Download single ventricle indications and evolution

1/23/2009
SINGLE VENTRICLE
INDICATIONS AND
EVOLUTION
Mohammed Al Aklabi
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At the end of the talk you
should be able to…
Identify group(s) of lesions that function
physiologically as single ventricles
 Identify how these babies present to medical
attention
 Know key features of pre-operative
stabilization and management
 Identify the basics and indications of the
staged operative approach and postoperative management

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3 main ways babies present with
congenital heart disease…
1.
2.
3.
SHOCK (obstructed flow to body)
“BLUE” (obstructed or restricted flow to
l
lungs)
)
HEART FAILURE (excess volume load, ie
large AV canal defect)
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INTRODUCTION
90% of children with single ventricle
lead good quality life with minimal
restrictions.
 Ongoing challenges.
 Many
M
unresolved
l d controversies.
i

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EMBRYOLOGY



Mechanisms and theories
Poor alignment of the common AV valve with
Ventricles.
Incomplete septation of the ventricular chambers.
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Ventricular septation

Ventricular septation is
a complex process
involving different
septal structures from
various origins and
positioned at various
planes.
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EMBRYOLOGY


Formation of the
outflow tract and
vascular septation.
The cardiac outflow
tract includes the
ventricular outflow
tract and the
aortopulmonary
septum.
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ANATOMY
Van Praagh’s segmental approach
 3 main segments
 Situs of the patient
patient’s
s heart: S or I
 Looping of the ventricles: Dextro or
Levo (D or L)
 Location
L
ti off the
th greatt vessels:
l
Dextroposition or Levoposition

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Anatomy
RV morphology


Heavily trabeculated
Multiple
p chordal
attachments of the
tricuspid valve to the
ventricular septal
surface
LV morphology


Smooth finely
trabeculated
endocardial surface.
Tow papillary muscles
on the free wall (not
p
on the septum
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Anatomic variants of the single
ventricle:
NOT just hypoplastic left heart syndrome
(HLHS)
 All generally have mixing of systemic /
pulmonary venous return
 May
y also have obstructed venous return

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Single ventricle with obstruction to systemic
outflow
Classic HLHS (small left-sided structures with
aortic atresia)
 Critical aortic stenosis/coarctation
 Interrupted aortic arch
 Mitral valve atresia
 Tricuspid atresia (with transposition of great
arteries

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Obstruction to pulmonary outflow
Tricuspid atresia (normal related great
arteries))
 Pulmonary atresia
 Ebstein’s anomaly

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Major single ventricle anomalies
Tricuspid Atresia including Pulmonary Atresia.
( first successfully managed in 1960s by Fontan)
 Double inlet single ventricle
 Unbalanced complete AV canal.
 Heterotaxy: asplenia/polysplenia syndrome and
atrial isomerism.
 Mitral Atresia including HLHS.

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Pathophysiology
Parallel versus in series circulation
 In normal biventricular circulation, blood has
pass through
g the
no choice other than to p
systemic resistance.
 Single ventricle has parallel circulation and
flow will depend on both pulmonary and
systemic resistances
 Balanced single ventricle

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Clinical Features
Dependent on the balance of blood flow
between the systemic and pulmonary circulation
 Spectrum
S t
off symptoms
t
based
b d on severity
it off
obstruction
 Cyanosis, CHF, or shock

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Key feature for presentation and
management decisions is:


Presence of outflow obstruction to
lungs OR body? (or both)
Is atrial septum open or “restrictive”
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The importance of the atrial
septum…
Single ventricles must have complete mixing at
atrial level
 Restrictive defect will cause high CVP (3rd
spacing of fluid…) on systemic side
 Pulmonary venous hypertension due to high LA
pressures can cause significant hypoxemia

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Systemic outflow obstruction
lesions cont’d…




Ductal dependent SYSTEMIC flow
Ventricular outflow to lungs predominantly
R  L shunt at ductal level
If no prenatal diagnosis, will present with SHOCK as
ductus closes:
Poor perfusion, pulses, metabolic acidosis
 Cyanosis due to profound low systemic output
 Often accompanying end organ failure (kidney, liver, CNS…)

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Keys to adequate resuscitation…
RECOGNITION!
 Ductal dependent lesions just as common as
sepsis
p in neonatal shock
 ABC’s--usually involves intubation, sedation
 Correct metabolic acidosis, usually need fluid
boluses +/- inotropy

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Resuscitation cont’d…

Prostaglandin infusion!
 Any neonate in shock should be started on PG’s
 Opens ductus
 Improves blood flow in ductal-dependent
ductal dependent lesions or
inter-circulatory mixing in D-TGA
 Dose 0.01-0.1 mcg/kg/min
 Side F/X include apnea, vasodilation, fever
 If worsening
i hhypoxia
i thi
thinkk off pulmonary
l
venous
obstruction
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Resuscitation cont’d…
Aim for oxygen saturation 70-85% (ie not
FiO2 = 100%)
 Beware of potential for too much pulmonary
blood flow (over-circulation) as PVR falls in the
first few days
 Tolerate “highish” PaCO2 to restrict pulmonary
blood flow (ductal-dependent systemic
circulation)

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Diagnostic Workup







A thorough clinical assessment.
ECG.
Ch t x-ray.
Chest
Oximetry
Echocardiogram evaluation.
Cardiac cath.
MRI
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Surgical management
Goals :




Achieve optimal systemic oxygen delivery in
conjunction with low systemic venous pressure.
Optimizing compliance of the single ventricle.
Optimizing pulmonary arteries growth.
Ensure patient will be candidate for Fontan type
operation in the future.
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Neonatal palliation-stage 1








pulmonary
l
bl
blood
d
flow:
Inadequate:
Blalock shunt
Central shunt
Atrial septectomy
TAPVD repair
Excessive :
PA band

SSystemic outflow
fl
obstruction:
Damus kaye stansel
Damus-kaye-stansel
 Norwood procedure

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Neonatal palliation-stage 1




Surgery for inadequate
pulmonary blood flow
Classic Blalock shunt
Modified Blalock
Central shunt
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Surgical stages
Stage 1: Norwood type surgery
 First week of life
 Stage 2 : Bidirectional cavo-pulmonary
connection
i ( Gl
Glenn shunt
h )
 4 – 6 months of age
 Stage 3 : fenestrated Fontan
 1 – 5 years

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Norwood operation

Classic Norwood
operation:
Blalock-Taussig shunt 
3.5 or
o 4 mm graft
g a from
o
innominate or subclavian
artery to pulmonary
artery
 Arch augmentation
(d ff
(different
techniques)
h
)
 Atrial septectomy

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Modified Norwood operation-Sano




Archh augmentation
A
i
Right ventricle to PA
conduit (5 mm usually,
dependent on size)
D
Described
ib d initially
i iti ll b
by
Norwood but
abandoned (large shunts
used)
Resurrected in Japan by
Sano
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Sano modification cont’d…
Published data: showing less need for “ICU
care” to manipulate circulatory balance
 Seems less prone to sudden circulatory
collapse
 In 2003, malec et al described mortality
improvement from 35% with classical
Norwood to 5% with Sano

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Post-operative management…
G
General
l principles:
l
 Similar
to pre-op management of circulation in series
with addition of the effects of CPB on PVR/myocardium
 Emphasis has been on balancing PVR/
/ SVR with
respiratory or pharmacologic management
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Post-operative management…
Emphasis on central venous oxygen saturation to
estimate adequacy of O2 delivery
 Remember that difference between arterial and
mixed venous saturation is more indicative of
overall oxygen delivery

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Results
985 neonats between 1994 – 2000 with critical
aortic stenosis or atresia, 710 of them
underwent stage 1 Norwood procedure.
 Survival was 76% at one month,, 60% at one
year and 54% at five years
 Risk factors for death included low birth weight,
smaller ascending aorta, and older age at the
time of the Norwood procedure

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Results cont…



By 18 months, 58% of patients undergone a
bidirectional Glenn shunt
Of those who underwent Glenn shunt, 79%
y achieved a third - stage
g Fontan
successfully
circulation within 6 years.
Mortality for the third stage was 9%
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Glenn shunt
SVC connection to
RPA
 Cardiac cath. Pre op
 Measure
M
pulmonary
l
resistance
 4-6 months of age.

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Fontan operation



Completion cavopulmonary connection
IVC connected to PA
L
Lateral
l tunnell or
extracardiac fontan
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Fontan operation
Extracardiac Fontan
With fenestration.

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Fontan operation

Fontan risk Factors:
Pulmonary arterry distortion
 Pulmonary artery resistance > 2 wood units.
 AV valve regrgitation
 Systemic ventricular dysfunction

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Is fenestration necessary?


Some reports suggested fenestration is not helpful
as described by Thompson et all from San Francisco
in 1999.
Other reports
p
suggest
gg that fenestration is helpful
p in
reducing morbididty, partiuclarly pleural effusions,
shortening hospitalization and possibly reducing
mortality
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Developmental outcome

In 2000 Wernovesky et al reviewed the
developmental outcome in 133 patients following
Fontan procedure at Children Hospital Boston, mean
full scale IQ was 95.7±17.4 which was significantly
below normal
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summary
JJustt lik
like allll congenital
it l heart
h t disease:
di
needd to
t
know where the blood goes/flows
 Counter-intuitive to think of low SpO2 as
being better…
 Rational
 Under certain morphological circumstances,
biventricular repair , although theoretically
possible, may not be advisable.

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