HEART DISEASE (Cardiomyopathy, Valvular Heart Disease, Congestive Heart Failure) HEART DISEASE (Cardiomyopathy, Valvular Heart Disease, Congestive Heart Failure)Principal Natural Treatments
Taurine, carnitine, hawthorn, natural diet, Coenzyme Q10
Other Natural Treatments
Omega-3 fatty acids, antioxidants, glandulars, DMG, bugleweed, burdock, coptis, dandelion leaf, devil’s claw (possible anti-arrhythmic), garlic, ginger, Ginkgo biloba, goldenseal, gotu kola, hawthorn, goldenseal, Oregon grape, red clover, and maitake mushrooms
In dogs and cats, the most common types of heart disease include cardiomyopathy and valvular heart disease. Congestive heart failure occurs late in the course of any type of heart disease as the heart muscle fails to adequately pump blood throughout the body.
Valvular heart disease is the most common heart disease in dogs, occurring most commonly in older small breed dogs (the prevalence is estimated at 75% of dogs over 16 years of age). This condition occurs as the heart valves (most commonly the mitral valves that separate the left atrium from the left ventricle) degenerate as a result of acquired chronic structural changes in the valves. Small nodules of myxomatous degeneration occur in the valves, causing them to thicken, become irregular, and retract from each other. This retraction allows blood to flow in a “backward” direction as well as a forward direction. This abnormal blood flow causes “regurgitation” of blood, which is heard through the stethoscope as a result of turbulence caused by the regurgitation. With time, coughing and exercise intolerance may occur as regurgitation worsens and the heart can no longer adapt, leading to early congestive heart failure.
Dogs may also be afflicted with cardiomyopathy, where the heart muscle itself is actually diseased. Larger breeds of dogs (especially Boxers and Doberman Pinschers) may be afflicted with dilated cardiomyopathy, although increasing incidence is reported in Cocker Spaniels. The average age of affected dogs is 4 to 8 years. The cause is unknown, although the higher incidence in purebred dogs when compared to mixed breed dogs suggests a genetic cause. Additionally, L-carnitine or taurine deficiency has been shown in some dogs.
In dilated cardiomyopathy, the heart enlarges as the heart muscle progressively becomes thinner. The thinner muscle does not pump blood adequately, and with time congestive heart failure occurs.
Cats with heart disease are most commonly affected with hypertrophic cardiomyopathy. In the past, dilated cardiomyopathy was also common. Recent evidence that taurine deficiency contributed to most cases of feline dilated cardiomyopathy has resulted in manufacturers increasing the amounts of taurine in commercial cat foods. As a result, dilated cardiomyopathy is rare in cats today (unless owners prepare food at home and do not adequately supplement with taurine. This is especially problematic if owners insist on feeding cats vegetarian diets, as vegetables do not contain taurine.
Hypertrophic cardiomyopathy appears to be genetic in origin in cats. Hypertrophic cardiomyopathy most commonly occurs in younger (4- to 8-year-old) male cats. In this condition, the heart muscle thickens, often to the point where the chambers of the heart diminish in size to the point where little blood is able to be pumped around the body. This lack of forward movement of blood results in heart failure in severe, chronic cases of hypertrophic cardiomyopathy. In some cases of cardiomyopathy in cats, emboli (a collection of clotted platelets) forms in the heart and travels to another area of the body, most commonly the lower aorta. This embolus then causes lack of blood to the body part served by the blocked aorta, usually one or both hind limbs, causing paralysis. Often this secondary effect of cardiomyopathy prompts the client to bring in the cat for a veterinary visit, allowing the diagnosis of the underlying heart disease.
Supplementation with taurine may be beneficial in both cats and dogs with heart disease. In cats with taurine deficiency that results in dilated cardiomyopathy, clinical improvement is usually seen within 2 to 3 weeks following supplementation; 250 to 500 mg of taurine daily is suggested. Improvements in the EKG and radiographs will often take 3 to 6 weeks. The goal of taurine supplementation is to achieve plasma taurine levels of at least 60 nmol/mL (normal cats usually have levels >40 nmol/mL). Not all cats with dilated cardiomyopathy have taurine deficiency as the cause of the cardiomyopathy; those cats with normal taurine levels would not be expected to respond to supplementation with taurine (although since taurine supplementation is safe, any cat with heart disease could probably receive a diet containing additional taurine).
In dogs, dilated cardiomyopathy can also occur, leading to congestive heart failure. Preliminary work shows that supplementation with taurine may be beneficial in American Cocker Spaniels and Golden Retrievers with dilated cardiomyopathy. Supplementation with taurine (500 mg twice daily) and L-carnitine (1,000 mg twice daily) in a small number of dogs with low plasma taurine levels resulted in improvement in a few of the patients. Since American Cocker Spaniels are predisposed to dilated cardiomyopathy with concurrent taurine (and possibly) carnitine deficiencies, supplementation with these two compounds is suggested for Cocker Spaniels with dilated cardiomyopathy (although not all researchers agree on this recommendation, supplementation is safe even in those cases where it is difficult to determine if it is truly needed).
Dogs with chronic valvular disease (leaky heart valves), the most common heart disease reported in dogs, usually have normal plasma taurine levels, making routine supplementation unlikely to be of benefit.
Taurine deficiency can be diagnosed based upon testing levels in the blood. Plasma levels are more indicative of recent taurine intake; whole blood levels are more suggestive of chronic taurine intake. However, even with normal blood levels, it is possible that levels of taurine in the heart muscle cells might not be adequate. Even for those pets without low blood taurine levels, supplementation can be tried without side effects.
Decreased carnitine levels may also be related to dilated cardiomyopathy in dogs, especially in Boxers, Doberman Pinschers, and American Cocker Spaniels. Carnitine deficiency is difficult to diagnose and usually requires a heart biopsy for a definitive diagnosis. Carnitine supplementation of 2 gm (2,000 mg) given 3 times daily is often recommended for dogs with cardiomyopathy.
Carnitine can also be used for pets with any type of heart disease (and is included in some heart supplements), but definitive proof for its use in heart diseases other than cardiomyopathy caused by carnitine deficiency is lacking. However, as with taurine, since carnitine supplementation is safe, supplementation will not hurt and other nutrients in the supplements (such as antioxidants and herbs) may be useful.
Carnitine is abundant in red meat (higher in beef than in chicken or turkey) and dairy products, which form the basis of the diets listed. Diets high in cereal grains and plants (which account for many commercial diets) may not support adequate carnitine levels in the heart.
Supplemental carnitine may improve the ability of certain tissues to produce energy. This effect has led to the use of carnitine in various muscle diseases as well as heart conditions, as carnitine accumulates in both skeletal and cardiac muscle. There is no dietary requirement for carnitine. However, a few individuals have a genetic defect that hinders the body’s ability to make carnitine. In dogs, a subset of pets with dilated cardiomyopathy that show variable response to carnitine supplementation has been identified (this was first shown in Boxers).
In addition, diseases of the liver, kidneys, or brain may inhibit carnitine production. Heart muscle tissue, because of its high energy requirements, is particularly vulnerable to carnitine deficiency.
The principal dietary sources of carnitine are meat and dairy products, but to obtain therapeutic dosages a supplement is necessary.
In people, carnitine is taken in three forms: L-carnitine (for heart and other conditions), L-propionyl-carnitine (for heart conditions), and acetyl-L-carnitine (for Alzheimer’s disease). The dosage is the same for all three forms.
Carnitine is primarily used for heart-related conditions. Without adequate carnitine to transport fatty acids into heart muscle cells, reduced levels of energy are available to the heart.
In people, fairly good evidence suggests that it can be used along with conventional treatment for angina or chest pain, to improve symptoms and reduce medication needs. When combined with conventional therapy, it may also reduce mortality after a heart attack. A few studies suggest that carnitine may be useful for cardiomyopathy.
Several small studies have found that carnitine, often in the form of L-propionyl-carnitine, can improve symptoms of congestive heart failure. There is better evidence for Coenzyme Q10 for this condition, and in fact, some veterinarians may prescribe both supplements.
In people, carnitine may help reduce death rate after a heart attack. In a 12-month, placebo-controlled study, 160 individuals who had experienced a heart attack received 4 g of L-carnitine or placebo daily, in addition to other conventional medication. The mortality rate in the treated group was significantly lower than in the placebo group, 1.2% versus 12.5% respectively. There were also improvements in heart rate, blood pressure, angina (chest pain), and blood lipids. A larger double-blind study of 472 people found that carnitine may improve the chances of survival if given within 24 hours after a heart attack. As a rule, pets do not experience “heart attacks” as people do. Pets can experience sudden onset of congestive heart failure due to valvular disease or cardiomyopathy. Whether or not administering carnitine following an acute episode improves survival is unknown.
Weak evidence in people suggests that carnitine may be able to improve cholesterol and triglyceride levels. In carnitine deficiency, increased blood trigylceride levels can occur.
In pets, heart levels (myocardial levels) of carnitine have been found to be low in up to 40% of dogs suffering with dilated cardiomyopathy. Diagnosing carnitine deficiency is difficult, as blood levels do not correlate with levels in heart muscle cells (although low plasma carnitine levels appear to be predictive of low mycardial carnitine concentration). Researchers must do heart muscle biopsies in order to determine myocardial carnitine deficiency. If the heart is unable to concentrate carnitine, levels can fall quite low despite normal blood levels. Studies show that only 20% of dogs with dilated cardiomyopathy with myocardial deficiency also had low blood levels of carnitine. Most dogs with myocardial carnitine deficiency and dilated cardiomyopathy suffer from a membrane transport defect that prevents adequate levels of carnitine moving from the blood into the heart muscle cells (in these pets, blood levels of carnitine are usually normal or higher than normal).
The dosage of carnitine recommended for dogs with carnitine deficiency cardiomyopathy is 50 mg/kg 3 times daily, or alternatively 2,000 mg per pet 3 times daily. Rare side effects include diarrhea and flatulence (intestinal gas). Improved heart function, appetite, and exercise tolerance are often noted within 2 months following supplementation in some dogs.
Note: Carnitine supplementation has also been suggested for pets with other heart diseases, including endocardiosis (valvular heart disease), ischemic heart disease, and congestive heart failure. Definitive proof is lacking, although carnitine supplementation is safe and can be tried for pets with these other cardiac disorders under veterinary supervision.
To sum up, current benefits and recommendations regarding carnitine supplementation for dogs with heart disease include:
Since true carnitine deficiency may exist in a small number of dogs such as Boxers with dilated cardiomyopathy, supplementation with L-carnitine may be of benefit in these pets.
In some dogs with dilated cardiomypathy (approximately the 40% that have myocardial carnitine deficiency), supplementation may improve clinical signs and cause some improvement in the echocardiograms of these patients.
Supplementation with L-carnitine may improve survival in some dogs with dilated cardiomyopathy, especially those who have myocardial carnitine deficiency.
The main disadvantage of carnitine supplementation is the cost, approximately $75 per month. While carnitine deficiency is not the cause of dilated cardiomyopathy in most dogs, supplementation is safe and can be used as an adjunct to other therapies.
L-carnitine in its three forms appears to be safe, even when taken with medications. People are advised not to use forms of carnitine known as “D-carnitine” or “DL-carnitine,” as these can cause angina, muscle pain, and loss of muscle function (probably by interfering with L-carnitine). The maximum safe dosages for young children, pregnant or nursing women, or those with severe liver or kidney disease have not been established; similar precautions are probably warranted in pets.
Dietary therapy is designed to regulate sodium levels. In heart failure, sodium is retained rather than being excreted by the kidneys. Sodium retains fluid in the body, which causes fluid to leak from the blood vessels into the lungs, liver, and other organs causing the signs (coughing, abdominal fluid, and such) seen in pets with congestive heart failure.
To reduce sodium retention, salt is reduced in diets designed for pets with heart disease. Since commercial pet foods have excessive amounts of sodium to increase palatability and act as a preservative, these diets are not recommended for pets with heart disease. There are several medicated diets prepared for pets with heart disease. However, they may contain by-products and chemical preservatives that are not always consistent with a holistic nutritional program, although they may have a place in the management of heart disease if the owner cannot prepare a homemade diet or if the pet will not eat the homemade diet. Homemade diets can fit the need for holistic, low-sodium diets.
Pets with heart failure may have low potassium levels resulting from decreased food intake (common in pets with heart failure) and the use of diuretics such as furosemide (Lasix). Even with normal blood levels, cellular levels of potassium may be decreased. Extra potassium can be supplied using supplements or potassium chloride (salt substitute). Discuss this with your veterinarian before beginning potassium supplementation.
Magnesium may also be decreased in pets with heart failure, once again due to reduced food intake and use of diuretics. Magnesium depletion is difficult to prove based on blood levels as, similar to potassium, blood levels do not coincide with cellular levels. Magnesium supplementation under veterinary supervision may be warranted.
Supplementation with Coenzyme Q10, taurine, and carnitine may be helpful in pets with heart disease and heart failure. Taurine deficiency can cause dilated cardiomyopathy in cats. This disease is quite rare today as pet food manufacturers have increased the levels of taurine in commercial pet foods. Cats are true carnivores. Unlike dogs, they cannot make enough taurine to meet their daily needs and must receive taurine from their diets. Homemade diets for cats containing animal proteins such as meat or fish contain adequate taurine levels. However, processing results in loss of taurine if the meat juices are removed. Pouring the juices over the diet, or feeding raw meats if the owner is comfortable with this—see the discussion in Part Three, on feeding raw diets—can replace this taurine. Eggs and cottage cheese contain little or no taurine and must be supplemented with taurine. Vegetarian diets (including tofu-based diets) do not supply taurine as plants do not make taurine; these diets must also be supplemented with taurine to meet the cat’s needs.
Diets for dogs with heart disease are usually lower in sodium and higher in potassium.
Extra fat can be added to maintain weight if weight loss due to heart failure occurs. The basic dog diet can be used, but do not add extra salt. In the place of eggs, ¾ pound lean ground beef or chicken or other meat can be used. Canola oil is added as per the basic diet.
The diet provides approximately 900 kcal with 45 grams of protein and 37 grams of fat.
Fresh, raw or slightly steamed vegetables (carrots, broccoli, etc.) can be used as a top dressing for the diet for extra nutrition and variety (approximately ½-1 cup per recipe.)
Most vegetables provide approximately 25 kcal per ½ cup.
Five bonemeal tablets (10 grain or equivalent) or 1-1 ¼ teaspoon of bonemeal powder to supply calcium and phosphorus with a multi-vitamin mineral supplement using the label instructions is added. Alternatively, a natural product from Standard Process (Calcifood Wafers or Calcium Lactate) can be used (use 1 Calcifood Wafer or 2 Calcium Lactate tablets for each 2 bonemeal tablets.)
When possible, natural vitamins made from raw whole foods, rather than synthetic vitamins (although both can be used in combination) are preferred, as the natural vitamins also supply plant phytochemicals, enzymes, and other nutrients not found in chemically-synthesized vitamins. Catalyn from Standard Process can be used as the natural vitamin in this recipe, at a dose of 1 Catalyn per 25 pounds; Canine Plus (VetriScience) could also be used following label dosages.
The nutrient composition of the diet will vary depending upon which ingredients are used. In general, the above recipe supplies the daily nutritional and calorie needs for a 30 pound dog. The actual amount to feed will vary based upon the pet’s weight (feed less if weight gain, more if weight loss.)
Added supplements which can be beneficial include omega-3 fatty acids, plant enzymes, and a super green food or health blend formula The health blend formula may contain excess sodium that could be harmful (check with the manufacturer.)
Diets for cats with heart disease are usually lower in sodium and higher in potassium.
Extra fat can be added to maintain weight if weight loss due to heart disease occurs. The basic cat diet can be used, but do not add extra salt. Low sodium tuna or salmon (5-6 ounces) could be substituted for the meat for variation. Brown or white rice (½ cup) can be added if desired.
Taurine (100-500 mg) should also be added.
The diet provides approximately 550 kcal with 55 grams of protein and 30 grams of fat.
Fresh, raw or slightly steamed vegetables (carrots, broccoli, etc.) can be used as a top dressing for the diet for extra nutrition and variety (approximately ½-1 cup per recipe), but most cats do not like eating vegetables.
Two bonemeal tablets (10 grain or equivalent) or ¼ - ½ teaspoon of bonemeal powder to supply calcium and phosphorus with a multi-vitamin mineral supplement using the label instructions is added. Alternatively, a natural product from Standard Process (Calcifood Wafers or Calcium Lactate) can be used (use 1 Calcifood Wafer or 2 Calcium Lactate tablets for each 2 bonemeal tablets.)
When possible, natural vitamins made from raw whole foods, rather than synthetic vitamins (although both can be used in combination) are preferred, as the natural vitamins also supply plant phytochemicals, enzymes, and other nutrients not found in chemically- synthesized vitamins. Catalyn from Standard Process can be used as the natural vitamin in this recipe, at a dose of 1 Catalyn per 10 pounds; NuCat (VetriScience) could also be used following label dosages.
The nutrient composition of the diet will vary depending upon which ingredients are used. In general, the above recipe supplies the daily nutritional and calorie needs for a 10-11 pound cat. The actual amount to feed will vary based upon the pet’s weight (feed less if weight gain, more if weight loss.)
Added supplements which can be beneficial include omega-3 fatty acids, plant enzymes, and a super green food or health blend formula The health blend formula may contain excess sodium that could be harmful (check with the manufacturer.)
Hawthorn is a well-known heart and vascular tonic, often being prescribed for pets with early congestive heart failure. It may be a possible alternative to digitalis. Hawthorn also possesses antioxidant properties. Although not as potent as foxglove, hawthorn is much safer. The active ingredients in foxglove are the drugs digoxin and digitoxin. However, hawthorn does not appear to have any single active ingredient, although the flavonoids and proanthocyanidins have been suggested as the active components. This has prevented it from being turned into a drug.
Like foxglove and the drugs made from it, hawthorn appears to improve the heart’s pumping ability. But it offers one very important advantage. Digitalis and some other medications that increase the power of the heart also make it more irritable and liable to dangerous irregularities of rhythm. In contrast, hawthorn has the unique property of both strengthening the heart and stabilizing it against arrhythmias by lengthening what is called the refractory period, the short period following a heartbeat during which the heart cannot beat again. Many irregularities of heart rhythm begin with an early beat. Digitalis shortens the refractory period, making such a premature beat more likely, while hawthorn protects against such potentially dangerous breaks in the heart’s even rhythm. Also, with digitalis, the difference between the proper dosage and the toxic dosage is very small. Hawthorn has an enormous range of safe dosing.
In people, several double-blind studies strongly suggest that hawthorn is an effective treatment for congestive heart failure. Comparative studies suggest that hawthorn is about as effective as a low dose of the conventional drug captopril (a relative of enalapril, used in pets with heart failure), although whether it produces the same long-term benefits as captopril is unknown.
Due to the flavonoid content, hawthorn is often recommended for pets with heart disease, heartworm disease, and kidney disease. The flavonoids appear to decrease “leakiness” of the capillaries, improve cardiac blood flow by dilating coronary arteries, and improve the contractility of the heart. Hawthorn may also be useful in controlling mild heart arrhythmias. It may act by inhibiting the enzyme phosphodiesterase or as an ACE inhibitor, making it a possible substitute for drugs such as enalapril (Enacard). Doctors may prescribe hawthorn for pets undergoing chemotherapy, especially when the drug chosen for chemotherapy may produce cardiac side effects.
In people, the standard dosage of hawthorn is 100 to 300 mg 3 times daily of an extract standardized to contain about 2 to 3% flavonoids or 18 to 20% procyanidins. Full effects appear to take several weeks or months to develop.
In pets, a recommended dosage of 100 mg/25 to 50 pounds of body weight twice daily has been used with positive results.
Hawthorn is safe to feed to animals; older animals that may be prone to heart or kidney disease can be given hawthorn on a daily basis. Caution is warranted in pets with low blood pressure and hypertrophic cardiomyopathy. In people, side effects are rare, mostly consisting of mild stomach upset and occasional allergic reactions (skin rash).
Safety in young children, pregnant or nursing women, or those with severe liver, heart or kidney disease has not been established. Similar concerns in pets are probably warranted.
Coenzyme Q10 (ubiquinone) is a powerful fat-soluble antioxidant that is found in every cell in the body. It plays a fundamental role in the mitochondria, the parts of the cell that produce energy from food. Coenzyme Q10 appears to control the flow of oxygen within the cells as well as functioning as an antioxidant to reduce damage to cells by harmful free radicals. Every cell in the body needs CoQ10, but there is no U.S. Recommended Dietary Allowance since the body can manufacture CoQ10 from scratch.
Because CoQ10 is found in all animal and plant cells, we obtain small amounts of this nutrient from our diet. However, it would be hard to get a therapeutic dosage from food.
CoQ10 appears to assist the heart muscle during times of stress, perhaps by helping it use energy more efficiently. While CoQ10’s best-established use is for congestive heart failure, ongoing research suggests that it may also be useful for other types of heart problems and for a wide variety of additional illnesses. Preliminary research has shown reduced levels of CoQ10 in the hearts of people and pets with heart disease.
In people, the typical recommended dosage of CoQ10 is 30 to 300 mg daily, often divided into 2 or 3 doses. CoQ10 is fat-soluble and is better absorbed when taken in an oil-based soft gel form rather than in a dry form such as tablets and capsules. In pets, the typical dosage is 30 mg every 24 to 48 hours, although your veterinarian may alter this dosage depending upon your pets size and individual needs. (Some doctors feel that increasing the dosage is necessary for larger pets; for example, 80 mg every 24 to 48 hours might be recommended for a 100-pound dog.)
In people, the best-documented use of CoQ10 is for treating congestive heart failure and when taken along with conventional medications, not instead of them. People with congestive heart failure have significantly lower levels of CoQ10 in their heart muscle cells than healthy people. While this does not prove that CoQ10 supplements will help people with heart failure, it has prompted researchers to try using CoQ10 as a treatment for heart failure. In people, at least nine double-blind studies have found that CoQ10 supplements can markedly improve symptoms and objective measurements of heart function when they are taken along with conventional medication.
Weaker evidence suggests that it may be useful for cardiomyopathy (several small studies suggest that CoQ10 supplements are helpful for some forms of cardiomyopathy) and other forms of heart disease. It has also been suggested as a treatment for high blood pressure (although the scientific evidence for this use is weak) and to prevent heart damage caused by certain types of cancer chemotherapy (such as adriamycin). Since CoQ10 might conceivably interfere with the action of other chemotherapy drugs due to its antioxidant activity (although there is no good evidence that it does so), check with your veterinarian before using CoQ10 if your pet has cancer that requires chemotherapy.
CoQ10 may also help periodontal (gum) disease (by reducing the size and improving the health of periodontal pockets, as well as decreasing inflammation, redness, bleeding, and pain) and diabetes in people and pets. Since most pets with heart disease also have periodontal disease, an extra benefit might be achieved in pets with heart disease taking CoQ10.
In experiments in dogs, Coenzyme Q10 was found to exert a protective effect against oxidative injury to the heart. Stabilization of body weight, improved clinical status, and a slowing of the progression of signs has been seen in dogs with heart disease treated with Coenzyme Q10.
CoQ10 appears to be extremely safe. No significant side effects have been found; however, pets with severe heart disease should not take CoQ10 (or any other supplement) except under a veterinarian’s supervision.
The maximum safe dosages of CoQ10 for young children, pregnant or nursing women, or those with severe liver or kidney disease have not been determined; the same is true for pets of similar circumstances.
Treatments for pets with cancer include omega-3 fatty acids, antioxidants, glandulars, DMG, and the herbs bugleweed, burdock, coptis, dandelion leaves, devil’s claw (possible anti-arrhythmic), garlic, ginger, Ginkgo biloba, goldenseal, gotu kola, Oregon grape, red clover, and maitake mushrooms.
These can be used in conjunction with conventional therapies as they are unlikely to be effective by themselves in most patients with severe heart disease. The natural treatments are widely used with variable success but have not all been thoroughly investigated and proven at this time.
As with any condition, the most healthful natural diet will improve the pet’s overall health.
Conventional therapy for heart disease includes medications such as diuretics and various cardiac drugs (digitalis, calcium-channel blockers, ACE inhibitors).
The most commonly used and safest diuretic is furosemide (Lasix). This loop diuretic is structurally related to the sulfonamide antibiotics. Furosemide works to increase excretion of fluid and electrolytes from the body. The medication should be decreased in pets with kidney failure and should be used with caution where there are preexisting electrolyte imbalances, diabetes mellitus, and liver disease. Pets should be monitored for electrolyte imbalances, especially potassium deficiency. The risk of side effects (including kidney failure) increases when furosemide is used concurrently with other medications, including aminoglycoside antibiotics, enalapril, NSAIDs, and corticosteroids. Furosemide may alter insulin requirements in diabetic pets, and the effects of theophylline may increase in pets taking furosemide.
Calcium-channel blockers commonly used include diltiazem or verapamil. By blocking the calcium channels in the cells of heart muscles and the smooth muscles of blood vessels, these medications dilate arteries and slow heart rate. Overdosage may cause excessive slowing of the heart, low blood pressure, and heart failure.
Digitalis is a synthetic medication that is a purified form of the active ingredient in the purple foxglove plant. Digoxin and digitoxin are the two most commonly prescribed digitalis medications. These drugs work to slow heart rate and strengthen the contractile force of the heart. Side effects include various heart arrhythmias, vomiting, diarrhea, and lack of appetite. These medications have a narrow therapeutic index, which means there is a very small difference between the effective dose and the toxic dose.
A newer class of medications commonly used in the treatment of various cardiac disorders in dogs and cats are angiotensin-converting enzyme inhibitors (ACE inhibitors). Enalapril is the most commonly prescribed ACE inhibitor (captopril is another popular ACE inhibitor). Enalapril, after biochemical conversion in the liver to the more active form, enalaprilat, prevents the formation of angiotensin II by inhibiting the angiotensin-converting enzyme. Side effects include loss of appetite, vomiting, and diarrhea. Low blood pressure and kidney failure can occur when ACE inhibitors are combined with diuretics, including furosemide. NSAIDs may reduce the effectiveness of ACE inhibitors, especially when the ACE inhibitors are used to control high blood pressure.