Cardiology > Tricuspid Atresia in Adults   

Background 

I) Definition 

Tricuspid atresia is a congenital heart defect characterized by the complete absence of the tricuspid valve, resulting in no direct communication between the right atrium (RA) and right ventricle (RV). Blood from the systemic venous return must bypass the atretic tricuspid valve, typically via an atrial septal defect (ASD), and reach the pulmonary circulation through a ventricular septal defect (VSD) or a patent ductus arteriosus (PDA). This defect is a form of single-ventricle physiology and represents about 1–3% of all congenital heart disease cases. With modern palliative surgical approaches, many patients now reach adulthood. 

Classification/Types 

By Pulmonary Blood Flow: 

• • Type I: Decreased Pulmonary Flow 

• • • Pulmonary stenosis or atresia present 

• • • Cyanosis dominant; requires systemic-to-pulmonary shunt 

• • Type II: Increased Pulmonary Flow 

• • • Large VSD or PDA with unrestricted flow 

• • • Risk of pulmonary overcirculation and heart failure 

By Great Vessel Relationship: 

• • Type A: Normally related great arteries 

• • Type B: Transposition of the great arteries (TGA) 

By Surgical Status: 

• • Fontan Completion: Most adults have undergone staged palliation ending in Fontan physiology 

• • Partially Palliated or Unrepaired: Rare in developed countries; associated with severe morbidity 

Pathophysiology 

The absence of the tricuspid valve forces systemic venous blood to shunt through an ASD to the left atrium, mixing with pulmonary venous blood. Depending on the size of the VSD or presence of PDA, blood reaches the pulmonary artery either from the left ventricle or via collateral flow. This leads to chronic volume and pressure loading of the single ventricle (usually the LV), risking eventual dysfunction. In Fontan physiology, systemic venous return is directed to the pulmonary arteries without a subpulmonary ventricle, relying entirely on passive flow. 

Epidemiology 

• • Accounts for ~1–3% of congenital heart defects 

• • Male-to-female ratio approximately 1:1 

• • Survival into adulthood is increasing due to surgical advances 

• • Fontan survivors now represent a significant portion of adult congenital heart disease clinics 

Etiology 

I) Causes 

• • Congenital malformation due to embryologic failure in tricuspid valve development 

II) Risk Factors 

• • Family history of congenital heart disease 

• • Genetic syndromes (e.g., heterotaxy, asplenia, polysplenia) 

• • Maternal conditions (e.g., diabetes, rubella) 

Clinical Presentation 

I) History (Symptoms) 

• • Dyspnea on exertion 

• • Cyanosis (particularly in unrepaired or Fontan failure) 

• • Fatigue 

• • Palpitations (arrhythmias) 

• • Edema or ascites (Fontan-associated liver disease or failure) 

• • Exercise intolerance 

• • Syncope (from arrhythmia or low output) 

II) Physical Exam (Signs) 

• • Cyanosis or clubbing 

• • Prominent a-wave in JVP (from elevated RA pressure) 

• • Single second heart sound (S2) 

• • Murmur (if VSD or pulmonary stenosis present) 

• • Hepatomegaly, peripheral edema (in Fontan failure) 

Differential Diagnosis (DDx) 

• • Eisenmenger syndrome with cyanotic shunt 

• • Other single ventricle defects (e.g., double inlet LV) 

• • Ebstein anomaly 

• • Unrepaired TOF 

• • Pulmonary hypertension 

• • Arrhythmogenic right ventricular cardiomyopathy (ARVC) 

Diagnostic Tests 

Initial Evaluation 

• • ECG: Left axis deviation, LV hypertrophy, possible atrial enlargement 

• • Chest X-ray: Cardiomegaly, reduced pulmonary vasculature (in low-flow types) or increased (in high-flow) 

• • Transthoracic echocardiogram (TTE): Assessment of anatomy, VSD, ASD, ventricular function, Fontan circuit 

Advanced Imaging 

• • Cardiac MRI: Gold standard for assessing Fontan circuit patency, ventricular function, and collateral flow 

• • CT Angiography: Useful in surgical planning or suspected complications 

• • Holter/Event Monitor: To detect atrial arrhythmias 

• • Cardiac catheterization: To evaluate pressures and oxygen saturations; assess for Fontan pressure >15 mmHg 

Treatment 

I) Acute Management 

• • Arrhythmias: Management with beta-blockers, amiodarone, or cardioversion 

• • Heart failure: Diuretics, afterload reduction 

• • Thromboembolism: Anticoagulation, especially in Fontan patients 

II) Definitive/Long-Term Management 

• • Fontan completion: For those not yet completed 

• • Surgical revision: For failing Fontan or conduit obstructions 

• • Heart transplantation: In end-stage Fontan failure 

• • Catheter interventions: For pulmonary artery stenosis, fenestration closure/opening 

Medications 

Device Therapy 

• • Pacemaker: For sinus node dysfunction or AV block (common post-Fontan) 

• • ICD: Rare; considered if documented sustained ventricular arrhythmias 

• • Fenestrated Fontan stent/valve: To regulate pressure and improve output in failing circuits 

Patient Education, Screening, Vaccines 

• • Lifelong surveillance with an adult congenital heart disease (ACHD) specialist 

• • Emphasize early recognition of worsening symptoms (cyanosis, edema, palpitations) 

• • Endocarditis prophylaxis for high-risk procedures 

• • Routine immunizations: Influenza, pneumococcal, COVID-19 

• • Reproductive counseling (high-risk pregnancies) 

• • Liver surveillance due to risk of Fontan-associated liver disease (FALD) 

Consults/Referrals 

• • ACHD cardiologist: Primary long-term care 

• • Electrophysiologist: For rhythm monitoring and device evaluation 

• • Hepatologist: For FALD surveillance and management 

• • Cardiac surgeon: For Fontan revision or transplant evaluation 

• • Maternal-fetal medicine: For preconception planning and pregnancy care 

• • Geneticist: If syndromic features are suspected 

Follow-Up 

Short-Term 

• • TTE or MRI: At least annually to assess ventricular function, Fontan patency 

• • ECG/Holter: Regular screening for arrhythmias 

• • Liver function tests and imaging: Annually to monitor FALD 

Long-Term 

• • Surveillance imaging every 1–3 years 

• • Lifelong cardiac follow-up essential 

• • Consider exercise testing to assess functional status 

Prognosis 

• • Repaired (Fontan) patients: Good survival into mid-adulthood; complications increase with age 

• • Fontan failure: Associated with high morbidity—arrhythmia, liver disease, protein-losing enteropathy 

• • Unrepaired or palliated cases: Rare survivors with poor long-term prognosis 

• • Heart transplant remains the only curative option for advanced failure