Thank you, and what I'm going to try to accomplish in my talk
is really give a broad overview of our modus operandi
now at Boston Children's Hospital
and when faced with a child with very complex heart disease.
But I want to start off, really, with the definition
of the borderline left heart because I think this varies
from institution to institution and surgeon to surgeon,
and rightfully so.
Really, this is what we're getting at.
You've got a patient who has relatively normal left
sided structures, and has a long term
probability of biventricular circulation
that's closer to 100%.
We're going to have no hesitation
with going with the biventricular repair upfront.
Now biventricular repair is really a fancy term for fixing
whatever lesion-- or lesions--
appears to be abnormal, whether it's
a coarctation repair, or an aortic valve,
or mitral valve repair.
On the other hand, you have a child
who absolutely has no chance of survival with a biventricular
circulation, and we call that, therefore a single ventricle
patient.
And we assume that this patient needs
to have a single ventricle palliation
for the rest of their life.
In between, however, are really a large cadre of patients who
have a potential for a biventricular circulation,
but are really high risk to some degree--
depending upon the institution, and the surgeon,
and the care system--
to achieve that goal of a good long term survival.
And they may be considered borderline
for multiple reasons.
It could be hypoplasia of the left ventricle-- which
is what we're most focused on-- or the aortic valve,
mitral valve disease.
It might be a patient with a neonatal mitral regurgitation.
I was speaking to one of our audience
earlier today who said that, you know,
really when I'm faced with the patient
with neonatal mitral regurgitation,
I don't want to take a biventricular approach.
I'd rather go down a single ventricle pathway.
Reasonable, if you look at the long term
probability of success and you say that that's just not
right in my hands.
But it could be because of pathways
straddling valves, et cetera.
Unfortunately, our approach to these patients
has classically been just two-pronged.
We've got a decision.
We've got a fork in the road here.
Are we going to go down a single ventricle palliative
route, which definitely means that we're going to head
towards the Fontan circulation?
Or do we go down a primary biventricular repair,
and have to ask the questions of, is this child really ready
for a primary biventricular repair?
Are there tools to assist us with this decision making?
That's been a good part of the past 20 years,
trying to decide who can be primary biventricular
repair versus not?
But here's the catch.
We're trying to use tools that will tell us
who will succeed with a one-shot biventricular repair.
And the problem with these tools is that they're not reliable,
number one.
They're not reliable from institution to institution
because there's clearly going to be
variability in the outcomes between institutions.
And number three, it doesn't really
harness the full potential of a child's ventricle.
If you suddenly load a left ventricle
that's not quite ready to handle, of course
it's going to fail.
But does that mean that it could not achieve that?
So this is where the idea of the staged left ventricular
recruitment came in.
We said, well, we don't like being
put between a rock and a hard place.
So why don't we try to pull ourselves from that situation?
Let's try to do this gradually over time.
Let's try to see if we can get the left ventricle
to contribute to the circulation, the most
successful way possible.
So the idea is you take the relatively reproducible outcome
of a single ventricle palliation upfront,
you take the time to maneuver the valve and ventricular
structures, to load the left heart, and eventually,
if you get ventricular growth-- as Dr.
Powell mentioned in his talk--
then you can convert the child to a biventricular circulation.
If not, then you continue down a single ventricle pathway.
The idea here is to really keep your options open,
and to think of a single ventricle palliation
as not being terminal single ventricle palliation,
but in fact, an opportunity to take the time to step back
and to recruit the ventricle.
So if you're faced with a patient
that you feel is high risk, and this may differ from place
to place, palliate first.
Whether it be with a stage one, a PA band, in some cases,
a hybrid.
But don't give up necessarily on the left heart.
Come back and through another procedure
perform surgical rehabilitation of the valves,
the left ventricle, EFE resection,
and try to see if you can recruit the left heart.
And perform this two-ventricular biventricular conversion
more electively.
So distinguishing it from primary biventricular repair
and a staged recruitment followed
by a biventricular conversion.
Now, the downside is more surgical procedures.
And that's one of the things that
has to be considered and weighed against a single ventricle
palliation, but in our hands now, as surgical techniques
have improved, we're not afraid of multiple surgical procedures
anymore.
Our survival from a surgical procedure is improved.
But this really gives you more time
to assess the risk factors for both approaches
and make a more clarified decision
as you commit this child to a long term circulation.
So this is kind of how this might look.
This is a patient with a hypoplastic left heart
syndrome who's had aortic arch hypoplasia, and coarctation,
and borderline left heart structures, so we
term as the borderline LV.
And we performed a postnatal aortic valve balloon dilation
followed by a neonatal palliation with the stage 1
and subsequently performed some work on the aortic and mitral
valves with the goal of really creating
a stable single ventricle circulation.
And then at four to six months of age,
we bring this child back for a bidirectional Glenn
and a left heart rehabilitation consisting
of more work on the aortic and mitral valves, EFE resection
and fenestrated closure of the atrial septal defect.
One point that was brought up in Dr. Powell's talk
is addition of additional blood flow to the left ventricle
by either leaving a RVDPA conduit in place
or adding a shunt.
And if we do that, I would suggest
that you actually separate the shunted side
of the circulation from the Glenn to avoid reversal of flow
in the Glenn.
So the way we do that now is either
by placing a band between the shunt and the Glenn
or a membrane with the fenestration.
And that allows the Glenn pressures not
to be too high if you have a shunt in close proximity.
But note you that the patient still has a single ventricle
circulation, so you haven't burned
any bridges for the single ventricle repair
if the left heart does not have a chance to grow.
In patients with an unbalanced AV canal defect,
you can leave the ventricular septal defect open
and simply fenestrate the atrial septum,
and that actually is good for the AV valve that's
leaking most commonly in the single ventricle circulation.
Anyway, because it helps stabilize the central portion
of the leaflet.
So we found that there are multiple benefits
to taking this approach, even if you don't end up going down
a biventricular circulation.
So finally, we give it time.
Six months to two years of age, we're observing these patients
through echocardiogram.
If there are any changes to the circulation, particularly
if the trans-septal gradient increases
or if the patient starts to develop any concerns for SVC
syndrome, we bring them back and perform catheterization
to either dilate or stent the atrial septum
or manipulate the shunt.
At two to four years of age is when
we perform the assessment that Dr. Powell mentioned earlier,
with an MRI catheterization and echocardiogram,
and look for predictors of a successful biventricular
circulation.
I won't go into a lot of the details
since that was covered in Dr. Powell's talk,
but we review all the data and make
a decision regarding biventricular conversion
versus heading to a Fontan.
And as you saw earlier, there is clear evidence
that the left ventricle can grow.
And I think intuitively we all feel that children do
have this potential for growth.
Whether this growth involves recruitment of new myocytes
or it's simply a dilation of ventricle is still unclear.
But what is clear is that you have to restrict
the atrial septal defect.
You have to push blood flow into that left ventricle in order
for it to grow.
If you don't we've found that the ventricle does not grow.
This slide here shows patients who've had
staged left ventricular recruitment,
either with or without atrial septal defect restriction.
And the top curve are the patients
who've had ASD restriction compared
to the patients on the lower curve who
had an ASD that was left unrestricted
at the time of recruitment.
So you have to restrict the atrial septal defect.
So this is our experience at latest check.
We've attempted a staged left ventricular recruitment in 120
patients, and this includes hypoplastic left heart
syndrome, it includes unbalanced AV canal, double outlet right
ventricle with unbalanced canal, and a whole cadre of patients.
Biventricular conversion was performed in 51 patients.
Thank you for that reminder.
And 69 patients are currently in a single ventricle palliation
state.
So that means that some of them are still awaiting potential
for either biventricular conversion versus heading down
the Fontan pathway.
This slide is simply to show that there have been patients
who have either died, had a transplant,
or had their circulation taken down.
It's 11 out of the 51.
And I think the important learning point from this
was that the patients with the hypoplastic left heart complex
syndrome variants--
that is patients with EFE--
are the ones who tend to do worse than the unbalanced canal
patients who do not have EFE.
And this is really starting to factor into our approach
for selecting patients for the biventricular conversion.
And I think one of the issues is really
their pre-operative left ventricular
and diastolic pressures tend to be higher.
And so we're trying to use this data to modify our selection
techniques, and we're integrating,
on a regular basis, the new data that comes through
to help optimize or outcomes.
So in summary, the tools to predict
success of a, boom, two ventricle repair right now,
I think, are poor.
And I think they underestimate the true biventricular
potential of a child.
I think a high risk primary biventricular repair is
probably worse than a single ventricle,
so I wouldn't advocate for that.
But buy some time--
initial single ventricle palliation.
Don't commit necessarily to that,
but use that as an opportunity to recruit the left ventricle.
Just remember that atrial septal defect restriction enforcing
more flow into the left ventricle
is a critical portion of the recruitment strategy.
But in patients who demonstrate a growth
of that left ventricle, we've had success
with converting to a biventricular circulation.
And patients with the EFE have worse outcomes
compared to the AV canal or other types of patients.
Thank you very much.
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