Tetralogy of Fallot

KEY FEATURES

ESSENTIALS OF DIAGNOSIS

• Neonate, infant, or child with cyanosis (typically a neonate) or heart failure (infant or child)

• Central cyanosis, mildly prominent right ventricular (RV) impulse, murmur of pulmonic stenosis (with sufficient pulmonary blood flow), and absent pulmonic component of S₂

• Membranous ventricular septal defect (VSD) and obstruction of the RV outflow tract (subvalvular, valvular, supravalvular, or branch pulmonary artery stenosis)

GENERAL CONSIDERATIONS

• RV outflow tract obstruction is often at multiple levels

• Associated cardiac anomalies occur in approximately 40% of patients, including: right-sided aortic arch, coronary artery anomalies, systemic to pulmonary collateral vessels, patent ductus arteriosus, multiple ventricular defects, atrioventricular septal defects, and aortic cusp prolapse and regurgitation

• Fifteen percent of patients have extracardiac anomalies, including Down’s syndrome, Alagille’s syndrome, DiGeorge’s syndrome, and velocardiofacial syndrome

• Physiologic manifestations depend on the degree of RV outflow tract obstruction

  • – More severely obstructed RV outflow tract leads to greater shunting right to left across the VSD and into the aorta, resulting in cyanosis and polycythemia

• Women who have had corrective surgery without severe hemodynamic abnormalities before pregnancy generally have good maternal and infant outcomes

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

• Symptoms depend on the degree of RV outflow tract obstruction

• Children may present with profound cyanosis at birth, dyspnea related to heart failure due to increased pulmonary blood flow, or no symptoms

• Infants may have spells with profound cyanosis

PHYSICAL EXAM FINDINGS

• Central cyanosis

• Digital clubbing

• Single S₂

• Early systolic click along the left sternal border due to flow into a dilated ascending aorta

• Harsh systolic ejection murmur along the left mid to upper sternal border that radiates posteriorly owing to the RV outflow tract obstruction

• A murmur from the VSD is not usually appreciated

DIFFERENTIAL DIAGNOSIS

• Truncus arteriosus

• Double outlet right ventricle

• VSD and pulmonic stenosis

• Transposition of the great vessels

• Other causes of cyanosis with exercise intolerance

DIAGNOSTIC EVALUATION

LABORATORY TESTS

• No specific laboratory tests

• Arterial blood gases consistent with hypoxia

• Erythrocytosis in cyanotic patients

ELECTROCARDIOGRAPHY

• Right atrial enlargement and RV hypertrophy with right-axis deviation, prominent anterior R waves and posterior S waves, upright T wave in V1, and qR in the right chest leads

IMAGING STUDIES

• Chest x-ray findings: classic boot-shaped heart with an upturned apex and concave main pulmonary artery segment; normal heart size; normal or decreased pulmonary flow pattern; 25% of patients have a right aortic arch

• Echocardiography: demonstrates all essential features of tetralogy of Fallot for the diagnosis and preoperative evaluation

DIAGNOSTIC PROCEDURES

• Transesophageal echocardiography: usually not ...