Transcript Fontan Circulation

Fontan Circulation
Leilani Mullis, MD
George Sheplock, MD
December 19, 2007
Fontan Circulation
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Fontan Procedure
Fontan Physiology
Patient Selection
Post-Fontan Complications
Fontan Outcomes
Post-Fontan Pregnancy
Anesthesia Implications
Fontan Procedure
• First described in 1971 by Francis Fontan
• It is used to treat complex congenital heart diseases
when bi-ventricular repair is not possible:
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Tricuspid atresia
Pulmonary atresia
Severe pulmonic stenosis
Single ventricle
Hypoplastic left or hypoplastic right heart
• The above conditions rely on one functional ventricle to
maintain systemic and pulmonary circulations that are
not connected in series but in parallel
Fontan Procedure
• A single ventricle parallel circuit creates 2 major
disadvantages:
– Systemic arterial desaturation at rest
– Chronic volume overload to the ventricle
• Without surgical intervention, there is about a
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90% mortality before age 1
A completion Fontan is the definitive palliative
step in a series of surgeries used to improve
oxygenation and cardiac function
How to achieve a Fontan Circuit
• At birth, it is impossible to create a Fontan
circulation:
– PVR is elevated for several weeks
– SVC and IVC veins and pulmonary arteries
may be too small
• A staged approach allows the body to
adapt progressively to the different
hemodynamic conditions
How to achieve a Fontan Circuit
• Neonatal period
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Achieve unrestricted flow from the heart to the aorta
Improve limited flow to the lungs
Achieve unrestricted blood return to the ventricle
The infant is allowed to grow for several months
• Pulmonary vasculature will develop more
• PVR will stabilize
• The heart will be subjected to chronic volume overload
• Ventricular function may deteriorate
• Expect mild progressive desaturation of the infant
How to achieve a Fontan Circuit
Normal Heart
Single Ventricle – BT Shunt
http://www.cincinnatichildrens.org/health/heart-encyclopedia/anomalies/sv.htm
How to achieve a Fontan Circuit
• At age 4-12 months
– The superior vena cava will be connected to
the pulmonary artery (Glenn)
• This will decrease the volume load to the
heart
– The patient will remain cyanotic as the
desaturated blood from the IVC is still allowed
to flow to the aorta
How to achieve a Fontan Circuit
Single Ventricle – BT Shunt
Single Ventricle – Bidirectional
Glenn
http://www.cincinnatichildrens.org/health/heart-encyclopedia/anomalies/sv.htm
How to achieve a Fontan Circuit
• At 1-5 years of age
– The Fontan circuit is completed by connecting the IVC
to the pulmonary artery
Single Ventricle –
Bidirectional Glenn
Single Ventricle –
Completed Fontan
http://www.cincinnatichildrens.org/health/heart-encyclopedia/anomalies/sv.htm
Fontan Modifications
Fontan surgical techniques: Classical atriopulmonary connection (A), Lateral tunnel (B),
and extracardiac conduit (C)
d'Udekem, Y. et al. Circulation 2007;116:I-157-I-164
Copyright ©2007 American Heart Association
Fontan Physiology
• The sub-pulmonary ventricle is bypassed
• Systemic venous return is diverted directly into
the pulmonary arteries
– Goal is to provide adequate pulmonary blood flow and
cardiac output with minimal elevation in venous
pressure
• Systemic and pulmonary venous returns are
separated:
– Cyanosis is relieved
– Volume loading on the ventricle is significantly
reduced
Patient Selection
• After a Fontan operation, the left atrial pressure and the
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transpulmonary gradient must be low in order for the
repair to be successful
Pre-op cardiac requirements:
– Unobstructed ventricular inflow
– Unobstructed ventricular outflow
– Reasonable ventricular function
• Pre-op pulmonary requirements:
– Good sized pulmonary arteries
– Near normal pulmonary vascular resistance
– Unobstructed pulmonary venous return
Fontan Circulation Complications
• Complications after Fontan repair are
common and are related to:
– Increased venous pressure
– Increased venous congestion
– Chronic low cardiac output
Fontan Circulation Complications
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Early and late mortality
Mild to moderate exercise intolerance
Residual cardiomegaly
Ventricular dysfunction
Rhythm and conduction disturbances
Hepatomegaly
Lymphatic dysfunction with protein losing enteropathy
Systemic venous thrombi
Ascites
Peripheral edema
Fontan Circulation Complications
• Ventricular Function
– All post-Fontan hearts have a ventricle that is
dilated, hypertophic and hypocontractile
– Dysfunction may be caused by the congenital
malformation itself, previous surgery or the
abnormal hemodynamic changes encountered
through the various stages of palliation
Fontan Circulation Complications
• Ventricular Function
– During the first months after birth, the
ventricle will always be volume overloaded
• Ventricular dilation and spherical reconfiguration
• Cardiac overgrowth
• Eccentric hypertrophy
• After the Fontan completion, some
normalization will occur
Fontan Circulation Complications
• Ventricular function evolves from being volume
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loaded and overstretched to overgrown and
underloaded
Systolic and diastolic dysfunction are common
Reduced preload is the dominant factor
contributing to poor ventricular function
Inotropes, afterload reducers, vasodilators and
B-blockers are generally ineffective
Pulmonary vascular resistance will control
cardiac output
– Improving pulmonary blood flow will improve cardiac
output
Fontan Circulation Complications
• Predisposition to atrial dysrhythmias
– Up to 40% of patients 10 years post-op
– Most commonly intra-atrial re-entry
tachycardia or atypical atrial flutter
– Survival depends on ventricular contractility
and vascular resistance
– Safest treatment is immediate DC
cardioversion
– Long term treatments include medication,
ablation, pacemaker, Fontan take-down
Fontan Circulation Complications
• Predisposition to coagulopathies
– Thrombosis is more likely in patients with low
CO and venous stasis
– Increased incidence of coagulation factor
abnormalities because of hepatic congestion
• Protein C
• Protein S
• ATIII deficiency
– Anticoagulation of all patients is controversial
Fontan Outcomes
• Despite the abnormal circuit, most
patients with a Fontan circulation can lead
a nearly normal life, including mild to
moderate sport activities
• More than 90% of hospital survivors are
NYHA functional class I or II
• Patient’s remain slightly desaturated with
values in the low 90s
Fontan Outcomes
• University of Melbourne
– 305 consecutive Fontan operations between
1980-2000
– 10 hospital deaths (3%) none after 1990
– 20 year survival was 84% (257 pts in longterm follow up)
– Freedom from Fontan Failure was 70% at age
20
Fontan Outcomes
• University of Melbourne
– Fontan failure was defined as:
• Death
• Fontan Take-down
• Transplantation
• NYHA functional class III or IV
Fontan Outcomes
• Boston Children’s Hospital
– Intermediate-term follow up study
– 220 pts aged 11 mo to 32 years
– Lateral tunnel Fontan between 1987 - 1991
– 91% survival at 10 years
– 87% Freedom from failure at 10 years
Post-Fontan Pregnancy
• Normal pregnancy
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30-40% increase in CO by 24 weeks
30-40% increase in circulating blood volume
Decreased SVR
Myocardial oxygen consumption increases 20%
Heart rate increases 15-20%
• Fontan patients may develop “right heart” failure
symptoms
– Atrial arrhythmias, peripheral edema, ascites
– Increased risk of venous thrombosis/PE
Post-Fontan Pregnancy
• Of 39 completed pregnancies reported in
the literature, 16 patients experienced a
decline in NYHA functional status
• Overt heart failure occurred in 4 patients
• Spontaneous abortion rate 50% (normal
population 10-15%)
• Increased risk of premature delivery
Anesthetic Implications
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Multi-disciplinary pre-operative approach is mandatory
SBE prophylaxis
Anticoagulation
Maintain adequate intravascular volume
Ventilation
– Spontaneous ventilation provides significantly increased
pulmonary blood flow when compared to positive pressure
ventilation
– Avoid hypoxemia and hypercarbia (increase PVR)
– If positive pressure ventilation is necessary, low rates, short
inspiratory times, low PEEP and moderately elevated tidal
volumes (~15/kg) are recommended
Review
• The Fontan procedure is considered palliative and
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enables survival for several decades
In a Fontan circulation, systemic venous return is
diverted directly into the pulmonary arteries
Complications after Fontan are related to increased
venous pressure, increased venous congestion, and
chronic low cardiac output
Post-Fontan anesthetic goals include maintaining
adequate preload and minimizing increases in pulmonary
vascular resistance
References
• D’Udekem, Y., et al. The Fontan procedure: Contemporary
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techniques have improved long-term outcomes. Circulation. 2007.
116: I-157 – I-164
Gersony, D., et al. Management of the postoperative Fontan.
Progress in Pediatric Cardiology. 2003. 17: 73-79
Gewillig, M. The Fontan Circulation. Heart. 2005. 91: 839-846
Redington, A. The physiology of the Fontan Circulation. Progress in
Pediatric Cardiology. 2006. 22: 179-186
Walker, F. Pregnancy and the various forms of Fontan Circulation.
Ed. Heart. 2007. 93: 152-154
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