A newborn boy is assessed in the newborn nursery due to central cyanosis that does not respond to oxygen therapy. The patient was born to a G1P1 mother at 39 weeks gestation. The mother had diabetes that was managed with exercise and insulin during the pregnancy. The mother has never been vaccinated and did not follow routine prenatal care. The newborn's temperature is 99.5°F (37.5°C), blood pressure is 70/30 mmHg, pulse is 160/min, respirations are 27/min, and oxygen saturation is 80% on room air. The initial workup of the patient includes a chest radiograph seen in Figure A as well as lab values as seen below. Hemoglobin: 14 g/dL Hematocrit: 42% Leukocyte count: 6,500/mm^3 with normal differential Platelet count: 197,000/mm^3 Serum: Na+: 139 mEq/L Cl-: 101 mEq/L K+: 4.3 mEq/L HCO3-: 24 mEq/L BUN: 12 mg/dL Glucose: 99 mg/dL Creatinine: 0.5 mg/dL Ca2+: 10.0 mg/dL AST: 12 U/L ALT: 10 U/L An electrocardiogram is obtained as seen in Figure B. Which of the following is the most likely diagnosis?
Truncus arteriosus
Transposition of the great vessels
Tricuspid valve atresia
Total anomalous pulmonary venous return
Transposition of the great vessels
This patient is presenting with right axis deviation on ECG and an "egg on a string" heart on chest radiograph suggesting a diagnosis of transposition of the great vessels.

Transposition of the great vessels occurs when the spiral septum that divides the truncus arteriosus into the aorta and pulmonary artery fails to spiral and connect the right ventricle to the pulmonary artery and the left ventricle to the aorta. Patients will present with central cyanosis and must have another cardiac defect/shunt in order to remain viable (such as an atrial septal defect, ventricular septal defect, or patent ductus arteriosus). Chest radiograph will reveal an "egg on a string" heart and ECG will reveal right axis deviation. The diagnosis is confirmed with echocardiography and treated surgically.

Cohen et al. review the treatment of patients with transposition of the great vessels. They discuss how multiple surgical procedures have been performed in an attempt to address this congenital abnormality. They recommend using MRI to characterize the success of these procedures.

Figure A is a chest radiograph demonstrating an elongated cardiac shadow (red circle). This classic "egg on a string" appearance of the heart is seen in transposition of the great vessels.

Figure B is an ECG demonstrating right axis deviation as revealed by being down in lead I (red circle) and up in aVF. Right axis deviation is classically seen in transposition of the great vessels.

Incorrect Answers:
Answer A: Tetralogy of Fallot presents with a boot-shaped heart on a chest radiograph and classic "Tet spells" where patients will squat thus improving shunting and cardiac performance. Treatment is with surgical correction of the abnormal spiral septum.

Answer B: Total anomalous pulmonary venous return occurs when pulmonary veins drain into the right heart circulation. It presents with cyanosis that does not correct with oxygenation but does not present with an "egg on a string" heart on a chest radiograph. Treatment is with surgical reconfiguration of pulmonary venous return.

Answer D: Tricuspid valve atresia occurs when the tricuspid valve never forms and thus there is no connection between the right atrium and right ventricle. Patients will present with cyanosis and poor feeding/poor growth. Treatment is with surgical creation of a connection between these chambers.

Answer E: Truncus arteriosus occurs secondary to failure of the spiral septum to divide the aorta and pulmonary artery. It presents with poor feeding, diaphoresis, tachypnea, and cyanosis. Treatment is with surgical separation of these arterial chambers.

Bullet Summary:
Transposition of the great vessels presents with central cyanosis, an "egg on a string" appearance on a chest radiograph, and right axis deviation on ECG.