Fallot’s tetralogy

Published on 02/04/2015 by admin

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Last modified 22/04/2025

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29 Fallot’s tetralogy

Instruction

Examine this patient’s heart.

Salient features

History

• Syncope (in 20% of cases)

• Squatting

• Shortness of breath

• Decrease in exercise tolerance

• Growth retardation.

Examination

• Clubbing

• Central cyanosis

• Left parasternal heave with normal left ventricular impulse

• Second sound is single (absent second pulmonic sound)

• Ejection systolic murmur heard in the pulmonary area

• Signs indicating Blalock–Taussig shunt:

• The left radial pulse is not as prominent as the right
• The arm on the side of the anastomosis (usually the left) may be smaller than the other arm
• Blood pressure is difficult to obtain because of the narrow pulse pressure in the arm supplied by the collateral vessels
• Thoracotomy scar.

Diagnosis

This patient has Fallot’s tetralogy with a Blalock–Taussig shunt and is mildly cyanosed, indicating a right to left shunt (functional status).

Questions

What are the constituents of Fallot’s tetralogy?

• Ventricular septal defect with a right-to-left shunt

• Pulmonary stenosis (infundibular or valvular)

• Right ventricular hypertrophy

• Dextroposition of the aorta with it overriding the ventricular septal defect.

What are the complications of Fallot’s tetralogy?

• Cyanotic and syncopal spells

• Cerebral abscess (in 10% of cases)

• Endocarditis (in 10% of cases)

• Strokes: thrombotic secondary to erythrocytosis and hyperviscosity

• Paradoxical emboli.

Advanced-level questions

What anomalies may occur in association with tetralogy of Fallot?

• Right aortic arch in 25% of patients

• Atrial septal defect in 10% (so-called pentalogy of Fallot)

• Coronary arterial anomalies in 10%.

What do you understand by a Blalock–Taussig shunt?

It is the anastomosis of the left subclavian artery to the left pulmonary artery with the intention to increase pulmonary blood flow.

Why is a Blalock–Taussig shunt seen less frequently in adults in the recent past?

With ready availability of cardiopulmonary bypass, such patients have total correction of their anomalies at an early age.

What is the survival of Fallot’s Tetralogy?

The rate of survival in uncorrected patients (Am J Cardiol 1978;42:458–66) is:

66% at 1 year of age

40% at 3 years

11% at 20 years

6% at 30 years

3% at 40 years.

The rate of survival 32 years after surgery in one series was 86% among patients with repaired tetralogy and 96% in an age-matched control population (N Engl J Med 1993;329:593–5); the difference reflected the increased risk of sudden death.

What do you know about the embryological development of Fallot’s tetralogy?

It arises from the anterior displacement of the conal septum, which leads to unequal partitioning of the conus at the expense of the right ventricular infundibulum and results in the obstruction of the right ventricular outflow tract and failure to close the intraventricular foramen.

What do you know regarding the relation between congenital heart disease and embryology of heart development?

In order of embryologic development, the steps embryogenesis include:

1 Looping, laterality and single-ventricle defects (e.g. double-inlet LV, situs inversus totalis)

2 Conotruncal defects (e.g. tetralogy of Fallot, double-outlet RV)

3 Atrioventricular canal defects (e.g. endocardial cushion defect, common atrioventricular canal defect)

4 Right ventricular outflow tract obstruction (e.g. pulmonary valve atresia or stenosis, Ebstein’s anomaly)

5 Left ventricular outflow tract obstruction (e.g. aortic valve atresia or stenosis, hypoplastic left heart)

6 Septal defects (e.g. ventricular septal defect, atrial septal defect)

7 Total or partial anomalous pulmonary venous return.

What is the treatment for Fallot’s tetralogy?

• Total correction under the age of 1 year when there is no need for an outflow transannular patch. A second-stage total correction can be performed when the child is over the age of 2 years. The mortality associated with surgery is <3% in children and 2.5 to 8.5% in adults.

• Blalock–Taussig shunting is performed nowadays only if the anatomy is unfavourable for a total correction.

• Modified Blalock–Taussig shunting is the interposition of a tubular graft between the subclavian and pulmonary arteries.

• The Waterston shunt involves anastomosis of the back of the ascending aorta to the pulmonary artery. It is used when surgery is required in a child younger than 3 months, because the subclavian artery is too small for a good Blalock–Taussig shunt.

• The Potts shunt involves anastomosis of the descending aorta to the back of the pulmonary artery (JAMA 1946;132:627).

• The Glenn operation involves anastomosis of the superior vena cava to the right pulmonary artery. The bidirectional Glenn procedure involves anastomosis of the superior vena cava to both pulmonary arteries.

• Pulmonary balloon valvuloplasty is sometimes used as an alternative for surgery.

What cardiac lesions favour an initial shunt?

• Anomalous coronary artery

• Single pulmonary artery

• Hypoplastic pulmonary arteries

• Single pulmonary artery.

What is Fallot’s triology?

Atrial septal defect, pulmonary stenosis and right ventricular hypertrophy.

What is Fallot’s pentalogy?

Fallot’s tetralogy with associated atrial septal defect.

What conditions are associated with Fallot’s tetralogy?

• Right-sided aortic arch (in 30% of cases)

• Double aortic arch

• Left-sided superior vena cava (in 10% of cases)

• Hypoplasia of the pulmonary arteries

• Atrial septal defect.

Mention the common congenital heart diseases

Ventricular septal defect, atrial septal defect of the secundum type, patent ductus arteriosus and Fallot’s tetralogy are the common congenital heart diseases, in order of frequency.

What are the findings from investigations?

Chest radiography

• Boot-shaped heart (Fig. 29.1)

• Enlarged RV

• Decreased pulmonary vasculature

• Right-sided aortic arch (in 30% of cases).

image

Fig. 29.1 Radiograph in classic cyanotic Fallot’s tetralogy. The left ventricle (LV) is small and underfilled and lies superior to a relatively horizontal ventricular septum and an elevated interventricular sulcus (arrowhead) inferior to which lies the concentrically hypertrophied apex forming right ventricle (RV). The ascending aorta (Ao) is prominent, the main pulmonary artery segment (PA) is concave, and the lungs are oligaemic.

(With permission from Perloff 2003.)

ECG

Right axis deviation right ventricular hypertrophy (Fig. 29.2).

image

Fig. 29.2 Electrocardiogram in tetralogy of Fallot, with tall R waves in the right precordium, deep S waves in V6, and positive T waves in V4R and V1 characteristic of right ventricular hypertrophy.

What are the arrhythmias detected with Holter monitoring with repaired tetralogy of Fallot?

• Ventricular arrhythmias can be detected in 40–50% of such patients and are most likely to occur in those who:

• are older at the time of surgical repair
• have moderate or severe pulmonary regurgitation
• have systolic and diastolic left ventricular dysfunction
• have prolonged cardiopulmonary bypass
• have prolongation of the QRS interval (to >180 ms).

• Atrial fibrillation or flutter, which may cause considerable morbidity

What do you know about the Taussig–Bing syndrome?

In this condition, the aorta arises from the RV; the pulmonary trunk overrides both ventricles at the site of an interventricular septal defect.

What are long-term complications in patients with repaired tetralogy of Fallot?

• Pulmonary regurgitation may develop as a result of surgical repair of the right ventricular outflow tract).

• Enlargement of the RV occurs, resulting in RV dysfunction, and repair or replacement of the pulmonary valve may be required.

• An aneurysm may form at the site where the RV outflow tract was repaired.

• Residual or recurrent obstruction of the RV outflow tract, requiring repeated surgery.

• Residual ventricular septal defects in approximately 10–20% of patients with repaired tetralogy of Fallot; such patients may require repeated surgery if the defects are of sufficient size.

• Right bundle branch block is common after repair of tetralogy of Fallot, but complete heart block is rare.

• Aortic root dilatation resulting in aortic regurgitation, usually mild.

Further reading

Apitz C, Webb GD, Reddington AN. Tetralogy of Fallot. Lancet. 2009;374:1469-1471.

Etienne-Louis Arthur Fallot (1850–1911), Professor of Hygiene and Legal Medicine in Marseilles, published his ‘Contribution to the pathologic anatomy of morbus coeruleus cardiac cyanosis’ in 1888.

The tetralogy was first described by Niels Stensen, Professor of Anatomy in Copenhagen, in 1672 but the term tetralogy of Fallot is attributed to Canadian Maude Abbott in 1924. (Fallot A. Contribution à l’anatomie pathologique de la maladie bleue (cyanose cardiaque). Marseille Med 1888;25:418–20).

Helen Brook Taussig (1898–1986) is the founder of American paediatric cardiology. She collaborated with Alfred Blalock (1899–1964), a vascular surgeon, in the development of palliative surgery for Fallot’s tetralogy (JAMA 1945;128:189).

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