Transcript Slide 1

FONTAN
CIRCULATION
Dr Bijilesh u
Senior 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
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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 years
2. presence of normal sinus rhythm
3. normal systemic venous connections
4. normal right atrial size
5. normal pulmonary arterial pressure (mean≤ 15 mmHg)
6. low pulmonary vascular resistance (4 Woods units/m2)
7. adequate-sized PA with diameter ≥75% of the aorta
8. normal left ventricular ejection fraction ≥ 60%
9. absence of mitral valve insufficiency
10. absence of complicating factors from previous surgeries
• 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
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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)
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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
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
• 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.
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
• 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 reentry 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
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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
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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
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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 Perioperative
Survivors
• 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