Cardiology > Tetralogy of Fallot (TOF) in Adults   

Background 

I) Definition 

Tetralogy of Fallot (TOF) is a congenital heart defect characterized by four key anatomic abnormalities: ventricular septal defect (VSD), right ventricular outflow tract obstruction (RVOTO), overriding aorta, and right ventricular hypertrophy (RVH). It is the most common cyanotic congenital heart disease in children. With advances in surgical repair, many patients now survive into adulthood. Adults with TOF may be fully repaired, partially repaired, or unrepaired and present with a broad spectrum of clinical issues, including arrhythmias, pulmonary regurgitation, right heart failure, and residual shunts. 

Classification/Types 

By Surgical Status: 

• • Repaired TOF: Complete surgical correction (typically in early childhood) 

• • Palliated TOF: Shunt procedures (e.g., Blalock-Taussig) without full repair 

• • Unrepaired TOF: Rare in developed countries; may present with Eisenmenger physiology 

By Residual Defects: 

• • Residual VSD 

• • Severe pulmonary regurgitation 

• • RV outflow tract aneurysms 

• • Arrhythmias (atrial or ventricular) 

By Anatomic Variant: 

• • TOF with pulmonary atresia 

• • TOF with absent pulmonary valve 

• • TOF with atrioventricular septal defect 

Pathophysiology 

The hallmark lesion, RVOTO, leads to right-to-left shunting through the VSD, causing systemic desaturation and cyanosis. Over time, chronic pressure overload results in RVH. Surgical repair involves VSD closure and relief of RVOTO, but often at the cost of pulmonary valve incompetence. Adults post-repair may develop progressive RV dilation due to chronic pulmonary regurgitation, increasing the risk of arrhythmias and right heart failure. 

Epidemiology 

• • TOF accounts for ~10% of all congenital heart defects 

• • ~90% of patients now survive into adulthood post-surgical repair 

• • Adult congenital heart disease (ACHD) clinics are seeing a growing number of TOF patients 

• • Slight male predominance 

Etiology 

I) Causes 

• • Sporadic congenital defect due to abnormal neural crest migration 

• • Chromosomal abnormalities (e.g., 22q11.2 deletion—DiGeorge syndrome) 

II) Risk Factors 

• • Family history of congenital heart disease 

• • Genetic syndromes (e.g., Down, Alagille, or CHARGE syndrome) 

• • Maternal diabetes or rubella during pregnancy 

Clinical Presentation 

I) History (Symptoms) 

• • Dyspnea on exertion 

• • Fatigue or decreased exercise tolerance 

• • Palpitations (atrial or ventricular arrhythmias) 

• • Cyanosis (in unrepaired or failing palliated cases) 

• • Right heart failure symptoms (edema, abdominal distension) 

• • Syncope or presyncope 

• • History of previous surgical repair 

II) Physical Exam (Signs) 

• • Surgical scars (median sternotomy, thoracotomy) 

• • Right ventricular heave 

• • Murmur of pulmonary regurgitation or residual VSD 

• • Loud single S2 (if pulmonary atresia) 

• • Cyanosis or clubbing in unrepaired or failing palliated TOF 

Differential Diagnosis (DDx) 

• • Eisenmenger syndrome (with large unrepaired VSD) 

• • Primary pulmonary hypertension 

• • Arrhythmogenic right ventricular cardiomyopathy (ARVC) 

• • Other repaired congenital heart diseases (e.g., TGA, truncus arteriosus) 

• • Idiopathic right heart failure 

Diagnostic Tests 

Initial Evaluation 

• • ECG: Right axis deviation, RVH, RBBB (common post-repair), QRS >180 ms (predicts arrhythmia risk) 

• • Chest X-ray: “Boot-shaped heart” in unrepaired TOF, RV enlargement, pulmonary artery hypoplasia 

• • TTE: Evaluation of VSD closure, RV size/function, pulmonary regurgitation 

Advanced Imaging 

• • Cardiac MRI: Gold standard for quantifying RV volume, pulmonary regurgitation, and residual lesions 

• • CT Angiography: Useful in surgical planning or complex anatomy 

• • Holter monitor or event recorder: For arrhythmia detection 

• • Cardiac catheterization: Reserved for hemodynamic assessment or suspected coronary anomalies 

Treatment 

I) Acute Management 

• • Arrhythmias: Acute management with antiarrhythmics or cardioversion 

• • Heart failure: Diuretics for volume overload 

• • Hypoxemic spells (rare in adults): Oxygen, beta-blockers (e.g., propranolol), fluids 

II) Definitive/Long-Term Management 

• • Pulmonary valve replacement: For severe pulmonary regurgitation with RV dilation 

• • Implantable cardioverter-defibrillator (ICD): For secondary prevention or high-risk patients 

• • Surgical reintervention: For residual defects or RVOT aneurysms 

• • Catheter-based interventions: Closure of residual VSD, stenting of RVOT 

Medications 

Device Therapy 

• • ICD: Indicated in patients with sustained VT, prior cardiac arrest, or high-risk features 

• • Pacemaker: For sinus node dysfunction or AV block (post-surgical scarring) 

• • Cardiac resynchronization therapy (CRT): Rarely used unless significant dyssynchrony 

Patient Education, Screening, Vaccines 

• • Emphasize lifelong cardiology follow-up 

• • Educate on arrhythmia symptoms and stroke warning signs 

• • Routine endocarditis prophylaxis in specific high-risk scenarios 

• • Vaccinations: Influenza, pneumococcal, COVID-19 

• • Avoid competitive sports if at risk for arrhythmias 

• • Family planning and pregnancy counseling (high-risk obstetric care required) 

Consults/Referrals 

• • Adult congenital cardiologist: Central to care coordination 

• • Electrophysiologist: For arrhythmia risk stratification and management 

• • Cardiac surgeon: For valve replacement or reintervention 

• • Maternal-fetal medicine: Preconception counseling and management of pregnancy 

• • Geneticist: If syndromic features or family history 

Follow-Up 

Short-Term 

• • Echocardiography: Annually or more frequently if RV dysfunction 

• • ECG and Holter: Annually to monitor QRS duration and arrhythmias 

• • MRI: Every 2–3 years to track RV size and function 

Long-Term 

• • Lifelong surveillance with an ACHD specialist 

• • Repeat imaging post-valve replacement or arrhythmia intervention 

• • Monitor for progressive RV dysfunction, arrhythmias, and need for device therapy 

Prognosis 

• • Excellent survival in repaired TOF with timely interventions 

• • Risk of sudden cardiac death increased in those with QRS >180 ms, ventricular arrhythmias, or RV dysfunction 

• • Pulmonary valve replacement improves symptoms and may reduce arrhythmia risk 

• • Lifelong specialized care is essential to optimize quality of life and prevent complications