FONTANCIRCULATION

Dr Bijilesh uSenior Resident,

Dept. of Cardiology,Medical College, Calicut

• Normal mammal cardiovascular system double circuit connected in series—systemic—pulmonary

• powered by a double pump —the right and left heart

• 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

• 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

• 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

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

SELECTION OF PATIENTS 1978, Choussat et al

• 10 criteria for optimal results following the Fontan

1. age at operation between 4 and 15 years2. presence of normal sinus rhythm3. normal systemic venous connections4. normal right atrial size5. 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 aorta8. normal left ventricular ejection fraction ≥ 60%9. absence of mitral valve insufficiency10. absence of complicating factors from previous surgeries

• 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

• 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 - 2.5 U/m2– unobstructed pulmonary venous return

– Marc Gewillig , Heart 2005;91:839–846. doi: 10.1136/hrt.2004.051789

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

• 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

• 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

• 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

• 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

• 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

• 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

• 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

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

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

• When patients reach 1–5 years of age total cavopulmonary 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

• Internal conduit - pass through the right atrial chamber

• External conduit - run completely outside the heart to the right side of the right atrium

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

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

• 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

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

• Now, fenestrations are seldom created during the completion of the Fontan – improved patient selection and preparation– improved staging

• FONTAN PHYSIOLOGY

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

• 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

• 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.

• 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

Early diastolic dysfunction

• 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

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

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

Systemic vascular bed

• Many studies have reported uniformly elevated systemic vascular resistance after Fontan

• Senzaki H, Masutani S, Kobayashi J, et al

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 2 1997;96(5):1507–12.

• 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

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

• 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 15 1995;91(2):372–8.

• 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

• 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 9 1999;99 (9):1215–21.

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

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

• 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

• 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

• 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):

• COMPLICATIONS OF FONTAN CIRCULATION

• 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

• 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

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

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

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

• 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

• 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

Arrhythmia

• 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

• 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

• 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

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

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

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

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)

• 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

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

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

• 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%

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

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

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

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.

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.

• 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

• 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

• 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)

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%)

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

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 -36.7%– 1982 to1989 - 15.7% – 1990 or later - 1.9%

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

• 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

• 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

Predictors of Thromboembolic Death in PerioperativeSurvivors

• Atrial fibrillation • Lack of aspirin or warfarin therapy • Thrombus within Fontan

Heart failure

• 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.

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.

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