Lovely, thank you, Nandini, for the introduction. Thank you all for your time today. And there we go. I have no disclosures. So in the next 10 minutes, I'm gonna quickly move through some highlights in terms of basic concepts, talk about some recent literature, and identify some future opportunities for improvement, of which there are many. If we think about mechanical circulatory support in its most basic form, we are looking to effectively replace the work of the heart, both arterial perfusion and venous decompression. And if we can do that well, we offer our patients some time, and time is an opportunity for future. We're all quite familiar with ECMO and the technology associated with ECMO. It can be deployed and discontinued at the point of care, i.e. at the bedside. It offers support to a broad range of patients in terms of age, size, anatomy. And it's generally used as a bridge to recovery, a bridge to decision in some cases, and in a few cases, a bridge to transplant. But it's a major Achilles heel, and if you look at the mostly ELSO literature on this, is after approximately 14 days, you see a sharp uptake in the incidence of morbidity and mortality. So it's really a short-duration therapy. Over the past 15 years or so, VADs have emerged as a pediatric therapy, and offer a range of opportunities as well as some limitations. They require deployment and discontinuation in the operating room as opposed to at the bedside. Especially for our smallest patients, there's some limitations in the technology and some anatomic considerations. They have, however, been a very successful bridge to recovery, to decision, to transplant, and are increasingly discussed as a potential opportunity for long-term destination to home and quality of life outside the hospital. They've supported our patients for weeks, months, and in some cases, years. I think cardiac intensives are a bit masochistic in that we revel in unconventional circulations, but for the purposes today, I thought I'd focus on the single ventricle. And in front of you have the three stages of surgical palliation for hypoplastic left heart syndrome, which is one of the more common things that we see. On the far left, the stage one NOR would with BT shunt, or you can have the RV to PA conduit modification. In these patients, you now have the pulmonary and the systemic circulation in parallel. So any mechanical circulatory support is going to have to allow for that, meaning upwards of 150 to 200% the flows of a septated circulation. Glenn's and Fontan's both share passive pulmonary blood flow, which itself is exquisitely dependent on many things, including end diastolic pressure, the function of your AV valve, your pulmonary vascular resistance, and in the setting of your SVC, right or left, cerebral vascular resistance. And so these patients are important in terms of thinking about your venous cannulation strategies and what do you need to maintain preload to your pump, as well as to effectively decompress your central venous circulation and protect your end organs. And this is a growing population of patients, and they are very heavy in terms of resource requirements. If we look in the literature now, almost half of all pediatric patients placed on ECMO for cardiac indications have a single ventricle circulation. And in addition, heart failure in patients with a single ventricle circulation has become the most common indication for transplant in children. So we really need to think about how to do this better and how to have a future. And when you look in the literature, there's increasing conversation about this, quote, fourth stage of single ventricle palliation, which historically has been heart transplant, but recognizing the growing numbers of older and older patients, as well as the limited pool of available donor organs, we're going to have to start thinking outside the box, and we're going to hear about that more with our next speaker, but this is where, quote, destination VADs may come into play. As of right now, patients with a single ventricle circulation requiring mechanical support have a 30 to 50% survival to hospital discharge. So there's lots of opportunity out there. In terms of the stage one patients, these are neonates, typically around four months of age. The most common reasons we think about for mechanical support are postoperative, systolic and diastolic heart failure with refractory low cardiac output state, AV valve regurgitation, arrhythmias, hypoxemia, and cardiac arrest. These are typically kids that are on ECMO, at least initially, and if you go to the ELSA registry for some outcome data, you'll see that the approximate survival to hospital discharge in this group of patients is around 31%. I have, however, put an asterisk by hypoxemia, because that's an important exception to that 31%. In patients with hypoxemia, due to obstruction of the source of pulmonary blood flow, so not low cardiac output state, but obstruction of either your PTB, TT shunt, or your RV to PA conduit, those patients have around 80% survival to hospital discharge, if that's dealt with quickly and effectively, meaning taking the child to the cath lab, taking the kid to the operating room. And if we think about that idea, identifying a lesion and taking care of it efficiently, and as a way to improve chances of decannulation and hospital discharge, then this next article becomes particularly relevant for our practice. This was accepted into JTCVS. I don't believe it's in print yet, but it's looking at the influence of intraoperative residual lesions and timing of ECMO in stage one palliation patients. So this was 20 years worth of data from a single institution, approximately 500, no, 500 patients, with approximately 15% needing ECMO in the immediate postoperative period. And what the authors found was that patients with at least minor intraoperative residual had an approximately fourfold increased risk of postoperative ECMO when compared to those with a perfect or nearly perfect surgery. Those residual were aortic arch issues, AV valve issues, source of pulmonary blood flow, PAs, stanzal, coronary concerns. In addition, the authors also found that approximately half of the patients who required ECMO in that postoperative period, they were diagnosed with at least one residual lesion after being initiated on ECMO support. So what that translates to me as a cardiac intensivist is I have to have a high index of concern about a patient's circulation if I know that there are residual lesions on the handover from the operating room. And if I have a patient following stage one who requires ECMO, then it is up to me to do due diligence to look for those residual lesions and really to advocate for either a cath lab trip or an operating room trip to fix anything that is fixable and ideally do that sooner rather than later and get my patient decannulated and then discharged. Glens and Fontans get a little bit muddier when it comes to mechanical circulatory support and I've batched them into early and late indications. Early indications are similar to what we saw for the stage ones. I've added acute lung disease, remembering that that source of pulmonary blood flow was all passive and cardiac arrest I've put into italics. And the reason being is that I think resuscitation in ECPR and glens and Fontans gives many of us a little bit of angst. And the reason is that if we think about our ideal ECPR candidates, we want a witnessed event, a reversible etiology, an immediate and effective CPR. And if we think back to all those things we discussed about the passive pulmonary blood flow in glens and Fontans, effective CPR is a very difficult, if not impossible thing to do in this circulation and protecting those end organs is very hard. With that in mind, as we think about late indications for glen and Fontan and mechanical circulatory support, the literature around systolic heart failure is fairly optimistic. What is not so optimistic is these patients presenting with diastolic heart failure because that tends to come hand in hand with other problems, things like PLE, so protein losing enteropathy, plastic bronchitis and irreversible end organ dysfunction, primarily renal and hepatic. Chronic arrhythmias in this patient population tend to be due to anatomic or pathophysiologic issues, for example, chronic AV valve regurgitation leading to atrial enlargement. And those rhythm issues tend to be much more refractory to medical therapy. And here's where cardiac arrest really starts to feel more uncomfortable. What do you do in someone who's had longstanding end organ injury and potential for reversibility there? We did try to look at this using the ELSO registry again for ECMO patients, both in the glens and in the Fontans. And when we looked at the subcategory of eCPR as indication for ECMO, we actually didn't find a difference into survival to discharge compared to those with either cardiac or pulmonary indications. I will say that there are about 10% of both populations in these two studies, and the numbers are relatively small. Especially for the glens, it makes you wonder if there might be a signal with larger numbers. What we did come away with was a significant incidence of neurologic injury, significant incidence of renal injury. And with many registry data sets, I think we come along with more questions perhaps than answers. Knowing more about the indications and timing of ECMO, more details about the resuscitation, especially as our CPR science improves, impact of cannulation strategies. We as an institution tend to advocate for cannulating the SVC circulation first so as to decompress the brain. We actually don't know if that improves your long-term neurologic outcomes. And then understanding end organ injury preexisting on circulatory support and then reversibility in the future. This slide was actually already shown, but this is 2019 data from PDMAX looking at the VAD experience. And again, highlighting that difference between outcomes following VAD implant in patients with congenital heart disease versus those with acquired heart disease. And you really see that dramatic drop off in patients in those first few months following implant. What the authors took away is similar to what we took away from our ELSO data, which is to say anatomic complexity, chronic circulatory abnormalities, prior surgeries, and related end organ issues all seem to contribute to the worst VAD outcomes in patients with congenital heart disease. They did break it down by subgroups. Interestingly, the biventricular and single ventricle population doesn't really have much of a difference, at least in these first few months after implant. But when you look at the subtype of single ventricle palliations, you can see that those stage one and those Glenn patients are really our most vulnerable group. It's likely because they're smaller, so they have limitations in terms of technology of the VADs. But also that they tend to get a VAD implanted at a time when they're in much more physiologic and organ distress. And the author's takeaways from this was understanding the mechanism of failure is as important because it may impact how we choose to cannulate and which device we choose, especially as the technology starts to improve and we have some more options. So in summary, and I think you've heard this already from the prior speakers, but understanding individual patient considerations, anatomic and physiologic is critically important, if we need to think about mechanical support in this group, what are gonna be our real vulnerabilities. Recognizing these patients early, ideally avoiding ECPR and avoiding irreversible end organ injury. And if you are thinking that you may need to involve mechanical support, getting that strategy established sooner rather than later and making sure your entire team is on the same page. So not just the physicians, but also the bedside nursing staff, your ECMO perfusionist, your anybody who's involved in respiratory support. Having a multidisciplinary team involved with these kids once they are on ECMO or VAD to really think about how to ideally protect the end organs and optimize recovery. And then we need more data as everything in pediatric congenital heart disease, certainly, but pediatric critical care medicine, it would seem we need more and more data really to help guide future decision-making. So thank you very much and I look forward to the conversations.

mechanical circulatory support

pediatric patients

congenital heart disease

ECMO

VADs