Heart Failure In Your Dog

Congestive Heart Failure (CHF) & Mitral Valve Problems

   
   
Your pet's genes might also play some part in its response to the ACE inhibitors your vet prescribes for its failing heart . (ref)
 
For some non-heart related causes of coughing, go here.
If your pet is a puppy or kitten with a heart defect go here too

Ron Hines DVM PhD

 

 

Lots of my articles are plagiarized and altered on the web to market products and services. There are never ads running or anything for sale with my real articles. Try to stay with the ones that begin with http://www.2ndchance.info/ in the URL box or find all my articles at ACC.htm.

This is the third of four articles I have written on heart disease in pets. This one describes the most common heart problem that occurs in small, medium and toy breeds of dogs, Congestive Heart Failure. It is also called CHF. Your pet’s heart is a complex organ. Many things can go wrong with it but they all eventually lead to CHF.

This article focuses on heart valve problems which are the most common cause of CHF in dogs. Another one, Canine Dilated Cardiomyopathy, described a common specific problem in larger breeds of dogs. Another, Subaortic Stenosis describes a heart condition occurring in puppies and a third article discusses heart problems in general in dogs and cats. If you read them, you will find that much of the information in them repeats. That is because all failing hearts are destined to go through similar stages - regardless of the initial cause.

People’s hearts and pet hearts fail for different reasons. In humans, it is damage to the heart muscle itself (heart attacks) that usually begin the process of CHF. In pets, it is most commonly due to malfunctioning of the valves that direct blood flow through the heart. But although people develop heart disease for different reasons, the mechanics of what is occurring in your pet’s heart is very similar to what occurs in the damaged human heart. All of the medications your veterinarian will use and all the techniques he will use to diagnose the problem are the same ones - used for the same reasons - in humans. So you can learn allot by reading about heart disease in humans. (ref)

How Blood Flows Through

Your Pet’s Body

ENLARGE THIS DIAGRAM

The circulatory system is a very complicated system with each part relying on a complicated interaction of chemicals and organs. I am going to try to keep my explanations as simple as I can and not dwell on minor stuff. If you want to learn more, check out a book on human cardiology at your library.

The heart of all mammals is made up of four chambers. The upper left and right chambers are called the atria (atrium) and the lower left and right chambers are called the ventricles. Each of the four chambers has an inlet and an exit valve to prevent back-flow of blood. In smaller and medium breeds of dogs it is these valves – particularly the mitral valve that divides the left atrium from the left ventricle - that often fails first leading to an enlarged, inefficient heart. Go to some diagrams I have put together to help you understand the anatomy of your pet’s heart and heart valves.

Blood returning from the body enters the right atrium (RA) chamber. You will see the RA on my diagram. At this point, the blood needs to be re-loaded with oxygen. When the RA contracts, the blood is squeezed through a valve, the tricuspid valve (TCV), into the lower right chamber, the right ventricle (RV). When that chamber contracts, the blood is squeezed through another valve, the pulmonic valve (PV =pulmonary=pulmonary semilunar valve) , and into an artery that lead to the lungs (PA). In the lungs, the blood is re-oxygenated and CO2 is removed. The blood then flows back to the heart through the pulmonary vein (PulV) and arrives in the left upper chamber, the left atrium (LA). When the left atrium contracts, the blood is squeezed into the lower left and strongest chamber, the left ventricle (LV). To get there, it must pass through another valve, the mitral valve (MV).

When the left ventricle is full, it contracts. Its enormous power forces the blood through another valve, the aortic valve (AV), on down the aorta (A) and throughout the body. This contraction is the pulse you feel in your pet’s groin and which your veterinarian hears through his stethoscope.

These four chambers to not fire one after another like a car motor. They all work together in rhythmic waves to keep the blood flow continuous. When the powerful left ventricle contracts, blood pressure is at its highest (systolic), between contractions it is at its lowest (diastolic).

The Electrical System Of Your Dog’s Heart

There has to be a bandmaster to coordinate the heart’s contractions. The signals for heart muscles to contract are electrical signals and the heart contains a system of wire-like nerves (perkinje fibers) to distribute that signal.
It all begins in a small area at the top of the right atrium. (the yellow bean-shaped structure in my fanciful animation) There, a structure called the sino-atrial node (SA Node) rhythmically fires off an electrical pulse. It is somewhat like a metronome. The signal first reaches the muscles of the upper chambers (atria); so they contract. Then it reaches another node, the AV node, that is located near the bottom of the right atrium. The AV node passes the electrical pulse to the ventricles causing them to contract and force blood on its way to the lungs or body. So the pacemaker for the whole system is the SA node. The heart won’t stop beating if the nodes fail – but it will not pump blood efficiently.

When the electrical system fails, heart blocks, abnormal pulse rhythms, and uncontrolled quivering (fibrillation) of the heart, or portions of it, occur. These electrical signals are what are measured by an electrocardiograph (ECG aka EKG).

Your Pet’s Heart Valves

For reasons we do not know, dogs and cats do not develop plaque in the arteries of their hearts leading to heart attacks in the way it occurs in people. Instead, it is the valves that direct the flow of blood through the heart that tend to wear out. About three-quarters of heart problems in dogs are due to heart valve problems.
Very small, and very large breeds of dogs are a bit more prone to valvular heart disease and it is slightly more common in male dogs. It is quite uncommon in cats.
Any valve, or multiple valves, can wear out; but the most common one to wear out first is the mitral valve – the one that must close before the left ventricle can force blood throughout the body. Its job is the hardest of the four valves because the pressure difference across this valve is the greatest of all the valves when your pet's heart beats.

The heart of a dog with CHF enlarges and changes in shape. As the heart’s shape changes, other valves no longer close properly. In dogs that have been diagnosed with a mitral valve problem (insufficiency), cardiologists often find that the tricuspid valve between the right atrium and right ventricle is also abnormal.

Mitral valve, or mixed valve, problems are given many names. Some are acquired mitral regurgitation, mitral insufficiency, chronic valvular fibrosis, endocardiosis and mucoid valvular degeneration. They all describe different aspects of the same basic problem. In these dogs, the two flexible portions (cusps) of the valve become stubby, thickened or nodular and no longer close completely.
When this happens, something akin to backfire occurs and blood flows in the wrong direction back into the left atrium.

The mitral valve is a good place for bacteria that enter the blood stream to become trapped – particularly if the valve is already misshapen. I have noticed in my practice that pets with severe dental disease have mitral murmurs more frequently than those that don’t. Dentists have noticed the same thing. I have seen these murmurs disappear in pets after a course of antibiotics.

Many valve problems result in heart murmurs that your veterinarian might detect on a routine examination. However, not all of them lead to CHF. When they are detected, other tests should be done to determine if the heart murmur is something you should be concerned about. Anemia, valve infections (endocarditis), hyperthyroidism, fever and pregnancy can all cause heart murmurs. Quirky heart anatomy can also cause them. When it does, these are called innocent murmurs.

The majority of dogs 8-10+ years of age have these defects to varying degrees. At first, the leak is minor and produces no more than a high-pitched murmur with no health problems. When it is the mitral valve producing the murmur, it is most audible on the left side of the chest just behind the dog’s elbow.

In some breeds, such as Cavalier KC Spaniels, increased susceptibility to valve disease is an inherited genetic defect.

What Happens When My Dog’s Heart Valves Fail ?

Volume And Pressure Overload

When the powerful left ventricle contracts to force blood throughout the body and the mitral valve can not stand up to the pressure, it leaks blood back into the left atrium (regurgitation). When that happens, the freshly oxygenated blood coming from the lungs has nowhere to go. The left atrium, where the blood was headed, is already too full with blood that should have moved from the left ventricle to the general circulation through the aorta. Pressure increases in that part of the circulation (increased pulmonary pressure, pulmonary hypertension). The lungs expand with this blood and some of it leaks out (pulmonary edema) through its small capillaries and into the small spaces normally filled with air (alveoli). This doesn’t happen independently, as the valves deteriorate, the heart also enlarges to try to keep up with its increasing workload. The enlarged (hypertrophied) heart begins to press on your pet’s windpipe. This, plus the excess fluid in its lungs is the cause of its cough.

The right side of the heart deals with blood returning from the body. With time, the tricuspid valve which separates the right upper chamber (atrium) from the lower one (right ventricle) will also fail. When this happens, blood backs up into the venous side of the system, pooling fluid and leading to large, pear-shaped, bellies (ascites). This is not all free fluid – the liver and spleen also become congested with blood and enlarge.
These events cause all sorts of things to happen. The pet’s heart rate speeds up (tachycardia). Enzymes are released that constrict blood vessels (increased resistance and tone) of all blood vessels (angiotensin-converting enzyme or ACE, Angiotensin II) and rising aldosterone hormone levels result in fluid and sodium retention. These events make the pulmonary edema problem worse.

These events occur slowly and at different rates. Dogs with mildly to moderately enlarged hearts often show no signs at all. The first sign might be just a little reluctance on the part of your pet to play as actively as it once did. When an actual problem finally occurs, it is usually a dry cough accompanied by gagging. These coughs tend to be worst when the dog is down and at rest.

As the condition progresses, and as pressure builds up in the heart, first the left side and then the right side of the heart begin to enlarge. This enlargement is not accompanied by any increase in pumping efficiency. The more the heart enlarges, the less the four valves of the heart are able to seal themselves during contraction.

What Symptoms Will I See In My Pet ?

Most pet owners find out their dog has a heart murmur during it’s yearly health checkup. A listen with a stethoscope should always be part of your pet’s yearly examination. When a murmur is detected, the vet needs to make some other observations and, perhaps, run some tests even though your pet appears completely healthy.

If your dog lives in a heartworm-prone area, they may want to run a heartworm antigen test. They will listen more thoroughly to your pet’s lungs and palpate its abdomen for the presence of excess fluid. They will press on your dog’s gums and check how long the pressed area stays pale (CRT) and they will feel your pet’s femoral pulse to judge its strength. They may look for evidence of a jugular pulse in the veins of its neck – something that shouldn’t be. Depending on the vet’s finding, they may suggest additional blood tests or a chest x-ray.

When heart failure is more advanced, owners tend to bring their pets in because of a group of problems that they say came on very gradually. The most common one is a dry cough. Most owners will say that this cough is worst when the dog is resting. They usually also tell me that their dog doesn’t play as much as it used to and lays around more. They may notice that it breathes faster than it once did and is reluctant to climb stairs or hop onto the bed. These dogs are in still in early heart failure.

Other owners put off seeing the vet until the dog is having serious problems. These dogs have all the symptoms of the prior groups. But they also have a distended pot belly. The gums of their mouth are redder and the blood vesicles in them prominent and spidery (injected). Their gums and tongue may turn purplish (cyanotic) when the dog exerts itself. Heart murmurs in these dogs tend to be loud, lungs tend to give sounds that indicate fluid, a jugular pulse tends to be present, their pulse is weak and thready and their heart rate is elevated (tachycardia). Late in this intermediate stage the heart beat is often irregular and some beats may not be felt in its femoral pulse (pulse deficit).
These dogs are in an advanced stage of heart failure. Although they may have enlarged tummies, their prominent ribs and spine show that their body has lost muscle mass.
Anything worse is a medical emergency. Heart failure progresses to fainting, profound weakness, a racing pulse and difficulty obtaining enough air.

As heart function declines, the pet’s body is able to compensate for several weeks or months. However, at some point, its ability to compensate is no longer effective. At this point, dogs can go into severe heart failure in what appears to be a matter of hours. Rapid, heavy breathing, blue tongue (cyanosis), excessive drooling, or collapse may be the first time some owners realize that something is seriously wrong. When this occurs in a beloved pet, it means that the dog deteriorated unusually fast or it was not CHF. When it happens in a “yard dog” it means the owner wasn’t paying attention or didn’t have the funds to pay a veterinarian. Not all of us do.

Most Congestive Heart Failure develops over many years. Its effects on blood flow also develop slowly and the signs I mentioned may not appear in the order I gave them.

How Will My Veterinarian Decide If My Pet Has Congestive Heart Failure ?

History and Physical Exam

What you tell your veterinarian about your pet is as important as the vet’s examination of your dog. As I mentioned before, most dogs developing CHF have clues that something is amiss. Veterinarians rely on you to gather much of their information. There are certain buzzwords that set a vet off to thinking about your pet’s heart. Some are “more tired than usual” “less active” “chronic cough” “panting” and “gagging”. Some of these pets have trouble finding a comfortable position at night.

With the history in mind, your veterinarian will begin to examine your pet. He/she will check its gums for evidence of poor circulation (blush gums = cyanosis). He will judge its respiratory rate and the quality and regularity of its pulse. Then he will spend some time listening to your pet’s heart with a stethoscope. Stethoscopes have been around since 1816. They still provide an amazing amount of information. They easily detect heart murmurs and give a clue as to which valve is involved. They detect excess fluid in the lungs (pulmonary edema) and they judge the adequacy of the heart’s electrical system (arrhythmias). With those results in mind, he will check how quickly your pets blood moves through the body using the capillary refill time (CRT) test on its gums.

People, inexperienced in listening to the hearts of dogs, sometimes confuse the normal fluctuations in heart rate (sinus arrhythmia) with abnormal arrhythmias. The heart rate of healthy dogs is more likely to increase with every inspiration than that of people. Veterinarians assign a number to your pet’s heart murmur when one is present. The faintest murmur is given a 1 and the loudest a 6. By the time it is a 6 you can often feel it over the dogs left chest.

Chest X-ray

If your veterinarian physical exam and the history make him/her suspicious of a heart problem, the next thing he will suggest is a chest (thoracic) X-ray. He needs to see how much space your pet’s heart occupies in its chest, the shape of the heart and the condition of its lungs. Failing hearts loose fine detail and become rounder (globular) in their outline.
Veterinarians with ultrasound machines can obtain much of this information without an x-ray, but not all of it.

In early CHF, the veterinarian will be looking for evidence that the left atrium is enlarge, If the heart shadow (image) occupies more than the 3rd to 6ths rib spaces. If an increased heart mass has pushed the windpipe (trachea) upward. If the pulmonary veins seem distended and if the lungs appear to contain fluid (pulmonary edema).

ECG (EKG, electrocardiogram)

You have probably had one of these multi-wired machines applied to you. They measure the natural electrical impulses traveling through the heart. Many veterinarians rely on electrocardiograms (EKG) to detect early heart abnormalities. When the portion of the EKG paper tracing called the QRS complex lengthens and increases in height (amplitude) it signifies left ventricular enlargement. Heart rates are often faster than normal in the tracing and premature contractions of the ventricles give the tracing an abnormal or irregular rhythm.

It is hard to get pets to sit still enough during the ECG examination and the sticky pads used on people don’t stick well to furry pets. The vast differences in pet body size also makes interpretation more difficult than in people. So veterinarians often transmit the machines results to an international service for interpretation.

The interpretation of the ECG reading or tracing is a science in itself – much to complex for me to discuss. I, myself, have only a basic knowledge of it – as do most vets. If you want to know everything, go to this site.

Blood And Urine Tests

Blood chemistry and urine test tests are usually normal until heart disease is well advanced. When tests are abnormal, it is because organs have become starved of oxygen or congested with pooling blood. Routine blood tests cannot diagnose heart disease. But they do let your veterinarian know how well your pet will tolerate heart medicines when they need to be given.

ProBNP Test (Cardiac Biomarkers)

Sometimes, it can be difficult for your veterinarian to distinguish between problems that originate in the heart and problems that originate in the lungs. In those cases, the proBNP test can be very helpful. This test detects a marker chemical (a hormone) that are released by damaged hearts. The test is one that your regular veterinarian can run before deciding if it would be wise for your pet to be referred to a veterinary cardiologist. Like most test, it has it’s limitations. (ref) It is fine as a rule-out test for heart failure. But results can be in the gray, intermediate area where interpretation and is difficult and significance unknown.

Echocardiography (cardiac ultrasound, ECHO)

Visualization of the heart as it is actually beating (realtime) is the most informative way to evaluate it.

There are three kinds of machines, M-mode (a single beam) , two dimensional
(a cross-sectional "slice" of the beating heart) and 3-D echocardiographs that combine a Doppler to assess blood flow. The last is the most sophisticated and yields the most information in the hands of a skilled operator.

As with ECGs, interpretation of these images requires specialized training. When one has that training, an enormous amount of knowledge can be gathered about the current condition of your pet’s heart. Using these machines, each of your pet’s heart valves can be measured as to thickness and shape. How far the valve is pushed into abnormal position as the heart beats (valvular prolapse) how much it fails to open can all be seen. So can the amount of blood flowing in the wrong direction (regurgitation) and the increased volume of a weakened heart.

Doppler Exam

Stand-alone Dopplers are instruments that measure the speed and direction of blood flow. When these are determined, one can infer the problems in the heart and its surrounding blood vessels that probably caused them.

Heart Terminology

For a list of common words that veterinarians use to describe the heart and heart problems, go here.

What Medical Treatments Are Available For My Pet ?

No known medication will repair hearts. What they will do is allow your pet to live comfortably for a time. Veterinarians concentrate on giving medications that help eliminate excess fluids leaking from its circulation, increase it’s force of contraction and the pressure (work load) it must pump against. Late in heart disease, we give medications to keep the heart’s electrical system running smoothly. Generally, more than one type of medication is given so that all these problems are addressed.

Diuretics

Diuretics accomplish the first goal. They rid the chest and abdomen of excess fluid (water). They do this by encouraging the pet to urinate. They are very effective in stopping coughs and respiratory distress, when lung fluid buildup is the cause. The most commonly used diuretic is furosemide (Lasix). Diuretic dose varies between patients depending on the severity of their condition. Giving too much or too frequently during the day can dehydrate the pet or lead to kidney damage.

Furosemide (Lasix)

Furosemide diuretic has been the mainstay treatment for CHF for many years. It is very effective in flushing excess fluid out of the body and, in most cases, causes relatively few side effects. It, like bumetanide, are called loop diuretics because they do their work at small loops (loop of Henle) that occur in the filtering apparatus of your dog’s kidneys.

Dogs on this medication, particularly at higher doses, need to have their blood potassium level and kidney function monitored every few months and they need to be observed for dehydration. Pets that start furosemide generally stay on it for the remainder of their lives.

The improvement you see in your pet, once it begins taking furosemide, can be dramatic. As fluid drains from its lungs, its cough should go away and it should breath freer. The amount of fluid pooled in its abdomen should also decrease. Remember, however, that the drug has done nothing to improve the pet’s heart function. It does its work in the kidneys.

When your pet begins taking furosemide, you will notice it drink and urinate more. Do not restrict its access to water – give it all it desires. You will have to make arrangements for it to relieve itself during the night. I have not had problems when it limit the pet’s access to water in the evening and replace their water bowls in the morning in an attempt to get them to sleep through the night – but that is something you should discuss with your veterinarian. On higher doses of furosemide or other loop diuretics, your pet might need a potassium supplement.

Spironolactone (Aldactone)

When the maximum dose of furosemide diuretic is not longer sufficient to eliminate fluid buildup in your pet’s lungs (pulmonary edema) or tummy (ascites), another diuretic, spironolactone, can be added to the medications your pet receives. Spironolactone has the advantage of not depleting the body’s potassium reserve.
You need to be patient. Unlike furosemide, it takes 2-4 days for the full effect of spironolactone to be reached. Spirolactone can increase the toxicity and effect of digoxin so if your pet is on digitoxin, its dose may need to be lowered. It can also cause an increase in serum potassium, which can also be dangerous. To monitor potassium, a blood sample need to be taken and measured for serum electrolytes and kidney function. Often this is done on the 3-4th day, the 7th day and periodically there after.

Thiazide diuretics

Hydrochlorthiazide or chlorthiazide are alternatives to spironolactone when furosemide is no longer sufficient to keep fluid buildup under control.

ACE Inhibitors (angiotensin-converting Enzyme Inhibitors)

The most common drug in this group, used to treat CHF, is enalapril. But benazepril, captopril, lisinopril and other ACE medications are also used. Drugs in this class differ in their absorbability and the stress they put on the kidneys and liver. (ref) Their effect on your dog is not immediate and it will take a week or so before you see improvement.

These medications decrease the effort your pet’s heart must make to pump blood through its circulation by relaxing and expanding blood vessels throughout the body. They do this by reducing the formation of a hormone in the lungs, (angiotensin II), that increases your pet’s heart work load (peripheral or systemic vascular resistance). Angiotensin II is also bad because it increased the production of a hormone your pet’s adrenal glands (aldosterone) that causes sodium and water retention and high blood pressure (RASS system) In doing so, ACE inhibitors lower blood pressure and decrease salt (sodium) and water retention. Their doses need to be periodically adjusted in response to the improvement you see.

Dogs in heart failure often have fragile kidneys as well. Since these drugs, as well as the diuretics, can have negative effects on the kidneys (azotemia) , kidney function needs to be checked before these drugs are given and then monitored periodically. Doses need to be kept to the effective minimum and the diuretic dose may need to be adjusted downward as the ACE inhibitor dose is increased.

ACE-inhibitor medications have the opposite effect of furosemide diuretic, they tend to raise blood potassium - sometimes to dangerously high levels. This is another reason periodic blood monitoring is necessary.
Vomiting and a poor appetite are occasional side effect. They can usually be dealt with without stopping the medication.

Enalapril (Enacard, Vasotec, etc.)

This ACE-inhibitor medication has been used the longest and is the one most commonly dispensed to pets. It is rarely given without furosemide included in the treatment plan as well.

Dogs on anti-arthritic medications (NSAIDs) may need a bit higher dose than those that are not. Its effectiveness is also lessened in the presence of liver disease and it has been known to cause further damage to kidneys that are already fragile. Damaged kidneys tend to leak protein which can be detected when the pet’s urine is examined.

It is approved for once-a-day use; but seems to work more effectively when the total daily dose is divided and given in the morning and evening. It will occasionally cause nausea, diarrhea and loss of appetite. If the dose is higher than necessary, low blood pressure can occur, leading to listlessness and weakness.

Benazepril (Lotensin, Fortekor)

Benazepril is another ACE-inhibitor commonly used in pets with Congestive Heart Failure. Like enalapril, it is usually given along with a diuretic and like enalapril, it can be given with or without food. The ability of a portion (50%) of the drug to leave the body through the liver perhaps makes it a better choice than enalapril in dogs with kidney disease. All enalapril must leave via the kidneys. In humans, the danger of compounding pre-existing kidney problems appears slightly less for benazepril than for enalapril.

Hydralazine

Hydralazine is not an ACE-inhibitor, but it has a similar effect. This potent medication dilates blood vessels and so lowers the resistance that the heart must pump against. Because the drug can cause dangerously low blood pressure and a racing heart (tachycardia), it must be used cautiously. It is best given and monitored in an animal hospital setting under close observation and monitoring.

Is There Any Benefit In Beginning ACE Inhibitors Before My Pet Shows Signs of Heart Failure ?


This is currently being debated. One might see how reducing the heart’s workload before severe damage occurs might postpone that damage. The only study to date in dogs did not find that to be the case, but it was a study of Cavalier King Charles Spaniels, a breed with multiple, genetic, health-related problems.
So some cardiologists go with their instincts and prescribe ACE-inhibitors before the pet’s hearts have deteriorated to the point where they need it much the way the ACE drugs have been used to head off strokes in humans (ref)

Positive Ionotropes

Pimobendan (Vetmedin)

Pimobendan (Vetmedin) , combined with the other two groups I have already mentioned, is rapidly becoming a standard treatment for CHF in dogs. All positive ionotropes increase the strength of heart muscle while decreasing the pressure the heart must work against.

Calcium is important in the mechanism of muscle contraction. (ref) The force of heart muscles contraction is related to the amount of calcium ion present. Pimobendan increases the heart’s sensitivity to the calcium that is already there.

Vetmedin opens up the blood vessels and eases resistance in the circulatory system dilating blood vessels, and improving the efficiency with which the heart functions as a pump. The combined effect is therefore to improve cardiovascular function and the blood flow to major organs. Vetmedin is licensed and appropriate for both the major causes of heart failure in dogs. In one clinically controlled trial, dogs with congestive heart failure survived on average (median) 42 days without Vetmedin, 217 days when Vetmedin was part of their treatment.

Digitalis compounds (digoxin, digitoxin, Cardoxin, Lanoxin etc)

Digitoxin and digitoxin are two other drugs in the positive ionotrope class. They too increase the force of heart contractions by increasing the heart’s sensitivity to blood calcium, but they have many negative side effects. These include vomiting, depression, refusal to eat and, cardiac rhythm abnormalities.

Dogs receiving this medication need to be closely monitored and the dose finely adjusted to the pet’s needs and ability to tolerate it. Digoxin and digitoxin are slightly different, the first is excreted through the kidneys and the second metabolized by the liver. So digitoxin is probably a better choice when the patient’s kidney function is poor.

Both these compounds have fallen out of favor in human medicine since a study that found that women with CHF who received them died sooner than those that didn’t. (ref)

I have seen too many cases to toxicity to be a fan of either drug. When they are given, it should be under the supervision of a veterinary cardiologist.

Anti-arrhythmics (Drugs that stabilize heart beat)

Dogs with irregular heartbeats or fainting episodes (syncope) may benefit from this group of medications. Their use must be carefully monitored and they are usually given in conjunction with a Holter monitor that continuously records your pet’s heart rate.
The two most commonly used antiarrhythmics are sotalol or a combination of mexiletine and atenolol.

Beta Adrinergic Blockers (ß-adrenergic blocking drugs)

The best-known drugs in this class are propranolol and atenolol. These medications protect the heart from the excessive levels of stress hormones (catecholamines, adrenaline and noradrenaline) present in the blood of dogs with CHF. In doing so, they lower blood pressure, reduce the heart’s oxygen demand and also help protect against heart beat abnormalities (arrhythmias).
These drugs appear more effective in combating the sudden heart deterioration of Dilated cardiomyopathy and atrial fibrillation when combined with digoxin.

Other Drugs That May Help Your Pet:

Calcium Channel Blockers

The most commonly used drug in this class is Diltiazem. Diltiazem increases the diameter of blood vessels (vasodilator), increasing blood flow and slows heart rate. It is used primarily in the acute form of heart failure seen in larger breeds of dogs.

Drugs To Make Your Dog Breath Easier (Bronchodilators)

Theophylline and aminophylline are the most commonly used drugs in this group. They work by increasing the diameter of the passages (bronchioles) in your pet’s lungs. Their primary use is in conditions affecting the lungs – not the heart. But they seem to reduce the frequency of fainting in some pets with CHF.

Cough Medicine

Cough suppressants are generally un-necessary in dogs with CHF. Coughs due to lung congestion need to be treated with diuretics – not masked with cough suppressants. However, if x-rays show the pet’s lungs are clear and dry and the coughing is due to an enlarged heart pressing on its windpipe (trachea), these cough suppressants may be helpful.

Nutritional Support

We all want to do everything we can to keep our precious pets with us. But the products I have listed here are not a substitute for the science-based medicines that I previously discussed.

Many pet food companies make low-sodium diets designed for pets with heart failure. They are sold only through veterinarians. If your pet will not eat them, there are some recipes for low sodium home-cooked diets on this webpage.

Low sodium diets may be helpful in lessening fluid retention. But one must not restrict their pet’s salt intake too severely or too soon into the disease.

L-carnitine

There have been studies that indicate that a few cases of cardiac failure, particularly in boxers, are due to a deficiency in the amino acid, L-carnitine. L-carnitine is naturally founding meat and dairy products and is also made by the body.

A test to determine if an L-carnitine deficiency actually exists in your pet is not feasible at this time (ref) , but their is no harm in giving it. Too much of the compound will cause vomiting and diarrhea. It is already added to Hills H/d prescription heart diets.

Taurine

Taurine is a compound similar to an amino acid that is naturally synthesized in the body. Meat and Fish are rich in taurine. Cats are unique in that they can not synthesize it and must obtain it through their diets.
Taurine responsive heart diseases also occasionally occur in dogs. (ref) The most expansive investigation of its use was done in cocker spaniels
. (ref)

Taurine deficiency was once the most common cause of sudden heart failure in cats. When the relationship in cats was discovered, taurine supplementation of cat foods became the norm and the condition in cats is now quite rare. Taurine appears to have similar heart-protective abilities in humans. (ref)

There are two approaches to giving this compound to your pet. You can have its blood level of taurine checked to see if it is low, or you can just give it. Taurine appears to be non-toxic and is a common addition to Energy Drinks. It is also sold where human supplements are sold.

Coenzyme Q

Coenzyme Q is a natural substance that is involved in the body’s energy production. Its level in our bodies naturally declines with age. It is found in high levels in the red flesh of mackerel but it is present in tuna and salmon as well. Much of it is destroyed by cooking. It is sold where human supplements are sold.

The results of its use in humans have been problematic. (ref) Some studies find it beneficial but others do not. Some human cardiologists recommend it for heart disease but some feel there is not enough evidence one way or the other.

This is another product that there is no harm in giving. Prescription diets designed for heart failure in dogs keep coenzyme Q levels high . Perhaps it will do some good.

Omega-3 fatty acids

Some of my clients noticed improvement in their pets when they are given fish oil capsules containing Omega-3 fatty acids. Cold-water fish oil is a rich source of omega-3 fatty acids, Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA). These essential fatty acids seem to reduce inflammation throughout the body. It seems particularly effective in reducing abnormal heart rhythms (ref) but probably has other beneficial heart effects as well (ref). Always use the gelatin capsulated form and never straight fish oil. Purchase capsules marketed for humans that are known to be mercury-free.

Maintaining A Healthy Body Weight

Over time, pets with CHF loose weight due to loss of muscle mass (cardiac cachexia). Their abdomens may seem large, due to a congested liver and pooled fluids, but their ribs and spine become very prominent. This is a sign of their low cardiac output. It is important that you do everything you can to encourage pets with CHF to eat. Protein and vitamins needs to be high in its diet. Geriatric pets often have poor teeth – so feeding them their food in soft or canned form is often best.

How Will I Know If The Medications Are Working ?

The most common reason pets with heart problems come to see veterinarians is because of breathing problems. These pets tend to breath faster than they should and they tend to be congested. One can have complicated tests performed to evaluate if the medications are doing their job, but monitoring your pet's breathing rate and freedom from congestion at home is just as accurate - perhaps more so. If the medications are working, your pet will breath slower and easier when it is at rest. If you want to confirm your decision about its progress based on its respiration, do so by having your vet run occasional pro BNP tests to confirm their level is dropping or holding steady. You can read an article that confirms this here.

Procedures And Treatment That May Become Necessary

Oxygen

When your pet cannot catch its breath after exertion, or during heart emergencies, supplemental oxygen will help. All pet emergency centers should have sealed cages to administer oxygen. But trips to the emergency center can be stressful to your pet in themselves. If you are determined enough, you can improvise an oxygen “tent” at home for small pets or use a human oxygen face mask for larger ones. PURE OXYGEN CAUSES ORDINARY THINGS IN YOUR HOME TO BECOME VERY FLAMABLE. If you contemplate using it at home for your pet, have a human respiratory therapist instruct you in its use. Small canisters of oxygen do not last long. In Texas and Florida, my medical oxygen suppliers filled their industrial and medical grade oxygen from the same bulk tank. They told me that the only difference was in the degree that the tanks were periodically inspected, but I cannot guarantee that this information is correct.

Removal Of Chest Fluid

Pets become very uncomfortable when leaked fluid in their chest prevents normal respiration. Draining this fluid (Thoracocentesis), gives them rapid dramatic relief. However, the relief is temporary. It can be used in emergency situations until the effects of diuretics, like furosemide, occur. And in newly discovered cases of CHF until a thorough treatment plan for your pet can be developed.

Removal Of Abdominal Fluid

Diuretic medications will usually remove the excess fluid (ascites) that pools the tummies of dogs with congestive heart failure. When it doesn’t, it is usually due to their kidneys being damaged as well as their heart. (ref)

This fluid can be tapped and drained periodically (Abdomenocentesis) when it brings discomfort to your pet. When it is done frequently, have its blood protein level checked occasionally.

Exercise Restriction

Our pets can be so happy to see us that they over exert themselves. As much as your pet may enjoy it, encouraging your pet to work its heart at its maximum capacity is not a good idea. Modify your play-time and your pets life style to minimize its daily exertion.

What Can A Veterinary Cardiologist Offer Me That My Regular Vet Can Not ?

A veterinary cardiologist is likely to offer you a more precise diagnosis than your regular veterinarian can. This is because equipment, such as the 3-D color echocardiograph is very expensive and not cost-effective for your regular veterinarian to purchase. New, state-of-the-arts, units can cost upward of $100,000. As important is interpretation of the results once they are obtained. It takes very specialized knowledge to interpret the images displayed on these machines. A cardiology specialist, working out of a large center or Veterinary college can also perform delicate techniques, such as cardiac catheterization that is beyond the capability of most animal hospitals.

Precise diagnosis does not necessarily give you more treatment options to extend your pet’s life. But if you have the financial resources to have your local veterinarian’s diagnosis confirmed by a veterinary cardiologist, by all means do so. The cardiologist can also work out a treatment plan for your regular veterinarian to follow.

Cardiologists are also valuable when your local veterinarian is uncertain of the diagnosis or when several veterinarians have given you different advice. It is also wise to seek out their advice when medications are not performing up to expectation or when your pet has other medical problems that complicate treatment.

The treatment of heart arrhythmias (abnormal rhythm) requires the use of medications, often in cocktails, that can have very serious consequences if improperly designed or used. They are best designed and monitored by a veterinary cardiologist.

If you contemplate heroic measures to attempt to maximize your pets life, they are best performed at large veterinary centers under the supervision of a veterinary cardiologist. This applies to heart catheterization, pacemakers , the use of Holter monitors or open heart surgery. There are limitless tests and procedures available – but there is no guarantee your pet will live a day longer if you do them.

Most pets in the US do not undergo these complicated procedures. Most are managed by the owner’s local veterinarian using diuretics, ACE-inhibitors, Positive ionotropes (pimobendan) and prescription diets. In most States, local veterinarians are obligated by law to inform you of the availability of veterinary specialists. If they do not, they face legal and licensure issues. Ask them what they would do if it were their dog.

There is absolutely nothing neglectful or cruel about accepting your local veterinarian's diagnosis without seeking the input of a cardiologist. You and your pet can enjoy each other’s companionship during the remaining time that God allows it. Guilt or the expectation of miracles is not a good reason to have your pet seen by specialists. Good food and good loving time together are a kind alternatives to more drugs, more needles and more stress. Dogs do not fear or anticipate death.

How Much Longer Will My Pet Live ?

Dogs with mild to moderate heart disease can have a good quality life for years. Every dog differs in the rate at which CHF advances and no statistics are available for me to give you. In humans, half of patients are alive 5 years after CHF diagnosis. The shorter natural lives of our pets shorten that time. How suddenly the heart problem appeared in your pet tends to predict survival time. The more sudden the onset, the shorter the pet is likely to live. In dogs with dilated cardiomyopathy (DCM) leading to CHF, the average patient survives only 4.2 months. (ref)

) However, when valve failure is the cause, pets tend to survive much longer.

Your nursing care, and your veterinarian’s assistance are important factors in maximizing your pet’s lifespan once CHF has been recognized. All dogs on therapy for CHF should be monitored every 3-6 months and their therapy adjusted according to the results. It is wise to include a thyroid hormone check, a blood chemistry panel, ECG, and chest radiographs - but your assessment at home of your pets energy level and general comfort are just as valid indicators of when medications might need to be added, changed or their doses adjusted.

Is Open Heart Surgery An Option For My Pet ?

In some parts of the World, it is an option in cases where the anchoring fibers (chordae tendineae) that hold your pet's left upper heart valve (mitral valve prolapse) in place have torn. Veterinarians at Nihon University in Tokyo are perfecting that procedure. (ref) In the USA, I would discuss the issue with cardiologists at the Vet School in Davis CA. (ref)