Thank you, Dr. Devekar, for the kind invitation. It's been absolute pleasure to be part of this webinar to understand the pacing requirements for single ventricular patients. I have no financial disclosures, but the most important disclosure I want to make is I don't do pacing. I'm an interventional cardiologist working in one of the largest single ventricle programs at Birmingham Children's Hospital and the University Hospital in Birmingham, where we have the adult congenital unit. And we talk about anatomy. We think about normal anatomy, and very rarely, obviously, we talk about morphology or the pathology of the heart. But Fontan is more or less a modified circulation that we have created over the years to palliate the single ventricles. And in this diagram, we can see the different types of Fontan, the old AP Fontan, and then the lateral tunnel, and the third one with the extracardiac. Now, majority of the units are now doing extracardiac Fontans, but there are some patients which are still the old lateral tunnel, and very few adult patients, maybe atrial pulmonary connections might still be there. So when we look at the anatomy, what important anatomical factors do we need to think of? First and foremost thing is the venous anatomy. Obviously, the axis is not just about the percutaneous axis, but axis in terms of how we are gonna get into the venous atrium, the pulmonary venous atrium. Is it gonna be through the Fontan conduit, or is it gonna be through the pulmonary artery, or is it gonna be through from the IVC side of things, from the lower half aspect of the Fontan circulation? And for that, it's very important to understand what underlying cardiac anatomy is, because the size of the venous atrium may be depending upon what the underlying anatomy was. And some of the isomeric patients may have an interrupted IVC, and the only thing you might be actually draining from the lower half would be just the hepatics. Some of the time, the hepatics are very useful access to actually get through the Gore-Tex tube if you need to make a perforation into the Gore-Tex tube to get into the atrium. And my experience predominantly is with the interventions on the univentricular circulation children who would potentially need a new fenestration or dilate the existing fenestration. In today's day and age, we are lucky that we do get nice 3D models of either a CT or MRI scan of Fontan circulation. And it's actually quite nice to get a spatial orientation with where the conduit stains and what the relationship of the venous atrium is with it. Here, you can see clearly how the pulmonary arteries also lying on top of the venous atrium. In good old days, when we take the patients to cath lab, we never had this models in our hand. And even for sometimes today, there's a Fontan struggling on the ward with excessive fluid losses, we would just take the patient to cath lab and create a new fenestration if it was not there without having a 3D model in the background. So cardiac catheterization still remains one of the best ways of orientating ourselves in terms of anatomy. I think the reason I included the size was, though it is not anatomy, it's important to understand which unit does what kind of Fontan and how did they put their conduit? Because some of the times, the conduit is supposed to go towards the left pulmonary artery. But as however, in some units, you might find actually the angle at which the conduit goes is different. So you need to know how your surgeon puts the conduit. And don't forget that the conduit and the atrium does have a big gap in between. The only way it's attached to the atrium is through where the fenestration is. So when we do try to perforate the vortex, there is a gap in between the vortex tube and the atrium. And ideally, if there's a pre-existing fenestration, it would be the best opportunity to kind of stretch the fenestration and see whether we could extend it to put the leads through. Other thing is sometimes the pre-existing fenestration may actually allow you to only put the pacing in a particular direction. It might be facing more anterior. And if you want your pacing to go posteriorly, it might struggle to the existing fenestration. That might make them an indication to create a new fenestration. I've used this picture again to essentially show a slice of the back of it and emphasize the fact that if you have this kind of a model, which you can see very clearly that on the back, if you had to perforate this vortex, there's hardly any gap seen over here. In the same way, if you had to make a communication between the pulmonary artery and the atrium through the roof of the atrium, then again, there's not much of a distance which needs to be covered to allow communication between the two cavities. However, if you look at the model on the right side, this is basically a bilateral cavopulmonary shunt with the pulmonary artery. And if you see the gap between the pulmonary venous atrium and the pulmonary artery, also the gap is fairly seen between the conduit and the venous atrium. So there, your preparation has to be slightly more in terms of you will have to prepare that you're going to end up into a dead space in between those two structures if you have to make a communication through. And that is where having this model does help you decide your intervention. Though there's not much to talk about anatomy over here, I thought I'll share some cases where we have done those without the pre-existing model. So this is the patient who's post-spontane had a pacemaker in place, which is an epicardial pacing system you can see. There is already a device seen which has closed the previously existing fenestration. And there's a stent in the left pulmonary artery. And basically we have a small window where the Gore-Tex tube is entering. And from there, the fenestration was, the Gore-Tex tube was perforated and was crossed across to the venous atrium. And then subsequently the communication was kept patent by implantation of a diabolo-shaped stent. And you can just about see the final result in the final angiogram. So this stent can be modified based upon what you need in the future. It can be reduced in size in terms of the narrowing point. But if there are pacing leads going through it, then probably you want to keep it at the reasonable size. In Birmingham, all of our fontans remain on warfarin throughout life. And that's why we do keep a higher threshold sometimes to close the fenestration unless they don't need the fenestration. This is probably the first case which was done in 2007. Dr. Giovanni was the operator. I was assisting him at the time. This is a five-year-old fontan who had a tricuspid valve repair at the same time of the surgery. And the surgeon had sutures in the right atrium and he felt uncomfortable to create a fenestration and he left the child without fenestration. The child had prolonged pleural effusion. And we went to the cath lab with a view to create a new fenestration of transcatheter. And as I said, in those days, we did not have the CT and the MRI to assess the model. So basically we are assessing the anatomical features with multiple angiograms in AP and lateral looking at various positions of the aorta, of the superior vena cava, of the right ventricle and leaving catheters there as landmarks also to help us then create the renal fenestration. So just show a few more angiograms too. So that's the catheter going all the way to the right atrium. So you know how much distance is there for you to cross. And this was done both in AP and lateral. And ultimately at the right corner, you can see there's a broken bra needle along with the transceptional sheet, which is coming from the right superior vena cava. And you can just about stain the Gore-Tex over there to give you an idea of where you are. But the aim was where the sternal wires are because that was where the native tissue or native pulmonary artery floor was. From there, we wanted to enter the left atrium. So this is basically the perforation taking place. And once you're across, voila, we are into the pulmonary venous atrium. The sheet goes forward and basically a wire sent across. And with the sheet in place, we implanted the stent with the diabola-shaped effect. And this was the first case. And I think Dr. Giovanni and I published it together and we put it up. And I think it was in 2008. It was came as, and it has since then been put as a lot of reference article. And essentially since then there are multiple cases which has been done for pacing through, basically they've been put through pulmonary artery into the pulmonary venous atrium. So I think in terms of the anatomy for this, it's very important to realize that the access to the atrium in single ventricle is possible, but it can be challenging. Sometimes it is hampered by the toughness of the Gore-Tex or sometimes there are stents put in place of the pulmonary artery or devices which have been used to previously occlude the fenestration. Though pontine connections are standard, there are certain variations which people have done based upon what underlying morphologies. And that's what we need to understand what the surgeons have done. Always read the op note where the IVC is being plumbed into the lower half, lower part of the pulmonary artery. And native pulmonary artery to atrium is a very good alternative to perfecting Gore-Tex when you want access to the pulmonary venous atrium. Thank you.

single ventricular patients

Fontan circulation

cardiac anatomy

access considerations

pacing interventions