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Medical College, Calicut

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1 Medical College, Calicut
FONTAN CIRCULATION Dr Bijilesh u Senior Resident, Dept. of Cardiology, Medical College, Calicut

2 Normal mammal cardiovascular system double circuit connected in series
—systemic —pulmonary powered by a double pump —the right and left heart

3 Many complex cardiac malformations - one functional ventricle
Maintain systemic and pulmonary circulation - not connected in series but in parallel Major disadvantages arterial desaturation chronic volume overload to single ventricle - in time impair ventricular function Such a circuit has two

4 1971, Fontan and Baudet Goal 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 ventricle All shunts on the venous, atrial, ventricular and arterial level are interrupted

5 Advantages of a Fontan circuit include
(near) normalisation of the arterial saturation abolishment of the chronic volume overload Cost for such a circulation includes Chronic hypertension and congestion of the systemic veins decreased cardiac output Cardiac output is no longer determined by the heart,but rather by transpulmonary flow (itself mainly determined by pulmonary vascular resistance)

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

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

8 Refined 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 are unobstructed ventricular inflow (no atrioventricular valve stenosis, no regurgitation) reasonable ventricular function unobstructed outflow (no subaortic stenosis, and no coarctation

9 Pulmonary requirements
non-restrictive connection from systemic veins to the PA good sized PA without distortion a well developed distal vascular bed (near) normal PVR U/m2 unobstructed pulmonary venous return Marc Gewillig , Heart 2005;91:839–846. doi: /hrt

10 Fontan Procedure Since its original description, the Fontan circuit has known numerous modifications Early modifications of the Fontan procedure connected pulmonary arteries to the right atrium

11 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

12 lost contractile function
RA was included to - improve pulmonary blood flow, being a pulsatile chamber Instead RA dilated and lost contractile function Turbulence and energy loss Decreased pulmonary blood flow de Leval et al

13 Right atrial–pulmonary circuits - obsolete
Replaced with newer techniques - direct connection between each vena cava and PA Bypass the right atrium and right ventricle More efficient cavopulmonary blood flow to the lungs – reduce risk for arrhythmia and thrombosis

14 Modern Fontan procedure involves connecting SVC and IVC to the RPA
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 These two connections are

15 Currently total cavopulmonary 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

16 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

17 Initially in the neonatal period, management must aim to achieve
Unrestricted flow from the heart to the aorta coarctectomy Damus- Kaye-Stansel Norwood repair Well balanced limited flow to the lungs pulmonary artery band modified Blalock-Taussig Unrestricted return of blood to the ventricle Rashkind balloon septostomy

18 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

19 Bidirectional Glenn Shunt / Hemi-fontan
Cardiac end of the divided SVC is attached to MPA or the under surface of RPA Lower stump of SVC is connected to IVC with a conduit Open end of the SVC is either oversewn or occluded with a polytetrafluoroethylene patch Allows Fontan circulation to be completed later

20 When patients reach 1–5 years of age total cavopulmonary Fontan circuit is completed
IVC connected to pulmonary artery with a conduit

21 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

22 Internal conduit - pass through the right atrial chamber
External conduit - run completely outside the heart to the right side of the right atrium

23 Intraatrial tunnel method
Conduit is constructed with both the lateral wall of the right atrium and prosthetic material Inferior aspect of the tunnel is anastomosed to the IVC and the superior aspect is anastomosed to the pulmonary arteries Conduit enlarges as the child grows - may be used in children as young as 1 year old Internal conduit may lead to atrial arrhythmia A benefit of using this circuit is that the

24 Extracardiac conduit method
Usually performed only in older than 3 years PTFE tube graft is placed between the transected IVC and the pulmonary artery, bypassing RA Entire atrium is left with low pressure - less atrial distention, arrhythmia, and thrombosis

25 Cannot 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

26 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

27 Fenestrations decrease postop pleural effusions
May be closed after patients adapt to new hemodynamics Now, fenestrations are seldom created during the completion of the Fontan improved patient selection and preparation improved staging has been reported


29 Early increase in preload
Fontan circulation provides definitive palliation for complex cardiac lesions not suitable for biventricular repair Some form of palliation is done in early infancy Results in a parallel pulmonary and systemic circulation and a net increase in preload

30 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

31 Abnormal systolic ventricular performance is rarely a problem in early years of palliation prior to Fontan Is sustained or improved in most, after completion of Fontan circuit It was shown that restoration of normal systolic wall stress was achieved in most individuals undergoing a Fontan procedure prior to the age of 10 years Sluysmans 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.

32 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 Prolongation of the time constant of early relaxation (tau) and the isovolumic relaxation time are both inversely related to the c

33 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

34 Avoidance of factors known to lead to worsening compliance (persistent LV outflow tract obstruction, hypertension) is of fundamental importance

35 While diastolic abnormalities predominate early-on , systolic failure also becomes apparent in some patients late after the procedure

36 Systemic vascular bed Many studies have reported uniformly elevated systemic vascular resistance after Fontan Senzaki H, Masutani S, Kobayashi J, et al

37 dobutamine, 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 with dobutamine, was highly abnormal in the Fontan group Senzaki H, Masutani S, Kobayashi J, et al

38 Use of ACE inhibition in Fontan patients
Enalapril or placebo was given for 10 weeks in 18 patients approximately 14 years after the Fontan operation Tendency to worsen exercise performance. Reduced incremental cardiac index during exercise in the patients receiving enalapril Kouatli et al ,Enalapril does not enhance exercise capacity in patients after Fontan procedure. Circulation Sep ;96(5):1507–12.

39 Many patients continue to receive ACE inhibition, in the hope of a beneficial effect when given chronically It is possible that there are subgroups that may benefit e.g. severe systolic dysfunction Presently no evidence for this therapy being beneficial

40 The veno-pulmonary circuit
Major evolution in the hemodynamic design of the Fontan operation since its inception Initial right atrial to pulmonary connection has been abandoned in favor of more streamlined versions

41 There was no difference between the patient group at rest
Cardiac output - using respiratory mass spectrometry and an acetylene re-breathing method There was no difference between the patient group at rest Cardiac output & respiratory rate higher in the lateral tunnel group than the atriopulmonary group at low and moderate workloads Rosenthal 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.

42 Work 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 TCPC Redington AN, Penny D, Shinebourne EA. Pulmonary blood flow after total cavopulmonary shunt. Br Heart J Apr 1991;65(4):213–7

43 Philadelphia 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 TCPC Fogel 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.

44 Positive pressure ventilation
Increasing levels of PEEP during positive pressure ventilation is adverse to Fontan circulation Higher the mean airway pressure, lower cardiac index Maintain with minimum mean airway pressure compatible with normal oxygenation and ventilation Williams 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

45 The pulmonary vascular bed
Low PVR is a prerequisite for early success after Fontan operation Lower the total pulmonary resistance (PVR , pulmonary venous resistance and LA resistance) the better LA resistance is influenced by the abnormal ventricular response

46 Structural pulmonary venous abnormalities
Naturally occurring May evolve as a result of abnormal hemodynamics Atriopulmonary anastomosis- gross enlargement of RA may compress adjacent pulmonary veins

47 Abnormalities of arteriolar resistance adversely influence early outcome, in terms of morbidity and mortality Few 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

48 Pulmonary artery flow in Fontan is relatively low velocity, laminar
Different to the normal pulsatile flow of pulmonary vascular bed in normal circulation Release of nitric oxide from the endothelium is dependent on pulsatile flow in the normal circulation Experimentally, reducing pulsatility leads to reduced NO production and an increase in vascular resistance Nakano 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):


50 Creation of Fontan circulation is palliative by nature
Proved good results with ideal hemodynamics Substantial morbidity and mortality in those with unfavorable hemodynamics those who underwent older surgical techniques

51 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

52 Late mortality Late death is directly related to the number of risk factors for a Fontan operation Unfavourable haemodynamics and risk factors are associated with an increased early and late attrition

53 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

54 Ventricular dysfunction
Ventricle of a functionally univentricular heart Dilated, hypertrophic and hypocontractile May fail after years of systemic loading congenital malformation itself original hemodynamic state of volume overload Systemic ventricle may be a morphologic right or an indeterminate primitive ventricle previous surgical interventions High RA pressure may impair coronary blood flow - affect myocardial perfusion and function Coronary sinus blood may be surgically redirected to drain into the left atrium (3).

55 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

56 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

57 Little impact on ventricular function of
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 b blockers no impact on the reduced preload which is the dominant limiting factor The treatment of ventricular dysfunction in the setting of a Fontan circuit is very frustrating for a cardiologist.

58 Arrhythmia Dilatation predispose to
Many old circuits have atrial wall incorporated into the circuit causing atrial dilation 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

59 Occur in up to 40% of the patients 10 years after surgery
Most common atrial tachycardia is intra-atrial re-entry or atrial flutter Immediate direct current DC version Anticoagulation in view of the significant risk of a right atrial thrombus

60 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

61 Collateral Vessels and Shunts
Collateral vessels and shunts may lead to substantial right-to-left shunts and cyanosis Incomplete closure or a residual atrial septal defect 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

62 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

63 Blood Vessels 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 Reported incidences of venous thromboembolism and stroke are 3%–16% and 3%–19%, respectively

64 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

65 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)

66 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

67 Lymphatic System Fontan circulation operates at or sometimes 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

68 Protein-losing enteropathy
Relatively uncommon manifestation of failing Fontan circulation Cause is unclear Loss of enteric protein may be due to elevated systemic venous pressure that is transmitted to the hepatic circulation Lead to hypoproteinemia, immunodeficiency, hypocalcemia, and coagulopathy, May occur in the long term

69 PLE 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;115:1063–73 Very poor prognosis Five year survival rate was 59%

70 Treatment options for PLE
Diet high in calories High 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

71 Plastic bronchitis Rare but serious complication 1%–2% of patients
Noninflammatory mucinous casts form in tracheobronchial tree and obstruct the airway Dyspnea,cough, wheezing, and expectoration of casts - may cause severe respiratory distress with asphyxia, cardiac arrest, or death Exact cause unknown

72 Plastic bronchitis High intrathoracic lymphatic pressure or obstruction of lymphatic flow may lead to the development of lymphoalveolar fistula and bronchial casts Medical management is difficult - often require repeat bronchoscopy to remove the thick casts Surgical ligation of the thoracic duct may cure plastic bronchitis by decreasing intrathoracic lymphatic pressure and flow

73 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.

74 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.

75 Some clinicians recommend anticoagulating every patient with a Fontan circuit
Subgroups of patients with a very low risk Full anticoagulation in previous thrombi poor cardiac output congestion, dilation of venous or atrial structures, arrhythmia


77 All 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

78 Type of Fontan surgery was classified into the following 4 categories:
Right atrium (RA)–to–PA anastomosis RA–to–right ventricle (RV) connection Intraatrial lateral tunnel (LT) Extracardiac conduit (ECC) The latter 2 were considered subtypes of total cavopulmonary connections.

79 Baseline Characteristics
A total of 261 patients, 121 female (46.4%) had their first Fontan surgery at a median age of 7.9 years 33 (12.6%) of which were fenestrated Type of first Fontan RA-PA connection in 135 (51.7%), RA-RV in 25 (9.6%) LT in 98 (37.5%) ECC in 3 (1.1%)


81 Mode of Death Over a median follow-up of 12.2 years years
76 patients (29.1%) died 5 (1.9%) had cardiac transplantation 5 (1.9%) had Fontan revision 21 (8.0%) Fontan conversion - LT in 16 or ECC in 5 Overall, 52 deaths (68.4%) were perioperative 7 (9.2%) were sudden 6 (7.9%) were thromboembolic 5 (6.6%) were due to heart failure 2 (2.6%) were secondary to sepsis


83 Perioperative Mortality
Of 52 perioperative deaths, 41 (78.9%) were early and 11 (21.1%) were late Importantly, perioperative mortality rates decreased steadily over time First Fontan surgery Before % 1982 to % 1990 or later %

84 Long-Term Survival Actuarial 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 era In perioperative survivors, freedom from death or cardiac transplantation was comparable among all types

85 In 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

86 Death resulting from thromboembolism occurred at a median age of 24
Death resulting from thromboembolism occurred at a median age of 24.9 years 8.7 years after Fontan surgery Actuarial freedom from thromboembolic death was 98.7% at 10 years and 90.8% at 25 years All patients had RA-PA Fontan surgeries except for 1 patient with an LT

87 Predictors of Thromboembolic Death in Perioperative Survivors
Atrial fibrillation Lack of aspirin or warfarin therapy Thrombus within Fontan

88 Heart failure–related deaths occurred at a mean age of 22.9
4.3 years after Fontan surgery Actuarial freedom from death caused by heart failure was 99.5% at 10 yrs and 95.8% at 25 yrs Risk factors were single RV morphology, higher postoperative RA pressure, and protein-losing enteropathy.

89 Sudden death Sudden death occurred at a median age of 20.2 years in 7 patients 3 with RA-PA, 3 with LT, and 1 with RA-RV 2.9 years after Fontan surgery.

90 Conclusions Leading cause of death was perioperative, particularly in an earlier era Gradual attrition was noted thereafter, predominantly from thromboembolic, heart failure–related, and sudden deaths 70% actuarial freedom from all-cause death or cardiac transplantation at 25 years

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