| Snapshot |
| A 7-month infant presents with his mother for episodes of turning blue. The mother reports that his lips turn blue when he is crying or when he has fevers. The baby was born via a spontaneous vaginal delivery without any complications. His mother did not undergo routine prenatal care while pregnant with him. On physical exam, the infant is underweight. Cardiac exam reveals a harsh systolic ejection murmur. He starts crying in the middle of the exam and becomes cyanotic. The physician puts him in a knee-chest position, and the cyanosis resolves. |
| Introduction |
| Clinical definitiona congenital cardiac defect caused by anterosuperior displacement of the infundibular septum, characterized by PROV Pulmonary infundibular stenosis important prognostic factorRight ventricular hypertrophy (RVH)Overriding aortaVentricular septal defect (VSD) Epidemiologydemographicsneonates are affectedthe most common cyanotic cardiac lesionrisk factorsfamily historymaternal exposure to retinoic acidEtiologyconotruncal abnormality from failure of neural crest cells to migrate Pathogenesispulmonary stenosis causes right ventricular outflow obstruction and right-to-left shuntingin cases of severe lesions, neonates rely on a patent ductus arteriosus for survivalthe right-to-left shunt across the VSD causes cyanosiscyanosis causes marked clubbing and dyspnea on exertion if uncorrectedsquatting or knee-chest position can increase systemic vascular resistance, alleviating the right-to-left shunting caused by right ventricular outflow obstruction, and thus relieves the cyanosisAssociated conditionsthymic aplasia (DiGeorge syndrome)Down syndromePrognosisseverity of symptoms depends on the severity of right ventricular outflow obstructionlong-term survival is good with surgical repair |
| Presentation |
| Symptomstet spells (hypercyanotic episodes) patients often present with tet spells caused by crying, fever, or any physical exertionacute onset of restlessness causes increased cyanosis, dyspnea, and occasionally syncopetet spells often resolve with knee-chest position, oxygen, or morphineusual onset is around 2-6 months of agePhysical examsystolic thrill along the left sternal borderloud and harsh systolic ejection murmur on the upper sternal bordermay or may not have a preceding clicksingle S2clubbing (in older children with uncorrected defect) |
| Imaging |
| Radiography indicationfor all patientsviewschestfindingsboot-shaped heart dark lung fieldsEchocardiogram indicationperformed as the gold standard diagnostic testmost sensitive testfindingsfeatures of tetralogy of FallotVSDoverriding aorta |
| Studies |
| Electrocardiogram findingsright axis deviationRVHMaking the diagnosisbased on clinical presentation and echocardiogramin some cases, tetralogy of Fallot may be diagnosed prenatally with fetal echocardiogram |
| Differential |
| Transposition of the great vessels distinguishing factorsearly cyanosis that does not correct with squatting or knee-chest positionegg-on-a-string appearance on chest radiographyTruncus arteriosus distinguishing factorselectrocardiogram with left axis deviation and left ventricular hypertrophyrequires both atrial septal defect and ventricular septal defect |
| Treatment |
| Medicalprostaglandin E1 indicationfor all patients who are cyanotic at birthmechanism of actionmaintains a patent ductus arteriosus for adequate lower extremity perfusionβ-blockers indicationsfor patients prior to surgical repairto decrease the risk of tet spellsOperativesurgical repairindicationdefinitive treatmentsurgeriesclosure of VSDremoval of pulmonary outflow obstruction |
| Complications |
| ThrombosisInfective endocarditisHeart failure |
