Snapshot A neonatal boy is found to be cyanotic a few hours after delivery. The mother noticed the neonate turning blue when crying and feeding. The boy was born via a spontaneous vaginal delivery without any complications and to a 30-year-old mother. The mother received inconsistent prenatal care throughout her pregnancy. Physical examination is significant for a harsh systolic ejection murmur. A chest radiograph is performed and demonstrates a "boot-shaped" heart. Introduction Clinical definition a congenital cardiac defect caused by anterosuperior displacement of the infundibular septum characterized by PROV Pulmonary infundibular stenosis Right ventricular hypertrophy (RVH) Overriding aorta Ventricular septal defect (VSD) Epidemiology Demographics neonates are affected the most common cyanotic cardiac lesion Risk factors family history maternal exposure to retinoic acid Etiology Conotruncal abnormality from the failure of neural crest cells to migrate Pathogenesis pulmonary stenosis causes right ventricular outflow obstruction and causes right-to-left shunting in cases of severe lesions, neonates rely on a patent ductus arteriosus for survival the right-to-left shunt across the VSD causes cyanosis cyanosis causes marked clubbing and dyspnea on exertion if uncorrected squatting or knee-chest position can increase preload and systemic vascular resistance, alleviating the right-to-left shunting caused by right ventricular outflow obstruction and relieving the cyanosis Associated conditions thymic aplasia (DiGeorge syndrome) Down syndrome Presentation Symptoms tet spells (hypercyanotic episodes) patients often present with tet spells caused by crying, fever, or any physical exertion acute onset of restlessness causes increased cyanosis, gasping, and occasionally syncope tet spells often resolve with knee-chest position, oxygen, or morphine usual onset is around 2-6 months of age Physical exam systolic thrill along the left sternal border loud and harsh systolic ejection murmur on the upper sternal border may or may not have a preceding click single S2 clubbing (in older children with uncorrected defect) Imaging Radiography indication for all patients views chest findings boot-shaped heart dark lung fields Echocardiogram indication performed as the gold standard diagnostic test most sensitive test findings features of tetralogy of Fallot VSD overriding aorta Studies Electrocardiogram findings right axis deviation RVH Making the diagnosis based on clinical presentation and echocardiogram in some cases, tetralogy of Fallot may be diagnosed prenatally with a fetal echocardiogram Differential Transposition of the great vessels distinguishing factors early cyanosis that does not correct with squatting or knee-chest position egg-on-a-string appearance on chest radiography Truncus arteriosus distinguishing factors electrocardiogram with left axis deviation and left ventricular hypertrophy requires both atrial septal defect and ventricular septal defect Treatment Medical prostaglandin E1 indication for all patients who are cyanotic at birth mechanism of action maintains a patent ductus arteriosus for adequate lower extremity perfusion β-blockers indications for patients prior to surgical repair to decrease the risk of tet spells mechanism of action is reduction of right ventricular infundibular spasm, increasing size of right ventricular outflow tract Operative surgical repair indication definitive treatment surgeries closure of VSD removal of pulmonary outflow obstruction Complications Thrombosis Infective endocarditis Heart failure Prognosis Severity of symptoms depends on the severity of right ventricular outflow obstruction Long-term survival is good with surgical repair