2Normal mammal cardiovascular system double circuit connected in series —systemic—pulmonarypowered by a double pump—the right and left heart
3Many complex cardiac malformations - one functional ventricle Maintain systemic and pulmonary circulation - not connected in series but in parallelMajor disadvantagesarterial desaturationchronic volume overload to single ventricle - in time impair ventricular functionSuch a circuit has two
41971, Fontan and BaudetGoal was to create a circulatory system in which the systemic venous blood enters the pulmonary circulation, bypasses the right ventricle, and thus places the systemic and pulmonary circulations in series driven by a single ventricleAll shunts on the venous, atrial, ventricular and arterial level are interrupted
5Advantages of a Fontan circuit include (near) normalisation of the arterial saturationabolishment of the chronic volume overloadCost for such a circulation includesChronic hypertension and congestion of the systemic veinsdecreased cardiac outputCardiac output is no longer determined by the heart,but rather by transpulmonary flow(itself mainly determined by pulmonary vascular resistance)
6INDICATIONS FOR A FONTAN CIRCUIT Cardiac malformation and a single functional chamberdysfunctional heart valveabsent or inadequate pumping chamberTricuspid atresiaPulmonary atresia with intact ventricular septumHypoplastic left heart syndromeDouble-inlet ventricle
7SELECTION OF PATIENTS 1978, Choussat et al 10 criteria for optimal results following the Fontanage at operation between 4 and 15 yearspresence of normal sinus rhythmnormal systemic venous connectionsnormal right atrial sizenormal pulmonary arterial pressure (mean≤ 15 mmHg)low pulmonary vascular resistance (4 Woods units/m2)adequate-sized PA with diameter ≥75% of the aortanormal left ventricular ejection fraction ≥ 60%absence of mitral valve insufficiencyabsence of complicating factors from previous surgeriessuch as pulmonary artery distortion
8Refined by many centres After repair LA pressure must be low (determined by good LV fn)transpulmonary gradient must be low (determined by the pulmonary vasculature)Cardiac requirements nowadays areunobstructed ventricular inflow (no atrioventricular valve stenosis, no regurgitation)reasonable ventricular functionunobstructed outflow (no subaortic stenosis, and no coarctation
9Pulmonary requirements non-restrictive connection from systemic veins to the PAgood sized PA without distortiona well developed distal vascular bed(near) normal PVR U/m2unobstructed pulmonary venous returnMarc Gewillig , Heart 2005;91:839–846. doi: /hrt
10Fontan ProcedureSince its original description, the Fontan circuit has known numerous modificationsEarly modifications of the Fontan procedure connected pulmonary arteries to the right atrium
11Original procedure included SVC to RPA anastomosis (Glenn shunt)Anastomosis of RA appendage to LPA directing IVC flow through a valved homograftPlacement of a valved homograft at the IVS-RA junctionClosure of the atrial septal defect
12lost contractile function RA was included to - improve pulmonary blood flow, being a pulsatile chamberInstead RA dilated andlost contractile functionTurbulence and energy lossDecreased pulmonary blood flowde Leval et al
13Right atrial–pulmonary circuits - obsolete Replaced with newer techniques - direct connection between each vena cava and PABypass the right atrium and right ventricleMore efficient cavopulmonary blood flow to the lungs – reduce risk for arrhythmia and thrombosis
14Modern Fontan procedure involves connecting SVC and IVC to the RPA Originally performed at the same timeResulted in a marked increase in blood flow to the lungs - pulmonary lymphatic congestion, and pleural effusionsNo longer performed togetherThese two connections are
15Currently total cavopulmonary Fontan circulation done in two stages To allow body to adapt to different hemodynamic statesReduce overall surgical morbidity and mortalityAllows a better patient selection and intermediate preparatory interventions
16As no ventricular contraction to pump blood through the lungs, elevated PAH is an absolute contraindication for Fontan procedureAt birth, it is impossible to create a Fontan circulationPVR is still raised for several weeksCaval veins and pulmonary arteries - too small
17Initially in the neonatal period, management must aim to achieve Unrestricted flow from the heart to the aortacoarctectomyDamus- Kaye-StanselNorwood repairWell balanced limited flow to the lungspulmonary artery bandmodified Blalock-TaussigUnrestricted return of blood to the ventricleRashkind balloon septostomy
18Bidirectional Glenn Shunt / Hemi-fontan At 4–12 months of ageFirst half of creating a total cavopulmonary circulation circuitEnd-to-side anastomosis between SVC & RPARPA is not divided, resulting in blood flow from the SVC into the right and left PAChildren may remain cyanotic because blood from the IVC is not directed to the lungs
19Bidirectional Glenn Shunt / Hemi-fontan Cardiac end of the divided SVC is attached to MPA or the under surface of RPALower stump of SVC is connected to IVC with a conduitOpen end of the SVC is either oversewn or occluded with a polytetrafluoroethylene patchAllows Fontan circulation to be completed later
20When patients reach 1–5 years of age total cavopulmonary Fontan circuit is completed IVC connected to pulmonary artery with a conduit
21Modified Fontan directing IVC flow through the lateral portion of the RA into PA via an anastomosis to the underside of the RPASVC flow is already directed into the RPA by a previous bidirectional Glenn shunt
22Internal conduit - pass through the right atrial chamber External conduit - run completely outside the heart to the right side of the right atrium
23Intraatrial tunnel method Conduit is constructed with both the lateral wall of the right atrium and prosthetic materialInferior aspect of the tunnel is anastomosed to the IVC and the superior aspect is anastomosed to the pulmonary arteriesConduit enlarges as the child grows - may be used in children as young as 1 year oldInternal conduit maylead to atrial arrhythmiaA benefit of using this circuit is that the
24Extracardiac conduit method Usually performed only in older than 3 yearsPTFE tube graft is placed between the transected IVC and the pulmonary artery, bypassing RAEntire atrium is left with low pressure - less atrial distention, arrhythmia, and thrombosis
25Cannot enlarge as the patient grows Performed only in patients who are large enough to accept a graft of adequate size to allow adult IVC blood flow
26Fenestrated fontansmall opening or fenestration may be created between the conduit and the right atriumFunctions as a pop-off valve (a right-to-left shunt)prevent rapid volume overload to the lungsLimit caval pressureIncrease preload to the systemic ventricleIncrease cardiac outputcyanosis may result from the right-to-left shunt
27Fenestrations decrease postop pleural effusions May be closed after patients adapt to new hemodynamicsNow, fenestrations are seldom created during the completion of the Fontanimproved patient selection and preparationimproved staginghas been reported
29Early increase in preload Fontan circulation provides definitive palliation for complex cardiac lesions not suitable for biventricular repairSome form of palliation is done in early infancyResults in a parallel pulmonary and systemic circulation and a net increase in preload
30Reduction of preloadMost patients undergo a staged transition to their complete Fontan via Bidirectional GlennBDG procedure leads to marked decrease in preloadDegree of reduction depends on prior pulmonary to systemic flow ratio, which often exceeds 2:1Reduction of preload results in reduced ventricular dilation and work
31Abnormal systolic ventricular performance is rarely a problem in early years of palliation prior to FontanIs sustained or improved in most, after completion of Fontan circuitIt was shown that restoration of normal systolic wall stress was achieved in most individuals undergoing a Fontan procedure prior to the age of 10 yearsSluysmans T et al. Natural history and patterns of recovery of contractile function in single left ventricle after Fontan operation. Circulation Dec 1992;86(6):1753–61.
32Early diastolic dysfunction Increase in wall thickness coincident with the acute reduction in end-diastolic volumeResult s in abnormalities of early relaxation & characteristically reduced early rapid fillingConsequently, much of diastolic filling is dependent on atrial systoleEarly diastolic dysfunction negatively impact recovery after subsequent Fontan operationProlongation of the time constant of early relaxation (tau) and the isovolumic relaxation time are both inversely related to the c
33Persistently abnormal early relaxation with worsening ventricular compliance markedly reduces ability of the ventricles to fillReduces pulmonary blood flowAccounts for some of late failure seen in these patientsWorsen naturally with age as in the normal heart
34Avoidance of factors known to lead to worsening compliance (persistent LV outflow tract obstruction, hypertension) is of fundamental importance
35While diastolic abnormalities predominate early-on , systolic failure also becomes apparent in some patients late after the procedure
36Systemic vascular bedMany studies have reported uniformly elevated systemic vascular resistance after FontanSenzaki H, Masutani S, Kobayashi J, et al
37dobutamine, was highly abnormal in the Fontan group Compared with controls and patients after BT shunt , relationship between cardiac index and vascular impedance, at baseline and withdobutamine, was highly abnormal in the Fontan groupSenzaki H, Masutani S, Kobayashi J, et al
38Use of ACE inhibition in Fontan patients Enalapril or placebo was given for 10 weeks in 18 patients approximately 14 years after the Fontan operationTendency to worsen exercise performance.Reduced incremental cardiac index during exercise in the patients receiving enalaprilKouatli et al ,Enalapril does not enhance exercise capacity in patients after Fontan procedure. Circulation Sep ;96(5):1507–12.
39Many patients continue to receive ACE inhibition, in the hope of a beneficial effect when given chronicallyIt is possible that there are subgroups that may benefit e.g. severe systolic dysfunctionPresently no evidence for this therapy being beneficial
40The veno-pulmonary circuit Major evolution in the hemodynamic design of the Fontan operation since its inceptionInitial right atrial to pulmonary connection has been abandoned in favor of more streamlined versions
41There was no difference between the patient group at rest Cardiac output - using respiratory mass spectrometry and an acetylene re-breathing methodThere was no difference between the patient group at restCardiac output & respiratory rate higher in the lateral tunnel group than the atriopulmonary group at low and moderate workloadsRosenthal M et al Comparison of cardiopulmonary adaptation during exercise in children after the atriopulmonary and total cavopulmonary connection Fontan procedures. Circulation Jan ;91(2):372–8.
42Work of breathing is a significant additional energy source to circulation in Fontan Normal negative pressure inspiration has been shown to increase PBF after the atrial pulmonary connection and TCPCRedington AN, Penny D, Shinebourne EA. Pulmonary blood flow after total cavopulmonary shunt. Br Heart J Apr 1991;65(4):213–7
43Philadelphia group, using magnetic resonance flow measurements,have estimated that approximately 30% of the cardiac output can be directly attributed to the work of breathing in patients after the TCPCFogel MA,Weinberg PM, Rychik J, et al. Caval contribution to flow in the branch pulmonary arteries of Fontan patients Circulation Mar ;99 (9):1215–21.
44Positive pressure ventilation Increasing levels of PEEP during positive pressure ventilation is adverse to Fontan circulationHigher the mean airway pressure, lower cardiac indexMaintain with minimum mean airway pressure compatible with normal oxygenation and ventilationWilliams DB, Hemodynamic response to positive end-expiratory pressure following right atrium-pulmonary artery bypass (Fontan procedure). J Thorac Cardiovasc Surg Jun 1984;87(6):856–61y
45The pulmonary vascular bed Low PVR is a prerequisite for early success after Fontan operationLower the total pulmonary resistance (PVR , pulmonary venous resistance and LAresistance) the betterLA resistance is influenced by the abnormal ventricular response
46Structural pulmonary venous abnormalities Naturally occurringMay evolve as a result of abnormal hemodynamicsAtriopulmonary anastomosis- gross enlargement of RA may compress adjacent pulmonary veins
47Abnormalities of arteriolar resistance adversely influence early outcome, in terms of morbidity and mortalityFew data available regarding the long-term effects of the Fontan circulation on the pulmonary vascular bed.Pulmonary thromboembolism is not infrequent - lead to adverse changes in vascular resistance
48Pulmonary artery flow in Fontan is relatively low velocity, laminar Different to the normal pulsatile flow of pulmonary vascular bed in normal circulationRelease of nitric oxide from the endothelium is dependent on pulsatile flow in the normal circulationExperimentally, reducing pulsatility leads to reduced NO production and an increase in vascular resistanceNakano T et al, Pulsatile flow enhances endothelium-derived nitric oxide release in the peripheral vasculature. Am J Physiol Heart Circ Physiol Apr 2000;278(4):
50Creation of Fontan circulation is palliative by nature Proved good results with ideal hemodynamicsSubstantial morbidity and mortalityin those with unfavorable hemodynamicsthose who underwent older surgical techniques
51Risk factors for complications include elevated pulmonary artery pressureanatomic abnormalities of the right and left pulmonary arteriesatrial-ventricular valve regurgitationpoor ventricular function
52Late mortalityLate death is directly related to the number of risk factors for a Fontan operationUnfavourable haemodynamics and risk factors are associated with an increased early and late attrition
53Functional status and exercise tolerance Most patients with a Fontan circulation to lead a nearly normal life, including mild to moderate sport activitiesMore than 90% of all hospital survivors are in NYHA functional class I or 2However, with time there is a progressive decline of functional status in some subgroups
54Ventricular dysfunction Ventricle of a functionally univentricular heartDilated, hypertrophic and hypocontractileMay fail after years of systemic loadingcongenital malformation itselforiginal hemodynamic state of volume overloadSystemic ventricle may be a morphologic right or an indeterminate primitive ventricleprevious surgical interventionsHigh RA pressure may impair coronary blood flow - affect myocardial perfusion and functionCoronary sinus blood may be surgically redirected to drain into the left atrium (3).
55During the first months after birth - ventricle will always be volume overloaded Leads to dilation and hypertrophy of LVAfter unloading at the time of a Fontan operation, some regression to normalisation will occur - frequently incompleteCurrently only a small shunt is allowed to persist for several months
56Ventricle thus evolves from being volume overloaded and overstretched, to overgrown and (severely) underloadedLow preload results in remodelling, reduced compliance, poor ventricular filling, and eventually continuously declining cardiac output
57Little impact on ventricular function of Lack of reaction to classic treatment strategies has given the ventricle in a Fontan circuit a very bad reputationLittle impact on ventricular function ofinotropes, afterload reducing agents, vasodilators, and b blockersno impact on the reduced preload which is the dominant limiting factorThe treatment of ventricular dysfunction in the setting of aFontan circuit is very frustrating for a cardiologist.
58Arrhythmia Dilatation predispose to Many old circuits have atrial wall incorporated into the circuit causing atrial dilationDilatation predispose toarrhythmiaswirling of blood in the enlarged atrium - stasis & clot formationresults in poor blood flow to the lungsMay have undergone atriotomyinjure the sinus node or conducting fiberscause atrial arrhythmia
59Occur in up to 40% of the patients 10 years after surgery Most common atrial tachycardia is intra-atrial re-entry or atrial flutterImmediate direct current DC versionAnticoagulation in view of the significant risk of a right atrial thrombus
60Long term treatment of atrial arrhythmia can involve medication and ablation Conversion of the old Fontan circuit to an extracardiac cavopulmonary connectionTogether with a right atrial maze and a reduction plasty
61Collateral Vessels and Shunts Collateral vessels and shunts may lead to substantial right-to-left shunts and cyanosisIncomplete closure or a residual atrial septal defectSurgically created fenestration between the surgical conduits and RASurgical redirection of coronary sinus blood flow to LAFormation of pulmonary AV malformationsPatent collateral vessels between systemic and pulmonary veinsPatent systemic veins that extend directly into LA
62Left-to-right shunts Aortopulmonary collateral vessels - common May lead to hemodynamic shunting- results in volume overload of the systemic ventricle- increased PBF and pulmonary pressureArise from the thoracic aorta, internal mammary arteries, or brachiocephalic arteries
63Blood Vessels Increased frequency of pulmonary thromboembolic events Dilated atriumlow cardiac outputcoagulation abnormalities associated with hepatic congestionchronic cyanosis–induced PolycythemiaMassive pulmonary embolism is the most common cause of sudden out-of hospital death in patients with Fontan circulationReported incidences of venous thromboembolism and stroke are 3%–16% and 3%–19%, respectively
64Pulmonary Circulation Fontan circulation results in a paradox ofsystemic venous hypertension (mean pr >10 ) pulmonary artery hypotension ( <15 mm Hg)Due to absence of the hydraulic force of RV
65Absence of pulsatile blood flow and low mean pressure in the PA underfill the pulmonary vascular bed and increase PVRPulmonary arteries may be morphologically abnormal (small, discontinuous, or stenosed)
66PVR 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 flowPatients with borderline haemodynamics have been reported to deteriorate acutely after moving to altitude above 2000 m
67Lymphatic SystemFontan circulation operates at or sometimes beyond the functional limits of the lymphatic systemAffected by high venous pressure and impaired thoracic duct drainageIncreased pulmonary lymphatic pressure may result in interstitial pulmonary edema or lymphedemaLeakage into the thorax or pericardium may lead to pericardial and pleural effusions (often right-sided) and chylothorax
68Protein-losing enteropathy Relatively uncommon manifestation of failing Fontan circulationCause is unclearLoss of enteric protein may be due to elevated systemic venous pressure that is transmitted to the hepatic circulationLead to hypoproteinemia, immunodeficiency, hypocalcemia, and coagulopathy,May occur in the long term
69PLE is a relatively rare complication In an international multicentre study involving 35 centres and 3029 patients with Fontan repair between 1975 and 1995, PLE occurred in 114 patients - 3.8%Mertens L et al. Protein losing enteropathy after the Fontan operation J Thorac and Cardiovasc Surg 1998;115:1063–73Very poor prognosisFive year survival rate was 59%
70Treatment options for PLE Diet high in caloriesHigh protein contentMedium chain triglyceride fat supplementsDiureticsSeveral surgical options have been reportedrelief of obstructionconversion to streamlined cavopulmonary connectionatrioventricular–valve repair/replacement
71Plastic bronchitis Rare but serious complication 1%–2% of patients Noninflammatory mucinous casts form in tracheobronchial tree and obstruct the airwayDyspnea,cough, wheezing, and expectoration of casts - may cause severe respiratory distress with asphyxia, cardiac arrest, or deathExact cause unknown
72Plastic bronchitisHigh intrathoracic lymphatic pressure or obstruction of lymphatic flow may lead to the development of lymphoalveolar fistula and bronchial castsMedical management is difficult - often require repeat bronchoscopy to remove the thick castsSurgical ligation of the thoracic duct may cure plastic bronchitis by decreasing intrathoracic lymphatic pressure and flow
73Reproduction: pregnancy Most females after Fontan repair have normal menstrual patternsIncreased systemic venous pressure may trigger complications of right heart failure such as atrial arrhythmias, oedema, and ascitesRight-to-left shunt through a residual ASD willIncrease - decrease in arterial saturationIncreased risk for venous thrombosis and pulmonary embolusSuccessful pregnancy with delivery of normal children is possible.
74Coagulopathies Protein C, protein S, and antithrombin III deficiency Most common cause of sudden out-of-hospital death in patients with a Fontan circuitChronic multiple pulmonary microemboli may lead to pulmonary vascular obstructive disease, a late complicationparticularly lethal in a Fontan circulation.
75Some clinicians recommend anticoagulating every patient with a Fontan circuit Subgroups of patients with a very low riskFull anticoagulation inprevious thrombipoor cardiac outputcongestion, dilation of venous or atrial structures,arrhythmia
77All patients having undergone Fontan surgery and follow-up at Children’s Hospital Boston were included if they were born before January 1, 1985, and lived
78Type of Fontan surgery was classified into the following 4 categories: Right atrium (RA)–to–PA anastomosisRA–to–right ventricle (RV) connectionIntraatrial lateral tunnel (LT)Extracardiac conduit (ECC)The latter 2were considered subtypes of total cavopulmonary connections.
79Baseline Characteristics A total of 261 patients, 121 female (46.4%)had their first Fontan surgery at a median age of 7.9 years33 (12.6%) of which were fenestratedType of first FontanRA-PA connection in 135 (51.7%),RA-RV in 25 (9.6%)LT in 98 (37.5%) ECC in 3 (1.1%)
81Mode of Death Over a median follow-up of 12.2 years years 76 patients (29.1%) died5 (1.9%) had cardiac transplantation5 (1.9%) had Fontan revision21 (8.0%) Fontan conversion - LT in 16 or ECC in 5Overall, 52 deaths (68.4%) were perioperative7 (9.2%) were sudden6 (7.9%) were thromboembolic5 (6.6%) were due to heart failure2 (2.6%) were secondary to sepsis
83Perioperative Mortality Of 52 perioperative deaths, 41 (78.9%) were early and 11 (21.1%) were lateImportantly, perioperative mortality rates decreased steadily over timeFirst Fontan surgeryBefore %1982 to %1990 or later %
84Long-Term SurvivalActuarial event-free survival rates at 1, 10, 15, 20, and 25 years were 80.1%, 74.8%, 72.2%, 68.3%, and 53.6%Significant disparities between Fontan categories mainly due to periop deaths in an earlier surgical eraIn perioperative survivors, freedom from death or cardiac transplantation was comparable among all types
85In early survivors, overall actuarial freedom from death or cardiac transplantation at 1, 5, 10, 15, 20, and 25 years was 96.9%, 93.7%, 89.9%, 87.3%, 82.6%, and 69.6%, respectively
86Death resulting from thromboembolism occurred at a median age of 24 Death resulting from thromboembolism occurred at a median age of 24.9 years8.7 years after Fontan surgeryActuarial freedom from thromboembolic death was 98.7% at 10 years and 90.8% at 25 yearsAll patients had RA-PA Fontan surgeries except for 1 patient with an LT
87Predictors of Thromboembolic Death in Perioperative Survivors Atrial fibrillationLack of aspirin or warfarin therapyThrombus within Fontan
88Heart failure–related deaths occurred at a mean age of 22.9 4.3 years after Fontan surgeryActuarial freedom from death caused by heart failure was 99.5% at 10 yrs and 95.8% at 25 yrsRisk factors were single RV morphology, higher postoperative RA pressure, and protein-losing enteropathy.
89Sudden deathSudden death occurred at a median age of 20.2 years in 7 patients3 with RA-PA, 3 with LT, and 1 with RA-RV2.9 years after Fontan surgery.
90ConclusionsLeading cause of death was perioperative, particularly in an earlier eraGradual attrition was noted thereafter, predominantly from thromboembolic, heart failure–related, and sudden deaths70% actuarial freedom from all-cause death or cardiac transplantation at 25 years