Embryology

Question:

A full-term 2-week-old male newborn has cyanosis. Pregnancy and delivery were uncomplicated. His lungs are clear, and a midsystolic murmur is heard that is loudest in the left third intercostal space and associated with a thrill. Which of the following is the most likely diagnosis?

Correct Answer: E.  Tetralogy of Fallot

The midsystolic murmur heard best in the left third intercostal space associated with a thrill is consistent with the murmur of a ventricular septal defect (VSD). Of the answer choices above, only Tetralogy of Fallot includes a VSD. In addition to a VSD, patients with Tetralogy of Fallot also have pulmonary stenosis, right ventricular hypertrophy, and overriding aorta. These patients often present shortly after birth with cyanosis.

An atrial septal defect would present with a loud S1 and a wide, fixed split S2 on physical exam and it is unlikely that the patient would present with cyanosis.

The bicuspid aortic valve would not present with cyanosis. Many patients live with unrecognized bicuspid aortic valves until later in life with the development of aortic stenosis secondary to calcifications of the valve leaflets.

Patent ductus arteriosus likely would present with a continuous machine-like murmur.

Coarctation of the aorta is associated with elevated blood pressure in the upper extremities and decreased blood pressure in the lower extremities. If these patients present shortly after birth, they often have cyanosis of the lower extremity only.