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Clinical Summary

Tetralogy of Fallot (TOF) is most common cyanotic heart disease and consists of a spectrum of anatomic abnormalities (“tetrad”) that includes a large unrestrictive malaligned ventricular septal defect (VSD), right ventricular (RV) outflow tract obstruction (infundibular pulmonary stenosis [PS]), RV hypertrophy, and overriding of the aorta. The severity of PS ranges from mild to severe PS or to pulmonary atresia. Clinical presentation of TOF depends on the nature and degree of infundibular PS. An ejection systolic murmur is usually heard at the mid-upper left sternal border (murmur of PS) and may radiate toward the back. The loudness of the murmur depends on the volume of blood flowing across the outflow tract. Varying degrees of cyanosis due to right-to-left shunt resulting in an oxygen saturation of 75% to 85% is seen. Cyanosis shows minimal improvement with O2 supplementation. Other findings include increased RV impulse at the lower left sternal border (due to RV hypertrophy), loud single heart sound (pulmonary closure sound very soft) and digital clubbing. Cyanotic spells in infants and children with TOF are referred as hypercyanotic spells (also known as Tetralogy spells or “Tet spells”. Increased RV outflow tract obstruction exaggerates a right-to-left shunt, resulting in a decrease in pulmonary blood flow and a hypercyanotic spell (nearly all of the blood in the RV crosses through the VSD and enters the aorta). Complete blood count shows polycythemia (compensatory due to chronic hypoxemia). The ECG shows RV hypertrophy with right axis deviation. Radiography in infants may be normal or may show only decreased pulmonary vascular markings. In older children a “Boot-shaped heart” is seen.

Figure 5.26 ▪ Cyanotic Congenital Heart Disease.

Cyanosis of the lips (A) and cyanosis of the nail beds (B) are seen in this 4-month-old infant with TOF presenting with a hypercyanotic spell (lethargy and extreme cyanosis with hyperpnea and notable absence of a heart murmur). These photographs were taken after stabilization. (Photo contributor: Binita R. Shah, MD.)

Emergency Department Treatment and Disposition

Admit patients with hypercyanotic spells requiring more than O2 therapy and positional interventions to abate the spell and patients with complications related to prolonged hypoxemia (eg, seizures). Consult cardiology for further management of the hypercyanotic spell. Maintenance medical therapy may be required to control recurrent hypercyanotic spells (eg, propranolol) awaiting surgical intervention.

Figure 5.27 ▪ Clubbing and Cyanotic Nail Beds; Cyanotic Congenital Heart Disease.

This 12-year-old patient with TOF had a hemoglobin value of 22.5 g/dL, a hematocrit of 69.2%, an O2 saturation of 75%, and a Po2 of 45 mm Hg on room air. (Photo contributor: Binita R. Shah, MD.)

Figure 5.28 ▪ “Boot-Shaped Heart” in Tetralogy of Fallot; Cyanotic Congenital Heart Disease.

A frontal view of the chest in a 5-month-old infant with unrepaired tetralogy of Fallot (TOF) shows a “boot-shaped heart” (uplifted apex due to the RV enlargement associated with concavity of the upper left heart border due to a small or absent main pulmonary artery segment), diminished pulmonary vascular markings and a right-sided aortic arch (seen in about 25% of patients with TOF). (Photo contributor: Shyam Sathanandam, MD.)

Figure 5.29 ▪ “Egg on String Appearance” in Transposition of Great Arteries; Cyanotic Congenital Heart Disease.

A frontal view of the chest in a 1-week-old baby presenting to the emergency department with severe cyanosis shows an “egg on string appearance” with increased vascularity suggesting a diagnosis of D-transposition of great arteries. This appearance is secondary to a narrow mediastinum, which is secondary to superimposition of the great vessels. (Photo contributor: Shyam Sathanandam, MD.)

Figure 5.30 ▪ Total Anomalous Pulmonary Venous Return (TAPVR); Cyanotic Congenital Heart Disease.

(A) A frontal view of the chest in a 4-week-old infant presenting to the emergency department (ED) with tachypnea shows a “snowman” or a “figure of 8” appearance that is characteristic for supracardiac type of TAPVR. This appearance is secondary to the anomalous pulmonary veins draining into a dilated innominate vein. (B) A frontal view of the chest in a 6-day-old neonate presenting to the ED with severe cyanosis, lethargy, and poor feeding shows a ground-glass appearance secondary to obstructed pulmonary veins and a right pleural effusion. Echocardiogram demonstrated an infracardiac type of TAPVR. (Photo contributor: Shyam Sathanandam, MD.)

Figure 5.31 ▪ Tricuspid Atresia; Cyanotic Congenital Heart Disease.

Twelve-lead ECG obtained on a 3-day-old neonate presenting to the ED with respiratory distress and mild cyanosis shows a left axis deviation that is virtually pathognomonic for tricuspid atresia. (Photo contributor: Shyam Sathanandam, MD.)


  1. Two hallmarks of TOF are a PS murmur and cyanosis.

  2. Hypercyanotic spells of TOF are very dramatic in their presentation. Failure to recognize without immediate intervention may result in hypoxic seizures, profound metabolic acidosis, cerebrovascular accident (due to polycythemia/hyperviscosity), deterioration in cardiac rhythm, and death.

  3. Increasing cyanosis in a child with a history of heart disease or history of squatting with exertion is an important clue indicating a potential hypercyanotic spell.

  4. A notable absence or lessening of a previously heard heart murmur in a cyanotic child is the most important clue suggesting a hypercyanotic spell.

Table 5.13 ▪ Cyanotic Congenital Heart Disease
Table 5.14 ▪ Hypercyanotic Spell of Tetralogy of Fallot

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