Congestive Heart Failure & Mitral Valve Problems In Your Dog

(CHF)

Ron Hines DVM PhD

  Cardiomyopathy In Your Dog 

 Subaortic Stenosis In Your Puppy 

 Pulmonary Hypertension And Right-Side Heart Failure 

   Heart Disease In Your Dog    

This is one of several articles that deal with common heart problems that our dogs face. It is called Congestive Heart Failure or CHF. The links above concern the others. Congestive heart failure is a common heart problem of small, medium and toy dog breeds.  The most common reason these dogs develop CHF is the failure of a particular heart valve, the mitral valve  , that routs oxygen-rich blood from your dog’s lungs from the top left chamber of the heart (the left atrium) to the lower left chamber of the heart (left ventricle) and then on to the rest of the dog’s body. Mitral valve problems are only one of many potential causes of congestive heart failure. Your pet’s heart is a very complex organ.

A large number of things can go wrong with your dog’s heart, but the organ has very limited ways in which it can respond. The heart can beat faster. It can increase the amount of blood (stroke volume) of every beat. The dog’s heart can also release more of two hormones (natriuretic peptides). The compound released by the upper two chambers of the heart is ANP .  Another released by the lower two chambers, the ventricles, is BNP . Both peptides decrease the circulatory system’s resistance to the flow of blood within the  circulatory system.  Targets of these hormones are the most critical areas of the dog’s body. Veterinarians use the level of one of these cardiac hormones (BNP) as a marker to detect hard damage. Read about the proBNP test here

Your dog’s failing ability to keep up with its heart work load due to a faulty valve or another cardiac issue does not go unnoticed by other organs in its body. In a very complex manner, the dog’s cardiac situation activates the renin-angiotensin system (RAS). The RAS system also attempts to lighten the work load on your dog’s heart.  Some blood vessels increase their diameter to allow more blood to pass, other to less critical areas constrict. The RAS system has dramatic effects on your dog’s kidneys allowing for more water to be reabsorbed and less sodium to be excreted. ( read here & here)    

These circulatory system adjustments are effective in providing your dog’ body with sufficient oxygen for a while – perhaps months, perhaps years when effective medications are dispensed by your veterinarian. But the common canine heart issues that I linked to at the top of this article are all progressive. Eventually the dog cannot compensate for the heart’s decreased capacity to do its job. That is the point where your dog’s heart will begin to enlarge and alter its shape. It is a gradual process. That is also the point where the symptoms of heart disease, regardless of the underlying cause, become the same or quite similar: a cough, decreased exercise tolerance, fatigue, and eventual swelling of the abdomen and difficulty breathing. There are links at the beginning of this article to some of those other underlying heart issues not related directly to your dog’s heart valves: dilated cardiomyopathy , subaortic stenosis, and pulmonary hypertension  ; but even with those issues, as the dog’s heart enlarges and its heart’s shape changes, the heart valves are bound to distort in their shape too. To those causes of heart failure, consider adding  heartworm disease and, in the southern portions of the United States, Chagas Disease.

The best product to prevent heartworm-associated heart problems is monthly moxidectin. The best control product we have at this time against Chagas- related heart failure in dogs are deltamethrin  containing flea/tick collars like these. I live on the Mexican border, a hotbed of Chagas disease and heartworms. My dog Maxx receives both products. 

The most common cause of heart failure in humans like us and the most common cause of heart failure in dogs are quite different. In people, it is damage to the heart muscle itself due to blocked coronary arteries that usually begins the CHF process. ( read here ) For reasons still unknown, dogs and cats are extremely resistant to coronary artery disease no matter how greasy their diet or how obese they become. When our dogs become overweight they are subject to chronic generalized (systemic) inflammation and diabetes – but not heart attacks or coronary artery disease. (read here)

How Blood Flows Through Your Dog’s Body

 See my heart animated:

    

The Electrical System Of Your Dog’s Heart

Animate My Heart’s Electrical System:

Your Dog’s Heart Valves

I mentioned that we do not know why dogs 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 directing the flow of blood through the heart that tend to wear out. About three-quarters of heart problems veterinarians see in dogs are due to heart valve problems.

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 pet’s left ventricle can force blood throughout its body. Its job is the hardest of the four valves because the pressure difference across this valve is the greatest of all the four heart valves every time your pet’s heart beats.

When the mitral valve no longer opens and closes fully, the dog’s heart begins to changes in shape and increase in size. Pressure in the wrong locations within the heart causes its walls to become thinner and for the chambers to stretch – much like blowing up a balloon. And as the heart’s shape changes and stretches, the other three valves can no longer close properly either. In dogs that have been diagnosed with a mitral valve problem (mitral insufficiency), cardiologists often find that the tricuspid valve between the right atrium and right ventricle is also dysfunctional – not able to opening or closing completely.

Mitral valve, or mixed valve, problems have been assigned many different names. Some are: “acquired mitral regurgitation”, “mitral insufficiency”, “mitral valve prolapse”, “mitral/tricuspid valve regurgitation”, “leaky valve disease”, “chronic valvular fibrosis”, “endocardiosis” and “mucoid valvular degeneration”. They all describe different aspects of the same problem. In these dogs, the two flexible portions (cusps) of the mitral valve become stubby, thickened or lumpy (nodular). So they can no longer open and close satisfactorily. When this happens, something akin to backfire occurs (the valve “regurgitates”) and blood flows in the wrong direction.

Heart valves and their thready nest of attachments ( chordae tendineae ) are an excellent place for bacteria that have entered a dog’s blood stream to become lodged – particularly if the valve is already somewhat misshapen. Many suspect that pets with severe dental disease – a very common source of infection – have mitral valve murmurs more frequently than dogs that don’t. Dentists have noticed the same thing. (read here) Dog studies confirm it. (read here ) I have seen heart murmurs disappear in my client’s dogs after a course of antibiotics.

In many cases, heart valve problems result in heart murmurs that your veterinarian will detect on a routine examination. However, not all heart murmurs lead to CHF. When your veterinarian informs you that he/she has detected a heart murmur, other tests need to be run to determine if the murmur is something you should be concerned about. Anemia, heart valve infections (endocarditis), fever and pregnancy have all be known to cause heart murmurs. Quirks in heart anatomy and anatomical heart defects cause them as well. When nothing major is found to be wrong, these are called innocent heart murmurs. Echocardiography , although not infallible, is the most likely way to tell a serious heart murmur that needs to be followed up from an innocent heart murmur that can be ignored. 

The majority of dogs 8-10+ years of age have heart valve defects of varying degrees. That cannot be avoided and is part of normal aging.  At first, the leaks are minor and produces no more than a high-pitched murmur with no resulting health problems. When it is the mitral valve producing the murmur, it is usually most audible on the left side of the chest just behind the dog’s elbow.

There are some breeds, such as Cavalier KC Spaniels, with increased susceptibility to heart valve disease, This is thought to be due to an inherited genetic defects. (read here)

More About What Happens When Heart Valves Fail

Volume And Pressure Overload

When the powerful left ventricle contracts to force blood throughout your dog’s body but a mitral valve that can not stand up to the pressure, leaks blood back into the left atrium (regurgitation). When that happens, the freshly oxygenated blood coming from the dog’s lungs has nowhere to go. The left ventricle, where the blood was headed, is already too full with blood that should have moved from into to the general circulation through the aorta. But a weakened, distended heart can’t keep up. Pressure increases in that part of the circulation (increased pulmonary pressure, pulmonary hypertension). The lungs expand with this pooling blood and some of it leaks out (cardiogenic pulmonary edema) through the lung’s small blood capillaries and into the small spaces normally filled with air (the alveoli). This doesn’t happen independently. As the heart valve deteriorates, the heart also enlarges as it tries to keep up with its increasing workload. The enlarged (hypertrophied) heart begins to press on your dog’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, canine bellies (ascites). The belly enlargement is not all due to free fluid pooling in the dog’s abdomen – the dog’s liver and spleen are also becoming enlarged – congested with blood due to sluggish circulation.

These events cause all sorts of other things to happen. Your pet’s heart rate speeds up (tachycardia). Enzymes are released that constrict blood vessels (increased vascular resistance and tone). Chemical changes occur as well – (angiotensin-converting enzyme = angiotensin II) and rising aldosterone hormone levels released by the dog’s adrenal glands result in fluid and sodium retention. Rather than helping correct the situation, these events actually make the pet’s pulmonary edema problem worse. These things occur slowly and at different rates in different dogs. Dogs with mild to moderately enlarged hearts often show no signs at all. The first sign might just be a little reluctance on the part of your dog to play as actively as it once did.  You might just attribute that to advancing age. When dog owners finally bring their pet to their veterinarian, it is usually because of a  dry cough accompanied by gagging. These coughs tend to be worst when your dog is lying down and at rest. 

More About The Signs Of Congestive Heart Failure?

I mentioned that most dog owners find out that their dog has a heart murmur during one of its yearly routine health checkup. A listen with a stethoscope should always be part of your dog’s yearly health examination. What you tell your veterinarian about your pet (its medical history and life ) is just as important as your veterinarian’s examination. As I mentioned before, most dogs that are developing CHF have subtle clues that something is amiss. When a pet is relaxed at home it often shows symptoms that it will not exhibit to your veterinarian during an office call. There are certain buzzwords that set a veterinarian to thinking about your pet’s heart.  “More tired than usual”, “less active” , “chronic cough” “panting”, “gagging”, “reluctant to climb steps”, or have trouble finding a comfortable sleeping position at night are some of them. You might mention, or your vet might observe, premature graying hairs around its muzzle and paws. Some dogs chill easier due to their poor circulation. 

With your dog’s history in mind, your veterinarian will probably check your pet’s gums for evidence of poor circulation (bluish or grayish gums = cyanosis) and its capillary refill time. Observing your dog’s respiratory rate and the quality and the regularity of its pulse as well as listening to your pet’s heart through a stethoscope are standard procedures during an office viist. Stethoscopes have been around since 1816; but they still provide an amazing amount of useful information to veterinarians and physicians. Stethoscopes easily detect heart murmurs and give a clue by sound location and tenor as to which heart valve, if any, might be involved. Stethoscopes can detect excess fluid in the lungs (pulmonary edema) and they judge the adequacy of the heart’s electrical system (by detecting arrhythmias). 

Dog owners inexperienced in listening to the hearts of dogs or checking its pulse, sometimes confuse the normal fluctuations in canine heart rhythm (sinus arrhythmia) with pathological arrhythmias. The heart rates of healthy dogs are more likely to increase with every inspiration than the heart rates of people. Some veterinarians assign a loudness number to your pet’s heart murmur if one is present. The faintest murmur is given a 1 and the loudest a 6. By the time a mitral valve murmur is a 6 you can often even feel its vibration over your dog’s left chest.

Some dog owners will put off seeing their veterinarian until their dog’s problem is more advanced. Those dogs have all the symptoms of the prior groups – just more profound; but they might also have a distended pot belly. The gums of their mouth are redder and the blood vesicles  of the gums more prominent and spidery (injected). Their gums and tongue might turn purplish (cyanotic) when the dog exerts itself. The pet might actually faint when exited or stressed.  Heart murmurs in these dogs tend to be louder, their lungs tend to give sounds that indicate excessive fluid buildup (moist rales), a jugular pulse is often observable on the dog’s neck. Their arterial pulse, palpated in their groin,  is weak and thready and their heart rate is elevated (tachycardia). In this advanced stage, their heart beat is often irregular and some beats heard over the heart may not be felt in its femoral area (groin) (=a pulse deficit). Although the dog may have an enlarged tummy, its prominent ribs and spine show that its body has lost considerable muscle mass (= sarcopenia). Pooled fluids and distended organs can deceptively keep your dog’s scale weight deceptively high.

As I mentioned, as heart function declines, a dog’s body is able to adjust and compensate for months or even years. However, at some point, its ability to compensate is no longer effective. At that point, dogs can go into sudden heart failure in what appears to be a matter of hours. Rapid, heavy breathing, blue tongue, excessive drooling, or collapse may be the first time some owners realize how seriously wrong things have become. In the impoverished area of South Texas where I live, most of those cases never see a veterinarian. Here they are mistakenly written of to “poisoning by a neighbor” or perhaps a rattlesnake snake bite.

Chest X-rays

     

When your veterinarian’s physical exam and the dog’s history make her/him suspicious of a heart problem, the next thing generally suggested are chest (thoracic) X-rays or an ultrasound examination. Your veterinarian needs to see how much space your pet’s heart occupies in your dog’s chest, the shape of the heart and the condition of your dog’s lungs. I mentioned that failing hearts enlarge and become rounder (globular) in their outline. When fluid pools in the lungs or their surrounding, the image of the heart and lungs tend to be blurred (= “ground glass“). 

In early CHF, your veterinarian will be looking for evidence that the dog’s left atrium is enlarging, If the heart’s shadow (its image) occupies more than the 3rd to 6th rib spaces the heart is larger than it should be. If the increase in heart mass (size) has forced the dog’s windpipe (trachea) upward as it commonly does, that upward pressure plus any lung fluid accumulation often accounts for its cough. 

EKG = ECG = electrocardiogram

You have probably had one of these multi-wired machines applied to you. They measure the minute (tiny) natural electrical impulses traveling through the heart. Many veterinarians rely on electrocardiograms (EKG) to detect early heart electrical abnormalities. When the portion of the EKG paper tracing or screen image called the QRS complex lengthens and increases in height (amplitude) it generally signifies left ventricular heart enlargement. In CHF, heart rates are often faster than normal in the tracing and premature contractions of the ventricles can give the tracing an abnormal or irregular rhythm. Sophisticated interpretation of EKG results requires in-depth training beyond that of most practicing veterinarians. Online services are available to assist with that. ( see here )

Cardiac Biomarkers, Blood And Urine Tests

Sometimes, it can be difficult for your veterinarian to distinguish between problems that originate in the heart and problems that originate in the lungs or elsewhere in the body. In those cases, one of two test can be very helpful. These tests detect a marker chemical (a hormone) that is released by damaged hearts. I mentioned them earlier. The tests are ones 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. ( read here ) These tests are fine as a rule-out test for heart failure. But results can be in the gray or intermediate area where interpretation is difficult and the significance unknown. Both Antech Diagnostics and Idexx Laboratories, the two largest independent American veterinary diagnostic laboratories, offer these tests to detect heart damage. Antech’s is called Cardio-BNP and Idexx’s is called the proBNP test.

Standard  Blood chemistry tests and urine tests are usually normal until heart disease in a dog is well advanced. When any of those routine tests are abnormal, it is usually because organs have become starved for oxygen or congested with pooling blood. Although routine blood tests cannot diagnose heart disease, they do let your veterinarian know how well your pet might tolerate the heart medicines he/she intends to dispense.

Echocardiography Heart Ultrasound, ECHO

Visualization of the heart as it is actually beating (realtime) is the most informative way to evaluate your dog’s heart health.There are three kinds of echocardiographic machines, M-mode (a single beam) , two dimensional (a cross-sectional “slice” of the beating heart) and 3-D echocardiographs that combines a doppler to assess blood flow. The last is the most sophisticated and, in the hands of a skilled operator, yields the most information. It has or is now the standard throughout medicine.  When the operator has that training, a great deal of knowledge can be gathered about your dog’s current heart condition Using these machines, each of your pet’s heart valves can be measured as to its thickness and shape. One can also view how far the valve is pushed into abnormal positions as the heart beats (eg valvular prolapse) and how much it fails to open and close. The amount of blood flowing in the wrong direction (regurgitation) and the increased blood volume of a weakened heart are also evident.

Heart Terminology

enlarge

What Medications Might Help My Dog?

No known medications will repair damaged hearts; and stem cell approaches are still in their infancy – their benefits unproven. ( read here ) What medications will do is allow your pet to live more comfortably for a time. Veterinarians concentrate on giving your dog medications that help eliminate excess fluids leaking from its sluggish circulation (= diuretics), drugs that decrease the pressure (work load) your dog’s heart must pump against (= ACE inhibitors), and drugs that increase the force of its heart contraction (= positive ionotropes ).  The positive ionotrope most frequently dispensed by veterinarians is  pimobendan  (Vetmedin® ). I’ll go over them in that order. In late stage heart disease or whenever necessary, veterinarians also give your dog medications to keep its heart’s electrical system running as smoothly as possible. In most cases, more than one type of medication needs to be given so that all these problems can be addressed.

Diuretics

Diuretics accomplish the first goal. They rid your dog’s chest and abdomen of excess pooled fluid “water pills” There is more in this fluid than water, it contains a considerable amount of albumin protein and minor amounts of all the constituents of blood. Diuretics decrease pooled fluid through their effects on the kidneys and by encouraging your dog to urinate. They are very effective in lessening coughs and respiratory distress when lung fluid buildup (pulmonary edema) is the underlying cause. The most commonly used diuretic in dogs (and humans) with heart issues is furosemide (Lasix®). The diuretic dose and the frequency it needs to be given will be quite different from one dog to another depending on the severity of their condition. Giving too much or too frequently during the day can dangerously dehydrate your pet or lead to kidney damage.

Furosemide (Lasix®)

Furosemide diuretic has been a mainstay treatment for CHF in dogs for many years. It is very effective in flushing excess fluid out of your pet’s body and in most cases causes relatively few side effects. It and similar drugs like bumetanide/Bumex®  are in a class called loop diuretics because they do their work at small tubular loops (loops of Henle) that are part of the filtering apparatuses of your dog’s kidneys.  Dogs taking Lasix®, particularly when the dose and frequency is high, need to have their blood potassium level and kidney function monitored every few months and they need to be observed for signs of dehydration. Pets that start furosemide for heart issues 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 might rapidly go away and it should breath more easily. The amount of fluid pooled in its abdomen should also decrease. Remember however that this drug does not improve your dog’s heart function. It does its helpful work in your dog’s kidneys.

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

Spironolactone (Aldactone®)

When a high end (near the maximum) dose of furosemide is no longer sufficient to control fluid buildup in your pet’s lungs (pulmonary edema) and/or its tummy, your veterinarian might add spironolactone diuretic to the medications your pet receives. Spironolactone has the advantage of not depleting your dog’s potassium reserves. You need to be patient. Unlike furosemide, it takes 2-4 days for the full beneficial effects of spironolactone to be achieved. Spironolactone can increase the toxicity and effects of digoxin, so if your pet is taking digoxin, its digoxin dose might need to be lowered. Spironolactone can also increase serum potassium which can also be dangerous. To monitor your dog’s potassium level, a blood sample needs to be periodically taken and measured for serum electrolytes (and kidney function). That is often done on the 3rd or 4th day after beginning the medication, the 7th day and periodically thereafter.

Thiazide diuretics

Hydrochlorthiazide or chlorothiazide are alternative options to spironolactone when furosemide is no longer sufficient to keep your dog’s fluid buildup under control.

ACE Inhibitors (angiotensin-converting Enzyme Inhibitors)

The most common ACE Inhibitor medication used to treat CHF in dogs is enalapril (Enacard®/Vasotec®).  But alternative ACE inhibitors, benazepril, captopril and  lisinopril are also used. Drugs in this class differ in their absorbability and the stress they put on the kidneys and liver. ( read here ) Their effects on your dog are not immediate and it can take a week or two before you see full improvement. These medications all decrease the effort your pet’s heart must exert to pump blood throughout its circulatory system 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 undesirable for failing hearts because it increased the production of a hormone your pet’s adrenal glands produce (aldosterone) that causes sodium and water retention and high blood pressure (the 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 or desire to see in your dog.

Dogs in heart failure often have fragile kidneys as well. Since ace inhibitors, as well as diuretics, can occasionally have negative effects on the kidneys (azotemia), your dog’s kidney function needs to be checked before these drugs are given and then monitored periodically. Dose size and frequency needs to be kept to the minimum that yields positive results and the diuretic dose may need to be adjusted downward as the ACE inhibitor dose increases.

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 desirable.  Vomiting and a poor appetite are occasional side effects of ACE inhibitors. Your veterinarian can usually solve those problems without having to discontinue any of your pet’s medication. Enalapril is approved for once-a-day use in dogs; but seems to work more effectively for me when the pet’s total daily dose is divided and given half in the morning and half in the evening. The drug will occasionally cause nausea, diarrhea and loss of appetite. If the dose is higher than necessary, low blood pressure can also occur, leading to listlessness and weakness.

Benazepril (Lotensin®, Fortekor®) is another ACE-inhibitor commonly used in dogs 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 your dog’s 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 similar effects. This potent medication dilates blood vessels and in so doing lowers the resistance that  your dog’s 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 environment under close veterinary observation until the drug’s effects in your dog become known.

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

This is currently debated. One might assume that reducing your dog’s heart workload before severe damage occurred might postpone that damage. The only study I know of 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 veterinary cardiologists go with their instincts and prescribe ACE-inhibitors before the pet’s heart has deteriorated to the point where the dog needs them – much the way the ACE medications have been used to ward off strokes in humans ( read here ) Other animal studies have not found that strategy to be advantageous. ( read here )

Positive Ionotropes

Pimobendan (Vetmedin®)

Pimobendan (  Vetmedin® ), combined with a diuretic and ACE inhibitor, has rapidly become the standard first line treatment for advanced congestive heart failure in dogs. All positive ionotropes like pimobendan increase the strength of your dog’s heart muscle contractions. Ionized Calcium is an important part of the mechanism of all muscle contractions including the heart. The force of heart muscles contraction is related to the amount of calcium ion present in your dogs circulation. Pimobendan increases your dog’s heart muscle sensitivity to the ionized calcium that is already present there. Vetmedin® also opens up (dilates) blood vessels throughout the body easing resistance and pressure in the circulatory system. That also improves the efficiency with which your dog’s heart functions as a pump. In one clinically controlled trial, dogs with congestive heart failure survived on average of (median) 42 days without Vetmedin and 217 days when Vetmedin was part of their treatment plan.

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

Digoxin and digitoxin ( read here ) are two other drugs in the positive ionotrope group. They too increase the force of heart contractions by increasing the heart’s sensitivity to blood calcium. But both have many negative side effects. Those include vomiting, depression, refusal to eat and cardiac rhythm abnormalities.  Dogs receiving either medication need to be very closely monitored and their dose finely adjusted to their needs and their ability to tolerate the drug. 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 a dog’s kidney function is poor. I have seen too many cases of toxicity in dogs to be a fan of either drug. When they are given, it should be under the supervision of a veterinary cardiologist. ( read here )

Anti-arrhythmics (Drugs to stabilize your dog’s 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 begun after fainting episodes, or heart beat irregularities detected on an electrocardiogram or through the use of a Holter monitor that records your dog’s heart rate over time. The two most commonly used antiarrhythmics used in dogs in the USA are still probably sotalol or a combination of mexiletine and atenolol. 

Beta Adrenergic Blockers (ß-adrenergic blocking drugs)

The best-known drugs in this class are propranolol and atenolol. These medications protect your dog’s heart from excessive levels of stress hormones (catecholamines, adrenaline and noradrenaline) often present in the blood of dogs with advanced 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. 

Are There Other Drugs That Might Help My Pet?

Calcium Channel Blockers

Yes

The most commonly used drug in this class is diltiazem. Diltiazem increases the diameter of blood vessels (a vasodilator), increasing blood flow and slowing heart rate. It is used primarily in the acute form of heart failure seen most often in larger breeds of dogs – the dilated cardiomyopathy  I previously linked to.

Drugs To Help Your Dog Breath Easier (Bronchodilators)

Theophylline and aminophylline are the most commonly used drugs in this group dispensed by veterinarians. They both work by increasing the diameter of the small passages (bronchioles) in your dog’s lungs. The primary use of these drugs is to allow your dog to breath more freely. They also seem to reduce the frequency of fainting in some dogs with late stage CHF.

Cough Medicine

Cough suppressants are generally not necessary in dogs with CHF. Coughs due to lung congestion need to be treated with diuretics. Cough suppressants only mask them. However, if x-rays show that your pet’s lungs are clear of fluid and the coughing is due to an enlarged heart pressing on the pet’s windpipe (trachea), then cough suppressants might be helpful. 

Nutritional Support

We want to do everything in our power to keep our pets with us as long as we can. Dog food companies that are now mostly multinational conglomerates know that. They are quick to market products to please us. But the products they market are not necessarily science-based. (read here & here) They are more likely to echo whatever dietary trends are current in the popular press and then market those products heavily to veterinarians.  The only study that ever claimed to find one of those diets helpful in mitral valve heart disease in dogs (Royal Canin Early Cardiac™) was paid for by the Waltham Center, a division of Mars Inc. , the manufacturers of the Royal Canin brand that was used. (read here)  Does McDonald’s ever suggest that Burger King’s hamburgers are better? All mayor pet food companies now market “heart diets”. They are all lower in sodium and higher in profit. Traditional sodium level dog foods have never been identified as a cause of heart disease in dogs nor have low sodium diets been identified as helping dogs with heart disease. When low sodium diets were given to dogs in an attempt to lower their blood pressure, it was unsuccessful. ( read here & here) Lowering blood pressure is the chief reason low sodium diets are suggested for humans with heart disease. But these companies know that you know that low sodium diets are suggested for human heart issues. They then add ingredients such as fish oil, glucosamine, green tea extracts, marigold extracts and extra l-carnitine & taurine, antioxidants. Of those, only the taurine and carnitine have been proven to be helpful and that was only in dogs  that developed DCM, not the much more common heart valve congestive heart failure issues this article discusses. The DCM dogs that did benefit were all confirmed to have been deficient in taurine. (read here). 

Dog food companies sell these products only through veterinarians to maximize everyone’s profits and encourage veterinarians to suggest them. None of them are nutritionally inadequate, so those dog foods are just as fine as any mass-produced packaged diet is for your dog. You can also prepare a healthy diet for your dog yourself. (read here) Sodium is in your diet and blood for a reason. (read here )  

Coenzyme Q & Omega-3 Fatty Acids

Coenzyme Q10 is a natural substance that is involved in the body’s energy generation. ( read here ) Its level in our bodies naturally declines as we age. Organ meat such as beef heart, kidney, and liver is rich in Coenzyme Q10. It is also found in high levels in the red flesh of mackerel and is present in tuna and salmon as well. Much of the Q10 is destroyed by cooking. It is sold where human supplements are sold. The results of its use in humans with heart disease have been problematic. Some studies found it beneficial (read here) but others did not. (read here) Mice with a Q10 deficiency actually lived longer than those that had normal Q10 levels. Some human cardiologists recommend coenzyme Q for heart disease, others cardiologists feel there is not enough evidence one way or the other. (read here This is another one of the product out there that there is no harm in giving to your dog in reasonable amounts. Your dog might appreciate some lightly cooked, deboned mackerel  or beef liver – I know my dog would. 

Omega-3 fatty acid supplements are in the same category. Mackerel is a great source of them too. If you purchase these things in capsules, buy them at a human health food store so that you known they are mercury-free.

Helping Your Dog Maintain A Healthy Body Weight

Over time, dogs with CHF tend to loose muscle mass (cardiac cachexia). Their abdomens may still seem large to you and their weight may not change, but that is only due to a congested enlarged liver and pooled fluids. Their ribs and spine become quite prominent due to muscle wasting. All of this is the result of their low cardiac output. It is important that you do everything you can to encourage your dog with CHF to eat. quality meat protein and vitamins needs to be high in your dog’s diet. Geriatric pets often have tooth and gum issues – so offer them their food in a softened, freshly made or canned form is often best. You might look into Entyce® as an appetite stimulant. If you want to add your observations on Entyce to my blog, let me know.

Additional Procedures And Treatment That Might Eventually Become Necessary – Oxygen

When your dog can no longer 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 an emergency center are stressful to your pet and to you. Human home oxygen concentrators work just as well. You can improvise a clear oxygen “tent” at home for smaller dogs or use an improvised or commercial veterinary face mask for larger dogs. PURE OXYGEN CAUSES ORDINARY THINGS IN YOUR HOME TO BECOME VERY FLAMMABLE. If you contemplate using oxygen at home for your dog, have a human respiratory therapist instruct you on its use. A fire extinguisher might also be a wise purchase. Small home oxygen cylinders do not last long and are expensive to refill. I kept a tethered group of the large  145 cu. ft. hospital size oxygen cylinders at my animal hospital. When large volumes of oxygen are required, they are the more practical alternative. 

Removal Of Excess Fluids

Dogs become quite uncomfortable when leaked fluid in their chest or abdomen restricts their normal respiration. Draining this fluid (abdomenocentesis and thoracocentesis) can give them temporary relief. It it generally done in emergency situations to gain more time for the beneficial effects of diuretics, like furosemide and other heart medication to occur.

Diuretic medications  is usually sufficient to remove the excess fluid (ascites) that pools the tummies of dogs with congestive heart failure as well. When diuretics don’t succeed, it is usually because the dog’s kidneys are damaged as well as its heart. ( read here ) If you recall, I mentioned that leaked fluid (ascites) contains a lot of albumin. When you dog’s abdomen is drained too frequently, your pet’s blood albumen level can drop dangerously low. 

Exercise Restriction

Our pets are so happy and excited to see us when we get home that they gladly overexert themselves. As much as your dog would enjoy it, encouraging your pet to “work its heart out” at maximum capacity is not a good idea when CHF is an issue. Modify the style of your returns, you play-times and your pets life style to minimize its daily exertion. Its your closeness and touch that means the most to your dog’s happiness.

How Much Longer Will My Pet Live?

Dogs with mild to moderate heart disease can have a good quality life for many years. Every dog differs in the rate at which CHF advances and no statistics are available for me to provide you with. In humans diagnosed with CHF, half of the patients are alive 5 years after the diagnosis. The shorter natural lives of our pets shorten that available time window. How suddenly the symptoms of a heart problem appeared in your pet also tends to predict survival time. The more sudden the onset, the shorter your dog is likely to live. In dogs with dilated cardiomyopathy (DCM) that eventually leads to congestive heart failure, the average patient survives only 4.2 months. ( read here ) However, when a valve failure is the underlying cause of CHF, pets tend to survive much longer.

That always varies from case to case; but, with the exception of mitral valve surgery, the end result is never a cure. The outlook and longevity for your dog moderately improves  when their heart is enlarged but no electrical (rhythm) abnormalities are detected. Heart size increase is a relatively good predictor of the disease progression, but no better than your observations of your pet’s energy level and respiratory rate. Periodic pulse oxymetry accurately tracks the rate of decline in human heart function. But to my knowledge, that has never been attempted in on a continuing basis in dogs. The one reference on its use is in detect birthing problems in livestock.   (read here) You can bring periodic oxymeter reading with your veterinarian if you wish. Let me know the results. 

Your nursing care, and your veterinarian’s assistance are key factors in maximizing your pet’s lifespan once CHF has been diagnosed. All dogs on therapy for CHF should be reexamined  every 3-6 months and their therapy adjusted according to the results. Any change for the worse or improvement is something your veterinarian will want to know. 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?

That is sometimes an option for well-to-do dog owners whose pets have developed mitral valve disease. When the anchoring fibers (chordae tendinae ) that hold your pet’s left upper heart valve in place have torn or stretched. ( read here )  Veterinarians at Nihon University in Tokyo have perfected a procedure to correct it. (read here & here)  In the USA, I would discuss that option with cardiologists at the Vet School in Davis CA. 

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