Amara H. Estrada, DVM, Diplomate American College of Veterinary Internal Medicine (Cardiology)
University of Florida, College of Veterinary Medicine


Patient Observation & Tools

Hi, I’m Dr. Amara Estrada at the University of Florida and today I’m going to be talking about the cardiac physical exam.

Knowing how to do a good cardiac physical exam is a very important diagnostic tool, as you can oftentimes make a reasonable diagnosis (or at least get down to a very short differential list) just in the exam room with the patient and the owner.

Despite a lot of technological advances in cardiology, like echocardiography, cardiac physical exam really just relies on the 5 senses and a good stethoscope. A good stethoscope is not the most expensive stethoscope you can buy, it’s the one that fits well and snugly within your ear canals and feels comfortable. As a general rule, shorter tubing to avoid a lot of artifact while listening is better.

Stethoscopes are made in all different sizes and shapes. They come with double tubing, they come with single tubing, and they come with double tubing within a single tube. And again, the emphasis is not on the most expensive stethoscope, but the one that is most comfortable for the user. What I recommend to our students is to try out a lot of different stethoscopes to see which one is most comfortable for you, and then stick with that stethoscope for as many patients as you can and try not to borrow stethoscopes or change stethoscopes from patient to patient, and use the same one all the time.

Stethoscopes should have a chest piece that has both a diaphragm and a bell. The diaphragm is good for accentuating high-frequency sounds, such as murmurs, and attenuating low-frequency sounds, whereas the bell will be good at accentuating low- frequency sounds, such as gallop rhythms, and attenuating high-frequency sounds.

A lot of the patient observation is done while taking a history from the owner. So while you are talking to the owner about drugs and dosages and responses to drugs, you are watching the animal and observing it for any signs of respiratory difficulty, as in these 2 animals with their necks extended, showing orthopnea or tachypnea and dyspnea. You’ll also want to observe the animal as it walks 2 around the room, as in this animal with obvious ascites and this animal with obvious cachexia, which is likely cardiac in origin.

Evaluation of the mucous membranes in animals is important. This young dog has nice, pink mucous membranes and you don’t have to get real close to see them. Cyanosis is caused by arterial hypoxemia and is either caused usually by severe respiratory disease or severe cardiac disease. Types of cardiac disease that can cause what we call central cyanosis, where the whole body is hypoxemic, include right to left intracardiac or great vessel shunting. There’s also something called differential cyanosis, where the cranial half of the body or the head and neck vessels are receiving oxygenated blood and the caudal half of the body is receiving unoxygenated blood. And this is most often the case, with reverse patent ductus arteriosus.

Another important aspect that is sometimes neglected in the cardiac physical exam is inspection of the jugular veins. This can give you a really good idea of right-sided cardiac filling pressures. To do this, the animal should be either sitting or standing and the head extended so that the jugular vein area can be readily  seen. For animals with long hair, sometimes you can wet it down with alcohol, or if you really need to, shave an area to inspect the jugular veins. In a normal animal, when you apply direct pressure at the thoracic inlet, the jugular vein will extend and fill, but should rapidly dissipate. In an animal with right-sided heart disease, when you occlude the thoracic inlet it will take some time for the jugular vein to go down, or as in the animal on the right, it might be distended without any pressure whatsoever.

Another test that you can do, a provocative test to look for signs of right-sided heart disease in an animal who maybe has normal-appearing jugular veins, is called the hepatojugular reflex. This is a test that’s done, usually when the animal’s standing, and what’s done is slight—just mild—pressure is placed in the cranial abdomen over the liver. This increases venous return to the heart. In a normal animal, this would produce no change in the appearance of the jugular veins, but in an animal with right-sided heart disease, you’ll start to see pulsations or distension of the jugular vein, as in this animal who is having a hepatojugular reflex performed.


Pulses & Palpation

The next part of the cardiovascular physical exam, and an important aspect of it as well, is palpation of the femoral pulses. And you’re going to palpate the femoral pulses to assess for synchronization—whether both sides feel the same—for any arrhythmias, and also for the strength of femoral pulse quality. The normal femoral pulse… we have to remember what you’re feeling is the difference between systolic and diastolic pressure, and so a normal pulse will just be the difference between those 2 values.3

Animals with weak pulses may either have a low systolic pressure or a high diastolic pressure. We typically see weak femoral pulses with diseases like dilated cardiomyopathy or pericardial effusion, where the pulse pressure or pulse difference is not as great as in a normal pulse. On the flip side, animals with a low diastolic pressure or a high systolic pressure can have bounding femoral pulses. Sometimes these are referred to as water hammer pulses. We see this  with patients with patent ductus arteriosus (aortic insufficiency) and it can be a very good diagnostic clue in a young animal with a heart murmur.

Another change that you can feel in femoral pulse quality is when you have arrhythmias. If you have a pattern where you have every other beat being an arrhythmia, like a VPC with a bigeminal rhythm, you can oftentimes palpate that in a pulse. You can also have animals, or young animals with a loud murmur from subaortic stenosis, that will have what feels like weak pulses because they  have a delay in the rise up to their systolic pressure.

Another change in pulse quality is felt with animals with left-ventricular failure or myocardial pump failure, where you feel alternating weak and strong pulse quality.

In addition to palpating femoral pulses, you also want to palpate the thorax. Usually I do this on both sides of the chest, and I’m doing this for several reasons. One to feel where the atypical beat is, but also to get a sense of whether there are any thrills or vibrations which should direct me toward listening to a specific area closely.

I also palpate the abdomen to assess for any masses and ballot the abdomen to assess for any fluid accumulation.

The regions of cardiac auscultation… There are several on the left and right sides that need to be paid attention to. On the left, you want to listen over the mitral valve first and then slide cranially up over the harmonic and aortic valve areas, not forgetting to listen very, very cranially. This is a region that is oftentimes forgotten to be listened to and it’s an important place to assess for patent ductus arteriosus.

On the right side, we can listen over the tricuspid area and over the heart base area. In cats, it is very important in addition to listening to those areas, to listen right on the sternum. Cats, especially when they age, as seen in this radiograph, their heart starts to tilt toward their sternum and so all the valve areas kind of overlap and become just right or left of the sternum, and so it’s very important to listen over the sternum in a cat, as this is where most murmurs in cats are going to be ausculted.


Heart Sounds

So let’s talk about normal heart sounds. Normal heart sounds consist of S1, which is closure of the mitral and tricuspid valves, and S2, which is closure of the aortic and pulmonary valves. These don’t happen exactly simultaneously, but they happen close enough that our ears aren’t able to pick up the difference in the 2 valves closing at the same time.

Gallop sounds are either an S3 or an S4 sound, which occurs in diastole. An S3 is rapid ventricular filling; an S4 occurs with atrial contraction. This can be heard in animals with dilated cardiomyopathy or in cats with heart disease. In cats with heart disease and gallop rhythms, it can be very hard to distinguish whether it’s an S3 or an S4 because their heart rates are so rapid. It’s often described as  “horse hoof beats” or “gallop rhythms” because that’s what it sounds like, as in this cat with hypertrophic cardiomyopathy.

Midsystolic clicks are another pretty common auscultatory finding in dogs—older breed dogs with mild or early degenerative mitral valve disease. And it can sound somewhat similar to a gallop rhythm, but the important difference is that it occurs during systole and not during diastole, as in this dog with mild mitral valve degeneration.

Split heart sounds are another auscultatory finding that can sound similar to a gallop sound, but come a little bit sooner than what would be heard with gallop rhythm. Split heart sounds are most commonly heard with pulmonary hypertension, as in dogs with heartworm disease, and are usually due to delay of pulmonary valve closure. Now remember, the aortic valve and the pulmonary  valve don’t always (and usually don’t) close simultaneously, but with pulmonary  hypertension there’s going to be such a delay in pulmonary valve closure that our ears are able to pick up that split in the closure of the semilunar valves.

When listening, we also can pick up tachyarrhythmias, such as atrial tachycardia and ventricular tachycardia. Notice that in these 2 arrhythmias it’s almost impossible to tell the difference between an atrial tachyarrhythmia and a ventricular tachyarrhythmia. You just hear extra-fast sounds, you can’t tell the difference between the 2 of them.

Atrial fibrillation is another common auscultatory finding and is a very characteristic sound that can be distinguished from other arrhythmias upon listening.

Bradyarrhythmias are also something we can pick up on auscultation. You can hear complete heart block as in this dog with a bradyarrhythmia due to third-degree AV block. In this situation you can actually hear the atrial contractions followed about every third or fourth beat by a ventricular contraction.5

You should also get used to what a sinus arrhythmia sounds like, because this is a very common auscultatory—normal auscultatory—finding in dogs, but not in cats. And this should not be confused with a bradyarrhythmia; but this is a normal auscultatory finding.


Heart Murmurs

Cardiac murmurs are created by turbulent flow in the heart or adjacent great vessels created upon disruption of normal laminar flow. The relationship of cardiac murmurs with flow velocity, vessel size, and blood viscosity is described by the Reynolds number. When this number exceeds a certain critical value, a cardiac murmur can be auscultated. So, changes in things like the velocity of blood flow, viscosity of blood, or the radius of the receiving chamber can create a murmur.

For example a dog with high sympathetic tone or high inatropic state can create a physiologic murmur simply because it has exceeded the Reynolds number. Similarly, an animal with anemia or polycythemia can have a physiologic murmur because it has exceeded the Reynolds number. So, not all murmurs are due to pathologic heart disease.

Once a murmur is auscultated, classifying it a little bit can help us get to a short list of differentials within the exam room. Things that we try to look at to describe a murmur more fully are timing of the murmur, location of the murmur, the intensity of the murmur, the pitch, and the shape of the murmur.

Heart murmurs which occur between S1 and S2 are called systolic murmurs. Heart murmurs which occur between S2 and the next S1 are diastolic murmurs. And heart murmurs which occur throughout the cardiac cycle are called continuous murmurs.

The next thing that we want to note when we’re describing a heart murmur is the location—whether it’s a left apical murmur, as in mitral insufficiency or mitral stenosis, or a left basilar murmur, as with pulmonary stenosis or subaortic  stenosis. We can also hear pulmonary insufficiency and aortic insufficiency in this region (again, not forgetting to listen very cranially on the left side for the murmur of a patent ductus arteriosis). And on the right side, we can hear murmurs associated with tricuspid valve insufficiency or ventricular septal defect. And again these classifications and characterizations of murmurs are going to help us get to a differential list that is very short and can hopefully direct us to a diagnosis within the exam room.

Heart murmurs are also described by their intensity. A grade 1 murmur is a very soft murmur, which is only auscultable in a quiet room with a very calm dog. A grade 2 murmur is also a soft murmur, but a little bit easier to auscult. A grade 3 murmur is a prominent murmur readily heard easily upon auscultation and putting your stethoscope on the chest (but might be only in a focal area). A grade 46 murmur is a loud murmur that is not palpable and is not quite as focal as a grade 3. A grade 5 murmur is a very loud murmur similar to a grade 4, but there is also a palpable thrill when you palpate the chest associated with the murmur. And a grade 6 murmur, again, is building upon the intensity. It is a very loud murmur that has a palpable thrill, but is also still auscultable after you take the stethoscope off of the chest of the patient.

An important thing to remember is that not always is the intensity or loudness of a murmur associated with severity of disease. Take for example a patient with mitral valve insufficiency. If the jet is directed directly toward your ear, as in this animal on the left, you’ll hear a very loud murmur, but if this jet—same degree of insufficiency, same valve— is directed away from your ear, you won’t hear as loud of a murmur. So in this case, the animal has the same type of disease, but the murmur is a little bit softer with one versus the other. Another example is a patient with a ventricular septal defect. The patient on the left has a very large ventricular septal defect, while the patient on the right has a very small ventricular septal defect. Because of the difference in pressures, the patient on the left is going to have a softer murmur than the patient on the right. And the patient on the left actually has more severe disease than the patient on the right. So, just reiterating that the intensity of the murmur is not always correlated to the severity of the disease.

Murmurs can also be described by their pitch, as in this dog with mitral insufficiency who has a very high-pitched, high-frequency–sounding murmur. Same disease in a different dog with mitral valve insufficiency, his murmur sounds very different; it has a very low- frequency sound.

The next way we try to describe murmurs is based upon their shape. And again, this is trying to get us toward a differential diagnosis within the exam room just using our stethoscope. Murmurs that are associated with subaortic stenosis or pulmonary stenosis are oftentimes described as being diamond-shaped or crescendo/decrescendo–shaped murmurs and have a very characteristic ejection quality sound.

Murmurs associated with mitral valve insufficiency, on the other hand, or tricuspid valve insufficiency, will have more of a plateau shape. Diastolic murmurs associated with aortic or pulmonary valve insufficiency will have this decrescendo shape. And murmurs associated with mitral stenosis will also have a decrescendo shape, but will start later in diastole.

So what should you do now that you’ve ausculted a murmur and characterized it, and hopefully come up with a short differential list? Each situation is going to be different. Take for example the young animal that has a very soft murmur that could be a physiologic murmur. It is reasonable to wait a couple of weeks to make sure that the murmur isn’t getting louder or to see if the murmur goes away.7

It is a very different situation in the young animal who presents to you with a loud murmur. It is very suspicious for congenital heart disease. This patient should most likely be referred for a more thorough workup. Or at least have further diagnostics performed within your practice, such as thoracic radiography, electrocardiography, or echocardiography to identify the source of the murmur.

An older animal with a loud murmur—it will depend upon what type of breed it is. If it is a Doberman pinscher with a murmur, a likely diagnosis is dilated cardiomyopathy. And even if this patient is asymptomatic, further diagnostics, such as an echocardiogram or thoracic radiography are indicated.

The same is true for the older, small breed dog with a loud murmur that you are very suspicious has degenerative valve disease. Even if this patient is asymptomatic, this patient also needs further workup to establish a baseline for when the patient was asymptomatic so that you know what things looked like when the patient was asymptomatic. So, further diagnostics such as thoracic radiography, plus or minus echocardiography, will also be important in this situation, even if the patient is asymptomatic.

A cat with a murmur represents a special situation, as it is almost impossible to distinguish physiologic or dynamic murmurs from those associated with cardiac disease in cats. Any cat with a heart murmur should have an echocardiogram performed. Thoracic radiographs are helpful, but not as diagnostic in cats as they are in dogs.

Thank you very much for your attention today.

Dr. Estrada is an assistant professor in cardiology in the Department of Small Animal Clinical Sciences at the University of Florida. Dr. Estrada received her DVM from the University of Florida followed by an internship at the University of Tennessee. She completed her residency in cardiology at Cornell University.

Resources

Cardiovascular disease in small animal medicine. Ware W—London: Manson Publishing, 2007.

Effect of pimobendan or benazepril hydrochloride on survival times in dogs with congestive heart failure caused by naturally occurring myxomatous mitral valve disease: The QUEST study. Häggström J, Boswood A, O’ Grady M, et al. J Vet Intern Med 22:1124-35, 2008. 

Manual of canine and feline cardiology, 4th ed. Tilley LP, Smith FWK, Oyama MA, Sleeper MM—Philadelphia: WB Saunders, 2008.

Textbook of canine and feline cardiology: Principles and clinical practice. Fox PR, Sisson DD, Moise NS (eds)— Philadelphia: WB Saunders, p 960, 1999.