Hi, this is Eric Pistowski. Welcome to another segment of EPL&EP. With me is my friend and excellent electrophysiologist, Dr. Charles Barreau at Children's National Hospital and we're going to discuss today congenital heart block. So Charlie, thank you so much for joining us. Thank you, Eric, for having me. I really appreciate it. Well, this is a topic that's a crossover, right, because we as adult electrophysiologists also see it. Let's start from the beginning, though. How is it initially diagnosed and how do you view it in the pediatric age group? Sure. You're right. It's a combination of both pediatric and adult cardiology because it's typically diagnosed in pregnancy. And so when the pregnant woman has a low fetal heart rate and the obstetrician will get concerned about why is the fetus bradycardic and one of the causes of bradycardia is congenital heart block. The most common cause is maternal lupus or having the lupus antibody. Even if she doesn't have the systemic lupus disease, she could still have the antibody and it's surprising. But the the antibody to lupus attacks the AV node in utero and causes congenital heart block. So it's it's diagnosed early with fetal ultrasound, getting the heart rate. So as you suspect it, do you I know this is out of my realm, but do you have to do something like is the fetus in trouble? Do you typically have to get the baby out or I mean, what is the actual plan at that point? Right. Well, as as you'd expect, it's it's rate related. And so the lower the fetal escape rate, the less well the fetus does. And if the rate's not not high enough of a ventricular escape rate, there's usually fetal demise. And so far, there have not been successes at fetal pacing for more than a day or two. And so that's really been the holy grail is fetal pacing. So short of that, therapies include anti-inflammatory medications. If you can catch it before complete heart block. And so there's been several studies that look at treating mothers with with prednisone or some other steroid at the onset of first degree AV block. If you can catch it that early or maybe early second degree block, but before it progresses, once you get to complete heart block, it's pretty much irreversible. And you get the fetus as far as you can before delivery and early neonatal pacing. So let's say you deliver the fetus, if the fetus is doing OK, I mean, you're not worried about the fetus. The heart rate's good enough or maybe that doesn't happen. I don't know. Are there situations where you can just wait it out? Sure. Yeah. If the heart rate's, you know, fetal escape rate is 70, you know, the normal baby heart rate is about 140, 150. So a fetal heart rate of 70 is quite low, but usually adequate. When it gets below about 55 or so, then they usually need some support. And so early pacing is really the goal for those newborns if they come out with a fetal heart rate of, you know, 55 or below. When you say pacing, now again, this is all foreign to me as an adult, are you actually talking about putting at that point a permanent pacemaker in? What do you do? Right. Unfortunately, yes. Right now, there's no pacemaker on the market specifically designed for infants or even for children for that matter because of the business model, right? So there's not a lot of these babies that are being born. You're talking about, you know, less than 100 a year in the country and maybe, you know, less than a few hundred worldwide that could benefit from a neonatal pacemaker. And so there's not really a for-profit, you know, shareholder cause to do that. So people are innovating. If the baby's big enough, we'll put in a standard pacemaker. We usually put it in the abdomen and put in an epicardial lead. The surgeon would put in an epicardial lead and attach it that way because the veins are usually too small, particularly in a premature infant that has to be delivered early because of the heart block or because they have other forms of congenital heart disease that may go along with it. We and others are trying to develop a more miniaturized pacemaker specifically for use in this situation. Yeah. I remember you telling me about that. Can you tell us what's going on in that area? Yeah. So there's a few different places that are working on developing their own sort of unique pacemaker. What we're trying to do is develop something that's percutaneous through the size of either a large needle or a small straw to put on into the pericardial space through a port and deliver the pacemaker that way. Or at least a pacing lead at the very least, if not a whole integrated pacemaker. Right now it's still in animal studies, preclinical. And so if you're a piglet born with congenital heart block, you're in luck. But if you're a baby human, we're not quite ready for prime time yet. So do adult mother pigs get lupus? No. So I've always heard about, and I know it's one of the things I've been taught to teach, even adults, is to look for the lupus antibodies. What's the percent? What percent actually of congenital heart block turns out to have the lupus antibody issue? Of the babies with congenital heart block, probably about half are due to maternal lupus unless they have congenital heart disease. There are certain forms of congenital heart disease, like L-looping, L-transposition, that are associated with congenital heart block. But otherwise, the ones with a structurally normal heart, about half of them are due to maternal lupus antibody. So let's go now, do a transition if you would for me, Charlie, into the adult. Because obviously, as an adult electrophysiologist, I see them later on, and the usual story is somebody felt a slow pulse. And when you talk to the patient, you ask them, have people always said you have a slow pulse? And they said, yeah. But they've been fine. Right. So now I see them, and they're actually doing fine, they're just sad. And they have a narrow QRS, it looks like classic congenital complete heart block. And they're doing fine. And I read the pediatric literature, it's a little scary at times, if sudden death can occur, and what rate. And I've never been comfortable, honestly, with that whole area, because it's really anecdotal more than anything, right? So what would you recommend to the adult group of how to manage the asymptomatic patient who comes in like that? Right. And you're absolutely right. There are some patients that come in, either as teenagers or young adults, that that's their first presentation of symptomatic or incidentally identified complete heart block. And as you said, if their escape rate is OK, there's not an urgent need for pacing. I don't want to go against the guidelines on TV. It's a class two indication for congenital heart block with an adequate escape rate once you're adult size, teenager or adult size. And so you're right, it's based on old data and anecdotal information of the potential for sudden death. We do recommend that if you're an adolescent and older with complete heart block that's presumed to be non-reversible, that we do recommend a pacemaker on a non-urgent basis. Well, so I have several patients who have simply not wanted it. So I'm not ever unhappy saying it on TV that I don't want to go against a patient's wishes. And if their rate is 45, 50 and they can exercise and they usually get a junctional rate up to 110 or 20 and they're OK, I've not felt compelled to put a pacemaker because it's really not hard data, right? You're right. And I guess that's why the guidelines are guidelines. And a class two, whether it's 2A or 2B, doesn't mean you have to do it, right, as you know. And it takes, you know, the clinician common sense and experience like you to make those decisions along with the patients, the sort of shared decision making with the patient to decide if and when they need a pacemaker. Unfortunately, it's not a class one or a class three, so it's not as strong of a guide. The twos are crazy, right? Yeah. Yeah. For all of us. Well, Charlie, this has been a great discussion. It's going to be very useful to the listeners. Thank you for joining us today. Thank you, Eric. Thank you.

congenital heart block

pregnancy

low heart rate

maternal lupus

pacemaker