September 2013 Case 2

A newborn with cyanosis

Morgan Darrow M.D. and Jimmie SmithM.D.

Overview

A 6 day-old boy presented to cardiology clinic with cyanosis. He was born via spontaneous vaginal delivery at 37 weeks gestational age to a G1P0 mother following an uncomplicated pregnancy. Although he failed an "oxygen screen" in the hospital, he was otherwise well and was discharged to home on day 3 with instructions to follow up with the cardiology clinic. At his clinic visit, he was cyanotic with oxygen saturations in the 70s. After a chest x-ray and echocardiogram revealed congenital heart abnormalities, he was admitted to the pediatric intensive care unit. Following surgical exploration of his heart and great vessels, a palliative procedure was performed. A workup for hypocalcemia revealed a deletion of chromosome 22q11.2 by fluorescent in-situ hybridization. Over the following weeks, his condition deteriorated as he developed three episodes of necrotizing enterocolitis and infection of a peripherally inserted central catheter line. On his 81st day of life, he appeared mottled, became hypotensive and acidotic, and then went into pulseless electrical activity. Resuscitative efforts were unsuccessful and an autopsy was requested.

Gross Description

A representative chest x-ray from his admission to the pediatric intensive care unit is shown below (figure 1).

At autopsy, the heart was enlarged and boot shaped due to right ventricular hypertrophy (figure 2). It weighed 59 grams (the mean for his age is 30 +/- 7 grams). The pulmonary trunk and pulmonary valve were absent. A surgically placed aorticopulmonary vascular shunt was intact (figure 3). There were multiple collateral vessels between the aorta and lungs. The aorta was found to override a large membranous ventricular septal defect which measured 1.8 x 0.4 cm (figure 4). The aorta was also found to override both ventricles. The foramen ovale was probe patent. The pulmonary veins, superior vena cava, and inferior vena cava were patent and arose in a normal manner.

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Figure 1.A chest x-ray demonstrating the finding of a "cœur en sabot" (boot-shaped heart).
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Figure 2.Enlarged, boot-shaped heart (H). (RL is right lung, LL is left lung)
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Figure 3.A surgical anastomosis (asterisk) connects the aortic arch (Ao) to the left pulmonary artery at the hilum of the left lung (LL). (H is heart)
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Figure 4.A membranous ventricular septal defect (asterisk) is present beneath the aorta (Ao). (AV is aortic valve, TV is tricuspid valve, RA is right atrium, RV is right ventricle)

Diagnosis

Given the infant's clinical presentation and anatomic findings, which of the following best describes his congenital heart malformation?

Answer

Please select an answer above.

Discussion

With an incidence of approximately 577 per million live births, tetralogy of Fallot is the most common cyanotic congenital heart malformation [1]. It consists of four morphologic features: ventricular septal defect, right ventricular outflow tract obstruction, an aorta that overrides the ventricular septal defect, and right ventricular hypertrophy, all of which result from the anterosuperior displacement of the infundibular septum during embryologic development [1]. Taken together, these abnormalities result in a right-to-left shunt that moves poorly oxygenated blood from the right ventricle to the systemic circulation, resulting in cyanosis. The degree of shunting, and therefore the degree of cyanosis and severity of symptoms, is determined by the degree of pulmonary stenosis [1]. Due to higher pressures on the systemic side, minimal pulmonary stenosis may present with a left-to-right shunt similar to an isolated ventricular septal defect [1]. At the other end of the spectrum, as in this case, there may be pulmonary atresia which results in cyanosis early in the postnatal period, more severe symptoms, and a less favorable clinical course [1]. Males and females are affected equally and most cases are sporadic [2]. However, deletions of chromosome 22q11.2 (DiGeorge syndrome) are associated with both tetralogy of Fallot and pulmonary atresia [1-3].

Although tetralogy of Fallot may be diagnosed by ultrasound in the prenatal period, most patients present after birth. Classic clinical findings include severe cyanosis and recurrent hypercyanotic spells ("Tet" spells) relieved by squatting [2]. Chest x-rays often reveal a "boot-shaped" heart due to right ventricular hypertrophy [1, figures 1 and 2]. A clinically suspected case of tetralogy of Fallot can be confirmed by echocardiography [2].

The prognosis for children with tetralogy of Fallot was very poor prior to the invention of techniques for surgical repair, with half of all patients dying in the first few years of life and very few surviving longer than 30 years [2]. Complete surgical repair of tetralogy of Fallot is now possible and is often performed in the first year of life, with most patients surviving to adulthood [2]. However, surgical repair is more complicated with the addition of pulmonary atresia [1, 2, 4]. Occasionally, as with this patient, a palliative procedure (the creation of an aorticopulmonary shunt) is performed. A commonly performed shunting procedure used in tetralogy of Fallot is the Blalock-Taussig shunt, which involves using a subclavian artery or Gortex tube to create a connection to the pulmonary artery [4]. This results in shunting of blood from the systemic circulation to the pulmonary circulation which improves symptoms.

References

  1. Kumar, V, Abbas, A, and N Fausto. Robbins and Cotran Pathologic Basis of Disease, 7th ed. Philadelphia, PA: Elsevier Saunders, 2005.
  2. Apitz, C, Webb, GD, and AN Redington. 2009. "Tetralogy of Fallot." Lancet 374:1462-71.
  3. Momma, K, Kondo C, and R Matsuoka. 1996. "Tetralogy of Fallot with pulmonary atresia associated with chromosome 22q11 deletion." J Am Coll Cardiol 27: 198-202.
  4. Doyle, T et al. Overview of the management of tetralogy of Fallot. In: UpToDate, Basow, DS (Ed), UpToDate, Waltham, MA, 2013.