Screening for Healthier Hearts with Dr. Kathryn Meurs, DVM, PhD

Dr. Kathryn Meurs, DVM, PhD is a Professor, and the Associate Dean for Research and Graduate Studies at the North Carolina State School of Veterinary Medicine. She is a board-certified veterinary cardiologist who completed her residency and PhD at Texas A&M University. She is a true pioneer in the quest to identify dogs who are affected by or carriers of heart disease before they reach breeding age.

Her research has spanned multiple heart conditions and dog breeds, including cardiomyopathy, long QT syndrome, and Myxomatous mitral valve disease (MMVD). Her research has addressed the genetic causes of heart disease in Great Danes, Dobermans, Boykins, English Springer Spaniels, Rhodesian Ridgebacks, and Cavalier King Charles Spaniel, among others. Dr. Meurs was the first recipient of the Mark L. Morris Jr. Investigator Award from the Morris Animal Foundation in 2016.

If you liked Dr. Meurs's talk, you can find all of the Health Symposium videos here!

Transcript

Kathryn M. Meurs [0:00] Good morning! Thank you so much for inviting me here to be part of this first seminar in this fashion. I’m so excited to see all of these different attendees from such a wide geographical location. I’m going to be talking mostly about cardiac disease today. This is a great follow-up for Dr. Oberbauer because I’m going to discuss some of the available genetic things that can be done for dogs with heart disease, as well as some of the clinical evaluations. In my introduction: I’m a veterinary cardiologist. So that means that after veterinary school, I do an internship and then I do 3 years of specialized training in just hearts and heart disease in cats and dogs and horses. Predominantly, we see a lot of dogs with heart disease. What I noticed as a young clinician was a lot of these diseases that we see in dogs are very breed-specific. So that is one of the things that I will emphasize in my discussion today. 

[1:11] I’m going to begin by talking about some of the common heart diseases that we see in dogs and that you may be experiencing, working with your own dogs at home. I’ll talk a little bit about screening for these cardiac diseases. When you might want to do it: so, what cardiac diseases do we see in puppies, and what cardiac or heart diseases do we see in the older dogs? If you’re interested in screening, how could you screen for those? Is that something your veterinarian should do or a veterinary cardiologist or a genetic screening that might be available? Finally, I want to touch on why you might want to do the screening and it does fit in very well with Dr. Oberbauer’s presentation. We traditionally, as veterinarians, thought about genetics as a way to produce the next population of healthy puppies, and we assume that genetic screening would mostly be done by people breeding dogs to develop that next generation. But increasingly, we look at screening for cardiac or heart disease as something that even a pet owner with a beloved dog at home should be focusing on because early identification of heart disease and early intervention (starting medication sooner, perhaps changing a diet, those types of things) has been shown to make a big difference in longevity—how long your dog may live with heart disease and how comfortable it is. When I talk about heart disease, often we think that’s a severe thing and an individual (a dog or people) dies of heart disease. That is very true, but many, many dogs live with heart diseases for years and then die of cancer or other things that happen to us as we get elderly. I think an important aspect of screening is that early identification of whether your dog could have heart disease—and then is there an intervention available for it. That’s why screening has moved much beyond just thinking about it for breeding animals and much more to how that might help your individual pet.

[3:29] I want to focus a little bit on what the heart looks like before I start talking about heart diseases and really focusing on the specifics of it, because depending on your training and whether you took a lot of biology in high school and college and even beyond, you may know more or less stuff about the heart. So I want to bring everybody to the same level as we go forward. This is a picture of a heart and the different anatomical features. For dog heart diseases, whether your veterinarian (or if you’re working with a veterinary cardiologist)—the vast, vast, vast majority of heart diseases either affect the heart valves (so the aortic or mitral valves; it doesn’t matter so much now which one) or heart muscle. In human beings, in you or your family or friends, you may hear them talk about coronary artery disease. Those are the blood vessels that penetrate through the heart muscle. That is very, very, very rare in dogs. Dogs don’t have those same types of coronary artery issues that human beings do, and things like are they eating food with a lot of fats in it—that doesn’t tend to matter quite as much as it does in humans. So we don’t talk about coronary artery disease and heart attacks like humans have or the need to put your dog on lipitor or lipid controlling drugs. What we talk about is heart valve disease. Often that happens as the dog gets older from middle age to old age, or we talk about heart muscle disease, where the muscle is becoming weaker and not functioning quite as well as it normally would. So those are the things I’m going to function on: valves and muscles.

[5:34] Heart disease is actually very common in dogs. I like to emphasize that because sometimes I’ll have an owner come to me with their dog and—this happened to me just this week actually—they’d gone in for their annual evaluation with their dog to see their veterinarian and they said the veterinarian told them that their dog had heart disease. And they got home, they knew my name and that I was a cardiologist, and they emailed me right away and they were just so upset that that meant their 9-year-old Chihuahua was going to have a shorter life span and might die if it’s heart disease. This was awful, and what should they do? But heart disease is so common in dogs, and many, many, many dogs will live very comfortably with their heart disease. Maybe it’s on medication. Maybe we change the diet a little bit. But the diagnosis of heart disease in your dog does not mean this is awful and your dog is going to die very soon. First thing is to know that it’s very common in dogs. Two: don’t panic until you really understand how severe it is and what might be going on.

[6:55] Many dog breeds are predisposed to heart disease, so it’s common and it does follow certain breeds. I put a few of the pictures of the common breeds on here, so we see a lot of heart disease in Doberman Pinschers and Miniature and Toy Poodles—rarely Standard Poodles but the smaller Poodles. We see heart disease in Dachshunds and Lhasa Apsos. So a lot of the small breed dogs. I rarely see heart disease in a Collie. There’s an example of breeds where it’s very breed-specific and other breeds where cardiologists just don’t see a lot of Collies, maybe Pugs. I don’t see a lot of Pugs with heart disease. So heart disease is common, and if you have a breed in which heart disease likes to follow, you may have issues with it at some point in that dog’s life. Again, it doesn’t mean that dog is going to die of it. It just means, like us, like human beings, this is something that may need medication, and we may need to deal with it. When it is breed-specific, that often suggests it may have an underlying genetic cause. In some cases, we actually know the genetic mutation, and you can screen for it. You can do a genetic test, as Dr. Oberbauer was talking about. In some cases, we don’t know the genetic mutation. But when we see a disease following a breed, that often suggests to us that it is of an inherited nature. Some of these genetic, inherited diseases show up as a puppy. Some of them may not show up till middle age, so that dog has the genetic mutation that will lead or can lead to heart disease. It puts them at risk for heart disease. But it may not show up until they are middle or older age. That’s often confusing to people. If it’s genetic, why don’t they have that disease from birth? But think of it, again, as the human example: you may have had coronary artery disease in your family but those individuals that have it—it doesn’t show up until they’re 50 or 60 years of age. They have that genetic mutation but for whatever reason, the disease doesn’t show up until a certain age. Same thing in dogs. So, heart disease is common. Many breeds have a higher incidence of it. We’ll see it both in a puppy as well as older dogs. 

[9:42] Screening breeding animals, therefore, can be used to help produce some of the frequency of these genetic problems if done correctly, as Dr. Oberbauer was talking about—not using it as kind of a black-and-white tool, but using it to guide how you make decisions. I also like to emphasize the importance of screening your dogs for heart disease, so if they do have heart disease, we can identify it right away and think about: does that dog need to start heart medications? Behavior changes? More exercise or less exercise? Possibly diet? All of those things that we might be able to develop a management plan to help your dog live a long and happy life with its heart disease. 

[10:38] I just want to go back one more time as we start to talk about these specific heart diseases and just make sure everybody has this concept of how, just because something is inherited, doesn’t necessarily mean it shows up at the puppy stage, like all these Boxer puppies. So, inherited (or familial is sometimes another way to think about it) heart disease means that that puppy and that dog is genetically programmed to develop heart disease. That heart disease can be both what is called congenital (which means it’s present at birth; in some ways, you can think of it as a birth defect) or they’re genetically programmed to develop the disease, but it’s adult onset, so it will develop at some point later on. Now, the other aspect to that that is really important to understand is not all congenital or birth defects of the heart are inherited. Perhaps you’re a dog breeder, and you’ve been breeding your, let’s say Poodles, for years. You’ve been in this profession 30 years of breeding healthy dogs. You’ve never had a heart problem, and now you sell a puppy and someone comes back to you six months later and says that they’ve been to a cardiologist and that cardiologist says this puppy that you sold them has a heart defect. Perhaps it’s called a patent ductus arteriosus or it’s some type of septal defect, a hole in the heart. Just because a puppy has a heart defect doesn’t mean it’s inherited. Dogs, cats, horses—just like people—sometimes when their heart develops, it just doesn’t come together perfectly. That’s just something that can happen. That doesn’t mean that your line has a genetic defect that gets passed on and can create puppies with heart problems. It’s just that every once in a while, one of us or a puppy doesn’t develop just right. We don’t know why that is. But if it’s the first time you’ve ever had a problem with it and you don’t see it in any other litter mates or the parents or other related dogs, it likely is just a congenital heart defect or a birth defect. It’s not an inherited problem. Finally, as I mentioned, some heart diseases are inherited but won’t develop until that dog is a full-grown adult. Sometimes that means middle age and sometimes quite late onset. (I’ll talk about some examples of that.)

[13:34] When we talk about screening (and as I talk about the specific examples of heart disease, I’ll tell you when you might want to do these different types of screening) for heart disease, there are two types of different screenings that we can think about. One is clinical. That means that a veterinarian or a cardiologist (a veterinary cardiologist) is looking at your dog to try to determine whether they have heart disease. That often starts with a stethoscope. The first way that most veterinarians, general practitioners, or a specialist veterinarian (a cardiologist) would identify the heart disease is by doing a good examination, starting with just that patient, feeling their chest, feeling their pulses, the blood going through their legs. But very importantly: listening to the heart with their stethoscope to hear if they’re picking up abnormal heart beats and also something called a heart murmur, which really just means there’s turbulence in the heart, so the heart sounds a little bit different. They’re listening to that with their stethoscope to pick up those abnormalities. Now, that is a very non-specific finding. They’re just saying that they hear some abnormalities. To really diagnose what the cause of it is—is this a heart valve problem or a heart muscle problem (as I talked about at the start of this lecture)?—those things generally will require an echocardiogram, which is also referred to as a cardiac ultrasound. That’s what you see in this picture. That’s when a veterinarian cardiologist or sometimes a veterinary radiologist is ultrasounding the heart to actually look at that heart valve and assess the heart function to try to determine what the underlying cause of those heart abnormalities that they heard with that stethoscope are. Now, importantly, this screening with the stethoscope and the echocardiogram—they tell you whether heart disease is present today, at the time of examination. Is heart disease there: yes or no? They can’t tell you: Is heart disease going to develop 3 years from now? So if you’re looking at your 1-year-old dog and trying to determine whether they are ever going to develop a heart disease called cardiomyopathy that usually shows up in a Doberman Pinscher at 5 years of age, doing the echocardiogram today at 1 year of age isn’t going to tell you whether they can develop it later. It just tells you whether they have it today. That’s a very important thing to think about when we talk about screening. The clinical work tells you: Is the disease present today and should a veterinarian begin to think about some of those interventions that we talked about: medications, diet, exercise? 

[17:02] Now, that’s compared to a genetic screening where genetics are looking at that DNA that Dr. Oberbauer talked about that is being collected, perhaps from a mucal swab or a blood test. That’s going to tell you: Does your dog carry a genetic mutation that puts it at risk for developing heart disease? It does not tell you: Does my dog have heart disease today? It just says: Does this dog have the genetic mutation that puts them at risk for developing it or for passing it on to puppies that might be produced? Genetic mutations are identifying risk. Clinical evaluations tell you: is this disease there? 

[17:53] In a genetic evaluation, that means that you’re sending that mucal swab or a blood sample (sometimes a semen sample) and that DNA is going to a testing lab, and that testing lab is going to look at that actual DNA, like we’re showing here, looking at the sequence and is that going to be the same in a normal animal compared to your dog that has the DNA sent in. For example, these are two pictures of DNA samples submitted from dogs that could be at risk of cardiomyopathy. A normal dog should have a sequence that’s in this little red box here, GCC. The dog that is at risk of developing cardiomyopathy has a CCC, so a C changed out from the G. As a geneticist and a cardiologist, I look at that DNA and say: This dog has an abnormal DNA pair. It has a C instead of a G. It is at risk of developing cardiomyopathy. It is at risk of producing puppies that will develop cardiomyopathy. But having that DNA sequence does not mean that that dog has the disease today. It just says it’s at risk of developing it.

[19:22] It’s very important to understand the power and the limitations of genetic tests. It’s very, very powerful because it tells you: “There’s something here that puts my dog at risk of disease. I’m going to want to screen for it. I may want to consider this if I’m considering this dog for breeding.” But being at risk for it doesn’t mean that with great certainty this dog will develop heart disease. There are a lot of things that go into developing disease once you have a genetic mutation that puts you at risk for it. Many of those, we really don’t even understand. What we do know is that just because a mutation exists, doesn’t mean for sure that heart disease will develop. So this is another one of those areas where I urge: Don’t panic! Just because your genetic test comes back and says: “My dog is at risk of developing heart disease, and this is the type of heart disease,” that does not mean that my dog will absolutely develop heart disease. 

[20:40] If you look at the genetic mutations that can cause heart disease, both in people and in animals, even if all of the puppies you produced have that genetic mutation, only some of them will ever go on to develop heart disease. For example, if all of these puppies have a genetic mutation that can lead to heart disease, we know that only 20-60% of them will ever actually develop the disease. Why is that? If it actually is the right mutation—the scientists did all the right work and that’s the right mutation that can lead to disease—why don’t they all develop the heart disease? Genetics is complicated. Same thing in human beings. It’s not that the lab is wrong or genetic testing science is wrong. It’s just that it’s complicated. It might be that some of those puppies also inherited a genetic mutation that protects their heart. So some of them are lucky. They got a bad mutation, and they also got a good mutation. That’s great! Or it might be that there’s something about the environment that we don’t yet understand that some of them got the bad mutation, but they also were fed something special or exercised a certain way or didn’t exercise or that there’s some other factor yet to be understood that prevented or led to the development of the disease beyond just having the mutation. So, genetics is a really important aspect for screening disease because it alerts you that your dog may be at risk of developing this disease. That way, you can follow it more closely and you can make decisions about whether you want to use it for breeding or not. But keep in mind that it is not a 100% way of screening. It doesn’t tell you whether disease is there today, and it doesn’t tell you whether it will for sure develop. 

[22:55] Finally, when we think about genetics of heart disease, in many cases we don’t actually yet know the cause of the genetic mutation. I do a lot of work with different dog breeds that are very concerned about inherited heart disease in the breed. Puppies that are born with a hole in their heart called a septal defect—we see that with increasing frequency in some dog breeds. We have no idea what the underlying genetic mutation for that is. Breeders just have to make their best guess when they’re breeding those animals. I can’t advise them about a way to genetically screen them. 

[23:38] In the last 10 minutes here or so, I’m going to give some examples of specific heart diseases that you may see or may be dealing with in your own home right now. And then I’ll be sure to leave some time to answer some questions. 

[23:58] I’m going to emphasize those diseases that impact either valves or the heart because that’s where the majority of heart disease is.

[24:11] I’m going to begin by talking about ones that are what we call “congenital,” meaning these are heart diseases that we believe are inherited but show up at the puppy stage. It may be if you’re a dog breeder that the first time you bring this litter of puppies in to the veterinarian to get them vaccinated for their send-off to their new home, the general practitioner picks up this abnormality. Sometimes it’s a more frustrating situation, that that abnormality is there since birth but it’s not picked up until the puppy is placed into a new home and has gone to meet their veterinarian for their first shots and evaluation in that home. 

[24:58] The most common heart diseases that we tend to see in puppies (puppy onset) are called valvular stenosis (the valve is too narrow), valve dysplasia (when the valve doesn’t close properly), or blood shunts (when the blood circulates over in the heart).

[25:24] I’ll just give a few very brief examples of these. Valvular stenosis is one of the most common congenital or birth defects that we see in dogs. This is when the heart comes together pretty normally, except one of the heart valves (typically the aortic valve) is too narrow, so it just doesn’t open properly as the puppy forms. 

[25:55] This defect is present at birth but often it is not fully recognized until that puppy is maybe 3 or 4 months old. At that point, this narrowed heart valve that doesn’t open properly starts to cause a lot of turbulence, so blood trying to push through this narrow valve starts to make a lot of noise. An example of this might be if you had a hose and you’re out watering your flower bed perhaps, and you kink that hose a little bit with your thumb, that creates a lot of pressure behind that area, and it also creates a lot of turbulence. The water coming out beyond that kink comes out with a spray and a lot of noise. That’s exactly what happens in the heart when the heart valve is too narrow. It increases pressure beyond and below that heart valve, and it creates a lot of noise as blood goes through that narrowing. This is very common in large breed dogs. For instance, Newfoundlands, Golden Retrievers. Many dogs with this heart defect can live a normal life. They will have a little bit of abnormal heart sound, a heart murmur. They will have turbulence in their heart, but they never have any problem at all with it. They live a normal life. They can be placed in homes. It’s not a problem. Unfortunately, some puppies born with this have very severe disease. That narrowing is so narrow that it really creates a high pressure below that valve in the heart itself. Those dogs die suddenly of this disease, usually before 1 year of age. They don’t show any symptoms at all. They can be just out playing in the yard and fall over and die suddenly. It’s really an awful disease. It is inherited, although the genetics are not well understood. This particular defect has been studied very well by Dr. Josh Stern, who’s a veterinary cardiologist at the University of California–Davis. He’s been working on the genetics of it for some time. There is one known genetic mutation for it in Newfoundlands but it doesn’t appear to explain all of the cases. So screening for this disease (because the genetics are not very well understood) is probably best done by a veterinary cardiologist or your local veterinarian.

[28:43] Another common congenital or birth defect that we pick up in puppies is called valvular dysplasia, particularly on the right side of the heart, the tricuspid valve. In this particular defect, it’s not that the valve is too narrow but that the valve never closes properly, so it really leaks blood and the heart becomes very inefficient. 

[29:14] This is very common in Labrador Retrievers and, again, many dogs can have mild disease that they live quite comfortably with, but some dogs have very severe disease. They go into what’s called right-heart failure, where the heart simply cannot deal with this leaky heart valve. Blood backs up into their belly area, and many times the owners have to make a difficult decision to think about putting this dog to sleep because there’s no good way to control this with medications. This is a disease that we’ve been funded from the American Kennel Club, Canine Health Foundation, for some time to study the genetics of it. The genetics do appear to be quite complicated, so at this time, there is no good genetic test for this one either.

[30:11] I’m going to end by giving you a couple of brief examples of adult onset diseases. These are both diseases that are inherited but don’t show up until the dog is at least middle-aged. The first one is the most common heart disease that veterinarians deal with, and that’s called mitral valve disease (or mitral valve endocardiosis). That’s where the dog gets older but one valve on the left side of the heart leaks, similar to what I just described in Labradors, only these dogs are normal usually till about 5 or 6 years of age. It’s most common in middle-aged to older dogs. I had a professor who used to say, “If you can pick up a dog with one hand, this is a dog at risk of developing mitral valve disease,” so it is incredibly common in older, small breed dogs. Most of the dogs that develop this disease will live a normal life span, but may need to be on medication to help control their symptoms. Some dogs will develop severe disease and die of it. It is inherited, and we know it’s inherited in the Cavalier King Charles Spaniel, Miniature Poodle, Dachshund, many others—but there is no genetic mutation for it. So this is another one that is best screened for by your veterinarian who can identify it early by the presence of that turbulence in the heart, a heart murmur, and recommend starting on medication.

[32:00] Finally, I’m going to end with a disease called cardiomyopathy. This is the second most common heart disease that we see that veterinarians see. This is a disease of the heart muscle. When somebody says something is cardiomyopathy, myopathy implies muscle. It usually impacts the left side of the heart, and that heart becomes very dilated, and the muscle function doesn’t work very well anymore. 

[32:30] This is a disease diagnosed on echocardiogram, and these are two images of a normal heart (at the top) and an abnormal heart (on the bottom). The heart is much, much bigger and just doesn’t function very well anymore. 

[32:49] This is also an adult onset disease. Middle-aged to older dogs. But this is large breed dogs, whereas mitral valve disease (that’s the one I talked about how if you can pick it up with one hand, it’s a small dog, we think about mitral valve disease), with cardiomyopathy, it is most commonly large breed dogs. Doberman Pinschers are the most common breed we see with it in North America. But it also impacts Boxers, Great Danes, Irish Wolfhounds—really the large breed dogs. You can have mild disease but also very severe disease as well. The Doberman Pinscher and Boxer—there are genetic tests. They can tell you whether your dog is at risk for it and whether early intervention may be needed or whether it’s at risk of passing on this genetic trait. 

[33:50] But keep in mind that the genetic tests just tell you whether the dog is at risk for it, not whether it has the disease today. If you know that your dog, if you run a test for it, and your dog comes back showing that it has a genetic mutation, then you do want to see a veterinarian or a veterinary cardiologist to have them screen, clinically evaluated, to see whether they have that disease.

[34:26] Today, what I really tried to emphasize was that heart disease is very common in dogs. However, it does not mean they’re going to die of heart disease. Heart disease is very common, but in many cases, it’s very medically controllable in dogs. That’s why we do want to screen for it, and that is often best done by your veterinarian, perhaps a veterinary cardiologist, to determine whether they have disease present and whether some type of heart disease management plan should be started. That might be medication, it might be diet, it might be exercise changes. Or it might just be, “Okay, now we know your dog has this or is at risk of it. We just want to follow it more closely.” Genetic testing can identify those dogs that, when those tests are available, are at the most risk of it. Early intervention, early screening and those early interventions, are our best hope for managing these dogs long term. I’m going to stop there. Thank you for your attention today. I’d be happy to answer any questions in the last few minutes 

Nate Ritter [35:50] Dr. Meurs, thank you so much. Fascinating talk. We do have some questions coming in. Popular topic of discussion: dilated cardiomyopathy and the diet effect on that disease. I know you don’t have all the information—I know it’s an ongoing issue—but I was wondering if you could speak to that. Additionally, you mentioned genetic predisposition to DCM. If that relates to a predisposition, any effect that nutrition might have on that particular animal as well?

KM [36:19] Great question! I do have to say I’m not a veterinary nutritionist. Dr. Lisa Freeman, who’s at Tufts, is somebody who really has focused on heart disease and nutrition—that combination—quite a bit, so she’s the best expert on this. But what we can say is that there has been a lot of work done, a lot of evidence showing, that some dogs appear to be very sensitive to certain diets that can predispose them to the development of dilated cardiomyopathy, this heart muscle disease, and that when they’ve been changed to a different diet, those diseases (in many cases) reverse and resolve. What I would say is that it is really important that your dog be on a balanced diet. I used to do a lot of screening, going to dog shows, talking to people about their pets, looking for heart disease. One of the things that many people would come up to me and say is, “Well, I feed my dog just a raw diet or a meat-only diet because that’s the way dogs are kept in the wild. They catch wild rabbits, and they eat that, and I never hear about them eating grass, so a meat diet is what they need and it should be raw.” But remember that dogs in the wild—they also do get grains. And they are actually also chewing up things like bones and sticks and leaves in those things as they’re eating rabbits. Dogs really are not strictly carnivores. They do need a balanced diet. Also remember that our domesticated dog is quite a bit away from those wild coyotes and wolves that we might see when we’re out walking in the woods and exist that way. Our domesticated dogs today really do need a balanced diet. I recommend feeding dogs foods that have been really well studied, where you know that that company has carefully studied what goes into that diet and what happens if you feed a dog that diet for 5-10 years so that they’re really investing in the research of producing healthy dog diets. You had a second part of that question? 

NR [39:00] The second part was just when you discussed genetic predisposition before—I know you mentioned you’re not a veterinary nutritionist—but is there a genetic predisposition specific to the nutritional aspect of DCM for some animals? 

KM [39:15] This is, again, a great question. We think so. Although it is poorly understood. Probably 10-15 years ago, somebody looked at the role of taurine, which is another nutrient (and is particularly important to cats and healthy hearts). They did see that Golden Retrievers—I think there was also a family of Newfoundlands—that developed dilated cardiomyopathy, which are not typically common for those breeds. Those breeds were families, so it was a genetic problem, and that that genetic risk was increased by not having diets that had enough taurine in it. I think they’re likely—at least in some breeds and some families are at least a link to diet and genetic mutation. But it’s not well understood at this time. 

NR [40:09] Thank you so much. Really important question. I saw that all the time in practice, particularly with the new puppy visits discussing the diet, so thank you there. We had another question from Terry discussing holter monitors. I was wondering if you could just discuss them: their use, how often you would recommend it, those screenings for a breeding animal (obviously probably dependent on breed, but would love to get your thoughts). 

KM [40:31] Great question. A holter monitor is a 24-hour electrocardiogram that a dog wears home. It’s about the size of your cell phone these days. The dog wears it, and that picks up every single heartbeat that that dog has over a 24-hour period. We really encourage owners, when the dog is wearing that, to do normal activities. So if they go to the dog park, do that. Do everything they normally would except swim with the monitor on. Why it’s important is that that monitor will then look at every single heartbeat it has and be able to identify abnormalities of the cardiac electrical system that are associated with inherited heart diseases—most specifically in some unique breeds, so Boxers have a particular problem with inherited heart disease that impacts the electrical system. Sometimes we see this in Doberman Pinschers with cardiomyopathy, so those are two breeds that (in particular) when they’re adults—that’s a really important way of screening for their heart disease because abnormalities in the electrical system can lead to sudden death. I want to put one quick last plug, also for the Rhodesian Ridgeback. Rhodesian Ridgebacks have a juvenile disease that shows up as adolescents, so usually about 6 months of age until about 2 years of age. They do outgrow it. But that is an inherited issue with their cardiac electrical system that can lead to sudden death without any symptoms. Those dogs just die suddenly. The only way it can be picked up is a genetic test or a 24-hour holter monitor. Very important for young Ridgebacks. 

NR [42:26] Now we have a couple of questions that are a little more breed-specific, so I’ll try to make them a little more general, and we’ll see what you have to say. We have a question regarding Whippets. Are there diseases you see with Whippets primarily that you could speak to? 

KM [42:43] Whippets get mitral valve endocardiosis, that old age disease of the mitral valve. Whippets can get it a little bit younger, so closer to middle age. They can get it quite severely that they need medication and can be on heart failure. We believe it’s inherited in Whippets. The genetic mutation is not yet known. 

NR [43:07] Great, thank you. A couple of questions regarding Great Danes. People are interested in adding them to their breeding program or who already have them in their program, wondering what age to have these animals tested. Like you spoke to, it gives kind of a snapshot in time when we do the physical exam, if they’re affected currently. How often should they be tested, and what tests do you recommend for that breed? What diseases do you see often with Great Danes? 

KM [43:29] Great Danes get dilated cardiomyopathy, similar to Doberman Pinschers. Genetically, it’s very complex and there is no known genetic test yet for it. It generally shows up at 7 years of age but can be as young as 4 or 5, so I would say an annual evaluation, which includes an echocardiogram, every year from 5 years of age to perhaps 9 or 10 years of age. Once a year. 

NR [43:57] Great, thank you. Now some questions regarding Labrador Retrievers specifically. They’re wondering (I know you spoke to it before) stethoscope, an important first step. They’re wondering if that’s sufficient for screening their breeding stock, or if you would recommend for Labradors to add additional diagnostics as well.

KM [44:16] Yes, unfortunately for Labrador Retrievers, because it’s a problem with this valve on the right side of the heart, for breeding animals, sometimes that heart murmur can be missed. It can be very soft, because of its location. If you’re breeding them, they really should have an echocardiogram done to clear them of this disease. Really, they shouldn’t need it to be annually. For your breeding animals, if you do it at 1 or 2 years of age and they’re clear, that should be sufficient. 

NR [44:47] Thank you. The same question regarding the genetics of tricuspid valve disease, wondering if there were updates on current research or if you could speak to that topic a little bit more.

KM [44:59] We’ve worked very hard on trying to identify a genetic mutation, and there doesn’t appear to be a single one that explains all cases, which would likely suggest that they have two different genetic mutations in Labradors that can cause that. We’ve seen that in Doberman Pinschers, that there are at least two different genetic causes that can cause dilated cardiomyopathy. And in Boxers, with their disease. So it’s not a huge surprise, but it’s disappointing. It’s always nice when it’s a single mutation. So we’re making progress, but it’s not done yet. 

NR [45:40] Fair enough. Thank you. Relating to research, the same individual had a question regarding access to data that is acquired by OFA, the advanced cardiac exams and what have you. Where do you, as a cardiologist, pull the majority of your research and information? 

KM [46:00] It’s so important when you’re trying to work on these genetic tests. They can take a long time to do. It’s very expensive. That’s incredibly important, that that clinical information be 100% accurate so that I know that that DNA sample truly is from an affected or unaffected dog. Generally, we just get them from dogs that we’ve seen here in our clinic or a veterinary cardiologist that we are collaborating with where we all agreed at the start of the study on how we will make the diagnosis or the clearance. For those, we don’t generally use DNA from a database that’s been sent in, until we’re almost done with the study. 

NR [46:47] Looks like we have time for one more question. Just speaking in general, broadly, things that people/breeders should look out for? Or just owners at home in general, for heart disease. Signs and symptoms that you might see in the animals at home.

KM [47:02] Fainting is one of the symptoms that you might think could be a seizure and is almost never normal in a dog. A fainting dog and a coughing dog are often signs of heart disease that an owner might pick up at home and that can be caused by a lot of things. They could be lung disease. They could be similar to asthma. But those make me want to see my family veterinarian and have them take a good listen to the heart, perhaps an X-ray of the heart, and determine whether an ultrasound needed to be done, whether medications needed to be started, whether heart disease is really there or not.

NR [47:47] Fantastic. Well, Dr. Meurs, thank you so much. Thanks for answering those questions. Your talk is very helpful. Thank you so much for coming on and helping us out.

KM [47:57] Thanks for inviting me, and have a great day, everyone!