Fontan procedure

fontan

1. Fontan Procedure Dr. Dinesh Pandey MBBS, DNB (MED), Fellow DNB Cardiology

2. The Fontan procedure refers to any operation that results in the flow of systemic venous blood to the lungs without passing through a ventricle. In 1971, Fontan and Baudet described a surgical procedure for repair of tricuspid atresia Creation of Fontan circulation is palliative in nature, with good results in patients with ideal hemodynamics and substantial morbidity and mortality in those with poor hemodynamics.

3. INDICATIONS FOR A FONTAN CIRCUIT • Cardiac malformation and a single functional chamber – dysfunctional heart valve – absent or inadequate pumping chamber • Tricuspid atresia • Pulmonary atresia with intact ventricular septum • Hypoplastic left heart syndrome • Double-inlet ventricle

4. SELECTION OF PATIENTS (1978 , Choussat et al) • 10 criteria for optimal results following the Fontan 1. age at operation between 4 and 15 years 2. presence of normal sinus rhythm 3. normal systemic venous connections 4. normal right atrial size 5. normal pulmonary arterial pressure (mean≤ 15 mmHg) 6. low pulmonary vascular resistance (4 Woods units/m2) 7. adequate-sized PA with diameter ≥75% of the aorta 8. normal left ventricular ejection fraction ≥ 60% 9. absence of mitral valve insufficiency 10. absence of complicating factors from previous surgeries

5. • Original procedure included – SVC to RPA anastomosis (Glenn shunt ) – Anastomosis of RA appendage to LPA directing IVC flow through a valved homograft – Placement of a valved homograft at the IVS-RA junction – Closure of the atrial septal defect • Originally performed at the same time • Resulted in a marked increase in blood flow to the lungs - pulmonary lymphatic congestion, and pleural effusions • No longer performed together

6. • Currently total cavo pulmonary Fontan circulation done in two stages – To allow body to adapt to different hemodynamic states – Reduce overall surgical morbidity and mortality – Allows a better patient selection and intermediate preparatory interventions • As no ventricular contraction to pump blood through the lungs, elevated PAH is an absolute contraindication for Fontan procedure • At birth, it is impossible to create a Fontan circulation – PVR is still raised for several weeks – Caval veins and pulmonary arteries - too small

7. Bidirectional Glenn Shunt / Hemi fontan • At 4–12 months of age • First half of creating a total cavopulmonary circulation circuit • End-to-side anastomosis between SVC & RPA • RPA is not divided, resulting in blood flow from the SVC into the right and left PA • Children may remain cyanotic because blood from the IVC is not directed to the lungs • Open end of the SVC is either oversewn or occluded with a polytetrafluoroethylene patch • Allows Fontan circulation to be completed later

8. • When patients reach 1–5 years of age total cavo pulmonary Fontan circuit is completed • IVC connected to pulmonary artery with a conduit • Modified Fontan directing IVC flow through the lateral portion of the RA into PA via an anastomosis to the underside of the RPA • SVC flow is already directed into the RPA by a previous bidirectional Glenn shunt

9. Fenestrated fontan • small opening or fenestration may be created between the conduit and the right atrium • Functions as a pop-off valve (a right-to-left shunt) – prevent rapid volume overload to the lungs – Limit caval pressure – Increase preload to the systemic ventricle – Increase cardiac output • cyanosis may result from the right-to-left shunt • Fenestrations decrease postop pleural effusions • May be closed after patients adapt to new hemodynamics

10. Various techniques of the Fontan procedure. A , Atriopulmonary connection. B , Lateral tunnel total cavopulmonary connection (TCPC). C , Extracardiac conduit TCPC. IVC indicates inferior vena cava; RA, right atrium; RPA, right pulmonary artery; and SVC, superior vena cava.

11. FONTAN PHYSIOLOGY

12. Scheme of normal cardiovascular circulation and Fontan circulation at early and late stages. A , Normal biventricular circulation. The pulmonary circulation (P) is connected in series to the systemic circulation (S). The right ventricle (RV) ensures that the right atrial pressure remains lower than the left atrial pressure and delivers the driving force to the blood to overcome pulmonary impedance. B , Fontan circuit. The caval veins are directly connected to the pulmonary artery (PA); systemic venous pressures are markedly elevated. C , Fontan circuit late (superimposed on early Fontan circuit ). With time, a negative spiral ensues: Pulmonary resistance increases, resulting in a further increase in caval vein (CV) congestion but even more in reduced flow and ventricular stretch, which itself increases ventricular filling pressure. Line thickness reflects output; color reflects oxygen saturation. Reprinted from Gewillig and Brown.45 Copyright © 2016, BMJ Publishing Group Ltd and the British Cardiovascular Society. /

13. Early increase in preload • Fontan circulation provides definitive palliation for complex cardiac lesions not suitable for biventricular repair • Results in a parallel pulmonary and systemic circulation and a net increase in preload Reduction of preload • Most patients undergo a staged transition to their complete Fontan via Bidirectional Glenn • BDG procedure leads to marked decrease in preload • Degree of reduction depends on prior pulmonary to systemic flow ratio, which often exceeds 2:1 • Reduction of preload results in reduced ventricular dilation and work Reduction of preload

14. Early diastolic dysfunction • Increase in wall thickness coincident with the acute reduction in end-diastolic volume • Result s in abnormalities of early relaxation & characteristically reduced early rapid filling • Consequently, much of diastolic filling is dependent on atrial systole • Early diastolic dysfunction negatively impact recovery after subsequent Fontan operation

15. • Persistently abnormal early relaxation with worsening ventricular compliance markedly reduces ability of the ventricles to fill • Reduces pulmonary blood flow • Accounts for some of late failure seen in these Patients • Worsen naturally with age as in the normal heart • While diastolic abnormalities predominate early-on , systolic failure also becomes apparent in some patients late after the procedure

16. COMPLICATIONS OF FONTAN CIRCULATION

17. • Creation of Fontan circulation is palliative by nature • Proved good results with ideal hemodynamics The worldwide population of patients with Fontan circulation grew to an estimated 50 000 to 70 000 patients in 2018 , with 40% of patients > 18 years of age . The current estimate of 30-year survival after surgical Fontan completion is ≈85 %. • Substantial morbidity and mortality – in those with unfavorable hemodynamics – those who underwent older surgical techniques

18. • Risk factors for complications include – elevated pulmonary artery pressure – anatomic abnormalities of the right and left pulmonary arteries – atrial-ventricular valve regurgitation – poor ventricular function

19. Functional status and exercise tolerance • Most patients with a Fontan circulation to lead a nearly normal life, including mild to moderate sport activities • More than 90% of all hospital survivors are in NYHA functional class I or 2 • However, with time there is a progressive decline of functional status in some subgroups

20. Ventricular dysfunction • Ventricle of a functionally univentricular heart – Dilated, hypertrophic and hypocontractile • May fail after years of systemic loading • congenital malformation • original hemodynamic state of volume overload • Systemic ventricle may be a morphologic right or an indeterminate primitive ventricle • High RA pressure may impair coronary blood flow - affect myocardial perfusion and function

21. • During the first months after birth - ventricle will always be volume overloaded, Leads to dilation and hypertrophy of LV • After unloading at the time of a Fontan operation, some regression to normalisation will occur - frequently incomplete • Currently only a small shunt is allowed to persist for several months • Ventricle thus evolves from being volume overloaded and overstretched, to overgrown and ( severely) underloaded • Low preload results in remodelling , reduced compliance , poor ventricular filling, and eventually continuously declining cardiac output

22. • Lack of reaction to classic treatment strategies has given the ventricle in a Fontan circuit a very bad reputation • Little impact on ventricular function of – inotropes, afterload reducing agents, vasodilators, and beta blockers • no impact on the reduced preload which is the dominant limiting factor

23. AVV REGURGITATION Significant AVV regurgitation in patients with univentricular hearts was historically a contraindication for staged single-ventricle palliation

24. Arrhythmia Traditionally , sinus node dysfunction and atrial tachycardia have been attributed to injury to the sinus node or its arterial supply, atrial suture lines, atrial dilatation, and hypertrophy related to elevated atrial pressures • Dilatation predispose to – arrhythmia – swirling of blood in the enlarged atrium - stasis & clot formation – results in poor blood flow to the lungs • May have undergone atriotomy injure the sinus node or conducting fibers cause atrial arrhythmia

25. • Occur in up to 40% of the patients 10 years after surgery • Most common atrial tachycardia is intra-atrial reentry or atrial flutter • Immediate treatment is DC cardio version • Anticoagulation in view of the significant risk of a right atrial thrombus • Long term treatment of atrial arrhythmia can involve medication and ablation • Conversion of the old Fontan circuit to an extracardiac cavopulmonary connection together with a right atrial maze and a reduction plasty

26. CYANOSIS The purpose of the Fontan operation is to separate the systemic from the pulmonic venous blood returns, yet some mixing still occurs. Systemic arterial oxygen saturation at rest in room air rarely achieves levels > 95% and is commonly in the 90% to 95% range.

27. Collateral Vessels and Shunts Collateral vessels and shunts may lead to substantial right-to-left shunts and cyanosis • Incomplete closure or a residual ASD • Surgically created fenestration between the surgical conduits and RA • Surgical redirection of coronary sinus blood flow to LA • Formation of pulmonary AV malformations • Patent collateral vessels between systemic and pulmonary veins • Patent systemic veins that extend directly into LA

28. Left-to-right shunts • Aortopulmonary collateral vessels - common • May lead to hemodynamic shunting - results in volume overload of the systemic ventricle - increased PBF and pulmonary pressure • Arise from the thoracic aorta, internal mammary arteries , or brachiocephalic arteries

29. • Increased frequency of pulmonary thromboembolic events – Dilated atrium – low cardiac output – coagulation abnormalities associated with hepatic congestion – chronic cyanosis–induced Polycythemia • Massive pulmonary embolism is the most common cause of sudden out-of hospital death in patients with Fontan circulation

30. Pulmonary Circulation • Fontan circulation results in a paradox of systemic venous hypertension (mean pr >10 ) pulmonary artery hypotension ( <15 mm Hg ) • Due to absence of the hydraulic force of RV • Absence of pulsatile blood flow and low mean pressure in the PA underfill the pulmonary vascular bed and increase PVR • Pulmonary arteries may be morphologically abnormal (small, discontinuous, or stenosed )

31. • PVR is an important determinant of cardiac output in Fontan circulation • Stenosis or leakage of surgical anastomoses between the venae cavae and pulmonary arteries may adversely affect pulmonary blood flow • Patients with borderline haemodynamics have been reported to deteriorate acutely after moving to altitude above 2000 m

32. Lymphatic System • Fontan circulation operates at or some times beyond the functional limits of the lymphatic system • Affected by high venous pressure and impaired thoracic duct drainage • Increased pulmonary lymphatic pressure may result in interstitial pulmonary edema or lymphedema • Leakage into the thorax or pericardium may lead to pericardial and pleural effusions (often right-sided) and chylothorax

33. Protein-losing enteropathy • Relatively uncommon manifestation of failing Fontan circulation • PLE is the abnormal loss of serum proteins into the intestinal lumen. It occurs in 5% to 12% of individuals after Fontan palliation . Morbidity stemming from the disease is marked, and although improved in the current era, mortality remains high Cause is unclear • Lead to hypoproteinemia , immunodeficiency, hypocalcemia , and coagulopathy , • Five year survival rate was 59%

34. Treatment options for PLE • Diet high in calories and protein content • Medium chain triglyceride fat supplements • Diuretics • Several surgical options have been reported – relief of obstruction – conversion to streamlined cavopulmonary connection – atrioventricular –valve repair/replacement

35. Plastic bronchitis • PB is a disease characterized by the production of thick, tenacious casts within the airway lumen. It is reported to occur in <5% of individuals , although the prevalence of subclinical PB may be higher Rare but serious complication • Dyspnea, cough , wheezing, and expectoration of casts - may cause severe respiratory distress with asphyxia, cardiac arrest, or death • Exact cause unknown

36. LIVER FIBROSIS AND CIRRHOSIS Liver involvement in patients with Fontan circulation was brought into prominence after the description of chronic passive congestion, cardiac cirrhosis, hepatocellular carcinoma (HCC), and hepatic adenoma Cardiac failure with circulatory congestion typically manifests as centrilobular hepatic congestion and necrosis, with activation of inflammation in some cases. Over time, particularly if within the context of repeated insults , fibrosis may progress to cardiac cirrhosis.

37. Potential mechanisms of liver injury associated with the Fontan circulation.

38. Proposed Therapeutic Approaches All patients with Fontan circulation should undergo regular hepatic screening with assessments that are age dependent and may include laboratory serum screening and imaging Serum α- fetoprotein is a valuable early biomarker for conversion from liver fibrosis to carcinoma and may be incorporated into a regular screening scheme in older patients avoidance of liver toxins when possible, including alcohol and high-dose acetaminophen. The risks and benefits of potential hepatotoxic drugs such as amiodarone should be weighed carefully. Patients with Fontan circulation should be strongly advised to be vaccinated for hepatitis B, to avoid smoking, and to prevent overweight/obesity .

39. RENAL DYSFUNCTION The kidneys receive a substantial proportion (≈20 %–25 %) of cardiac output at rest. Therefore, the circulatory abnormalities common in the patient with Fontan circulation will eventually affect the renal system

40. Reproduction: pregnancy • Most females after Fontan repair have normal menstrual Patterns • Increased systemic venous pressure may trigger complications of right heart failure such as atrial arrhythmias , oedema , and ascites • Right-to-left shunt through a residual ASD will Increase - decrease in arterial saturation • Increased risk for venous thrombosis and pulmonary embolus • Successful pregnancy with delivery of normal children is possible .

41. Coagulopathies • Protein C, protein S, and antithrombin III deficiency • Most common cause of sudden out-of-hospital death in patients with a Fontan circuit • Chronic multiple pulmonary microemboli may lead to pulmonary vascular obstructive disease, a late complication – particularly lethal in a Fontan circulation.

42. • Some clinicians recommend anticoagulating every patient with a Fontan circuit • Full anticoagulation in – previous thrombi – poor cardiac output – congestion, dilation of venous or atrial structures, – arrhythmia