A 1-day-old boy is evaluated in the neonatal intensive care unit for central cyanosis. He was born at 40 weeks gestation to a healthy 25-year-old woman who had an uncomplicated pregnancy and delivery. Examination shows a dusky infant with a II/VI holosystolic murmur that is loudest at the left lower sternal border. The lungs are clear bilaterally. Chest radiograph reveals decreased pulmonary vascular markings without cardiomegaly. ECG shows left axis deviation and tall, peaked P waves. What is the most likely diagnosis in this patient?
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This infant with central cyanosis has peaked P waves and left axis deviation. These findings are consistent with tricuspid valve atresia, which is characterized by the following:
Absent tricuspid valve: No flow from right atrium (RA) to right ventricle (RV) results in enlarged RA (ie, tall, peaked P waves) and hypoplastic RV. Lack of flow through the pulmonary outflow tract leads to underdevelopment of the pulmonic valve and/or artery (pulmonary stenosis). Heart size is typically normal on chest x-ray, but flattening of the right heart border may occur.
Atrial septal defect (ASD): Atrial communication is necessary for survival of patients with tricuspid valve atresia; it provides a path for deoxygenated blood returning to the RA to reach the lungs. Rather than the fixed, widely split S2 characteristic of ASD, patients typically have a single S2 due to pulmonic stenosis. Because the entire systemic venous return is delivered to the left side of the heart, left-sided volume overload occurs (ie, left axis deviation).
The resulting systemic delivery of a large fraction of deoxygenated blood leads to central cyanosis in the newborn period.
(Choice A) Complete atrioventricular canal defect consists of a large ASD and VSD, with left-to-right shunting leading to ventricular volume overload and pulmonary overcirculation, causing heart failure symptoms in newborns (cyanosis is not typical). X-ray findings include increased pulmonary markings and cardiomegaly.
(Choice B) Isolated VSD is generally an acyanotic heart defect in which oxygenated blood is shunted from the left to right ventricle, with a large VSD causing pulmonary overcirculation and left-sided volume overload. Shunt reversal (Eisenmenger syndrome) due to elevated pulmonary pressure can result in cyanosis but develops over years.
(Choice C) In total anomalous pulmonary venous return, oxygenated blood from the lungs bypasses the left atrium and drains into the RA, leading to cyanosis. Right-sided volume overload results in RA and RV enlargement (ie, right axis deviation) and pulmonary overcirculation (ie, increased pulmonary markings).
(Choice E) Truncus arteriosus causes cyanosis due to mixing of blood between the aorta and pulmonary artery. A systolic ejection murmur is typical, and x-ray reveals cardiomegaly and increased pulmonary vascular markings.
Educational objective:
Tricuspid valve atresia is a cyanotic congenital heart defect characterized by absent communication between the right heart chambers. Findings include tall P waves (right atrial enlargement) and left axis deviation (left-sided volume overload) on ECG and decreased pulmonary markings on chest x-ray (hypoplasia of right ventricle and pulmonary outflow tract).