The Fontan Operation
The Fontan operation is performed for final palliation of functional single
ventricles[260]. Many modifications have been made and written about. A lateral-tunnel,
fenestrated Fontan is appropriate in most cases, however, the external conduit fenestrated
or non-fenestrated Fontan is also an excellent procedure[171, 337, 330].
Stage I: preparation & cardiopulmonary Bypass
- A monitoring line should always be placed in either of the internal jugular or
subclavian veins. This is important for later hemodynamic assessments.
- Standard procedures for re-do sternotomy are carried out.
- Cardiopulmonary bypass is started using bicaval cannulation and single arterial
cannulation, and the patient generally cooled to 25° C.
The venous cannulas should be kept as far away from the heart as possible. This is
important to allow for sufficient room in placing the intra-atrial tunnel or extra-cardiac
conduit.
The superior vena cava cannulation site should also be high. If the Fontan is being
performed following a bi-directional Glenn operation, it is important to encircle the
superior vena cava following cannulation.
A straight THI arterial cannula works best for re-do aortas. It is of the proper
stiffness, and can be more easily guided into the aorta in these circumstances.
- The left ventricle is vented with a cannula placed in the right superior pulmonary vein.
- Attention is given to cerebral protection and perfusion:
In the presence of significant aorto-pulmonary collaterals, hyperventilation can steal
blood from the brain to the lungs, and should be avoided.
The superior vena cava should invariably be cannulated, in order to decrease cerebral
venous pressure and increase cerebral perfusion pressure. This is of especial importance
when coming of cardiopulmonary bypass when there be may hypotension in the presence of
elevated central venous pressure. The preoperatively placed upper central venous pressure
monitor is of indispensable help in these considerations.
Stage II: Dissection
- The area between the aorta and the pulmonary artery is dissected at this point. This is
often a difficult dissection, especially in patients returning to operation for a third
time, as in staged-reconstruction for hypoplastic left heart syndrome.
The pulmonary artery is separated from the aorta. The under-surface of the aorta is
generally dissected away from the pulmonary artery, as opposed to the converse situation.
It is often helpful to start the pulmonary artery dissection on the right side of the
superior vena cava, as adhesions in this area may not be as dense as below the aorta. The
pulmonary artery should be dissected well underneath the aorta, if not on the left side of
the aorta, depending on the need, if any, for pulmonary artery angioplasty.
The relationship of the superior vena cava and right atrium should be clearly
understood from the preoperative studies and the prior operative notes. If there is
superior vena cava - right atrium discontinuity, then the area on the superior surface of
the right atrium is dissected, with care given to staying out of the right pulmonary
artery and the left atrium. If the superior vena cava and right atrium are in continuity,
then the dissection plane is taken anterior towards the innominate vein.
The circumference of the aorta is dissected free, and an umbilical tape placed around
it, for later use in retraction.
Great care is taken not to use the electrocautery around the phrenic nerves.
- The inferior vena cava and superior vena cava are snared.
- The aortic cross-clamp is applied, and the heart arrested with an infusion of cold
blood-potassium cardioplegia, (30 cc/kg, repeated about every 30 minutes). A temperature
probe is placed in the ventricular septum, and myocardial temperature monitored.
Stage IIIa: Lateral-Tunnel Fenestrated Fontan
- The right atrium is opened, and the edges retracted on silk. Note is made of
cardioplegia flowing from the coronary sinus. Myocardial temperature should drop
appropriately.
The first of two atriotomies is made away from the superior ‘roof’ of the right
atrium, as the latter area will be later used to connect to the pulmonary artery. In
general, the atriotomy is made one centimeter away from the atrioventricular groove,
heading towards the left of the inferior vena cava.
Assurance of an adequate atrial septal defect is made at this time. Occasionally, it is
helpful to cut back on the roof of the coronary sinus in order to extend the atrial septal
defect.
A second atrial incision is made on the superior ‘roof’ of the right atrium, where
the lateral tunnel will meet the pulmonary artery. A trap-door opening is made into the
‘roof’ of the right atrium, in such a way so that the trap-door will open downwards
towards the pulmonary artery to be sewn to its inferior cut edge.
- The pulmonary artery is opened. This is performed on its inferior edge, facing the
trap-door incision into the ‘roof’ of the right atrium. The incision is carried out
towards the take-off of the first right hilar branch, and towards the left pulmonary
artery underneath the aorta.
- The trap-door of the right atrium is sewn to the inferior cut edge of the pulmonary
artery using 6-0 or 7-0 Maxon. The roof of the connection is hooded with an appropriately
tailored piece soft GoreTex patch.
- The lateral-tunnel is placed. A tube of soft GoreTex, sized 12 to 16 mm is chosen
according to the size of the atrium and the distance to the pulmonary veins. The tube is
cut to size, and opened on one side. It is tailored appropriately.
The bottom suture line is placed first. It starts out on the inferior border of the
inferior vena cava, somewhat towards the coronary sinus. The suture line extends
superiorly towards the superior vena cava, and is sewn to the limbus of the atrial septal
defect. It heads towards the left of the superior vena cava. During placement of
the suture line, the tube of GoreTex is tailored appropriately. Once the left side of the
superior vena cava is approached, the top suture line is started.
The top suture line is placed next. The second limb of the suture on the inferior
aspect of the inferior vena cava is taken around the inferior vena cava towards the left,
and carried out on the anterior aspect of the inferior vena cava. It is often helpful to
take a bite of Eustachian valve on the anterior aspect of the inferior vena cava. Once the
crista terminalis of the right atrium is reached, the suture line is stopped and the
fenestration placed (see ‘the lateral-tunnel fenestration’, below).
Once the fenestration is placed, the top suture line is completed, heading towards the
right side of the superior vena cava. This suture line is then completed to the bottom
suture line, the two meeting on the anterior aspect of the right atrium.
The atriotomy is closed, before the aortic cross-clamp is removed, as there is expected
right-to-left shunting through the fenestration.
- The lateral-tunnel fenestration. Typically, a fenestration is placed on the edge of the
lateral tunnel where it meets the crista terminalis. Using either an aortic punch or a
free-hand cut with a No. 11 Bard-Parker blade, 4 mm fenestration is made, and sized with a
Hegar dilator.
A 2-0 Prolene suture is place around the cut edge of the fenestration and brought out
through the lateral wall of the right atrium. The suture is brought out through a large
felt pledget. The Prolene is secured to the cut fenestration edge with three interrupted
sutures of fine 4-0 Prolene or GoreTex.
A second heavy, 2-0 Prolene suture is brought out through the lateral wall of the right
atrium, through the heavy pledge, and tied to the pledget. This ‘opening stitch’ both
secures the large felt pledget to the right atrium wall, and also helps in opening a
closed fenestration. The free strands of the ‘opening stitch’ are tied in a knot in
order to identify them from the ‘closing stitch’.
The fenestration is tested in the operating room. When closed, (with the snare of the
inferior vena cava or superior vena cava temporarily removed in order to fill the lateral
tunnel), no blood should come through the fenestration. When the ‘opening stitch’ is
pulled, it should pull the lateral right atrium wall from the opening in the fenestration.
This operation can be done on the warm, beating heart, so that a calcium-enriched
cardiopulmonary prime is used in order to keep the heart beating.
A non-valved aortic conduit is used that is interposed between the inferior vena cava
and the cavopulmonary anastomosis. It is important to use a wide enough conduit, ones with
a defective valve are especially useful in that they cost less than valved conduits. For a
two-year old, a 20 mm conduit is of sufficient size. The operation is done on a warm,
beating heart. The inferior vena caval anastomosis is done first, after first oversewing
the cardiac end of the inferior vena cava. It is important to size the length of the
homograft before the cannulas are placed, in that the distance from the inferior
vena cava to the PA is often over-estimated with the inferior vena cava cannula in
place (the inferior vena cava cannula tends to pull the inferior vena cava away from the
heart). It is probably better to slightly shorten the graft as opposed to lengthen the
graft, as any kink in the homograft will lead to problems eventually. The slightly curved
end of the homograft is used to gently curve over the pulmonary veins, and is anastomosed
to the cavopulmonary anastomosis. The lateral side of the homograft should be somewhat
shorter than the medial side, the latter being kept somewhat longer in order to be
anastomosed underneath the aorta. Specifically, the pulmonary arteries are extensively
mobilized, and then incised from the take-off of the inferior branch of the right
pulmonary artery to the main pulmonary artery segment underneath the aorta. A 4 mm
hole-punch is then made into the aortic homograft, and a sizable portion of right atrial
appendage is excised. The edge of the right atrial appendage is sewn around the
fenestration, (not edge-to-edge), to complete the operation. A snare may be used around
the atrial side of the fenestration if later fenestration closure is appropriate.
Stage IV: Completing the operation
- With suction being applied both to the aortic root and the left ventricular vent, and
while the coronary arteries are being temporarily occluded, the aortic cross-clamp is
removed.
- The superior and inferior caval snares are released.
- Any needed pleural tubes are placed
- Ventilation is resumed
- The superior vena cava line is clamped and the cannula removed. The superior vena cava
cannula site is repaired with interrupted 6-0 Prolene if there is any distortion.
- The left ventricular vent is removed while a Valsalva is being performed.
- A left atrial line is placed as indicated
- Atrial and ventricular wires are placed.
- The patient is weaned from cardiopulmonary bypass, often on dopamine, 5 - 10 m g/kg/min.
- The inferior vena cava cannula is removed
- The heparin is reversed with protamine
- Diagnostic pressures of the aortic root and the superior vena cava are performed. Pulse
oximetry is followed. Transesophageal echocardiography is performed.
- Most, if not all the pump blood is returned to the patient.
- The aortic cannula is removed.
- Hemostasis and sternal closure are routine.
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