Successful Biventricular Conversion in Single Ventricle Patients

Melanie Cole (Host): Advancing health. Personalizing care. At Memorial Hermann, this is our mission. This podcast shares the science and stories behind those efforts. Welcome to Advance, the podcast series from Memorial Hermann. I'm Melanie Cole. And today, we're exploring successful biventricular conversion in single ventricle patients.

My guest is Dr. Jorge Salazar. As an affiliated physician with Children’s Memorial Hermann Hospital, Dr. Salazar is the Executive Co-director of the Children's Heart Institute, a collaboration of UTHealth Houston and Children's Memorial Hermann Hospital. Dr. Salazar is also a professor and Chief of Pediatric and Congenital Heart Surgery at McGovern Medical School at UTHealth Houston. He's also the Chief of Pediatric and Congenital Heart Surgery at Children's Memorial Hermann Hospital.

Dr. Salazar is here with us today to share more about biventricular repair in which he and his team can rearrange cardiac connections to enable normal two-ventricle circulation in eligible children born with a single ventricle.

Dr. Salazar, it's a pleasure to have you join us today. Can you tell us a little bit about where the journey begins for patients who could be considered for biventricular repair?

Dr. Jorge Salazar, MD: Well, first of all, it's great to be here with you. Thank you. This journey begins frequently in the womb with fetal diagnosis of a child with what seems to be a univentricular heart. And we have advanced tremendously in the last 20 or 30 years in the management of univentricular hearts or single- ventricle hearts, and being able to offer them the Fontan palliation; frequently, starting with the Norwood, or stage-one procedure, then followed by the Glenn and the Fontan, and the Fontan palliative steps.

As you know, my colleagues know, this has been very successful over the last few decades in offering life to children who otherwise would have no chance of a life. But there are some consequences and limitations associated with single- ventricle palliation and Fontan physiology. And those consequences can oftentimes, if not many times, lead to heart failure, need for heart transplantation, limitations to life and the ability to live a normal life and, then unfortunately, some of the children actually are not candidates for transplant and can pass away.

And so given that I've been in practice now for almost 20 years, and then 10 years before that, and importantly, I'm a father and I have my own children, I've been very determined, as others, to find other alternatives to the single -ventricle palliative sequence or the Fontan palliation, so that we could give kids a truly normal life as opposed to a palliated heart. And so, this is where all this has come from and we receive referrals from all over the world for children who may be candidates or may be candidates for conversion to a biventricular heart. We also receive a lot of referrals from around the world for kids who have already had their Fontan and are failing. And as a result, they're being referred for transplant or for consideration for biventricular conversion.

Host: Well, then tell us a little bit more about biventricular repair. Is it basically creating larger functioning hearts? How is this helping patients?

Dr. Salazar: Well, the key is to see the potential in the child who has been considered to be a single ventricle. Many of the children are considered to be single ventricles because one of the two pumping chambers or ventricles are too small. But many times, there is a ventricle there, it's just relatively small compared to the other. And these principles apply to both the small left hearts, as well as the small right hearts. But to generalize, I'll talk more about the small left hearts.

So, what we do is we recognize that there is a small left heart present in a child who's already gone through some of the steps of the single ventricle palliation, and we do something called a ventricular recruiting procedure where we can actually get the left ventricle or the right ventricle to grow. And I can explain how we do that in a second. But the big picture is that if one side of the heart is too small, we and others have discovered ways to get those ventricles to grow so that after a couple of stages, usually at least one or two stages, we can actually convert the heart to a biventricular or normal heart repair.

Host: Well then, expand for us a little about patient selection. And as this is an alternative option for patients who would typically undergo or maybe have previously undergone traditional treatment methods, speak about patient selection criteria.

Dr. Salazar: Well, the key is that they have to have something to work with because, you know, frankly, we can't conjure a ventricle out of thin air. You know, that would be God's work, not our work. But for kids that have some ventricle present, we promote flow through the small ventricle by increasing blood flow through the lungs, back to the left atrium and then streaming or redirecting that blood to the small ventricle, usually the case being the left ventricle. And we find that over time, by redirecting the blood flow into the left ventricle, that not only the left ventricle, but also the mitral valve can grow. And we now have many, many children where we've done this successfully. The left ventricle has grown, and then we can actually convert them from the single- ventricle palliation. We basically take down the single-ventricle palliation, which may include the Damus–Kaye–Stansel connection. It may include doing some intracardiac work in terms of baffling. We convert them from that single ventricle arrangement to literally a normal heart repair.

The key to this is that it be done in stepwise fashion. And the first step, which is the ventricular recruiting procedure, after we do that, we follow them with serial echocardiograms, MRIs, as well as heart catheterizations. So that way, we prove ahead of time before we consider the actual biventricular conversion that they're actually ready. And essentially, what we do is we simulate the full septation and the biventricular conversion in the cath lab and prove that the left atrial pressures and the left ventricular end diastolic pressures are appropriate to be able to justify the surgery, which actually completes the biventricular conversion.

I think it's very important to point out that this is not, you know, experimentation or wishful thinking, but it's done on the basis of very thoughtful interrogation of the child's heart in stepwise fashion before we actually proceed with the bigger procedure, which is the biventricular conversion.

There's another group of children who have a small right ventricle and the way that we recruit the right ventricle is, yes, by promoting more flow through the right ventricle, in particular by restricting the atrial septal defects. But the other way that we get the right ventricle to grow is by doing something called the right ventricular overhaul. And a right ventricular overhaul essentially is going into the right ventricle and coring out all of the unnecessary muscle bundles inside the right ventricular chamber, which are limiting the diastolic capacitance. And as a result, we get the right ventricle to grow by taking out those unnecessary sort of space-occupying muscle bundles that are present inside the chamber.

The good news with the right-sided patients is that we can oftentimes double the size of the right ventricle in doing this. And even if we may still end up requiring a Glenn or a bi-directional Glenn to help offload the right ventricle, the inferior vena cava is able to be reconnected back to the right atrium and therefore pass through the right ventricle. And as a result, you end up with what's called a one and a half-ventricle arrangement, which is fully septated and, importantly, avoids the Fontan physiology that we all know can cause so many problems in the long-term.

Host: Absolutely fascinating, Dr. Salazar. And thank you for telling us about some of the technical considerations and sharing that with other providers to help achieve better outcomes. Now, given the complexity with increasingly advanced treatment algorithms that are adding new options to your armamentarium of available therapies, how important is multidisciplinary management? Can you please speak about this approach and has the introduction of these kinds of therapies involving multiple subspecialists and the utilization of a multidisciplinary team been ideal for managing these complex patients?

Dr. Salazar: Well, I think you really hit the nail on the head there. I think it's actually the only way to manage these complex patients. There is no one individual on the team that is able to do this on their own. And it's because of the input and careful consideration of all of the team members that come together in unison for the sake of the child and for the sake of the family that we're able to achieve these types of advancements for these children. So, whether it's the imaging doctors, the critical care doctors, the anesthesiologists, the surgeons, the perfusionists, you know, really our nursing staff, all of the different members of the team are critical to be able to achieve these outcomes. And frankly, we're really excited to be able to offer these solutions to these kids because the Fontan is good and it's certainly better than nothing. But we've been doing this for a long time and we've seen the limitations of the Fontan circulation over time for these kiddos. And they do end up living a life that is, you know, moderately limited and sometimes severely limited. So because of the teamwork that's involved here over really many decades that we've developed these capabilities that we're able to give these families and these children the opportunity for a normal life.

And I can tell you speaking as a father, I have many children of my own, there's nothing that I want more than for my child to have a better life than me and to not suffer. And as a result, you know, all of us are extremely motivated in a very personal level to be able to give these kids, the children of other parents like us, the opportunity for a normal life.

Host: Such an important point, Dr. Salazar. And in terms of follow up care, when transitioning these pediatric patients with congenital conditions to adult care, and as you mentioned, it could go over many decades, can you just give us a brief overview of follow-up, some of the barriers? Just what you want other providers to know about transitioning these children as they go into their tweens and teens and beyond.

Dr. Salazar: Well, having a transition plan for the pediatric congenital patients to adult congenital providers is extremely important, something that our center and many other centers focus on quite intently. And this is a lifetime commitment to these kids, to their families and these kids who end up becoming adults, of course, very important to maintain continuity of care and that high quality throughout the continuum of the child's entire life as they become adults, even as they start becoming older adults where they develop what we say old people problems or acquired problems. So that kind of continuity between the pediatric and adult congenital ward is extremely important and certainly something that we are proud to say is seamless at our institution.

Host: As we get ready to wrap up, can you tell us about some promising new therapies? Are there any game changers? Tell us about the future of biventricular repair in this program and anything else you'd like to share with other providers?

Dr. Salazar: Well, something that we're extremely excited about, and in fact, I literally just finished doing one of these operations today before we got on this podcast is rather than having the kids go down the single ventricle pathway in the newborn and infant period, what if we never allow them to go on that pathway? What if we just do the full biventricular repair upfront as newborns? It is more surgery in the newborn period, but it saves them from going down the single-ventricle pathway and then having to back them out of that pathway by undoing what's been done and then redirecting them down the biventricular pathway.

What we're doing now, which I'm very excited about is we're actually offering upfront single-step biventricular repairs in newborns, and it saves the children a tremendous amount of morbidity and steps associated with the single-ventricle pathway. It also saves the families a lot of, you know, difficult steps that they have to go through. By offering a child a normal heart repair upfront in the newborn period, yes, it is a little bit more work for me, but it's so worth it because their physiology is normal and their outcomes are better. And it's really a blessing I think is the right word that we can offer these repairs to these kiddos and these families now upfront in the newborn period.

Host: What an exciting time to be in your field, Dr. Salazar. Thank you so much for joining us today and sharing your incredible expertise for this topic. To refer your patient or for more information on biventricular conversion in single-ventricle patients, please visit memorialhermann.org/childrensheart. That's Memorial Hermann with two N's.

That concludes this episode of Advance, the podcast series from Memorial Hermann. Please remember to subscribe, rate and review this podcast and all the other podcasts in our library. I'm Melanie Cole.