Walter Li, MD, discusses the various types of fetal arrhythmias, the use of advanced imaging in diagnosis, and the medical therapies used to control arrhythmias, both before and after birth. The role of early screening, detection and treatment -- key for optimal outcomes -- is also discussed.
So for me, I always feel like to discuss uh complicated abnormal topics. It helps to begin with starting with what's normal and in regards to a normal heart rate for fetus. Well, it's really important to understand that a fetus is cardiac output is much more reliant heart rate. So how fast it is versus how slow it is. Can be particularly sustained. Can be particularly more impactful than perhaps it is when you have a newborn and when you have a teenager. And part of the reason why is because of the way the heart is developing at this point time, the Fetus and in 76, a newborn just has a much more limited ability to augment the stroke volume. So what are the typical normal heart rate ranges. A lot of it depends upon gestational age and here are some general um ranges for those different time points. However, I will kind of make a note that normal range is particularly when we're talking about very river young patients tend to be quite narrow and there are a lot of aberrations, a lot of transition. So it's not just one particular time point that we're looking at, it's actually kind of the whole global picture. So, to go back to a prior analogy, we're talking about blood pressure management, it's not as you kind of know with some of your patients, it's not just one measurement that you're seeing that defines an illness. It's actually what you see over more lengthy period of time and I would encourage you to think about heart rates in the uh in a similar light, So to review what a normal sinus rhythm looks like and I know this is a very busy slide but this encompasses how the heartbeat is originates. And diplomats from electoral physiological standpoint, from a ion standpoint. But the important points to take from this are a sinus node, then innovates the top chambers of the heart, the atrium then innovates the A. V node. Slight pause there allows uh emptying of the atrium over into the ventricle and then going through the bundle of his and then contracting both ventricles. And the way I like determine is an efficient effective manner. So how that looks in terms of imaging. So this is a fetal a pulse wave Doppler. And we're just and it's a fixated upon when the outflow tracts here. So the timing in between which we can extrapolate what the heart rate is. You can see here Nice 140 beats per minute. This is exactly the middle ground, exactly what we want. We would want to see from all the different fetuses. So going back to outline the fast track, a cardiac arrhythmias. So the most common form that is seen when we see abnormalities with the fetus are gonna be super ventricular tachycardia owes by far the most common, generally speaking, they're short lived. The fetus is tolerated quite well. There's very minimal human dynamic compromise into it and the fetus will do great all the way through the rest of the pregnancy, however, it's really important to pick up on these things early because if these arrhythmias are sustained for prolonged periods of times, then there's an impairment in terms of the uh in terms of how the atrium empty over into the ventricles, in which case we can start seeing some really, really profound human dynamic effects and the fetus can suffer quite quite, quite tremendously less common forms are going to ventricular tachycardia does and this is really really, really quite rare. We rarely, rarely rarely see these things in the fetus if they are seen by far and large, most of the time they're social, maternal exposures, exposures, meaning um perhaps illicit substances, cocaine is probably the most commonly attributed um uh exposure. However, there is also the, possibly the global impairment in which case the prior assessments perhaps were not able to be completed and this baby had been quite ill. This fetus has been quite ill for quite some time. So in terms of the different types of super ventricle attack cards. In terms of the arrhythmia mechanisms um there are four primary types that we see. So there's one where it comes from the top chambers of the heart, the atrium. So at topic atrial tachycardia at times we also see atrial flutter, which is what a macro entry circuit within the atrium most commonly, it's probably a v nodal reentry tachycardia, which is when there's an accessory pathway. An extra nerve between the ventricle and the atrium that exists allows european occur and perhaps not quite as calm but a v nodal reentry um which is um somewhat analogous to a B. Re entry. But there's some minor uh differences. So how does this look well on a fetal echocardiogram? And this is just a nice four chamber view of baby active in super and SPT. Um It's usually pretty um obvious. Another example is just you're seeing it go really fast and then in which case you ask your feel like a cartographer saying hey can you give me a heart rate on this? You know measure what those outflow tracts are and and see how fast this baby's heart is going. However in looking at this um uh this clip I want you to kind of take a notice and see well everything else about that clip looks somewhat pretty reasonable. We're not seeing a lot of effusions around the heart. Uh In terms of fusions that would be shops as darkness. Blood is usually black on the ultrasounds. The heart function looks pretty well compensated. Pretty preserved. So yes definitely good pickup. But so far the fetus is pretty well compensated contrast that to a baby in this particular instance who had been in S. V. T. For quite some time. At least days if not perhaps a week or so. And in contrast to the prior image you're saying okay well the ventricles they still look pretty good because the baby's contractions there are going pretty well not seeing too many infusions in terms of the overall body. But in contrast to that prior image, you're seeing this hmm here and that's pretty big. This is a baby who started this is a fetus who started to show us some um profound long um cumulative effects of being in S. V. T. In which case that atrium now is not emptying as well as it is. And this is a baby who's heading towards trouble. So Oftentimes we'll have that baby referred to one of you like a cardiogram furs and they'll get us some nice extra information here. You can see that this is a heart rate of almost 270 piece for a minute. Which is not unusual for SPT whatsoever. However, the other things which is a real benefit to our having one of our feedback according to first consult and get us more information. They can get us some very very specific information about what this arrhythmia substrate is, which can give us some better sense of what perhaps is a more optimal medications to help treat the our mom and fetus. So in this case the image selection here is an M. Mode and we're timing between how long it goes from the atrium to the ventricle ventricle to the atrium. And this will then lead us to define this type of arrhythmia as a short V. eight ft attack card, which tells us gives us some good sense of what is the mechanism of this particular arrhythmia. And typically those are going to be either atria ventricles, re entrant tachycardia or atrial ventricular Notre ranch intact cardio. At times it could be atrial tachycardia, but this gives a good sense of what medications could be most impactful in terms of the most common form. And I would say atrial ventricular entrant tech cardio or a tachycardia mediated by an accessory pathway is probably by far the most common in which case and in this artist's rendition, it's an extra nerve traversing between the right ventricle and the right atrium and it allows the signals come back up from the ventricle agent and then turn back around to the A. V. Node and come back down into the ventricles. And that is in many respects to a re entrant circular arrhythmia going over and over and over again, in which case our goal is to break that cycle and it's just translate slow down the conduction to the savory note to terminate the arrhythmia. Well, how does it look on imaging studies? Well, the nature of SPT oftentimes is that they can be difficult to predict in terms of when they're going to occur, how long they will occur. It's not uncommon at all to have to see spontaneous termination as in this particular pulse wave. Doppler, you see a couple sinus speeds here and then it goes back. So these are the kind of patients that they definitely need to be kind of monitored for a bit. Um The other additional information we can get in terms of diagnosis. Sometimes we can put A. M. Mode through the atrium and the ventricle and we can kind of see what those relationships are. So perhaps not that short via time. We would see Before we see I see ventricular contractions but I see twice as many atrial contractions in which case this leads us to a diagnosis of atrial flutter and can lead us to say, you know, typically would the textbook would say we would use X. Medication but in this case I see atrial flutter. We need the medication. Why then? Perhaps a bit more rare instance would be in terms of that information from those in modes. We see the timing from the ventricle to the H and being a little bit longer. In which case we can either identify this as mechanistic lee in an april attack cardio or a typical ventricular reentry tachycardia. However the one that's particularly worse than with something called persistent functional reciprocating type card because those arrhythmias substrates tend to be quite persistent, quite difficult to manage, turns out preparing for treat. We've gotten a lot of good information but the fetus, it's just one of two patients we're dealing with in this instance. So it's very important to identify what the maternal risks can be. So at the very least a baseline E. K. G. For mom is needed. The things we're looking for Wolff Parkinson White Long QT syndrome, whether mom has had a prior history of heart block, she's had prior myocardial scheme. In terms of the history, all these things can matter in terms of what types of medical options we can offer. Um um the fetus because certainly mom has to be taken, the medication is going to affect mom before it ever gets to the fetus. So these things are really important to assess beforehand. So we make an optimal choice in terms of recommendations to this family. Oftentimes like a cardigan can be helpful uh screening for forms of congenital heart disease can be helpful and can be impactful in terms of medication choices. Whether not mom, his heart fairly can also be impactful in terms of what we would advise in addition to the maternal risk of the field risk. Some of them you've seen already in terms of those fetal echocardiograms um when it gets to be a really, really bad situation, we start seeing hydrostatic Alice in which case choices, in terms of medical therapies start to become limited and we have to start making some really hard choice in terms of whether or not this baby needs to be delivered early. Oftentimes when in conjunction or at the same time as saying he will feel hydro fatality. We'll start seeing some evidence of end organ dysfunction. We may perhaps often screen and find other congenital anomalies and it's also important to keep in the back of our mind that congenital heart disease. Oftentimes can present with fetal arrhythmias. So there are different types of treatments that are available. Most of them. We would prefer to give mom and then therefore get it into the fetal circulation. They can be delivered either orally and that would be a preference or they can be given intravenously. However, it's also important to identify whether this fetus has high drops because that can impair how well the medications can enter the fetal circulation in terms of direct field treatment. For the most part, those are somewhat experimental. There are some quite uh quite amazing things that are in clinical trials right now, but they are predominantly for braddock articulateness, but which will touch base in a few minutes. Sometimes medical therapy is just not going to be optimal and the largest will also depend upon the gestational age of the pregnancy in terms of whether or not it's advisable to go ahead and deliver the baby. Um Oftentimes just we deliver the baby with all the vagal tone being stimulated. Sometimes that often results in transition of everything back to sinus rhythm, but I would definitely advise and I think it's pretty standard across all institutions that post delivery monitoring is needed because once they've had SPT there's always a chance, generally speaking, most of us will quote families, that there's at least a two thirds chance that the rhythm is gonna come back at some point in their lives. So we definitely want to pick up on it whether that baby needs to have chronic medical therapy. There are other options available. Sometimes we can place a pacing catheter through the baby's Neri's going over to behind the esophagus and performance in overdrive pacing medication certainly can be delivered intravenously. Two babies still are to control the arrhythmia and then there are, of course cardio versions in terms of medical therapies that are available to. Um So I'll cover the three, perhaps the most common types of medical therapies. The one that's by far and large. Perhaps as the most history in terms of being treated is the Jackson. And here are just some few characteristics. Uh It's a renal excreted increase in diastolic calcium. Perhaps the most effective way in terms of controlling, increases the parasympathetic tone in which cases slows down the ap noted conduction and helps decrease the chances of recurrence of the SPT in terms of contradict cations and the abdominal, in terms of in terms of mom, it's gonna be for mom has Wolff Parkinson white syndrome because you could be increasing her risk of potentially dangerous arrhythmias if there's any kind of congestive heart failure with the cardiac output for mom is dependent upon high sympathetic tone. That will be particularly risky and also hypoglycemia. So these moms definitely need to be monitored in terms of the dozing. Typically, most times we would prefer to oral dozing and then there are ivy preparations are the most of times of preference to go orally in terms of half life, it's last pretty long. So it's a matter of just getting a certain amount in circulation and usually by then we'll get to a steady state and hopefully things have run pretty smoothly. Another potential medication that can use is a social laws, the class three anti arrhythmic. So it has some beta uh antagonistic effects but it's perhaps a little less potent than the than the um straightforward class to beta blockers. Um In terms of metabolism is mostly for the kidneys in terms of the side effects. Perhaps the most important thing is not to say that hypertension and the beta blocker effects aren't important. The ones I think are particularly worse. And we're going to be the prolongation of QT C. Predominately has to do with the fact that is a classic three anti arrhythmic. So it tends to affect the re polarization and the reason why that's important because you have significant prolongation of QT interval that you're also risking mom's life in terms of course odds and it's very important and this is a really really important number to kind of keep mindful of hoops. Is that 500 milliseconds because that's when the risk of potentially fatal ventricular and it starts going up. These are the does seen down here and typically will start pretty low but quite a large range in which we can use. And this was a study that our institution I participated in in terms of showing how the effectiveness of soda law treatment of fetal SPT. Um, and this is pretty much kind of to show that it's perhaps a bit more effective than just going to Jackson. And in many respects, it's kind of convincing in terms of saying, hey, perhaps the first line medication we should be using is so long in contrast to the traditional use of the Jackson. And then finally, and this is one that we rarely would prescribe, although sometimes if your hand is forced, you need to think of perhaps a bit more uh, riskier treatments is flat tonight. 10 speed metabolites and and deliver. And someone in the kidneys has a few other uh side effects of their business in laws. You know, the typical side effects we see for most medications in terms of contraindications, in terms of the mom and this is really, really worse than because they this medication tends to be a bit more pro arrhythmic than the other two. I've just shown you in terms of a B block, ischemic heart disease, cancer. Heart disease is all major risk factors for having um, pro arrhythmia for mom. And it's there are multiple other precaution in terms of what other medications may be on and predominately were mostly worried about other anti arrhythmic that mom maybe on In terms of dozing. Typically starting dose is about 100 mg twice daily. And um all of these patients all seemed to monitor to make sure they don't have any toxic effects ideally through sarin. But they definitely need to be monitored with routine EKGs and the situation in which one would start considering using flak. And I would be if the fetus is showing you evidence that he or she is running to trouble and that's going to be in the presence of fetal high drops. I know this is a little bit of a busy slide but I would like to draw your attention over to the right column here. So S. R. Stands for sinus rhythm and then SPT obviously is super ventricular tachycardia. The interesting thing about this study was that it showed in a particularly dangerous patient population. So fetuses who are already having high drops that this medication flak night even though it is a bit more risky in terms of maternal issues. And also to defeat us tend to be more effective suggesting that perhaps the high drops is not impairing how the flock and this medication is getting to the fetal circulation. In terms of other medications just kind of for a reference and included a number of other medications but by foreign large, those first three are going to be the ones that are most commonly used in terms of medical fetal SPT effectiveness, thankfully with early um recognition early treatment and close marching thereafter. Most of the vendors, almost all of them are going to survive until home delivery. So To me this is kind of a sign of really fantastic progress over the past 10 2030 years in terms of treatments. So again, going back to our outline once the babies are, we certainly have other options available to us. We certainly can give a dentist into the umbilical venous catheter, very short acting. That's why it has to be kind of given ideally through a central line followed by a sailing flush. You can certainly use a lot of the same medication to Jackson can often be used in this situation. Beta blockers can also be used once the baby is out. And of course when all else fails. This is an example of a neo Nate who was born with uh with atrial tachycardia. I mean sorry, atrial flutter. And then had a cardioversion to get the baby into sign and show them just. This was at an institution where we didn't have um transit oficial pacing available to us. Alright, so middle portion of the rhythm of the fast and the injuries. So and what do you mean by? And so I mean irregular rhythm. So predominantly referring to act up. So it can either be from the top chamber or they can be from the bottom chamber, premature atrial or ventricular contractions. The reason it's important to identify these situations is premature. Atrial contractions can often be the instigator for SPT. In fact when we are treating uh individuals for S. A. T. In the electrophysiology lab that's actually how we try to get patients to the recipes. Put a whole bunch of different places at different times to try to start it. So identifying that it's really important and those mothers probably need to be monitored a little bit more closely Pvcs on the hand not commonly seen and in in fetuses. However if you do see them you convinces pvcs that is particularly worse than that. This baby is having some uh whether it's heart failure type of symptoms or other signs of an organ dysfunction that baby's in trouble. So the way I kind of like this into the fast and the injuries is atrial premature contractions that are not conducted so oftentimes that can give you a sense like oh my goodness this baby's really bradycardia. But really all it is is that the P. A. C. S. Are not just being conducted to down to the ventricles. So these are some examples of premature atrial contractions on on pulse wave. Doppler. The interesting things with this is sometimes you get really really amazing information here in terms of the eyes of a little relaxation tired and I saw a contraction time. That can give you some ideas as to why we're having Pvcs and this is an enlarged picture of that slide and you can see this is a more typical form of P. A. C. S. And then the injuries. These are the arrhythmias and that are really really really dangerous. Which is why if label bradycardia every this is dangerous. If it's mala bradycardia, sinus rhythm generally speaking those areas will tolerate it pretty well Even if the problems are permanent. So let's say instead of seeing that typical 130 you're seeing 120 chances are left. It is going to do perfectly fine. It's probably something related to some hypothyroidism in general. That's what we would kind of a tribute to or enhance vagal tone. However there are few things that do need to be evaluated for at least if not actively evaluate for needs to be continually evaluated even after the baby's born. At times when we're seeing significant credit card debts to me. One of the most worrisome things we can see it of the philosophy too long. QT syndrome which is something that perhaps you're saving this fetus is life but you may also be saving one of the parents lives by identifying it. An atrial ventricular block particular regards to this particular fetus. This particular pregnancy that can be highly dangerous. So when we're starting to see bradycardia we're at least seeing some degree of secondary heart block most concerning would be if we see more bits to However once you start seeing third degree heart block that's starting to get some get to be some dangerous areas here in terms of what causes atrial ventricular block most commonly. If we can identify um a maternal risk factor for it's going to be an autoimmune disorder most commonly lupus. Although certainly a number of autoimmune disorders can be associated with it. Uh huh. Other times we'll also see uh being idiopathic but in relation to an overall congenital heart defect for me, uh as an interest as a pediatric cardiologist, um which if I hear it's not an autoimmune disorder, I think it's a hetero taxi syndrome. And these patients can be particularly challenging both from a rhythm and a structural standpoint. How does long QT syndrome look? Well, if we can identify it with the fetal echocardiogram, it often looks like this. You'll have heart block. So the ventricle, he's only going between the two. Once here. However, the atrium going twice for every ventricle in terms of auto immune regulated heart block. This is an example of a fetus relatively late presentation to us who had a complete heart block Again. Nice four Chamber image here, ventricles. You can see, I think we're in a little bit of trouble here, ventricles are like hearing a little bit dilated hmm. Are not really being conducted all the way through to the ventricle all the time. Not seeing a whole lot of evidence of fetal high drops as of yet. But this is definitely a very very, very worrisome picture. And this is I think the same patient perhaps about another couple days perhaps a week later. And we're starting to see black around the heart repair karl effusion here. This is definitely a baby in a great deal of trouble. So if I can impress upon you something um very important regards to hot block, that is the early detection and screening is extremely important. So important, in fact that they're this study that came out. I think it was october last year, um, basically was showing the effectiveness of their um algorithm in terms of monitoring these suspected patients. I want I want to draw your attention to is, well, yes, sometimes it's a concern. But then there's a thorough evaluation and we find out that okay, we don't have heart block, this baby's doing fine and continue to kind of monitor things closely. However you look over here, There are certain number, there was a four patients out of 315, An anti Rohinton essay or patients with lupus or lupus like autoimmune disorders. There were four patients who already had evidence of emerging heart block. And what is amazing about it is with this screening algorithms. So they were teaching the mothers how to screen or families, I should say, not just moms families, how to screen the fetuses heart rate twice daily. And with that they were able to get early treatments and this is amazing. Second or third degree heart block, early early interventions, early detection, early screenings, none of them went up having heart block when they were born. And that's fantastic. It's a fantastic outcome. So, before birth, what treatments are available. Well, ideally if we know even before mom gets pregnant as you're getting pregnant, we can offer them some auto immune modulating medications in the form of plaque. We know if we start seeing signs and evidence that there's heart block emerging, then steroids can be helpful in. Oftentimes it can reverse the process. Uh, it's also really important to, of course counsel the families in these instances counsel them in terms of what is the range of therapies that is available to them. What may they may be taking on as time goes on after birth, the assessment continues. I would say. At the very least, EKGs needs to be done to make sure this wasn't an episode of Long QT syndrome. Also to make sure that the baby doesn't continue to have heart block. If there's no heart block when the baby is born, then highly unlikely that that baby is going to have heart block later on in life. In fact, I think one paper had quoted in their series that there was less than a 5% chance. Pretty good huts. Um, if there's identification of Long QT syndrome, there are medications that can be used to treat it and then after birth, let's see if we're in a bad situation and the heart block has persisted. It continued. Well, we can consider pace making. Yes, we can put pacemakers in very very very very little little babies. Um indications for it certainly can just have heart failure that heart's not compensating for such a low heart rate in a good way. If there's persistent high grade A. V. Block that would be a reason to consider in longitude. That would be another reason to consider a pacemaker. So we've got a long way in terms of pace maker on the left is an image of the actually very first pacemaker that was ever made. And I promise you the temporary pastry will be available on the right howard nowhere near in similar size to the first ones. However we also there are also implantable pacemakers that are made. This is perhaps the smallest one that is available on the market. You can see how small that is. Uh Yeah in fact we even had a I think she was about 28 or 30 week premature infant who got one of these pacemakers. It's still pretty sizable relative to that baby. But uh it's amazing uh kind of how things have progressed over the years. See if I get this to play. So this is the same patient who I showed you earlier who had the heart block in the atrium started to dilate so that baby was starting to get into trouble and didn't respond to a round of steroids and such. So the baby got delivered and got one of those temporary pacemakers that that amusing slide with the two. Uh the old one and the temporary one. And this is the baby with pacing. And so they were able to recover function. You can see the heart chamber sizes and typical floor chamber really quite reasonable. However sometimes things don't work out. Um This is that same family however they had another pregnancy and for one for reasons that are difficult to understand um didn't seek attention early on during the pregnancy wasn't monitored. Same issue. Heart block, no early identification and this is a ventricle. You can see it's dilated its movement, its motion, its function is really really quite limited. The baby's essentials fetus essentially just having recurrent venture to carter envy uh adventuring, fibrillation and unfortunately this this fetus didn't make it. So when are fetal arrhythmias diagnosed. Oftentimes during prenatal visits. When do we need to feel like a cardigan as well? For one we want to make sure there's no structural heart disease because that can add another layer of complications onto managing this family. Um The M. Mode analysis is particularly helpful in terms of identifying the particular rates can help in terms of identifying what do with the substrate is helpful in terms of guiding us in terms of what is often medical therapy. The other thing that is helpful. It's just really old school methods going back to our original training. It's just a good history and really pertinent questions. So it's really asking very important questions of the mom and her extended family. His year of history of long QT. Some were suspected Long QT syndrome. The way I kind of asked those questions. Not just long QT syndrome. I often asked like does anyone have a pacemaker, pacemaker type device placed on their shoulder? Has anyone had unusual fainting or seizures? Sometimes I can, the patient may not be able to tell you exactly what their diagnosis, but they can tell you certain things that can lead you down that path. And then the other part is lupus and connective tissue disorders. And those are the times like, yeah, you definitely need to be screened and monitored very closely. So where the outcomes of fetal arrhythmias? Well, a lot of it depends upon the substrate. SPT We have much much much more higher rate of success in treating in terms of this study at a 28 patients with SPT, only one had to feel demise. That's atrial flutter. None of them had any demise. But the one that worries me heart block, particularly wise man should say heart block out of nine patients and doing everything that's within reason impossible. Still two out of nine a field mice. It's a pretty uh pretty harrowing. And I like to think we can do better. So overall conclusions feel arrhythmias. Yes, definitely potential dangers. Most if they're very very short duration, most reasonably well tolerated. There are a lot of implications. Not just for the fetus but also keep mindful insurance implications for other family members. There are many effective treatments. Medical therapies can be started immediately and oftentimes have very good outcomes, very promising outcomes. Even more outcomes are available once the baby is born. And to me, I think the most important thing that I've learned in terms of looking through all this literature and my limited time in practices, barely screening and recognition is key. The earlier we know about things, the more options are available and it's key to get to these patients before they start showing signs of an organ dysfunctions with that veil for questions.
