Heart Disease In Dogs And Cats

Dogs and cats suffer from heart disease just like humans do. Fortunately they do not develop fatty lesions in the blood vesicles of their heart (arteriosclerosis, coronary artery disease) so they do not get heart attacks. The heart is a unique muscle. Microscopically, it is unique among muscles of the body. the Dogs and cats, like all mammals, have a four-chambered heart consisting of a left and right atrium and a left and right ventricle. The left and right atria receive blood from the lungs and body respectively. The left ventricle is responsible for pumping blood throughout the body while the right ventricle pumps the blood to the lungs for oxygen. Valves located between the atria, ventricles, and the two vessels leading to the heart, prevent blood from flowing in the wrong direction.

Typical signs of heart disease in dogs and cats include weakness, poor appetite, coughing, fainting (syncope), difficult breathing (dyspnea), enlarged abdomen (ascites), pale bluish gums (cyanosis) and a rapid, weak heart rate (tachycardia) and heart murmurs. Heart murmurs due to heart disease must be differentiated from heart murmurs do to thin blood viscosity (anemia). Some pets with heart disease develop a palpable venous pulse and many have an abnormal heart rhythm. As the circulatory system fails, the kidneys and liver flood with blood and work inefficiently. Biochemical blood tests then indicate failure of these organs.

In dogs the valves are often the first structures affected. Heart disease in cats usually involves the entire heart muscle and not just the valves. We are usually unaware of the problem in cats until the heart is well on its way to failing. Signs of all forms of heart disease in cats are quite similar and can not be used to separate one form of heart disease from another. Often the only signs are weight loss, and difficulty breathing. Cats with this form of heart disease do not survive long.

Feline Dilated Cardiologist:
The most common cause of this disease was a deficiency in the amino acid, taurine. Taurine deficiency caused the muscles of the heart to loose their strength. Lack of taurine also caused degeneration of the retinas of the eye. Cats with this disease were weak and lost weight. They had difficulty breathing and gasped for air. One common symptom of the disease was clots that form within the heart and broke loose obstructing blood flow to the rear legs. These cats acted as if they were paralyzed. X-ray and ultrasound studies showed an enlarged, thin-walled, heart. We frequently saw this disease prior to the mid 1980s. At that time taurine was first recognized as an essential nutrient for cats.. Now that taurine is added to cat foods, we rarely see this condition. It can still occur when cats are fed dog food or other low-taurine diets. A second, genetic form of the disease occurs in Siamese, Burmese and Abyssinian cats. We treat this condition with medicines that increase the hearts efficiency in pumping blood and decrease pooled fluid in the lungs. We also give them drugs to reestablish normal heart rhythm. Many veterinarians include a taurine supplement in any heart condition in cats. Heart disease can also occur secondary to hyperthyroidism.

Hypertrophic Cardiomyopathy Of Cats:
In this disease the walls of the heart thicken, leading to inefficient pumping of blood. Blood pressure rises and fluid accumulates in the lungs. Eventually the chambers of the heart enlarge and abnormal heart rhythms occur. Signs of this disease are labored breathing, rapid heart rate, heart murmurs, weakness, collapse and death. Rare heart valvular disease, hyperthyroidism and asthma can mimic hypertrophic cardiomyopathy. We diagnose this disease with x-rays electrocardiograms (EKG or ECG) and ultrasound. We treat the disease with low salt diets, diuretics, aspirin to prevent blood clots, and medications such as diltiazem and atenelol.

Restrictive Cardiomyopathy Of Cats:
In this condition localized scarring of the heart muscle prevents the normal beating of the heart. This leads to the enlarged, weak heart of congestive heart failure. Signs of the disease are poor appetite, weight loss and difficult respiration. Sometimes blood clots that cause paralysis of the limbs occur. X-rays, EKG and ultrasound all show atrial enlargement. We treat these cats with calcium channel blockers such as diltiziam, diuretics such as furosemide and low doses of aspirin. Aspirin must be used with extreme caution in cats. Low sodium diets are also helpful if the cats will eat them. If we are fortunate, cats with this disease will live about a year.

Dilated Cardiomyopathy Of Dogs:
In this condition, as in cats, the heart chambers enlarge to the point where they can no longer pump blood efficiently. It is most common in large breeds of dogs and rare in small breeds. Doberman Pinschers, Great Danes, German Shepherds and Labrador Retrievers are particularly at risk. The disease is most common in middle-aged dogs, especially males. Usually the cause is unknown. However, taurine deficiencies, parvovirus and the use of adriamycin can all cause the disease. Overly stretched heart muscle is an inefficient pump. Signs of the disease are those of congestive heart failure, difficult breathing, weakness, coughing and fluid enlargement of the abdomen. We diagnose the condition with x-rays, EKG and ultrasound. We treat the disease with medicines to improve heart contractility (digoxin, dobutamine), ACE inhibitors and diuretics. These dogs may need oxygen until the medicines have an opportunity to work. Low salt diets as well as supplements that contain taurine, L-carnitine (carnatine) and coenzyme Q may also be helpful. Dogs do not survive long with this condition.

Hypertrophic Cardiomyopathy Of Dogs:
This disease is quite rare. As in cats, the muscles of the heart thicken and become inefficient at pumping blood. The signs of the disease are the signs of congestive heart failure e.g. difficulty breathing, coughing, heart murmurs and exercise intolerance. We diagnose the condition with x-rays, EKG and ultrasound. Treatment consists of diuretics, beta blocking drugs such as atenalol or propanolol and calcium channel blockers such as diltiziam. Low salt dies may also be helpful.

Congestive Heart Failure:
Congestive heart failure (CHF) is the end result of many different heart problems. It occurs when the heart is unable to meet the circulatory demands of the body. Many things can cause the heart to be faced with increased pressure and decreased effectiveness as a pump. Valvular defects, tumors, heartworms, heart beat abnormalities, and damaged to the muscle itself all cause the heart to enlarge and blood to pool in the organs and lungs. The net effect of all this is called congestive heart failure.

We treat CHF with vasodilator drugs that increase the diameter of blood vessels. Most of the medicines of this class that are in use today are also called ACE inhibitors. The most common one is enalapril . I prefer it to Lisinopril. ACE inhibitors medicine decreases heart rate and decreases cough and pulmonary edema. The most common side effect is lack of appetite and vomiting. Other vasodilators used include captopril and benazepril and hydralazine. This class of drugs may not be as effective when non-steroidal-anitinflamatory agents are also give to control arthritic pain.

We also administer diuretics (Lasix, furosemide) to these patients to remove the excess fluid that accumulates in the lungs and abdomen of pets with CHF.

Positive inotropic agents increase the force of heart contractions. The digitalis glycosides, are extracts of the foxglove plant known as early as the Romans. I do not use it as commonly today because of it's potent side effects. One trade name of digoxin is Digitek. It is definitely a last resort medication.

When arrhythmias are present we often attempt to correct them with procainamide(Pronestyl; Procan-SR), propranolol (Inderal) or tocainide (Tonocard).

Some veterinarians administer coenzymeQ (30mg tid) because of its beneficial effects in people with dilated cardiomyopathy.

Valvular Disease Of Dogs And Cats:
In certain breeds of dogs, particularly toy breeds, there is a tendency to develop fibrosing heart valve problems or endocardiosis. This is the most common form of heart disease in dogs and the rarest in cats. Age-related scaring of the mitral valves is also a common occurrence in dogs. The mitral valve divides the lower and upper left chambers of the heart. It is often the first heart valve to wear out. Sixty percent of dogs over 8 years old have some degree of this fibrosis. But less than half the dogs with this condition have overt symptoms of cardiac disease. The valves become blunted and shriveled and do not open or close properly. When this occurs blood does not flow in the normal pattern but leaks back in to the atrium or ventricle. With time, increased pressure causes one or more chambers of the heart to enlarge. As the chambers of the heart enlarge they press on the windpipe resulting in a dry, hacking cough. The enlarged heart also stretches the nerve fibers that control heart rhythm resulting in abnormal beats or arrhythmias. Blood squirting backwards (“backfiring”) through the system of valves and chambers on the right, causes blood to back up into the lungs resulting in lung edema and a moist productive cough, It is worst when the patient is laying down. These pets may faint or collapse on exertion.

In the left-hand side of this disease, mitral valve insufficiency, the left atrio-ventricular valve (mitral valve) fails to open and close properly. In another, Aortic Stenosis, the valve separating the left ventricle from the aorta fails from birth to open properly and the aorta is narrower than normal. Valvular endocarditis, an inflammatory condition of the valves, is often the result of systemic bacterial infections. One source of these infections is gum and tooth disease. Heart murmurs are very common in valvular disease. Ultrasound lets us visualize these defective valves. I usually place these dogs on an extended course of antibiotics and clean or extract affected teeth. If congestive heart failure has already occurred I treat these dogs with diuretics, and ACE inhibiting drugs. Drugs that dilate blood vesicles such as diltiazem, hydralizine and prazosin are also used.

Defective Heart Development:
Dogs and cats are sometimes born with heart disease. We call this congenital disease. Some of these diseases are pulmonic stenosis (a narrowing of the pulmonary artery), valvular stenosis (narrowed valves) and patent ductus arteriosis in which an embryonic shunt between the pulmonary artery and the aorta fails to close. All these problems can eventually lead to congestive heart failure. All of these conditions have been repaired successfully at veterinary colleges but they are beyond the abilities of ordinary veterinary hospitals. When your veterinarian suspects a heart condition in your pet the best thing to do is to schedule a consult with an experienced group of veterinary cardiologists such as the ones at Cardiopet (http://www.idexx.com/animalhealth/telemedicine/ ).
Dogs and cats suffer from a number of heart conditions. The most common two are disease of the left atrio-ventricular valve (mitral valve insufficiency) and a generalized enlargement, and weakening of the heart called dilative cardiomyopathy. Approximately one in ten dogs will develop one of these two conditions.

Vetmedin is the trade name for Pimobendan. It is in a clalss called positive inotrope and mixed vasodilators. It's effect is similar to ACE inhibitors such as enalapril but it works by a different mechanism. It works by increasing the amount of calcium available to the heart muscles and also lowers vascular resistance and blood pressure (increased blood vessel diameter or vasodilatation). In doing so, the pet’s heart needs to do less work.
Vetmedin increases blood calcium levels. The more calcium that is present, the stronger are the heart’s contractions. The Drug was originally used in human medicine about 10 years ago. At the time, it was thought that it might offer hope to people with heart conditions similar to your pet’s. It did increase the force of human heart contractions, but it sometimes made the hearts pump too forcefully. Dogs and cats do not develop coronary artery disease as humans do. But human hearts with blocked or occluded coronary arteries became starved for oxygen when on this drug. This led to heart attacks and angina (chest pain). Because dog and cat hearts differ from human hearts in this respect, the drug has been reintroduced in Europe and Canada for use heart failure in pets. The published dose of Vetmedin is 0.1-0.3mg/ pound body weight/day. It should be given about an hour before meals with half the dose given before breakfast and half before supper. I obtained this dose from Boehringer-ingelheim’s Spanish language website. Their Dutch website gives the minimum daily dose as 0.15mg/lb/day. An occasional dog will experience vomiting on this drug. If your veterinarian has trouble obtaining this medication or if it's expense is too great, it can be ordered from a Canadian Pharmacy.

Forticor (benazepril HCl, Lotensin, Novartis Animal Health, Canada, etc.)
Benazepril is also an angiotensin-converting enzyme (ACE) inhibitor drug. It is similar in it’s effect to enalapril (Enacard) and Vetmedin. Forticor is used to increase the efficiency with which failing hearts pump blood and is also used to treat high blood pressure in pets. In the liver, the drug is metabolized to benazeprilat, the active compound. It can be given with or without food. It is also effective in lowering blood pressure (hypertension) in cats with kidney failure.

Spirolactone (Aldactone)
When the maximum dose of furosemide diuretic (1-3 mg/lb every 8-12 hr in dogs and 0.5-1.5mg/ pound every 8-12 hrs in cats) is not sufficient to eliminate fluid buildup in the tummy (ascites) and lungs (pulmonary edema) of your pet, another diuretic, such as spirolactone, can be added to the medications your pet receives. You need to be patient - it takes 2-4 days for the full effect of the drug to be reached. Spirolactone can increase the toxicity and effect of digoxin so your pet’s digitoxin dose may need to be lowered. It can also cause an increase in serum potassium, which can be dangerous. To monitor potassium, a blood sample should be taken and measured for serum electrolytes and kidney function on the 3rd or 4th day, the 7th day and periodically there after.

Diltiazem is in a class of drugs called calcium channel blockers that increase the force of heart contractions. This drug can also cause many side effects. These side effects are most likely when given with diuretics such as furosemide or with Enalapril. Diltiazem can slow the heart rate so much that the dog does not receive enough oxygen.

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7/19/06
Subject: CHF activity and exercise limits Dr. Hines, You discuss treatments with prescription drugs and other medical devices but you do not discuss limitations related to activity and exercise with specific breeds such as hunting dogs who have a natural tendency to pursue the prey. It would be helpful to have information regarding limitations or suggestions for alternative activities that are recommended to be included with your treatment information.
Thanks Dahly
You make a good point. Dogs bred to work rigorously will continue to attempt to do so, long after it is desirable for their health.. By the time they limit their own activity, they are late in this disease. When a dog begins to show signs of decompensation (cough, fluid retention, heart enlargement,panting), one should take a timer with you when the dog is outside and limit the length of activities. Several short exercise periods would be better than one long one. Restrict these play periods to the early morning and late afternoon when days are hot. Bring water with you. Develop less strenuous play activities with your per that offer equal enjoyment but less exertion.

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Subject: Preventative treatment for dogs with mitral valve disease Dear Dr. Hines: My chihuahua/beagle mix went to the vet for an allergic reaction (itching, chewing, redness) to a flea bite. She never had fleas before this, and only had one or two, which I think she picked up in a beach house we had just been to. The vet said she was not infested. She got a cortisone shot and flea treatment, and was fine within 48 hours. Anyway, while there, the vet noted a "left murmer" and suspected Mitral Valve regurgitation. A few days later, Xena had a chest X-Ray and cardiac ultrasound. Here are the results as the vet reported them to me: . Normal chest X-Ray . Left atrium "mildly enlarged." . Normal contractility, "the lower end of normal, but still in normal range." . "On a scale of 1-5, with 5 being the most severe, her mitral valve disease is a 2." . Overall her mitral valve issue is rated "mild." The doctor recommended 25 mg of CoQ10 (I had inquired about it), Omega 3's (how much and in what form?) and wants to put her on Lisinopril. The took blood to test kidney and liver function before starting this drug, and the pharmacist is figuring a dose for her since she is so small (currently 8 lbs exactly.) Xena's last visit about a year ago for a regular check up including a full panel of blood work and a lime disease titer (she had lime disease in 2000) was entirely normal. there was no murmer noted at that time or at any previous visit over her 11 years. This is very new, and I am obviously trying to determine the very best course of action. Xena has been a lively, perky, zealous defender of the fort, a lap dog, the family friend but really "my" dog, and I am anxious to forestall any further worsening and prolong a good quality of life for her. I am very interested in natural courses of treatment, and more skeptical of drugs. What do you think of Lisinopril? What ACE inhibitor would have the least side effects, the least toxicity? Should she be exercised more frequently to strengthen the heart? Are valve replacements done on dogs? Does this ALWAYS get worse? Can she live with this for years? Should I even put her on the lisinopril? I don't like what I read in terms of side effects.--------------------------------------------------------------------8/08/06
Dear Ms. C, Mitral valve murmurs are very common in older dogs. Many dogs in their later years have them. It is almost a routine finding in elderly patients. It is generally just due to the wear and tear of time as the valve opens and closes innumerable times. However, Zena, at 11, is not that old. I do see many more Chihuahuas and toy breeds with this condition than I do in larger breeds. I believe that in toy breeds, mitral murmurs are more common because chronic dental infections are so common in toys. Some, such as Maltese, have soft teeth. But many more of them have periodontal disease due to eating canned foods and table scraps. I know that Zena does not eat table scraps but she is eating canned food. Periodontal disease in dogs does not involve the teeth themselves and no cavities are present. It is the tissue around the base of the teeth that is infected and receding back. This gives bacteria a place to set up shop. Please examine Zena and be sure this is not present. Dogs with this problem have a very strong breath odor. When dogs have this problem, small clumps of bacteria break loose, enter the blood stream, and lodge of the heart valves and other organs. If this proves to be true in Zena's case, she should go on three weeks of a broad spectrum antibiotic. Trimethoprim/sulfa might be a good beginning choice. Most dogs tolerate it well. An alternative is Clavamox ( ammoxicillin and clavulanic acid). If her teeth and mouth are not in good shape, her teeth need to be cleaned with an ultrasonic scaler paying special attention to infected areas below the normal gum line. Then she needs to have her teeth brushed at home every day with a doggy toothpaste such as C.E.T. brand. But it may be that her teeth are not the root of her mitral valve problem. If it is just the aging process, it is important she not be overweight. It is also important that her diet contain sufficient Taurine (an amino acid). All name brand foods are supplemented sufficiently and dogs can produce their own Taurine when other specific amino acids are present in their diet. Taurine deficiency is not known to have any influence on mitral valve disease but the lack of it has been associated with a particular form of heart failure. A second correctable cause of heart murmurs is anemia. But I assume her blood PCV (Hct) and red blood cell count were normal. I find many dogs with grade 2 heart murmurs that do perfectly well for years. I do not treat these dogs with medications. Grading the severity of a heart murmur using a stethoscope is not a highly accurate procedure. Also, the loudness of the murmurs does not always correlate with the severity of damage. Dogs in the later stage of the disease often have a much softer murmur that dogs in the initial stages. Keeping track of the size and shape of the heart with periodic x-rays is a more accurate method of following the course of the disease. You could have this done every six month or yearly. An ultrasound performed by a veterinarian with adequate experience in evaluating the cardiac shadow is just as good. I suggest a certified veterinary radiologist or cardiologist. Many make circuits between veterinary hospitals just to do this. When I do start to see the symptoms of persistent hacking cough, increased respiratory rate, bluish gums or abdominal enlargement, the first drugs I use are Furosemide (Lasix) to remove accumulating fluids from the lungs (cough) and abdomen (swelling). This drug has very few or no side effects. Many many humans are on it. When it is given in moderate to large doses the pet needs to be on a potassium supplement. But I see no need for Zena to take this medicine and it will not slow or prevent valvular heart disease (or any form of heart disease) The other drug I use frequently is enalapril (Enacard, Vasotec). From what I have read, I feel that enalpril is a safer drug than lisinopril. Both are a from a group of drugs called ACE inhibitors. They enlarge the diameter of blood vessels throughout the body so that the heart does not have to pump as hard or as fast to provide proper circulation. Again, many many humans are also taking this drug to reduce blood pressure. It is a very safe drug when given at recommended doses. I do have one client that associates her giving enalapril with a cough that developed but I and her cardiologist are unsure if this is actually the case. Zena does not need Enalapril to relieve signs either. I have never used enalapril or read of it being used in dogs to prevent heart disease from progressing. However, in humans enalapril apparently slows the progression from no symptoms (asymptomatic) to the time symptoms occur (symptomatic). You can read this the article . However, a Scandinavian study I read did not show this positive effect in dogs.
Many nutriceuticals are marketed as being able to slow or reduce heart failure. Non have been proved scientifically - they are all in the realm of alternative medicine. Vets and physicians often recommend them or agree to client use because they do not seem to cause any adverse consequences - that is, they probably can do no harm. I often suggest them. It is common for me and others to be in a position where traditional drugs are no longer working and we have all been taught that we must do something , make some effort, even if its an unsubstantiated treatment. Co-enzyme Q, L-Carnitine and antioxidants such as Omega-3 fatty acids . Vitamin E and C also fall into this group. In theory, they could help. A good Omega-3 dose would be one fifth of the suggested human dose per day. The same goes for vitamin E and C. Excessive E can slow blood clotting and excessive C can cause stomach upset and diarrhea. Some clients are convinced that these agents helped their pets. I can not confirm that they will work but I see no problem in using them. Try to minimize the amount of corticosteroid that Zena receives. An occasional dose of oral prednisone or dexamethasone is not a problem but it should not be given more frequently than every three months without a very justifiable need. Topical cortisone sprays are much safer. Please let me know if you have further questions. Best wishes, R.S.H.

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11/16/06 Hello, Dr. Hines, I just read your very thorough, but not overly technical, article re DCM. Our 12 year old Irish Terrier was diagnosed with the disease after going into CHF (Congestive Heart Failure) after surgery last January Thanks to a caring vet, and her consult with a radiologist and cardiologist, Zack was put on all the meds you described in your article. In July, Pimobenden was added to his regimen, and he seemed to perk up even more. It is now almost 10 month since diagnosis (we were given 6 months), and although I just returned from the vet's where Zack got a large dose of IV Lasix, (he has spells where he retains fluid, even though he gets 20 mg of lasix a day - we'll probably be increasing that) he generally is doing very well. I thought you might want to add something about the Pimobenden to your great article.Thanks - it really helps in the middle of the night to have somewhere to turn! S.R.

Ask the Veterinarian, Veterinary question, Ask the Vet, Veterinary Advice, Dr. Ron Hines.