Fontan physiology and failure mechanisms: Fontan completion connects systemic venous return (SVC and IVC) directly to pulmonary arteries, bypassing the subpulmonary ventricle. Critical features - 1) elevated central venous pressure (CVP) maintains pulmonary flow passively; 2) normal cardiac output requires low pulmonary vascular resistance; 3) pulmonary blood flow is preload-dependent, ventilation-dependent. Failure mechanisms - 1) ventricular failure (systolic and/or diastolic); 2) elevated pulmonary vascular resistance; 3) AV valve regurgitation; 4) atrial arrhythmias (IART, atrial fibrillation); 5) outflow obstruction; 6) Fontan circuit thrombosis or stenosis; 7) lymphatic dysfunction (PLE, PB); 8) chronic congestive hepatopathy (FALD).
Late complications and surveillance: 1) Atrial arrhythmias (>50% by 20 years post-Fontan) - intra-atrial reentrant tachycardia (IART), atrial fibrillation; manage with antiarrhythmics, catheter ablation, anticoagulation; 2) Thromboembolism (10-30% lifetime; aspirin or warfarin/DOAC indicated); 3) PLE (5-15%) - lymphatic dysfunction, hypoalbuminemia, edema, lymphopenia; manage with steroids, sildenafil, octreotide, lymphatic embolization, transplant; 4) Plastic bronchitis (1-5%) - thoracic duct lymphatic leakage into airway; manage with sildenafil, sirolimus, lymphatic embolization, transplant; 5) FALD (>50% with cirrhosis by 20 years) - chronic congestion, regenerative nodules, cirrhosis, HCC risk; surveillance with US, MRI, FibroScan; consider combined heart-liver transplant; 6) Protein-energy malnutrition; 7) Chronotropic incompetence; 8) Cyanosis from veno-venous collaterals; 9) Renal dysfunction.
Surveillance and treatment strategies: comprehensive annual evaluation - 1) clinical (NYHA, growth, edema, ascites, exercise tolerance); 2) echocardiography (ventricular function, AV valve, Fontan circuit, pulmonary veins); 3) cardiac MRI biennially (ventricular function, Fontan obstruction, ascites, thrombus, FALD); 4) cardiopulmonary exercise testing (VO2max, anaerobic threshold; declining VO2 prognostic); 5) cardiac catheterization with angiography in declining patients (CVP, PVR, ventricular function, address obstructions, fenestration creation); 6) liver evaluation (LFTs, fibrosis markers, abdominal MRI, FibroScan, AFP); 7) immunology (lymphocyte subsets, total protein/albumin); 8) Holter monitoring; 9) thromboembolism prophylaxis. Therapies - pulmonary vasodilators (sildenafil, bosentan), ACE inhibitors, beta-blockers, MRA, diuretics, sirolimus (lymphatic disease), lymphatic embolization, Fontan revision, fenestration, mechanical circulatory support, heart or heart-liver transplant. Cardiac transplant 10-year survival 50-60% in Fontan recipients.