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Fontan Operation Seoul National University Hospital Department of Thoracic & Cardiovascular Surgery Fontan Operation Introduction Fontan operation in 1971, Fontan et al, for tricuspid atresia Technical modifications & advances Better understanding of physiology Improvement of the management For a wide spectrum of complex congenital heart diseases Fontan Procedure Concepts • In patients with single ventricle physiology 1) Separate the systemic and pulmonary venous return 2) Establish the passive, unobstructed pathway between the systemic venous return & pulmonary arteries Physiologic benefits 1) Relief of cyanosis 2) Alleviation of ventricular volume overload Fontan Operation History • • • • • • • 1971 1973 1979 1984 1988 1990 1990 Fontan Kreuzer Bjork Kawashima de Leval Bridges Giannico Fontan operation Modified Fontan op.(APC) RA-RV connection TCPS TCPC with lateral tunnel Fenestrated Fontan op. Extra-cardiac Fontan op. Right Heart Bypass (I) Evolution • Starr et al. 1943 – Canine nonfunctional RV model by cauterization – Not result in systemic venous hypertension • Bakos. 1950, Kagan. 1952, Donald et al. 1954 – Similar experiments – RV is not absolutely necessary for pulmonary circulation • Rodbard. 1948 – Low PAP in most animal species – CVP is adequate driving force for pulmonary circulation Right Heart Bypass (II) • Robard & Wagner. 1949 – Proximal MPA ligation – RA appendage to distal MPA – Possibility of bypassing the RV, when RA Pressure of 9-14 cm H2O * Functional TR - some contribution to PBF(?) Right Heart Bypass (III) • Warden et al. 1954 – Staged obliteration of TV, period of progressive RA hypertrophy & dilatation – Subsequent RA appendage to MPA * Some pumping action of RA to PBF (?) Right Heart Bypass (IV) • Carlon et al. 1951 – Partial diversion of caval blood to RPA – After adding heparin, long-term survival • Glenn & Patino. 1954 – Similar experimental results • Glenn et al. 1958 – First successful clinical trial of classic cavopulmonary shunt Right Heart Bypass (V) • Hurwitt et al, Shumacker. 1955 – Early clinical trial for TA (RA to PA) – Promising but no survival • Harrison. 1962 – Staged RA to PA & ASD closure • Haller et al. 1966 – TV obliteration – SVC to RPA side by side Right Heart Bypass (VI) • Fontan & Baudet. 1971 Physiologic correction – Classic Glenn shunt – RA-RPA with aortic valve homograft – Closure of ASD – Pulmonic valve homograft – MPA ligation Right Heart Bypass (VII) • Kreutzer et al. 1973 : – Anterior atriopulmonary connection – Direct RAA to MPA – Pulmonic valve preserved – No valve in IVC • Ross & Somerville; Stanford et al. 1973; Miller et al. 1974 – RAA to MPA using homograft valve Right Heart Bypass (VIII) • Bowmann et al. 1978 – Atrioventricular connection, – Porcine valved conduit • Bjork et al. 1979 – Atrioventricular connection, – Atrial tissue flap & pericardial roof Right Heart Bypass (IX) • Doty et al. 1981 – Direct & posterior atriopulmonary connections – Less susceptible sternal compression – Wide applications Fontan Operation Ten commandments 1. Minimal age of 4 years 2. Sinus rhythm 3. Normal caval drainage 4. Right atrium of normal volume 5. Mean pulmonary artery pressure ≤15 mmHg 6. Pulmonary vascular resistance < 4 clinical units/m2 7. Pulmonary artery to aorta diameter ratio ≥0.75 8. Normal ventricular function (EF ≥0.6) 9. Competent left atrioventricular valve 10. No impairing effects of previous shunt Choussat, 1978 Now, not absolute but relative criteria Fontan Operation Selection of candidates I. Age • Tendency to earlier correction Ventricular volume overload & cyanosis Prevent late ventricular failure • Optimal age : 2 - 4 years II. Cardiac rhythm • Preoperative NSR is not necessary • Why? – Preexisting AF : easy to control after Fontan – Atrial contraction : turbulence & impeding flow Fontan Operation Selection of candidates III. Pulmonary artery pressure • Consideration of pulmonary blood flow and pulmonary vascular resistance IV. Pulmonary vascular resistance • Absolute criteria • Linear relation between PVR & survival • < 2 Wood U : good 2 ~4 : risk >4 : absolute contraindication Fontan Operation Selection of candidates V. Pulmonary artery anatomy • Size of the PA – PAI ( Nakata Index ) > 250mm/m2 – McGoon ratio > 1.8 • More important factor than PA size itself – Distal pulmonary vascular bed – Arborization pattern of peripheral PA • Other options – Staging approach : BCPS, Hemi-Fontan operation… – Balloon dilatation : local stenosis – Angioplasty at corrective operation Fontan Operation Selection of candidates VI. Aortopulmonary collaterals • Risk in previous BCPS or BT shunt • Results of chronic hypoxemia as an adaptive mechanism to deliver more pulmonary blood flow • Origin from IMA, thyrocervical trunk • Volume overload pulmonary blood flow L-R shunt mismatch of Qp/Qs Elevated PA & LA pressure with heart or respiratory failure Prolonged tube drainage & pleural effusion Adversely affect patient survival Need transcatheter occlusion Fontan Operation Selection of candidates VII. Ventricular function • LVEDP : < 25mmHg & associated with correctable causes such as increased PBF, or AV valve insufficiency Not a risk factor • Ventricular hypertrophy : Associated with increased PBF, subaortic stenosis, PA banding, & increased age Fontan Operation Selection of candidates VIII. AV valve insufficiency • Remained stenosis & insufficiency are risk factors , corrected at preliminary stage operation if possible IX. Anatomic morphology • Systemic and pulmonary vein : location & pathway • Pulmonary venous obstruction Fontan Operation Criteria Absolute contraindications • Early infancy (age < 6-10 months) • Severe hypoplasia of parenchymal pulmonary arteries • Pulmonary vascular resistance > 4 clinical units Relative contraindications • • • • • • • Age < 1-2 years Pulmonary artery pressure > 15 mmHg Ventricular end-diastolic pressure > 15 mmHg Pulmonary vascular resistance 2-4 clinical units Previous pulmonary artery banding Substantial ventricular hypertrophy Mitral or aortic valve insufficiency > mild Sade et al., 1995 Fontan Operation Surgical diseases • • • • • • Tricuspid atresia Double-inlet ventricles Hypoplastic left heart syndrome Many forms of heterotaxia syndrome Pulmonary atresia with intact ventricular septum Hypoplastic right or left ventricle in biventricular hearts with VSD , with or without straddling AV valve • DORV with noncommitted VSD Right Heart Bypass By systemic venous bypass Complete Incomplete (partial) Glenn shunt BCPS with or without additional PBF Hemi-Fontan Kawashima shunt(=TCPS) Residual shunt adjustable fenestration communication By connection Atrioventricular Atriopulmonary Cavopulmonary bidirectional or unidirectional Intracardiac(intraatrial) - lateral tunnel Extracardiac Unidirectional Pre-Fontan Palliation Before 6 months age I. Systemic to pulmonary artery shunt – – – – Central shunt Pott’s shunt Waterston shunt Blalock-Taussig shunt II. Pulmonary artery banding – Preparation for Fontan : ventricular volume overload ↓ prevention of PVOD – Trusler’s rule – Adjust to PA pressure < 1/3 of systemic artery pr. SaO2 > 75% Pre-Fontan Palliation Before 6 months age III. Norwood operation • In HLHS • Control of pulmonary blood flow – balance between SVR & PVR – shunt size IV. Palliative arterial switch opertion • DILV with ventriculo-arterial discordance • Tricuspid valve atresia with ventriculo-arterial discordance complicated by a restrictive VSD & arch obstruction Pre-Fontan Palliation After 6 months age I. Bidirectional Cavo-Pulmonary Shunt • 1958 , Glenn • 1972 , Azzolina : 1st clinical report of BCPS • 1985 , Hopkins : physiologic rationale for BCPS : 1st clinical report of Glenn shunt pre-Fontan staged operation • 1989 , Mazzera : clinical applications as definitive palliations Pre-Fontan Palliation BCPS Advantages Improved oxygenation Decreased volume loading on the single ventricle Preservation of pulmonary vascular architecture Decreased risk for PVD Staged palliation & eliminate risk for Fontan operation Definite palliative procedure Surgical procedure of choice after failed Fontan operation Pre-Fontan Palliation BCPC Disadvantages Development of venous collaterals from SVC to IVC – – – – Pulmonary AV fistula Abnormalities in regional pulmonary perfusion Decreased angiogenesis of PA due to nonpulsatile flow Lower oxygen saturation in older children • Optimal operation time – 6m ~ 1 yr age Pre-Fontan Palliation Hemi-Fontan operation • BCPS , with patch occlusion of the SVC & RA junction • Similar hemodynamics to BCPS • Easy conversion to later Fontan op. • More suture line than BCPS late arrhythmia Pre-Fontan Palliation Total Cavopulmonary Shunt (TCPS) • Kawashima. 1978 • LA isomerism, Exclusion of hepatic vein Bidirectional Glenn Procedure Advantages • Advantages of the staged approach for the Fontan-type operations are giving effective pulmonary blood flow and stepwise adaptation of ventricular geometry to the reduction in volume load • The bidirectional Glenn procedure with additional pulmonary blood flow may provide patients with higher oxygen saturation and more growth of pulmonary arteries than BDG without APF. • However, there are disadvantages to BDG with APF, such as the elevation of venous pressure and volume overload on the ventricle Bidirectional Glenn Procedure Additional pulmonary blood flow • Antegrade pulmonary blood flow to be controlled and APF should be reduced at BDG. • CVP of 16 mm Hg or less might be ideal at the operating theater as it is well known from our experience that CVP decreases 2 to 3 mm Hg by extubation after BDG. • For banding the pulmonary trunk, an expanded polytetrafluoroethylene tube, 3 mm in width, was used. • For banding the BT shunt, an ePTFE graft of 8 mm length and same with the shunt or smaller in size was used to wrap the previously created BT shunt. Fontan Operation Surgical options I. Atriopulmonary Connection II. Atrioventricular Connection III. Total Cavopulmonary Connection ( Lateral Tunnel ) IV. Fenestrated or Adjustable Fontan Operation V. Fontan with Unidirectional Cavopulmonary Connection VI. Extracardiac Total Cavopulmonary Connection Atriopulmonary Connection (I) Fontan & Baudet. 1971 Physiologic correction – Classic Glenn shunt – RA-LPA with aortic valve homograft – Closure of ASD – Pulmonic valve homograft – MPA ligation Atriopulmonary Connection (II) Kreutzer et al. 1973 – Anterior atriopulmonary connection – Direct RAA to MPA – Pulmonic valve preserved – No valve in IVC • Ross & Somerville, Stanford et al. 1973 / Miller et al. 1974 – RAA to MPA using Homograft Atriopulmonary Connection (III) Doty et al. 1981 – Direct & posterior atriopulmonary connections – Less susceptible sternal compression – Wide applications Atriopulmonary Connection General approach • Methods – Location : anterior / posterior – Connection : direct / valved conduit – Separation of flow : simple ASD closure / atrial partitioning • Advantages – Simple, reproducible, wide applications • Disadvantages – More turbulent, atrial hypertension Atriopulmonary Connection Considerations • Use of valve ? : not helpful • RA contraction – Not essential to maintain C.O – Turbulence energy loss • Exposure of RA to high CVP • RA dilatation & hypertrophy – Supraventricular arrhythmia – Venous congestion – Need separation of RA to pathway of systemic venous return : Conversion to TCPC Atrioventricular Connection (1) Bowmann et al. 1978 – Atrioventricular connection, – Porcine valved conduit Atrioventricular Connection (II) Bjork et al. 1979 – Atrioventricular connection, – Atrial tissue flap & pericardial roof – Prevent conduit associated obstruction • Atrioventricular connection – No advantage Total Cavopulmonary Connection Lateral Tunnel De Leval et al. 1988 • Atrial partitioning with PTFE or Dacron tube graft • Creating a nearly straight pathway : laminar flow without turbulence & energy loss Total Cavopulmonary Connection Lateral Tunnel Advantages – Favorable flow patterns within systemic venous pathway with reduced risk of atrial thrombosis – Reproducibility irrespective of atrial & AV valve morphology – Reduction of risk of early & late arrhythmia – Low risk of surgical damage of sinus node artery Disadvantages – Possible injury from myocardial ischemia during ACC – Baffle obstruction of the pulmonary veins or AV valves – Baffle leaks cause cyanosis and failure of palliation – Dysrhythmia from atriotomy & extensive intraatrial suture lines Fenestrated or adjustable Fontan Rationale • Reduce systemic venous hypertension – Decreased morbidity & mortality by reducing : Chronic LCO, pleural effusion, ascites, hepatic congestion, protein-losing enteropathy by creating a shunt • Maintain preload & C.O. • Adding preload regression of ventricular hypertrophy • Decreased O2 saturation compensated by C.O. Fenestrated or Adjustable Fontan Baffle Fenestration Snare-Controlled Adjustable ASD • Bridges et al. 1990 • Shunt amount : size & PVR • Laks et al. 1988 Unidirectional Cavopulmonary Connection History • Lins et al. 1982 • Delenon et al. 1993 • Laks et al. 1995 – – – unidirectional CP connection SVC to LPA, IVC to RPA : ideal pulmonary blood flow distribution Obligatory source of pulmonary blood flow : obtain acceptable arterial saturation Selective decompression of IVC Unidirectional Cavopulmonary Connection Baffle Fenestration Adjustable ASD Extracardiac Cavopulmonary Connection Rationale • Lateral tunnel Fontan operation ± fenestration – marked improvement in survival – several drawbacks previously mentioned Avoid complications due to intraatrial lateral tunnel op. Preserve hemodynamic effects of intraatrial lateral tunnel op. Result in Extracadiac TCPC Extracardiac Cavopulmonary Connection Extracardiac Conduit (1) • Giannico et al. 1990 • Gore-Tex tube graft Extracardiac Cavopulmonary Connection Extracardiac Conduit (2) • Concomitant PA enlargement with conduit patch • Shunt formation – between extracardiac conduit & RA – with Gore-Tex tube graft 4 or 5mm Extracardiac Fontan Operation Clipped tube fenestration surgical clips Extracardiac Cavopulmonary Connection Extracardiac Epicardial Lateral Tunnel (EELT) • Lashinger et al. 1992 • Gore-Tex patch or pericardium Extracardiac Pericardial Fontan Operative techniques The pericardial pedicle is fashioned and the anterior wall of the right atrium is sutured to the backwall of the ipsilateral pericardial flap. The completed EPPF. (EPPF = extracardiac pedicled pericardial Fontan; IVC = inferior vena cava; LPA = left pulmonary artery; RPA = right pulmonary artery; SVC = superior vena cava.) Pedicled Pericardial Conduit Operative techniques Large rectangular flap of pericardium was cut, leaving it pedicled so as to preserve its vascular connections, and the flap was then rolled into a tube shape. B, Conduit with the aid of a temporary bypass from inferior vena cava (IVC) to the atrium. Extracardiac Cavopulmonary Connection Considerations • Advantages – Closed no touch technique avoidance of ischemic arrest : helpful in patients with ventricular diastolic dysfunction – Maintain more favorable laminar flow – Reduce early and late atrial dysrhythmia , atrial thrombosis : RA wall stress , avoidance of atriotomy & atrial sutures – Technically simple in systemic or pulmonary venous anomalies • Disadvantages – Anticoagulation – Technical difficulty in applying large conduit size Arrhythmia in Fontan Operation Surgical options • Kao et al. 1994 – Conversion of atriopulmonary to cavopulmonary connection in the management of Af • Gandhi et al. 1996 – In an acute canine model – In the absence of hemodynamic alteration – Fontan suture lines alone permit the induction of AFL Arrhythmia in Fontan Operation Surgical options • Mavroudis et al. 1998 / Deal et al. 1999 • Conversion to TCPC + Arrhythmia circuit cryoablation + Antitachycardia pacemaker • 3 identified major tachycardia circuits 1) area between coronary sinus & IVC 2) lateral atriotomy 3) superior rim of the prior ASD patch 3 • Prophylatic cryoablation In first time Fontan reconstructions : intriguing issue 2 1 TCPC Geometry Optimization • Energy conservation – Very important to circulation • Flow separation of caval inlets to conserve energy (in vitro) Offset : de Leval et al. 1996 Flaring & offset : Ensley et al. 1999 Curvature : Sharma et al. 1996 Gerdes et al. 1999 Needs a further investigation & clinical application SVC Caval offset RPA LPA IVC Fontan Operation Postoperative management • Reduce pulmonary vascular resistance • Maintain adequate preload • Consider other surgical options when untolerable to Fontan physiology • Treatment of complications Fontan Operation Risk factors for death • • • • • • • • • Acute ventricular decompression Late pulmonary & ventricular deterioration Younger age & older age at operation Cardiac morphology Small central right & left pulmonary arteries Increased mean PAP and PVR Advanced chamber ventricular hypertrophy Atrial isomerism Right atrial connection to pulmonary artery Fontan Operation Complications • • • • • Arrhythmia Thromboembolism Effusion : pleural, pericardial, chylothorax Protein-losing enteropathy Fistulas – intrahepatic venous fistula – pulmonary AV malformation – systemic venous collaterals • Fontan take-down • Acute liver dysfunction Persistent Pleural Effusions Risk factors after Fontan • Persistent pleural effusions are the most troublesome complication in the early postoperative period and this problem to occur in 13% to 39% of patients after surgical intervention. • The risk factors that contribute to persistent pleural effusions after the extracardiac Fontan procedure have not been well established. • Lower preoperative oxygen saturation, presence of postoperative infection, smaller conduit size, and longer duration of cardiopulmonary bypass were associated with persistent pleural effusions after the extracardiac Fontan procedure. Persistent Pleural Effusions Contribution to development • Inflammatory response results mainly from exposure to CPB, causing increased capillary leakage and subsequent fluid retention. • Increased hydrostatic pressure in Fontan circulation results from factors increasing the pulmonary vascular resistance. Lack of atrioventricular synchrony also contributes to this mechanism. • Hormonal mechanism involves activation of the reninangiotensin system, and more recent evidence suggests involvement of atrial natriuretic peptide & vasopressin. Fontan Operation Management of complications • Supraventricular arrhythmias after extracardiac Fontan operation are probably multifactorial and mandate continuous surveillance. • Patients with systemic ventricular dysfunction, bilateral superior venae cavae, and heterotaxy syndrome and those undergoing completion Fontan may exhibit a high incidence of these arrhythmias. • The viable extracardiac Fontan may be the operation of choice in a selected subset of patients. • Serial dynamic radionuclide studies may be useful for evaluation of anatomic and functional flaws of the Fontan circuit Pulmonary A-V Malformations Nature • Pulmonary arteriovenous malformations develop embryologically owing to incomplete development of the pulmonary capillary system and are characterized by greatly increased numbers of nonessential pulmonary blood vessels that do not serve a critical gas exchange function but cause arteriovenous shunting. • The existence of PAVMs in normal lungs has been verified and under certain physiologic conditions these vascular channels may become dilated and more numerous. • PAVMs are also a feature of the hepatopulmonary syndrome that can occur in patients with hepatic cirrhosis, and of hereditary hemorrhagic telangiectasia Pulmonary A-V Malformations Development • An absence of a "hepatic factor" or "mesenteric factor" and that an unidentified element in the hepatic venous drainage inhibited the recruitment and dilatation of preexisting pulmonary arteriovenous connections • Angiogenic process, as well as recruitment of preexisting channels that dilated when there was an absence of hepatic venous return to the pulmonary circulation • Alternately hypothesized that the liver may be responsible for the degradation of an angiogenic substance which is not removed after BCPA. Pulmonary AV Malformations Diagnostic criteria • Rapid pulmonary AV transit (< 3 heart beats) of contrast on proximal PA angiography • Typical reticular or spongy pattern in the peripheral pulmonary vasculature on PA angiography • PV desaturation ( 92%) in angiographically affected lung segments. Pulmonary A-V Malformations Risk factors • The PAVMs appear within weeks of BCPA or the Kawashima operation and can be demonstrated earliest by contrast echocardiography. • Bilateral SVCs and an interval of more than 2 years were independent risk factors for the development of PAVMs after the Kawashima operation • Unilateral streaming of HV-PA flow is an important concern after HV inclusion in patients with heterotaxy and azygous continuation of the IVC Pulmonary A-V Malformations Management inferences • Development of PAVMs is facilitated by exclusion from the pulmonary circulation of a substance produced or metabolized in the liver • Resolution of PAVMs after CPA requires delivery of hepatic venous blood, and the putative hepatic factor, to the affected lung • Putative hepatic factor either has a short circulating half-life or is eliminated/inactivated during passage through a systemic or pulmonary capillary bed Approaches to Single Ventricle Single Ventricle Surgery Aims of treatment How do we achieve 1. The highest success rate 2. The highest long-term survival rate 3. The best quality of life Fontan Operation Pulmonary flow pattern • 63% of systemic venous flow during inspiration • Negative intrathoracic pressure is a principal draining force • Gravity plays a role in SVC flow to the pulmonary arteries. • Hemidiaphragmatic paralysis decrease pulmonary function by approximately 25%, but stability of adult rib cage & strength of accessory muscles of respiration help to compensate for decreased diaphragmatic function. Fontan Operation Changes of systemic venous return • Lack of a right-sided pump increase afterload. • In series may add additional resistance to systemic venous return. • At risk for transient ventricular dysfunction for a systemic venous return Fontan Procedure Identification • • • • • Reurrent obstruction in aortic arch Prognosis or new development of subaortic stenosis Distortion of the pulmonary arteries Deterioration of ventricular, or atrioventricular valve function Development of elevated pulmonary vascular resistance Fontan Procedure AV valve regurgitation 1. Incidence ; 6% (5-40%) 2. Natural factors Amount of pulmonary flow & length of time with ventricular volume loaded 3. Mechanism * Functional ; central jet, improve after BCPC * Structural ; dysplastic, cleft, prolapse, restricted, frequent in common AV valve, rarely improve after BCPC 4. Solution * Small shunt before BCPC * Early BCPC in young (reduction volume load by 33% after BCPC) Common AV Valve Repair • Regurgitation through central position of AV valve was repaired by supporting central portion of common AV valve by closure of cleft and suture of adjacent central portion of leaflets Fontan Operation Minimal age When children begin walking, standing, creeping, active extremity movement, around 8 months old or body weight more than 10 kg Single-ventricle patients can transition towards Fontan completion as early as 1 year of age • Advantages * Preservation of ventricular function through relief of chronic volume load and hypoxemia * Protection of pulmonary vasculature by removing shunt • Disadvantages * Small anatomical structure * More reactive pulmonary vascular bed after CPB Cyanotic Heart Diseases Advantage of early repair 1. Avoid the hazards of prolonged cyanosis on ventricular function & neurologic development 2. Prevent the effects of chronic ventricular volume overload 3. Reduce the risk of cerebrovascular embolism and brain abscess Early Fontan Repair Advantages o It appears that a period of approximately 6 months aftersuperior cavopulmonary connection is sufficient in most cases for the appropriate changes in ventricular geometry and diastolic properties of the single ventricle to occur for a successful Fontan circulation 1. Avoid multiple palliative surgery 2. Avoid chronic ventricular volume overload 3. Avoid chronic hypoxia 4. Prevent late ventricular failure and possible arrhythmia Fontan Operation Staging procedures • This policy involves the use of small shunt to provide limited pulmonary blood flow, construction of an early bidirectional cavopulmonary anastomosis, early identification and correction of systemic ventricular outflow obstruction, & avoidance of prolonged periods of PA banding. • But it remains unclear whether all children should undergo an intermediate bidirectioal Glenn shunt procedure prior to Fontan., the optimal timing of a bidirectional Glenn shunt, except in patients with complex anatomy excessively cyanosed by 4-6 months. • Pprimary establishment of Fontan circulation if the patient has good conditions of the Fontan circulation, otherwise we will proceed to a bidirectional Glenn procedure, probably at the age of 6 months. Fontan Operation Staging toward completion 1. Palliative procedures before 6 months of age 1) Palliative shunt procedure 2) PAB 3) Norwood operation 4) Palliative arterial switch operation 5) BCPS 2. Palliative procedures after 6monhs of age 1) BCPS 2) Hemi-Fontan operation 3) BCPS with DKS or with arterial switch operation or with subaortic or VSD resection 4) Total cavopulmonary shunt (Kawashima) Fontan Operation Aims of palliation 1. Maintain normal pulmonary compliance 1) PA pressure 2) PVR 3) PA shape & size 4) PVOD 2. Maintain normal cardiac compliance 1) Cardiac volume load 2) Cardiac pressure load 3) Cardiac muscle hypertrophy 4) Endomyocardial ischemia Partial Fontan Operation Hemodynamic interest * Due to persistence of right-to-left shunt 1) Decreases pulmonary artery pressure 2) Preserves the cardiac output 3) Unloads the univentricular hearts Fontan Operation Left Superior Vena Cava • Persistent left SVC arises from a faulty embryogenesis between the fifth and eighth week and affects approximately 0.3% of the population • Its prevalence increases to 2% to 4.5% in patients with other congenital heart defects. • The addition of that third inflow introduces supplementary parameters and issues into the quest for an optimal total cavopulmonary connection (TCPC) design and has not yet been investigated. Incomplete Atrial Partitioning Reasons of deliberation 1. Temporary pulmonary vascular or pulmonary dysfunction related to damaging effects of cardiopulmonary bypass 2. Temporary myocardial dysfunction related to inadequate myocardial management 1) Increased ventricular wall thickness and myocardial edema 2) Decreased ventricular compliance and volume 3. Expect to regress these responses over several weeks or months thereafter Partial Fontan Circulations Advantages of IVC-PA shunt 1. Fixed Qp/Qs not dependent on the transatrial gradients as for the fenestrated Fontan operation 2. Acceptable level of arterial oxygen saturation 3. Mainly an increased facility to perform the second step of the Fontan operation Partial Fontan Circulations IVC-PA shunt 1. Higher transpulmonary blood flow 2. Promote additional growth of the pulmonary artery 3. Oxygen delivery remains at a low level. 4. Exercise of the lower limb increases the flow of IVC. 5. Technical and hemodynamic ease of the second operative step 6. Avoiding the development of arteriovenous fistula in the lungs (hepatic factor) 7. No risk of collateralization between IVC and hepatic veins 8. Pleural effusions were minimal, although IVC pressure is slightly increased, due to low pressure in SVC and absence of thoracic duct drainage obstruction. Single Ventricle Palliation Mitigating factors in Down syndrome 1. Abnormalities of lung development 2. Pulmonary immunocompetence 3. Hypnotic and hyperventilation 4. Upper-airway obstruction with a propensity for nighttime hypercarbia, hypoxia and subsequent vasoconstriction Hemi-Fontan Operation Hemi-Fontan Operation Alternative Method Bidirectional Cavopulmonary Connection SVC Fontan Operation Risk Factors • Elevated pulmonary artery pressure • Elevated pulmonary vascular resistance • Ventricular dysfunction • Systemic AV valve regurgitation • Longer cardiopulmonary bypass • Significant pulmonary artery distortion • Systemic-pulmonary artery collaterals Fontan Operation Major risk factors 1. Pulmonary artery distortion 2. Elevated pulmonary arteriolar resistance (>2 Wood units) 3. Elevated pulmonary artery pressure (>15mmHg) 4. Presence of either left AV valve atresia or a common AV valve 5. Ventricular dysfunction (LVEDP >15mmHg) 6. Young age (< 3years) AP Fontan Operation Hemodynamic charateristics 1. Fluid losses associated with flow expansion from the vena cavae into the RA chamber 2. Collision and mixing of vena cava flows 3. Flow contraction from the distended RA into the main pulmonary artery Lateral Tunnel Procedure Advantages 1. Technically simple and reproducible in any atrioventricular arrangement 2. Maintenance of low pressure is possible in most of the right atrium and coronary sinus with possible improvement of atrial arrhythmias 3. A reproduction of energy loss as a result of lessened turbulence in the LT would decreases the cardiac index. Extracardiac Conduit Fontan • Unfavorable & Favorable Malposition of heart Redo operation Small heart size Old age Venous malformation No intracardiac procedure Bilateral SVC Decreased heart function Hepatic vein anomalies Pulmonary venous anomalies IVC interruption Good pulmonary artery size Coagulopathy Extracardiac Fontan Procedure (Extracardiac lateral tunnel & Extracardiac lateral conduit) Advantages 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Avoidance of aortic cross clamping Hemodynamic benefits of total cavopulmonary connection Avoidance of atriotomy and intraatrial suture line Preservation of sinus rhythm and no or low arrhythmia Drainage of the coronary sinus to low pressure atrium Allowance for early or late fenestrations Prevention of early and late baffle leaks Prevention of obstruction of pulmonary veins or AV valves Allowance for growth in lateral tunnel procedure Reduce the risk of systemic emboli Fontan Operation Criteria of fenestration • • • • • • • Elevated pulmonary artery pressure Elevated pulmonary vascular resistance Abnormal pulmonary artery anatomy Systemic right ventricle Impaired ventricular function Significant AV valve regurgitation Younger age Fontan Operation Results of fenestration • Spontaneous closure * 2.5-4 mm : 1 year closure 50-90% * > 4 mm : 1 year closure 40-70% • Risks * Thromboembolism * Prolonged desaturation * No thromboembolism less than 2.5mm TCPC Geometry General principle • In in vitro model, with no offset between the vena cava, hepatic blood distribution and concentration to each lung was similar to normal but energy loss involved is relatively high due to mixing of two vena cava flow. • This resistance to blood flow is mainly due to the geometry of the connection with bends,expansions and junctions all creating energy losses through increased friction and flow disturbance or mixing. • In general the greater the disruption to the flow, the greater the fluid energy loss TCPC Geometry Flow structures • In geometries with a single SVC, offsetting the IVC and SVC by 1.0 to 1.5 caval diameter minimizes the flow disturbances caused by the colliding inflows • Similarly, with dual SVCs, setting the IVC in between the 2 SVCs results in an offset between the IVC and each one of the SVCs, which in turn decreases flow instabilities, such as those observed in the original anatomy distal to the RPA • Suturing the LSVC closer to the RSVC in the hemiFontan or Glenn stage may be a better way to decrease the distance by which the IVC should be shifted in the final TCPC stage TCPC Geometry Toward surgical planning • It is important to keep in mind some possible TCPC design improvements. • Shifting the IVC in between the 2 SVCs seemed to be a feasible and efficient way to obtain a better repartition of the hepatic flow to lungs. • In extracardiac cases, for example, shifting the IVC toward the LSVC may compress the pulmonary veins and worsen the patient's outcome rather than improving it. Fontan Palliation Three-dimensional grids Fontan Operation Morphometry • FA ; Fontan area • SVA ; Systemic venous area Lateral Tunnel Fontan Extracardiac Fontan Operation • Total cavopulmonary connection with dextrocardia • Intra-extraatrial lateral tunnel technique Extracardiac Fontan Operation • Extracardiac Fontan operation without CPB and temporary atria to IVC shunt Extracardiac Fontan Operation • Extracardiac Fontan operation without CPB and temporary systemic arterial to pulmonary artery shunt Extracardiac Fontan Operation • Diagram shows completion of distal anastomosis without CPB Fontan Operation Postoperative care 1. Reduce the systemic vascular resistance Elevation of the venous pressure results in a reflex rise in the tone of the arterioles 2. Minimize the pulmonary vascular resistance Pulmonary vascular resistance is minimized when the lung is operating near functional residual capacity 3. Takedown the Fontan procedure to BCPC who cannot tolerate the Fontan physiology 4. Development of pleural or pericardial effusion Young age and hepatic capillary bed is the leakiest of the systemic capillary beds. Fontan Operation Right atrial pressure • RA pressure of 16 mmHg or less with maintaining cardiac output is ideal and they generally convalesce well. • Severe arterial desaturation in fenestrated Fontan may be the warning sign rather than elevation of RA pressure. • When LA pressure is elevated to within a few mmHg of RA pressure, ventricular dysfunction or AV valve dysfunction are etiologic. • When RA pressure remains 5mmHg, or higher than LA pressure, pulmonary vascular disease or pulmonary arteriolar spasm or small size of pulmonary artery may be responsible. • When RA pressure is high, but PA pressure and LA pressure are not, then an obstruction exists. Fontan Operation Takedown 1. Usually within 12 hours after after operation 2. Poor hemodynamic state, and presence of an elevated RA and PA pressure with a LA pressure 5 mmHg or more lower than the right 3. Conversion to a hemi-Fontan procedure in case of cavopulmonary connection 4. In other form of modified Fontan operation, removal of the patch alone results in severe and fatal arterial desaturation, thus usually the entire procedure must be taken down with bidirectional cavopulmonary shunt. Fontan Operation Chylothorax • Injury of the thoracic duct during surgery • Disruption of lymphatics during thymus gland removal • The leaking micropores gradually enlarge with time and with passage of macromolecules through them, so that chylomicron can pass. • Adequate drainage and high caloric intake are the mainstays of treatment. • Ligation of the thoracic duct rarely is useful. Single Lung Fontan Operation Strategies • The success of the Fontan procedure in selected cases of single-lung physiology is likely related to the functional and anatomic compensation by the remaining lung. • Pulmonary vascular resistance decreases significantly in the remaining lung postpneumonectomy over time (2 to 12 months) with an increase in maximal cardiac output . • Dgree of pulmonary compensation postpneumonectomy is greater in young than in adults, suggests a relationship between developmental and adaptive potentials • Fontan operation in patients with a single lung requires careful preoperative assessment and must be done to determine whether these patients are acceptable surgical candidates. Fontan Procedure Coagulation factor abnormalities 1. Protein C deficiency Natural anticoagulant synthesized in the liver as a Vit-K dependent protein, after activation by thrombin, protein C is a potent inhibitor of coagulation cascade and stimulate fibrinolysis. 2. Protein S deficiency Protein S acts as a cofactor in this pathway, and it futher stimulate fibrinolysis. 3. Factor Vll A coagulation factor and is part of the extrinsic pathway. Factor Vll interacting with tissue factor activates the extrinsic pathway. A low level can support the tissue factor-induced coagulation in pathologic state. Fontan Operation Thromboembolism # Virchow’s triad 1) stasis 2) presence of abnormal surface 3) change in coagulation 1. Hemodynamic factor Stasis and area of sluggish flow by 1) low cardiac output 2) less pulsatile pulmonary circulation 2. Coagulation abnormality 1) Protein C 2) Protein S 3) Factor VII 3. Use of prosthesis, sutures, intimal change Fontan Operation Reasons of desaturation • Early late systemic desaturation can occur from various systemic venous channels connecting to the pulmonary veins, coronary sinus, or left-sided atrial structures that may become manifest immediately or develop over time • Distinguish these entities from lung diseases or intrapulmonary arteriovenous malformation and specific morphology of venous connection • Surgical or interventional closure is indicated Pulmonary A-V Malformations Natures • Pulmonary arteriovenous malformations, pathologically, dilated capillary and precapillary vessels with evidence of direct arteriovenous communication are seen. • They may be hereditary as in Rendu-Osler-Weber syndrome, or acquired as in hepatopulmonary syndrome, or in complex congenital heart defects with single ventricle physiology palliated by superior cavopulmonary connections. • “Hepatic factor" is critical in preserving the integrity of pulmonary vasculature in normal subjects. • This hepatic factor could be related to regulators of nitric oxide, the polypeptide super family transforming growth factor and its antagonists; the absence of the latter would produce an unopposed pulmonary vasodilatation leading to PAVMs. Arrhythmias after Fontan Op. 1. Incidence 1) Early : 12~48% 2) Late : 50% more over 10~15 years 3) 5-30% after 5 years of TCPC 2. Mechanism 1) Early a. Automatic atrial tachycardia and flutter acute elevation of atrial pressure recent surgical procedure b. Junctional ectopic tachycardia myocardial dysfunction c. Heart block 2) Late a. Extensive atrial surgery b. Destruction of conduction tissue c. Disruption of SA node artery d. Direct damage to sinus node e. Increased atrial pressure f. Poor ventricular function Arrhythmia in Fontan Operation Atrial tachycardia 1) Early Atrial flutter Atrial ectopic tachycardia AV reentrant tachycardia 2) Late Atrial flutter (5~30% at 5-year follow-up) AV reentrant tachycardia Atrial ectopic tachycardia Failure of Fontan Circulation Consequences • Right atrial dilation, inefficient flow dynamics, baffle thrombus, repeated subclinical pulmonary emboli, and atrial arrhythmias, can coalesce to cause the Fontan circulation to fail • Loss of atrioventricular coordination & efficient ventricular preloading from atrial arrhythmias, combined with decrease myocardial perfusion from coronary sinus hypertension, eventually leads to systemic ventricular dilation & failure Adult Functional Single Ventricle Characteristics • As having a "failed" Fontan (chronic arrhythmias, protein losing enteropathy, pleural effusions, ventricular dysfunction, limited exercise capacity) • After long-term surgical palliation • As uncorrected. Fontan Conversion Indications for conversion • Interrelated combination of increasing symptoms of heart failure, • Systemic ventricular failure, • Elements of anatomic obstruction • Reefractory arrhythmias.