The Cardiorenal Puzzle in Cats

In the April open access episode of Chattering With International Cat Care, Kelly St Denis is joined by Dr Amanda Coleman and Dr Bianca Lourenço to explore feline comorbidities, focusing on the relationship between cardiovascular and kidney disease.

Together, they discuss the concept of the cardiorenal axis and the challenges of recognising and managing cases where these systems interact. The conversation highlights key considerations around diagnosis, treatment decisions, and balancing fluid therapy in complex patients.

For further reading material please visit:

Feline comorbidities: cardiovascular and kidney diseases

View The Transcript Here

Host:

Kelly St. Denis, MSc, DVM, DABVP (Feline), Co-editor of the Journal of Feline Medicine and Surgery and JFMS Open Reports & Guideline co-chair

Speaker:

Amanda Coleman, DVM, DACVIM (Cardiology), Professor at University of Georgia

Bianca Lourenço, DVM, MSc, PhD, DACVIM, Assistant Professor at University of Georgia

Creators and Guests

Host

Yaiza Gomez-Mejias

Veterinary Community Co-ordinator @ International Cat Care

What is Chattering with iCatCare?

Welcome to Chattering With iCatCare, the official monthly podcast of International Cat Care, hosted by Yaiza Gomez-Mejias (Veterinary Community Co-ordinator). Each month, we chatter about cats and cat-friendly practices with industry experts and contributors to The Journal of Feline Medicine and Surgery. Each episode contains highlights from our longer discussions and interviews, which are accessible to iCatCare members at portal.icatcare.org. If you would like access to our full episodes, would like to become an iCatCare Veterinary Society Member, or find out more about our Cat-Friendly schemes, visit icatcare.org.

Kelly St Denis: Hello. I am Dr Kelly St. Denis, co-editor of The Journal of Feline Medicine and Surgery and Journal of Feline Medicine and Surgery Open Reports. We are here today talking about our latest clinical spotlight article, Feline Comorbidities: cardiovascular and kidney diseases. I am joined by doctors Amanda Coleman and Bianca Lourenco from the University of Georgia College of Veterinary Medicine.

Kelly St Denis: Welcome to the two of you.

Bianca Lourenco: Thank you.

Amanda Coleman: Hi. Nice to see you.

Kelly St Denis: I am really glad to have you guys here, and I just wanna take a moment to say thank you for your hard work in putting this article together. I hope we're gonna be able to talk about it today in a little bit detail and get people interested so they'll go and have a look at it because it really is going to be a nice reference for them to have in their practice.

Kelly St Denis: You introduced this concept of the cardiorenal access early on in the article and I wondered if you guys could tell us a little bit about what that concept is?

Amanda Coleman: Yeah, I guess I can take that one, Bianca. I think thinking about the cardiorenal axis is maybe just most useful as a framework for reminding ourselves of this relationship between these two organs and the fact that there's tons of crosstalk in both directions and so I think it's just useful for us to think about this as maybe a conglomerate that talks back and forth, both in health, but also more importantly probably for us as clinicians, in disease. And it reminds us to think okay, if we're treating an animal or cat with heart disease or failure, how might our treatments or even the disease itself impact the kidneys and vice versa? And that sort of leads into this concept of the cardiorenal syndromes, which we introduce a bit in the article as well.

Kelly St Denis: Yeah, and that's a really great pathway to lead into everything that gets discussed, and you have a really intricate figure there on those interactions and specific pathways, and there's a real highlight that you guys have noted in increasing sympathetic nervous system, RAAS and systemic arterial hypertension.

Kelly St Denis: Do you guys have any thoughts about that aspect of that cardiorenal access that you've presented?

Bianca Lourenco: Yeah, we had so much fun putting that figure together. Historically probably the better known and explored link between the two would be systemic arterial hypertension as way to connect those two and physiologically regulation of blood pressure. That is certainly a very important part of this story, but it's not all of it.

Bianca Lourenco: So we took some time to think about some other pathways or some other methods for connecting the two, some of which do play into hypertension, such as sympathetic nervous system simulation and the renal defence and aldosterone system, but also thinking about other molecular pathways, including the roles of inflammation, inflammatory cytokines that are expected to be released in response to either substantial heart or kidney disease, for example.

Bianca Lourenco: Mineral and bone disorders that accompany kidney disease and how those could lead, for example, to dystrophic mineralization and have an impact on cardiovascular structures. Certainly blood pressure is the easiest one to measure clinically and to see effects on the heart, for example, echocardio graphically, but we know that there's this cytokine milieu that is occurring with both diseases and probably causing damage to the other system when one is affected.

Kelly St Denis: So that systemic arterial hypertension is really a good point of focus in that, even just in that diagram 'cause as you said, sympathetic nervous system and RAAS also impact systemic arterial hypertension. We don't see a lot of clinicians measuring blood pressure.

Kelly St Denis: And I certainly encourage people in clinical practice to get handy with understanding their machine and getting readings even from younger cats so that cats can get used to it. That's such an important part of this conversation because there's such an important link between the two. For you guys in terms of what we know about heart and kidney disease,

Kelly St Denis: how common is it for us to have concurrent conditions? So cats with both kidney and heart disease, would you say? And how do we know that? How do we figure these things out?

Amanda Coleman: Yeah, so I think for the most common cause of heart disease and failure in cats, we're usually talking about hypertrophic cardiomyopathy and if you look at large studies, the percentages that usually come out are somewhere around 16%, which is cool. It's been very consistent across studies of asymptomatic cats walking around have HCM and the prevalence of that increases with increasing age. Bianca can say better than me, the prevalence of chronic kidney disease in cats, but I think everybody who treats cats knows that it's age dependent and massively prevalent. So it stands as a reason that these two things would coexist, particularly in older cats.

Amanda Coleman: It's a little difficult to know, right? Because disease in one can cause disease in another and the other and some of the treatments that we give for one can mimic disease in the other, for example, cats and heart failure on diuretics. It's very common for us to see acute increases in serum creatinine and we don't know, is that because we have, I'm gonna use the word pre-renal. I know I'm on the talk with some internists, but, is this a pre-renal thing or is this intrinsic disease? And so a couple of studies we have looked at cats that present to emergency departments with acute congestive heart failure and trying to suss out like what is the prevalence of azotemia at the time of presentation before being treated with diuretics and things like that. And probably the largest study that we have looked at about 119 cats and it showed that 44% of those cats that presented with acute congestive heart failure were azotemic and the median age of that group as of note, it was 10 years, so it's a little difficult to know what caused or is that just concurrent CKD, for example. But that's the best guess that we have and I think if you're thinking about an older cat who has got substantial heart disease or heart failure,

Amanda Coleman: it's probably safest to just assume when they're older cats that they probably have CKD. But I think that it's hard to know the true, because of this crosstalk and the difficulty with diagnosing early CKD, like that's really difficult. How do we identify those iris stage ones without additional diagnostics, imaging and things like that?

Kelly St Denis: I noticed that in the article you talk about how when you have cats with chronic kidney disease, you guys have specific plans for evaluating the heart. So is that something in general practice? Should practitioners be thinking, oh, I've got a cat of chronic kidney disease.

Kelly St Denis: What should I be looking for to make sure that we don't also have concurrent cardiomyopathies or cardiac disease?

Bianca Lourenco: Yeah.

Bianca Lourenco: Like Mandy was saying, the prevalence of cardiomyopathies in asymptomatic cats is 16%. I think it would be very reasonable to echo many of these cats. It's just not very practical because it's a costly test. So at our institution, we pay special attention to cats that already have something else signalling that we might be concerned, or sometimes those that we are already predicting that we might be using a more aggressive fluid plan to restore volemia and hydration and, so for the former, certainly cats that have arrhythmias, gallop sounds, louder murmurs, recognising again that would still miss probably an important portion of cats that have neither of these and still have heart disease. We sometimes explore NT-proBNP, for example, but again, those can be hard to interpret because they're renal excreted, right?

Bianca Lourenco: So you can still not have a lot of confidence, but maybe you could trust a normal, for example, acknowledging that no test is perfect. Those would be candidates. Occasionally we have cats for whom, for example, we have placed nasogastric tubes for their food, feeding support, and again, detected something on thoracic radiography that made us concerned.

Bianca Lourenco: And I think more and more our interns and residents, and I think anybody who has access to ultrasound, they've started doing point of care ultrasounds for a subjective, non cardiology assessment of the heart, right? Many people are confident getting an left atrium to aortic root ratio that is at least within their capability to say, Hey, I'm already concerned or not.

Bianca Lourenco: So all of those would be really great candidates for the investment of an echocardiogram. Again, recognising that if finances are not an obstacle then probably almost all, particularly those that are gonna get an aggressive fluid plan, should be echoed.

Amanda Coleman: Another important point that I wanted to make is that the point of doing echocardiography, it's important to know that Echo is currently the gold standard, right? Of the most sensitive and specific tool that we have to detect underlying cardiac changes.

Amanda Coleman: The point of screening these cases is to identify cats that have more advanced stages of disease so that you can identify those as cases that might have cardiovascular complications. Is this a cat that's more likely to become volume overloaded and to go into congestive heart failure with aggressive fluid therapy, for example.

Amanda Coleman: And so one useful thing that I think folks can do in practice if they don't have access to a sonographer or cardiologist is use the combination of thoracic radiographs and NT-proBNP, and I think that's gonna miss some cases, right? Like you're gonna get some false positives and false negatives with that approach, but the likelihood that you miss a cat that has moderate or severe heart disease, if you have normal thoracic radiographs and a normal NT-proBNP, that's relatively low, I would say. So I think that's a reasonable starting point. So if you had a case that had one of these physical examination findings, I think Dr Lourenco hit it on the head, we know that certain physical exam findings are gonna tell us that a cat is more likely to have heart disease, a gallop arrhythmia, a murmur of grade four or greater. If you had a case like that and you were worried or you had a cat with known heart disease, just doing a thoracic radiograph and an NT-proBNP and using the combination of those, I would say it's a useful screening approach.

Amanda Coleman: Understanding that you are gonna miss cases that have heart disease, but you're likely to pick up those cases that are more severely affected. It's important to know too that NT-proBNP is really excreted and so if have an animal with CKD and it has a high value, then that could be a false positive.

Kelly St Denis: Yeah, that's important. Dr Lourenco pointed out if you're good with point of care and can get some of those basic heart measurements too, that probably increases your opportunity for finding things if you don't have access to Echo.

Bianca Lourenco: Yeah and it's important to acknowledge that there's immediately actionable information on the other side of these tests, right? So if you have a cat that you are already concerned that is in advanced stages of heart disease, your fluid plan should be altered, right? If you are dealing again with hypovolemia or dehydration, for example, you are probably gonna be slower in your correction.

Bianca Lourenco: You're more likely, or should I at least consider lower sodium containing fluids? At our institution when we are concerned, we will commonly place a nasogastric tube so that we could actually provide fluid support enterally that is virtually sodium free and less likely to overload the cat.

Bianca Lourenco: So there's meaningful information in addition to discussion with the owner, right? I think it opens the communication. I don't mean this as in we're condemning the cat, but already important discussion, right? This is the current health status of your cat. These are our goals. Challenges might be balancing the fluid needs of one with the fluid needs of the other 'cause they're often at odds.

Bianca Lourenco: I also think particularly in recent years, we have come a long way for treatment of kidney diseases in general and really have moved away from the flushing the kidneys or diuresis because even in cats without heart disease, we know that is promoting potentially over hydration, which has implications.

Bianca Lourenco: So over hydration can be associated with a myriad of negative consequences, including renal edema, which then might decrease glomerular filtration rate, right? So we're more and more cognisant of just keeping the animal normally hydrated and no more than that. And we'll be even more careful, right?

Bianca Lourenco: If we know that there's substantial heart disease. So there's meaningful information to get that can be helpful and helps us tailor our plans.

Kelly St Denis: Yeah, that is cool. As you're talking about this, I'm just wanting to draw attention to our listeners that there is a whole section in your article on maintaining optimal body fluid balance, where you present a numerous different scenarios and what you might wanna consider based on those particular situations.

Kelly St Denis: So that's a really helpful section in that article. So anyone wants to look at that it's nice to have these articles in your practice when you're in general practice, just so they're there, you've read them, but then you can go back and refer to them because there's so much valuable information.

Kelly St Denis: One of the other things I wanted to touch on a little bit today that you guys really cover well is just the common drugs. So we use specific drugs to treat certain things like congestive heart failure, furosemide being one that we all often use. And then for kidney disease we have some medications that we might use that those drugs may impact the heart or the kidney, vice versa.

Kelly St Denis: And I wondered if you, the two of you, wanted to just take a minute on addressing the impact of cardiac medications on the kidney and vice versa?

Amanda Coleman: I think that one of the things to say is that as cardiologists, we have selfish reasons, right? You know, we need to clear this edema. And obviously we'll talk about that, but I think we also have some altruism as well.

Amanda Coleman: And so I think a lot of us think about, we really worry about acute exacerbation of azotemia, like AKIs and our cases, particularly ones that are on diuretics and blockers of the Renin-Angiotensin-Aldosterone System, chronic worsening over time, like if we are making these animals chronically hypovolemic.

Amanda Coleman: And then in addition with these drugs, we are impacting renal autoregulation and tubuloglomerular feedback, all the things that Bianca can describe and define better than I. But I think that one thing to keep in mind is that we're all aware of this impact of being overly aggressive with these medications and how that can impact renal blood flow.

Amanda Coleman: But maybe taking a moment to also remember that these effects are worse if you have a cat who already has a degree circulating blood volume. So for what I mean by this is we have cats that are maybe being treated for heart failure and they're stable. They have chronic kidney disease and then they develop vomiting or diarrhoea for some reason and continue to get their diuretics and continue to get their ACE inhibitors.

Amanda Coleman: And it is in those settings when animals are already hypovolemic and becoming more hypovolemic, that this is the most dangerous. So I think that the two drug classes that we worry the most about overshooting are necessary, particularly diuretics, and keeping these animals out of heart failure.

Amanda Coleman: But we are very mindful that if we get into a situation where an owner has been monitoring sleeping respiratory rates in a patient that is in heart failure, and then that cat develops a reason to have increased losses or decreased intake, and we tell them skip a dose or two, give us a call and we can work things out from there.

Amanda Coleman: I'm sure Dr Lourenco will bring this up but we know that cats with cardiomyopathy are very sensitive to changes in blood volume and I think we start to get a little selfish when we think about treating chronic and acute kidney injury and chronic kidney disease with parenteral fluids.

Amanda Coleman: The effects of anaemia and the drugs used to treat that or transfusions, right? So I think that Dr Lourenco can talk a little bit more about that, but these animals are very sensitive, both the kidneys and the heart, to changes in blood volume, and I think that's why we focus so much of our energy in this article on trying to describe these scenarios.

Amanda Coleman: Like how do you balance this blood volume situation in an animal who might not have normal one or both of these are abnormal.

Kelly St Denis: This is a very delicate balancing game, Dr Lourenco?

Bianca Lourenco: Yeah. Again, starting from a place of empathy, this is hard and we don't always do it perfectly or rarely. I think a few themes for veterinarians to keep in mind would be the needs of the system that is at the present moment more severely impacting the animal's quality of life or risking their life itself need to be prioritised.

Bianca Lourenco: So if the animal is symptomatic for pulmonary edema, certainly we're gonna have to address that and put the needs of the kidney in that sense a little bit in the back burner. But concurrent with that, probably trying the lowest level of intervention that is gonna match what you need. So probably avoiding interventions that, again, are too aggressive in animals that have diseases of both the cardiovascular and the kidney. Prioritising the most important needs at the moment, but also trying to find the lowest level of intervention. I like to tell our residents that good monitoring forgives a lot of sins 'cause we make wrong fluid plans all the time, right? Again, even in cats that don't have heart disease, we overshoot or undershoot. So as long as you are keeping a close eye on body weights, markers of hydration, PCV, total solids, things that are fairly basic, your physical examination findings, right?

Bianca Lourenco: Again, if you have access to ultrasound, periodically doing point of care ultrasounds looking for effusions. But do that consistently to track changes so that you can alter your fluid plans is very important for some cats, for example, that have concurrent disease. And at the moment, what's keeping them in the hospital is worsening azotemia that is manifesting in clinical findings of uremia.

Bianca Lourenco: Sometimes all we do, for example, is take away their furosemide and see if that resolves the issue, and maybe then we can reintroduce it later at a lower dose. Also understand, what was the inciting event? Sometimes the cats with concurrent heart and kidney disease were doing just fine, but just had a period of GI disease or something else that just took them over the edge and so if we can support them through this more acute period, maybe we can slowly reintroduce certain drugs. So that's a common theme here.

Kelly St Denis: Thank you so much to both of you for spending this time with me today. I've really enjoyed speaking with you and highlighting the importance of this article that you've written.