcostal short-axis view at the great-vessel level?

• ASDs

• VSD location and size

• Pulmonary artery obstruction and its level

• Anterior deviation of the conal septum

What should be assessed from the apical views in Tetralogy of Fallot?

Ventricular function.

What should be assessed from the apical 5-chamber view?

The size and direction of flow through the VSD.

What should be examined from the parasternal long-axis view?

• Overriding aorta

• Malalignment VSD

What should be assessed from the parasternal long-axis outflow view?

• Measure the pulmonary valve.

• Interrogate the valve with color and spectral Doppler.

What 4 defects or structures should be measured and interrogated with color and spectral Doppler from the PLAX outflow view?

• Pulmonary valve

• VSD

• ASD

• PDA

What additional anatomy should be evaluated from the PLAX outflow view?

Coronary artery anatomy.

What should be demonstrated from the suprasternal notch view?

Aortic arch sidedness.

What should be measured from the left high sternal border view?

The pulmonary artery branches.

What Doppler pattern indicates dynamic RV outflow tract obstruction?

A late-peaking, dagger-shaped Doppler signal.

What Doppler pattern indicates fixed valvar or supravalvar obstruction?

A more symmetric Doppler signal with a midsystolic peak.

Why can multiple levels of pulmonary outflow obstruction be difficult to differentiate with Doppler?

Obstruction in series may produce overlapping Doppler patterns, with fixed and dynamic signals superimposed.

How is SPAP determined in Tetralogy of Fallot according to the PowerPoint?

Subtract the TR-derived pressure gradient from the systemic blood pressure:

SPAP = blood pressure − TR velocity converted to mmHg

Please list the Doppler velocities and gradients used to grade RVOT or pulmonary valve obstruction.

Please list the 5 associated defects of Tetralogy of Fallot.

• Right aortic arch

• ASD or PFO

• Anomalous coronary arteries — approximately 5%–10%

• Patent ductus arteriosus

• Major aortopulmonary collateral arteries, or MAPCAs

Please list the 4 differential diagnoses for Tetralogy of Fallot.

• Double-outlet right ventricle

• D-TGA with pulmonary stenosis

• Truncus arteriosus

• Pulmonary atresia

How are the symptoms of a Tet spell managed?

• Place the knees against the chest or have the patient squat.

• Provide supplemental oxygen.

• Give beta blockers for muscle spasms.

When is palliative treatment performed in Tetralogy of Fallot?

It is performed when the patient is cyanotic to improve pulmonary blood flow until complete repair can be safely completed.

Please list the 3 palliative treatments for Tetralogy of Fallot.

• Blalock-Taussig shunt

• RV outflow tract stent, especially in premature infants

• PDA stent

When is single-stage corrective surgery usually performed?

At approximately 3–6 months of age.

Please list the 7 components of complete Tetralogy of Fallot repair.

• Detach and remove a previous modified Blalock-Taussig shunt.

• Close the VSD with a synthetic patch.

• Close an ASD when present.

• Ligate the PDA if it remains open.

• Resect obstructive muscle from the RV outflow tract.

• Perform pulmonary valvotomy, valve repair, or valve replacement.

• Reconstruct the pulmonary annulus or pulmonary artery with a transannular patch.

Please list the 5 findings that should be evaluated after Tetralogy of Fallot repair.

• Residual atrial or ventricular shunts

• Pericardial effusion during the early postoperative examination

• Detailed RV outflow tract anatomy

• Pulmonary regurgitation

• Serial ventricular size and function

Please list the 3 transcatheter palliative procedures used for Tetralogy of Fallot.

• Balloon pulmonary valvuloplasty

• RV outflow tract stenting

• Patent ductus arteriosus stenting

What are the advantage and disadvantage of balloon pulmonary valvuloplasty?

• Advantage: It is technically the least challenging procedure.

• Disadvantage: It has a high failure rate.

What are the advantages and disadvantage of RV outflow tract stenting?

Advantages:

• Promotes good pulmonary artery growth

• Produces the most physiologic circulation

Disadvantage: The stent must be resected during complete surgical repair.

What are the advantages and disadvantages of PDA stenting?

Advantages:

• Promotes good pulmonary artery growth

• Relieves cyanosis

Disadvantages:

• May be technically challenging

• Has a learning curve

Which transcatheter approaches are preferred over balloon pulmonary valvuloplasty?

RV outflow tract stenting and PDA stenting are preferred over balloon pulmonary valvuloplasty.

How may transcatheter palliation benefit lower-weight newborns with Tetralogy of Fallot?

PDA stenting, RVOT stenting, and balloon pulmonary valvuloplasty may provide alternatives to staged surgical repair, especially in lower-weight newborns, although reintervention rates may be higher.

Why are large native RV outflow tracts challenging to treat with transcatheter pulmonary valves?

Their dimensions may be larger than the sizes covered by previously approved transcatheter valves.

Which transcatheter pulmonary valves are used for RV outflow tracts measuring 30 mm or less?

• Melody valve

• SAPIEN XT valve

• SAPIEN S3 valve

Which transcatheter devices may be used for RV outflow tracts measuring more than 30 mm?

• Harmony transcatheter pulmonary valve

• Alterra adaptive prestent

• Venus P-valve

What is the limitation of newer self-expanding transcatheter pulmonary valves?

They show promise, but the available long-term clinical data are still limited.