Hello, I'm, I'm Luca Ferrizine and I'm a veterinary cardiologist, and I'm going to talk about the secrets of heart murmurs in cats. Heart murmurs are a very common reason for a referral to a cardiologist in, in people and especially in children where approximately 50 to 70% of these murmurs are clinically insignificant. And similarly, in cats, the discovery of a heart murmur is common justification for a referral for identifying the, the cause of the murmur and the clinical significance.
But even in this piece, approximately 50% of all cats seen at our institutions are referred for further investigations of a, of a heart murmur. We know that heart auscultation in cats is challenging, so I would like to start with a general introduction, talking about the challenges that we may face on cardiac consultation in these species and then obviously, we'll move in depth into the description of, of heart murmurs. I tend to joke when, when it comes to cardia consultation in our profession, and I say that there are two different types of auscultation.
The first one is the one we see on the top left is called the clinical auscultation, where the clinician has to focus, has to concentrate in order to obtain all the clinical information for that auscultation. So that requires a quiet room and requires a a lot of, as I said, a lot of focusing. From, from the clinician.
And also we need to reduce as much as possible, all the interference coming from the environment, like, noises coming from, from the room, also noises coming from the patient like meowing or panting or paring. Conversely, when we do a social auscultation, which is the one on the right side, It's a little bit more challenging because not only we're dealing with this interference from the environment and the cats, but also we're dealing with interference from very loquacious owners that sometimes they distract us during this difficult topic. But, the difficult task.
But when we talk about pairing, that's very important to know how much pairing can interfere with our consultation. We done a study a few years ago. Looking at the prevalence of pairing in cats during cardia consultation and different techniques to reduce this, this issue.
And there is an issue because when we place the stethoscope on a pairing cut, the only thing we hear is the sound. And it really sounds like a helicopter. And when we have these pairing cuts, we can't hear the sounds of the heart, we can't hear the, the, the, we can't hear the sounds of the lungs.
So it can be very challenging. So we need to know how to stop it. And we know that from this study that approximately 18% of cats are pairing during cardiac consultation and It is, was based on a study on 341 cards, a study that was led by my friend and colleague, colleague, Chris Little.
And we also try to identify the best techniques to reduce the pairing. So what we did, we asked practitioners about their favourite techniques to reduce pairing cuts, and we came out with 6 different techniques that are described here in the, the top. Table.
So we could blow at the ear of the cat very gently or run a tap of, water, and the noise of the water can affect the parent in cats or use a squeaky toy or touch the tip of the nose of the cat, as well as, exposing the, the, the, the cat to surgical spirit or using the, the sound of an aerosol spray. And we found that of all these 6 techniques that were the favourite techniques used in practise, 3 of them were the most successful. So we looked at these major 3 techniques and looked at the one that is giving the most consistent results.
And that's the, the sound of water running. From an open tap. So what we do, we just like in this picture, we can hold the cat in our arms and then place the stethoscope in the right position and gently move towards the the, the, the running water, and the sound tends to stop the pairing in the majority of cases.
If for a few seconds, and that is usually sufficient to acquire all the clinical information of that particular auscultation. If the running water is not successful, then we can consider the second most successful intervention, which is the aerosol intervention. So whether we can spray you use something like fill way, not at the cat, we spray away from the cat, but it's the sound of the spray that can stop the pairing, and then Finally, we can gently blow at the ear of the cut if the first two techniques are not successful.
But with that, with this, knowledge, then we know how can, we can reduce this interference, which is quite annoying when it comes to auscultation. Then I would like to talk about the points of auscultation because if you read textbooks, then we will read the typical position of the stethoscope behind the elbow on the left side, which is the point of auscultation of the pulmonic valve and then slightly coldly and crane and, and, and dorsally, we got the sound coming from the earth and then more ventrally towards the sternum, the sound coming from the mitral valve and then the tricuspid valve. From the right side.
However, when it comes to cats, this is purely theoretical, because the bell of the status quo very easily covers all these points of auscultation. So we should probably just simplify the points of auscultation and just Use the sternum as a point of reference where we got actually the majority of sounds are coming of heart murmurs are heard at the level of the sternum or just on the sides of the right para sternum or left parasternum, and very rarely we can go. A little bit more specific to, for example, the base of the heart or the apex of the heart, or even under the axilla, where we can hear the sound of great vessels, like, for example, the prices of a patent to certain users that will generate a continuous sound very up in in the axillary region.
And we know that there are systolic sounds. We call them S1 and S2 or simply lab dub. And these are sounds that are caused by the closure initially of the mitral and tricuspid valve that will generate the first sound, S1, and then we go at the end of the closure of the semi-lunar valves.
Namely, pulmonic and aortic valve that will produce the second sound or S2. During diastole, we don't really hear very much, although there are possibilities where there are situations where we can hear abnormal sounds that we call the extra sounds or diastolic sounds. But let's focus on the normal sounds of a cat, which tends to be quite rapid in the majority of cats, and it sounds exactly like this.
As I said, there are also diastolic sounds. The first diastolic sound called S3 is caused by the distension of the ventricular wall during the initial diastole during the passive feeling, and then we got an additional sound or S4 that comes after an additional distension of the ventricle following the aual control. Action.
However, the loudness of these sounds is very low compared to the first two sounds and therefore, due to an adaptation of the human hearing, we tend not to hear these sounds, especially with rapid fast heart rates. Much easier to hear these sounds when it is . A low heart rate, and which is much easier in a, in a, in a large animal, in a horse or, or, or in a human being, but certainly small animals, that's not particularly common to hear these sounds in physiological situation.
What happens, however, if we have a disease affecting the myocardium, like in a cardiomyopathy, then the stiffness that, Occurs following the underlying pathology, the stiffness of the myocardium can increase the loudness of the ventricular distension and therefore we can hear this additional sound. And we can't really differentiate between S3 and S4 due to the fast heart rates. So we just hear an extra sound that will give, rather than a lab dub, we give a laded up, loaded up, loaded up sound that remembers to.
Finds like the sound of a galloping horse, and that's why we call it gallop sound. And I've got an example here of a cat with cardiomyopathy where we can hear the first sound and we can certainly say it's, it's a gallop sound. So this is obviously different from the normal sounds we heard at the very beginning.
This is very important because although sometimes we have gallop sounds due to stress or excitement, due to the increased catecholamine release, the majority of gallop sounds are associated with the myocardial disease. So this should prompt cardiac investigation immediately if we hear something like that. So after this introduction, we can now focus on the heart murmurs and our group has worked on heart murmurs for, for many years.
We have extensively published on heart murmurs in cats over the last, over the last few years. And This is Supported by the fact that it is a very common problem, commonly detected and very commonly heart murmurs can trigger a referral to a cardiologist to identify the cause of the murmur and identify the clinical significance. Unfortunately, the final answer comes from an echocardiographic examination.
It can be relatively expensive, but this is certainly indispensable to identify the exact cause and the exact significance of a, of a murmur. Previous studies have focused primarily on structural heart disease and they they did not actually focus on the origin of the flow turbulence, which is what causes the murmur. So the flow turbulence is due, for example, to a valve that is meant to be open and it's not, or a valve that is meant to be closed and it's not.
This can cause a turbulence or an intracardiac communication like in a ventricular septal defect or an extra cardiac communication like in patent to certain users. That's where we need to work. We need to identify the turbulence in order to know exactly where the murmur is coming from.
And then also we got something that is completely new in veterinary medicine. We were the first in our group to report the presence of iatrogenic murmurs. And iatrogenic murmurs are murmurs that we cause with our stethoscope or could be iatrogenic turbulence that we can generate with the probe of our ultrasound machine.
We're going to, to describe these situations in detail. But going back to the previous studies, we got this study here that was published in the Journal of Etric cardiology, approximately 15 years ago. There's a very elegant study and what they did here, they tried to see if there was a correlation or an association between the thickness of the ventricular wall with the presence of a murmur.
And as you can see from this table, there is no such. Association. But I think that the approach here was likely incorrect because what we need to do, we need to identify where the murmur is coming from, when the turbulence is coming from, rather than looking simply at the thickness of the murmur of the ventricle.
And this is not the cause of the murmur. This is just a pure structural identification, structural abnormality that we can detect on ultrasound. So our approach was slightly different.
We try to identify the exact cause of the murmur. And we came out with this publication 18 months ago, approximately on the prevalence and clinical significance of heart murmur. It's a large study on nearly 1000 cats.
So this paper is a free download, so you can read the entire study with with this. Download from, from the internet. And then we looked at the characteristics of these murmurs.
We look at the loudness, the point of maximum intensity, whether or not a murmur is fixed or dynamic, the, point of maximum intensity, as I said earlier, designed with a new terminology like steno parastenal rather than traditional apex and bass and and tricuspid valve. And then also we looked at the timing and the places of inducible murmurs. So let's start with the loudness and point to maximum intensity.
Surely you remember from your studies in academia that murmurs are classically classified, intensity of murmur, classically classified or graded according to the Levi scale, which is a scale from 1 to 6, where grade 1 is A very soft murmur that can only be heard with a particular effort. Then we call grade 2 that can be almost immediately, can be immediately heard on auscultation and but that is soft to the point that the loudness is actually lower than the loudness of the heart sounds. When the sound, the loudness of the sound and, and, and the murmur is similar, we call it grade 3.
But if the murmur is louder than the heart sounds, we call it grade 4. When we have also a vibration that we can appreciate on palpation of, of the chest, then we call it a palpable thrill, so we can have a grade 5. And when we can hear the sound, still by moving the stethoscope slightly away from, from the chest, we call it grade 6.
Very difficult, I know, very difficult to remember and that's why A few years ago in dogs, we have proposed a new system for classifying heart murmurs where we combined grade 1 and grade 2 into soft murmur, and then we have moderate loudness in grade 3 and then all the others would be loud murmurs. In dogs, we have found that there is no any difference if we group this Different grades of murmurs in three groups, we don't lose any clinical information. Therefore, we can simplify auscultation, especially in cats, I think it's very valuable in a soft, moderate, loud murmurs.
And obviously we've got a very few number of cats with a palpable murmur. That's the result of our study. We have 56%, nearly 57% of murmurs that were soft.
The majority of murmurs are soft in cuts. Then we got moderate murmurs, and then we got loud murmurs and very few palpable murmurs. And if we look at whether or not this loudness Changes during a quotation, we can call these murmurs dynamic or fixed.
Fixed means that the loudest doesn't change during our A quotation, but if it changes from one grade to another, then we call it dynamic. And we found that approximately 25% of these murmur. Are dynamic, so they can change in loudness very often due to the change in heart rate, but approximately 3/4 of murmurs are fixed, so the loudness we perceive at the beginning of a quotation will be the same loudness we perceive at the end of our quotation.
Now, going back to the point of maximal, maximal intensity, we know that 37% are primarily located in the left partternal area and we got 38.7% in the, the left . Base, we got, a small percentage of the left apex, but another big chunk is at the level of the the right paternal area.
In terms of timing, obviously, we got systolic murmurs, we got diastolic murmurs, and we got continuous murmurs. Now, systolic murmurs, as the word says, They appear between S1 and S2, and that's the systolic phase, and that's the majority of murmurs in class. I always say to young students, as I just said, if you don't, if you're not sure 100%, just say systolic, you've got a big chunk, a bigger chance to get the right, the right answer.
So, there's a systolic murmur. If the murmur appears during the diastolic phase between S2 and the subsequent S1, then we call it diastolic, very rare murmurs. And then we got the continuous murmur that covers the entire cardiac phase and that's why we have this typical characteristic.
Now, we do have also to and fro murmurs where there is a little, little pause, very short brief pause between . The two, continuous phases. So between one career cycle and the other, there is a little bit of a phase, but that's pretty much .
Sort of theoretical rather than practical, information. Now, when it comes to, human auscultation or even canine auscultation, we always try to identify the shape of the murmur in the humans they call it about a diamond shape or a crescendo de crescendo. The problem is that when we go high heart rates, it's very, very difficult to appreciate these behaviours of, of the sound, whether it's increasing and decreasing in loudness during the The genesis of the murmur.
So, I've got a recording here from a dog because the heart rate is relatively generally lower. And we can appreciate the harsh characteristic of this murmur rather than the proper crescendo the crescendo. Usually, when we hear a harsh sound, that's usually associated with an obstructive lesions like a pulmonic stenosis, like in this case.
And if we cannot appreciate the harsh characteristic of this murmur. Try to think about a saw cutting a log, that would be pretty much what would consider a harsh sound. Then we got the musical sound like a, a micro valve disease, a microval regurgitation in a dog where there is no such a harsh characteristic.
It's a little bit more fluid. This could also be the sound coming from a ventricular cept effect if it is large enough. However, when it comes to cats, because of the fast heart rate is very, very difficult to differentiate between these characteristics.
And I've got an example here of a cat where I can't really say whether it's a harsh or a a musical murmur, we just say murmur, and that is probably enough for our clinical information. And that's an example here. Excellent.
When it comes to diastolic murmurs, I, I said that earlier, they're very, very rare to the point that I never managed to record a diastolic murmur because every time I hear one, I do not have my electronic stethoscope with me for the Murphy's look. So, I've got this example here, which is generated by a computer, so it's an artificial murmur. It's a system done for training human doctors just to give you an idea about a completely, completely different music produced or noise produced by these diastolic murmurs.
It's a very prolonged sound, tends to be the crescendo type of, of sound and it's, as I said, very, very difficult to appreciate in CAT. So I just mentioned it to clarify this potential confusing factors. But continuous murmurs are possible in cats, so they cover both cystoline diastole and they are almost inevitably associated with the patent to, to certain uses, which is present in cats too.
It's not as common as in dogs, but we need to be very special in kittens, we need to be very, very careful and place the stethoscope under the left axilla in order to hear this continuous murmur. So that's one patient with the PDA. And we need to remember that if we don't place the stethoscope up under the axilla, we may miss these continuous murmurs.
So we can hear the murmur, but not as a continuous murmur. So, for example, in this bengal here with the eductus arteriosis, if we place the stethoscope to the, towards the sternum rather than under the axilla, what we hear is just the systolic component. And that's an example here, and we've got also a funocardiogram that shows the murmur here in in Sicily.
However, as soon as I move the stethoscope under the axilla, then I can hear the continuous murmur. The previous one, there was a pause between the C and Dias. In the second one is a continuous sound as demonstrated by the followlocardiogram that was recorded in this cat.
As I said before, majority of murmurs are systolic. 90% of murmurs are systolic. Then we got 5% of diastolic murmurs, and then we got 4% of continuous murmurs, 1% to and fro murmurs.
So just to remember, 90% of murmurs in cats are systolic. But obviously, we need to go to the very core of this presentation. We want to know what the most common causes of heart murmurs in cats are.
And I'm going to show you the results of our study. In a 55.9% of cuts, we had no abnormalities associated with the heart murmur.
No structural abnormalities. Obviously, we identified the cause of the murmur in the majority of cases, but no associated cardiac conditions, no associated cardiac abnormalities. Then we have approximately 30.
1% of murmurs that are coming from an acquired cardiac disease and then 13.3% of murmurs coming from a congenital heart disease. So that's the distribution.
Of murmurs in our population of approximately 1000 cats. And what are the causes? The causes are systolic anterior motion of the mitral valve in nearly 40% of cats.
32% of cats present dynamic right ventricular outflow obstructions. So I'm going to explain every Single condition here to also see where they're coming, these murmurs are coming from and what they mean. Then we got approximately 7% of murmurs that are called the flow murmurs.
Then we got the two important tricuspi regurgitation and micro regurgitation that are approximately 6% of . Murmurs in cats and they are usually associated with the atriventricular valve dysplasia. So that is obviously a congenital defect.
And then we got a number here you can see of conditions that all congenital diseases that can, can cause the presence of a murmur. But obviously, the big bulk here is Systolic anterior motion of the mitral valve, dynamic right ventricular outflow obstruction, flow murmurs, and AV valve regurgitation. So, let's go to systolic anterior motion of the mitral valve, which is the most common cause of murmurs in cats, is caused by An obstruction in mid-systole due to an abnormal movement of the mitral valve.
That's why systolic anterior motion is the anterior leaflet or septal leaflet of the valve that causes this sound, and I'm going to explain it with the cartoon this condition in a second. We don't really know what the cause of systolic aerial motion is. Could be multifactorial, could be deformation of the mitral valve architecture, could be a hyperdynamic state, for example, during the excitement or due to the process of the left ventricular hypertrophy, could be an intrinsic valvular disease causing dysplasia and, and deformation of the mitral valve apparatus.
It's interesting to know that some is presenting approximately 50% of cats with hypertrophic cardiomyopathy. So a common finding in 50% of these cats with HCM, but it's also true that 50% of cats with some do not have. Any structural abnormality.
Once again, we were the first team to report this finding where before the presence of systolic anterior motion was considered patternnomonic for HCM, which is not true and that's also been reported in dogs and and in humans. And then there is also this factor that needs to be taken into consideration that cats with systolic anterior motion seem to live longer than cats with without this echocardiographic finding. However, we need also to remember that the presence of a murmur means a much earlier diagnosis of And hypertrophic cardiomyopathy.
So it is possible that this prolonged survival is just due to the fact that it's an early diagnosis compared to a late diagnosis, usually when cats present a reading heart failure. So I think that this information needs to be perhaps taken with a pinch of salt. So systolic anterior motion is reported here in this diagram.
We see on the left side, we got a normal heart and in systole the mitral valve closes completely, so the anterior leaflet, the posterior leaflet coalesce and the blood is forced to only go in the outer tract into the aorta to deliver the oxygen and nutrients to every cell in the body. However, with hypertrophic cardomyopathy, but even without hypertrophy, we can have this abnormal movement on the right side of the screen. You can see this abnormal movement of the anterior septal lift the anterior mitral lifter or septal leaflet.
That will interfere with the outflows. It's like pretty much when I try to explain this to a client, I I try to imagine to put a thumb at the end of the garden hose when you water your plant, and the water will suddenly increase in have a faster velocity increased speed, which also associated with the turbulence. And the sound in our case, obviously it's the blood causing this turbulence and the sound comes from, from the outflow tract.
However, you should notice that if the valve is moving in mid system in the wrong direction, so it's moving towards the septal rather than going and and meet the counterpart, which is the posterior mitral lifter. We have the m mitral part that is partially open in Sicily and therefore we got also mit regurgitation. So there are two different sources of turbulence that can contribute to this murmur.
And I got here an echocardiographic examination that shows this typical double jet, one going into the aorta, one going into the left atrium. So this double turbulence is the cause of the murmur. In our group, we, when we diagnose systolic anterior motion, we just, we look not just at the movement of the mitral bike can be quite misleading, especially if you don't have a particularly high frame rate set on our roottrasound machine.
So, we want to see this, the presence of a double jet here in, in this view, then we want to see the abnormal shape of the outflow tract. Of the Arctic flow that we can see here on the left side of the screen. You can see it's got a lot of typical dagger shape, and I may be able to point with my laser pointer here.
There's, this dagger shape here is caused by the sudden acceleration in mid-systole, and that's when the anterior septal leaflet moves towards the septum. So that starts the interference, starts the obstruction, and therefore, the flow increases rapidly in the second half of Sisterly. And the other thing we want to see is in the M mode acquisition of the mitral val, we want to see this abnormal movement, this, this little bump here of the sepular leaflet that rather than staining attached to the parietal leaflet, moves for a fraction of a second towards the septum.
So we want to see these three components, these 3 features in order to make this definitive diagnosis. Years ago, Carsten Schubert, an American, well, German-American cardiologist, reported this, study on, the possible causes of the systolic anterior motion, very elegant study once again, really, really nicely, described as well. So you can see here on the, on the top of the screen.
We have a normal normal leaflets that coalesce in Sicily, so they, they touch each other, they block completed communication between leftedum and left ventricle and the blood can only flow into theorta. But then we got situations where the septal leaflet, for example, is abnormally elongated. It's too long, and therefore in Sily may move in this paradoxical motion towards the septum, which is certainly not something we'd like to see because otherwise we have the systolic anterior motion.
And this table from the same study shows the the, the, the, the, the relation between the length of the septolifle, which is reporting the Y axis and the degree of obstruction that is measured as velocity in the aorta. And we can see that. With a relatively short mitral leaflet, then we got, we got a mild obstruction.
If the leaflet is longer, then we got to moderate. If it's excessively long, we got a severe obstruction. So that's certainly a good explanation of this phenomenon.
But also, we can have the so-called cordula. So it's not the actual leaflet causing the obstruction, but the cord tendin associated to that, that leaflet are a little bit. Redundant and this lack of the, of the cord can cause the obstruction.
And then we got finally, the praises of false tendons, exuberant false tendons, a bar and cordi, that can also contribute to this abnormality. But the important thing to remember is that, yes, we can have, we can have obstruction due to systolic anterior motion due to hypertrophic cardiomyopathy, like in this case, we can see the ventricle is relatively thickened and then we got this elongated septal leaflet here that can be easily visualised in these images, but we can Also have systolic anterior motion in cats without signs of hypertrophy or without any evidence of cat disease in general. And we can see here that this perhaps in this particular case is probably the hyperdynamic state causing the systolic anterior motion.
This is the heart beating extremely fast. It is a very nervous cat. And indeed, if we sedate for any reason, one of these cuts with this systolic anterior motion due to hyperdynamic state, the murmur tends to disappear.
And that's why sometimes we hear the murmur on a quotation. We go to perform an echocardiographic evaluation and we don't see anything abnormal. So what we can do to start with, we can do a provocative testing.
So we can increase the heart rate or try to increase the heart rate of this cat simply by increasing the volume of the Doppler sound on our ultrasound machine. That It is usually an unexpected sound for the cat. So we got a moment of excitement, the heart rate goes up a little bit, and therefore, we may evoke the dynamic obstruction.
We can evoke the systoic anterior motion, as you can see here in this diagrams. So it was a, a normal looking or nearly normal looking outflow from the aorta here and then it suddenly doubled in speed due to this dynamic obstruction. So is a systolic anterior motion necessarily a bad guy since we saw that it might potentially be associated with a longer survival, but I, I doubt it.
I don't think it's, it's a benign condition at all. And if we look at this, postmortem imaging, images published by our colleague, Philip Fox, American cardiology with a strong interest in cardia pathology, we can see That the point of contact between the anterior mitral leaflet and the septum can cause a scar. The scar is seen here in blue and that's due to the trichromic as revealed by the trichromic stain here in this particular.
Specimen. And you can also see on the left side of the screen, you can see this white line here which is again a scar due to this continuous contact between the leaflet and the, and the septum. It's also called kissing lesion or contact lesion.
Depending on which textbook you read. And, you may notice also that the posterior mitral valli is also affected by a degree of fibrosis here and that's probably due to the jet lesion. Don't forget that we got also mitral regurgitation associated in these cases of the share of effect on the, on the surface of the leaflet can be responsible for these anatomical changes.
But even in people, some is taken quite seriously. To the point that they usually, I mean, human patients with a severe systolic anterior motion can faint. They can also experience sudden death in a few cases.
So, if they don't respond to beta blockers like atenolol, for example, then, very often they consider, an intervention to reduce this, obstruction. The intervention could be either a septo alkalization, so they inject alcohol in a coronary artery in order to kill. Cause an infarction here at the level of, this proximal part of the septum.
And by doing that, the, the, the, the myocardial at that particular point will, reduce in in thickness, making a, an outflow track a little bit more. More open or can be done surgically with a septal myectomy, so part of the septum is removed in order to open freely the outflow tract. Now, I'm not aware of any attempt done in CAS to reduce the systolic anterior motion with these surgical techniques.
However, we do use beta blockers in some occasions to in the attempt to reduce this obstruction. Now, I mentioned the places of systolic anterior motion in, in dogs. That's again, something we can see occasionally, not very common, and they tend to respond nicely to beta blockers to the point that very often we see a complete regression of the disappearance of the systolic anterior motion and regression of the left ventricular hypertrophy.
But how about cats? So we don't know whether some is necessarily, well, we know that it's not necessarily associated with hypertrophic atommyopathy, but we want to know whether the hypertrophic atommyopathy can be responsible of the sum or is the sum responsible for the left ventricular latrophy. The reason is that if we got an obstruction, the obstruction will cause an increased pressure in the left ventricle, and that is a stimulus for new fibres to be built in a concentric fashion and therefore end up with a concentric atrophy that mimics in a way hypertrophic and myopathy.
And for this reason, we try to see whether is the, well, since this is a chicken and next story, we try to see whether it's the HCM or the left ventricular hypertrophy causing some or whether it's the sum causing left ventricular hypertrophy. And in this study, we, what we did, we recruited cats that had systolic anterior motion of the mitral valve but did not have evidence of left ventricular hypertrophy. So what was the beginning.
Of of of a condition. And what we did, we measured the cardio biomarkers, we measured NT probMP to see if there was any evidence of stretch of the myocardium caused by some, and then we measured cardio troponin to see if there was any evidence of myocardial damage. And the result was quite, quite surprising because of, out of 34 cards in this study, we found that the majority had elevated antiro BMP indicated there is a degree of stress, or stretch of the myocardium.
Possibly associated with this dynamic obstruction. Of the 123, and 4 cats here that had the anti-prob within the normal range, these were all cats where some was only present after the provocative testing. Therefore, these cats will had no sound during normal day, but on the ultrasound table, they could do due to stress or exciting, they could have this na.
Obstruction on the right side of the screen, we got the level of cat troponin, which wasn't measured in all cats, but we can see that a lot of cats have evidence of hy troponin level which indicates a degree of myocardial damage. So these are cats with systolic anterior motion without signs of hypertrophy, but that increased pressure caused by the obstruction is certainly not beneficial. It could be potentially a dangerous condition.
Now, obviously we could argue. That, the, the, the, the, the level of NTR BMP we could speculate that the level of NTR BMP is associated with a degree of obstruction, and we found indeed a linear association between between these two. So, the higher the obstruction, the higher the level of NTR BMP.
Therefore, I think this is a pretty compelling evidence. So anti-robin conclusion, can be seen in all cats, majority of cats with Systolic anterior motion without left ventricular atrophy. Some of these cuts may also present a degree of myocardial damage suggested by the increase of a cardio troponin and the pressure of a load or early myocardial disease suggested by the increase of antiro BMP.
So interesting elements and as you can see, it's not a very easy, topic, but certainly something that has been clarified for a more successful cardiac investigation. The second common cause of murmurs in cats is the dynamic right ventricular flow obstruction, which was heard in 32% of heart murmurs in cats. Now, dynamic right ventricular flow obstruction tends to be considered a benign condition, and there's an obstruction that originates from the outflow tract, pretty much at this level here where I'm pointing my.
My laser here and you can see the turbulence that originates slightly before the opening of, of the pulmonary artery. So above here, above the pulmonary valve. And you can see on the right side here, we've got a very similar shape of, of the pulmonary flow that reminds the systolic anterior motion on the left side.
Here's exactly the same principle because we got the mid-systolic obstruction caused by the muscle in this case, we got a dagger shape appearance of the outflow. Now, the interesting thing is that over a year, over the years, we found that this dynamic obstruction can be caused iatrogenically. And initially, we reported this phenomenon in cats using Doppler echocardiography.
And you can see here on the, on this example, we got a laminar flow here in the outflow tract on the top left. And then with a very gentle pressure of the ultrasound probe, we can induce a turbulence. So basically, the obstruction in the outflow tract in mid-sistly here is caused by us.
Pressing too hard with the probe of the, of the ultrasound. And you can see here be after bit, we can see how we can change the profile of the of the outflow track, the right outflow tract, and the speed of it. So the more we press, the more we change the profile because we cause dynamic obstruction, we increase the, the speed of the blood flow.
And we can see here on this photocardiogram that we can induce the murmur by pressing with the stethoscope. So we can have exactly the same phenomenon by pressing on the right part of external area with the, the, with the head of the stethoscope. And I've got here.
A video and we have here a normal. No more heart sounds, and then at this point here, I will start pressing with the, the head of the electronic stethoscope and we will see the origin. We will hear actually the origin we can see on the graph here on the holocardiogram, but we can hear also the genesis, the onset of the murmur.
And how it changes. We go to groomer. And here the murmur disappears when we gently we remove the pressure on the On the chest.
And equally, we can see here that in terms of speed, if we don't press with the probe, we've got this velocity on the on the outflow tractor. As soon as we press gently, we can almost double the speed and therefore we create a turbulence in the outflow track. So this is a purely iatrogenic dynamic obstruction.
And one could argue and say perhaps when we start pressing the heart rate goes up and therefore we induce a murmur due to the increased heart rate, but in our study we have proven that there is not such association. It doesn't matter whether we press. It's a very gentle pressure anyway, but it doesn't matter.
It doesn't really change the heart rate, you see there is no correlation at all between the big velocity here and the heart rate in that in this cat. Right. And then, what we did, we sort of extended the study in general practise.
So with these amazing colleagues here working in practise and now actually, the first author, Katie Orwell, is now working in a, a referral institution. But what we did, we try to see whether we could induce this murmur just with the stethoscope in cats, healthy cats coming from annual vaccination. And we can see here on the left side of the screen, we got the 3 clinicians, where all the clinicians with the certificates or very experienced clinicians, very knowledgeable, and we can see that in approximately 30% of cuts.
All clinicians managed to evoke a murmur, and there was nothing here that was causing the murmur apart from the pressure of the stethoscope. And we found that there is an association with the age and the body condition, other words, the older the cat, And the thinner the cut, the easier is the easiest to evoke this murmur and probably because of the compliance of the chest is a little bit higher in a thin and old cat. And so, in this particular study, we have an average of 28.2%, so we can clearly say that approximately 1 in 31 in 4 is subject to aatogene murmur if we press a little bit too much with the tescope.
And It doesn't need, we don't need to have a massive pressure on the chest. So perhaps if we hear a murmur that is slightly louder on the right part of the area, let's try to remove gently the pressure and see whether the murmur disappeared, because if it does disappear, you've got a very high chance to be dealing with iatrogenic murmur. And then we have, as I said, the mitral and tricuspi regurgitation that represents approximately 8%.
Of murmurs, so 16%, 8 for mitral valve regurgitation, 8% for recuspid valve regurgitation. Very commonly associated with the displays and malformation of, of the valves due to the congenital defects that we can hear, we can see here very clearly. The regurgitation of the mitral valve in this left apical view and the regurgitation of the tricuspi valve.
You can see that both valves look quite abnormal, especially tricuspi here is severely abnormal with the seal leaflet, almost immobile attached to the sect due to very short cord the tendon. But if you remember, I also mentioned the flaw, very commonly called also innocent murmurs. Yes, these are possible.
Basically, it's a diagnosis by exclusion when we cannot identify any turbulence and despite all the different attempts, we say perhaps it's a flow murmur and which again could be Associated with the change in heart rate or body position as reported in children, for example. However, it's also true that perhaps we have, we, we might have missed murmurs that are, could have been reviewed by a provocative test, could it be, like a systolic anterior motion or a dynamic right ventricular flow obstruction. Simple reason we have not done a successful provocative test.
So 8% of cats remain sort of undiagnosed, but it means that if we don't identify any abnormality, probably most likely these are normal cats. And then I mentioned a number of congenital defects that are listed here. I'm not going to mention them all, but obviously, we can see that the most common defect we see in our institution is the ventricular sector defect.
Obviously, we got, after the microtracaspiva dysplasia, followed by all the other conditions, but certainly they represent a small percentage of murmurs and cats. So the murmur characteristics may help as we saw earlier. So if we do have a palpable, continuous diastolic loud murmur, usually, almost I would say 100% of the cases, these murmurs are associated with a significant congenital cardiac disease.
However, there is a negative association between the soft, moderate systolic heart murmurs, intermittent heart murmurs, murmurs with a point of maximum intensity over the right paternal area, and the presence of cardiac abnormalities. In other words, in these cuts, we might be dealing with Iatrogenic murmurs. In the right outflow tracks or intermittent systolic anterior motion from the left ventricular outflow tract.
So that's pretty much what we can achieve from a simple auscultation. However, since the majority of heart murmuring cats, appear to be systolic and mild to moderate in loudness, the echocardiography is, should be performed ideally by an experienced cardiologist because, the Doppler assessment is fundamental and is also fundamental to have a good experience and expertise in using this technique. And in my opinion, an investigation should always be made because it's true, we know these percentages, but we don't have a clear cut system based on those quotation to say whether or not this murmur can lead to problems in the future.
So at least in a young kittens, when we, we can hear the murmur, we should consider an echocardiography to rule out at least the presence of a congenital defect. And equally, if a murmur appears later in life, we want to make sure that it is not associated with the onset of hypertrophic cardiomyopathy or another form of cardiomyopathy, for example. And this is a particularly important because cats are also quite unique in the, in the way that they hide their pathology, carry pathology quite nicely until they develop over heart failure.
So we can really appreciate exercise intolerance and so on. And therefore, I think an echocardiophy. Should always be in considered for further investigations.
Also, I think there is a, a good merit to consider CD biomarks, in particular the NTR BMP. We saw the NTR BMP can be elevated. Even in the presence of, in the presence of systolic anterior motion without a periatrophy.
So we should probably, at least consider a SNA test, if not, a quantitative test for anti BNP because the SNAP test, if normal, is probably sufficient to rule out, at least that particular phase, a significant underlying kind of disease. So that's what I had to share with you about my knowledge of heart murmurs and cats and I really thank you for your attention. Thank you very much.