Nutritional and Herbal Therapies in the Treatment of Heart Disease in Cats and Dogs
Nutritional supplements such as L-carnitine and taurine have been found to be beneficial in dogs and cats with certain cardiac diseases. However, not all animals with cardiac disease respond to nutritional supplementation, which means that further work must be done to identify causes of cardiac disease. Herbal therapies have been used in dogs and cats based on information available from their use in humans. This paper reviews the possible benefits and side effects of L-carnitine, taurine, and herbal supplements.
Introduction
The goals of any therapy, whether it is therapy with drugs, herbs, or nutritional supplements, are to help improve the animal’s quality and longevity of life, as well as to prevent cardiac disease. Most clinical trials in humans with heart disease base a treatment’s effectiveness on its ability to prolong life in the majority of people using the treatment. Prolonging life is also one of the goals of veterinary clinical trials, but, unfortunately, not many cardiac drugs have undergone multicenter clinical trials. Improving quality of life is more difficult to evaluate in animals, especially when owners are surveyed, because some owners are not objective observers. The goals of treating heart disease and heart failure include controlling the problems of congestion (i.e., backward failure) and low output (i.e., forward failure). Standard therapy is based upon using diuretics and vasodilators for congestive heart failure and then adding other medications, depending upon the underlying disease process. Controlling the congestion makes an animal feel better.
For many cardiac diseases of animals, objective and scientific information is lacking regarding treatment of the underlying cause. Many of the drugs used in small animals with heart disease were first used in humans. Currently veterinary medicine is trying to switch to evidence-based medicine through the use of controlled, prospective, randomized, double-blind studies to determine the effectiveness of cardiac drugs. In-depth discussions of heart diseases and current therapies appear in several textbooks.1,2 The purpose of this paper is to review the information available about nutritional and herbal therapies for use in animals with cardiac disease.
Causes of Heart Disease
Besides treating the symptoms of the heart disease, cardiologists attempt to determine the cause and discover ways to prevent heart disease. Unfortunately, not many causes have been identified for acquired heart diseases such as dilated cardiomyopathy (DCM), hypertrophic cardiomyopathy, or mitral valve disease from endocardiosis. Some researchers are investigating whether these acquired diseases are related to abnormal genes and which genes may be involved with congenital heart defects. If connections are made between any heart disease and certain genes, blood tests may then be developed to screen animals for these diseases.
As researchers study how the heart works in health and disease, different proteins and amino acids are found that may be deficient in certain diseases. Whether these deficiencies are the cause or the result of cardiac disease is unknown; most animals receive supplements in an attempt to reverse their underlying heart disease. In small animals, only two amino acid supplements (i.e., L-carnitine and taurine) have been studied in controlled clinical trials or through case studies.3–20
Role of L-Carnitine in Dogs
The heart is a metabolically active organ and has high energy demands. L-carnitine is essential for the production of energy from fatty acid oxidation in the mitochondria of the heart. It may also play a role in the regulation of glucose metabolism and may help move pyruvate into the citric acid cycle, which is the common pathway for oxidation of amino acids, fatty acids, and carbohydrates. L-carnitine is a cofactor for making enzymes, especially those that move fat into the mitochondria, and it may play other roles in energy production and cell metabolism.3
Most of the carnitine found in the body is in skeletal and heart muscle. Normal dogs can synthesize carnitine in the liver and, to some extent, in the kidneys. Dogs also obtain carnitine from animal protein (e.g., lamb, beef) in their diets.
Carnitine deficiency has been reported to cause DCM in humans and dogs.4–7 The exact mechanism of how dogs develop carnitine deficiency and DCM is unknown. One study showed that a family of boxers with DCM had decreased levels of myocardial carnitine, and when they were supplemented with L-carnitine, two of four dogs lived long enough to have their cardiac function improve dramatically.5 Another study showed that 13 of 18 Doberman pinschers with DCM had low myocardial carnitine levels. The Dobermans that had low carnitine levels and were supplemented with L-carnitine lived longer than those that did not have low carnitine levels.7
Another study has shown that carnitine deficiency can cause a reversible DCM in dogs with cystinuria and associated aminoaciduria. Cystinuria is associated with an increased loss of both carnitine and its precursor, methionine, in the urine. When a prescription dieta was used long-term to treat cystinuria in affected dogs of the study, DCM developed in some of the dogs. The DCM was reversible with L-carnitine supplementation.8 The prescription dieta has been reformulated to include more L-carnitine, and DCM has not occurred as frequently as before.
L-Carnitine Supplementation
The studies done with L-carnitine in dogs have shown that the plasma levels of carnitine do not reliably reflect tissue levels in the heart or muscle.3 In general, if plasma levels are low, they are probably also low in the muscles of the heart, and carnitine supplementation can be tried in that animal. If plasma levels are normal, myocardial carnitine levels may be low, normal, or elevated. Heart or skeletal muscles may be biopsied to determine whether carnitine deficiency is present in a dog with DCM. If a dog with DCM has low carnitine levels, the only way to prove that a deficiency is the cause of the disease is to supplement the dog and monitor its progress. If the DCM improves dramatically, then carnitine deficiency may be considered as the cause.
Unfortunately, no dramatic improvement has occurred in most dogs with DCM that have been supplemented with L-carnitine (since the above studies and cases have been published). Based on a family of boxers with DCM (i.e., not boxer cardiomyopathy and its accompanying arrhythmias, such as ventricular premature beats), affected boxers should receive both standard therapy (e.g., diuretics, angiotensin-converting enzyme inhibitors, digoxin, or pimobendan) and supplementation with L-carnitine.5 However, more studies of other boxers with DCM are necessary to determine whether all boxers with the disease will benefit from supplementation. Dalmatians and English bulldogs with organic aminoaciduria should be supplemented with L-carnitine. L-carnitine may also be tried in dogs with DCM that are of an atypical size (e.g., small or medium size) or breed for the disease. Ideally, all these dogs should have carnitine levels (muscle biopsies are best) measured prior to supplementation.
L-carnitine has been established as being safe in the dog, but it is expensive depending on the size of the dog. In general, any dog with low plasma carnitine levels (i.e., 12 to 38 pmol/L) should be supplemented. Recommended doses of L-carnitine are 1000 mg orally (PO) q 8 hours for dogs weighing <25 kg and 2000 mg PO q 8 hours for dogs weighing 25 to 40 kg.3 The powdered form is less expensive and should be mixed with food. The L-form of carnitine must be used, as the dog does not convert regular carnitine to the L-form, which is used by the heart and muscle.7 Most commercial diets for dogs with cardiac disease have been reformulated to include an increased amount of L-carnitine. Mighty Dog beef dinnerb and Hill’s h/d, u/d, and l/dc all contain high levels of L-carnitine. It takes 2 weeks to 4 months to see a clinical response to L-carnitine therapy.3,7
Cocker Spaniel DCM
American cocker spaniels are affected by a form of DCM, called cocker cardiomyopathy, that is similar to that of large-breed dogs.9 Only taurine levels have been found to be low in these dogs, but both L-carnitine and taurine supplemented together have helped heart function to improve.3,9 After supplementation for 3 to 6 months, affected cocker spaniels were clinically normal, and the dogs lived much longer than large-breed dogs with DCM. The diseased hearts never returned to normal on echocardiography, however, and eventually affected dogs went back into heart failure.9
Role of Taurine in Cats
Taurine (2-aminoethanesulfonic acid) is another amino acid found in high concentrations in the heart, as well as in the retina, central nervous system, skeletal muscle, white blood cells, and platelets. An active transport mechanism moves taurine from the extracellular fluid into the cells of these tissues so that the levels tend to remain high. The exact mechanism of action of taurine is unknown, but taurine is necessary for normal retinal function and myocardial function.10–15
Certain animal tissues contain a high level of taurine, but it is absent in most plants. Dogs can synthesize taurine from the dietary amino acids, methionine and cysteine. Dogs use taurine plus other amino acids to conjugate bile acids and to detoxify xenobiotics via conjugation in bile. Cats have a limited ability to produce taurine. Cats also use only taurine to conjugate bile acids, so their supply is constantly being depleted.3,11 Cats must have taurine supplied by their diets. Truly carnivorous cats, such as feral cats, usually consume enough taurine from meat sources. Cat foods or diets based on plant material instead of animal protein are deficient in taurine. Certain diets, such as raw rabbit diets, are also low in taurine, and the processing of some diets affects the availability of the taurine and may lower the amount of taurine available from the diet.3–6 Inadequate amounts of taurine may be taken in by a dog or cat eating a commercial pet food diet.
In 1987, a study of cats with DCM showed that many were deficient in taurine, and when the taurine was supplemented, the DCM was reversible.11 It was concluded that this form of DCM was a secondary nutritional disease and not a primary cardiac disorder. Since this study was published, taurine levels have been increased in commercial cat foods, and now nutritional DCM is uncommon in cats. However, many factors can affect an individual cat’s requirements for taurine, and occasionally the cat’s requirement for taurine is not met by commercial diets. Factors such as genetic diseases, infiltrative or inflammatory bowel disease, other systemic diseases, and stress influence a cat’s ability to absorb taurine from the food and influence the cat’s requirements for taurine.3
Taurine Supplementation
To prove that a cat with DCM has taurine-deficient DCM, blood and plasma taurine levels must be measured. Normal plasma taurine is >60 nmol/mL, with taurine deficiency defined as levels <30 nmol/mL. Normal whole blood levels are >200 nmol/mL, and levels <100 nmol/mL are deficient.3 If a cat has central retinal degeneration along with DCM, then a higher probability of taurine deficiency exists. It is unusual, however, for central retinal degeneration and DCM to both be present in a cat with taurine deficiency. Taurine supplementation can be started in cats even before the results of taurine assays are received, and then a decision as to whether to continue the taurine can be made depending upon the results.
Because DCM has a very poor prognosis in cats, all cats diagnosed with DCM by echocardiography should be treated with taurine (250 mg PO q 12 hours) along with other appropriate medications (e.g., enalapril, lasix, spironolactone, and possibly digoxin) to see if they have a clinical response. It takes a minimum of 2 weeks to see a clinical response to taurine. If cats do respond, their heart function (on echocardiography) improves in 3 to 6 months and eventually returns to normal. Once cardiac function is normal, heart medications may be discontinued. If the supplemental taurine is discontinued, blood levels should be followed to make sure that the cat does not become taurine deficient again (i.e., ensure the cat is taking in an adequate amount of taurine from the diet).3
Role of Taurine in Dogs
Because dogs readily make taurine from free sulfur amino acids, only lose a small amount in their bile acids, and can maintain normal blood levels of taurine despite their diets, they do not tend to develop taurine-deficient DCM. However, a study of beagles fed a high-fat, low-protein diet showed they had decreased plasma and blood levels of taurine and had decreased myocardial function (albeit not DCM).16 A study of nine male Dalmatians with DCM showed that eight were on low-protein diets and six had low blood taurine levels.17 One of these dogs improved with a change in diet.17 In another study, 13 of 15 dogs with cysteine and urate urolithiasis had low plasma taurine levels, and four of these dogs had DCM. Myocardial function of these four dogs improved with L-carnitine and taurine supplementation.8
In a recent article, 12 dogs of various breeds with DCM that were on diets having main ingredients of lamb and/or rice had low plasma and blood taurine levels. These dogs received taurine supplementation plus standard treatments for their DCM, and for the dogs that lived >3 months, heart size and contractility improved. Dogs that survived for >1 year had their cardiac medications discontinued and were only left on taurine supplementation. The median survival time for these 12 dogs was markedly greater (i.e., 456 days) than that for dogs with primary DCM (i.e., 27 to 65 days). This study concluded that the DCM in these dogs was a secondary nutritional DCM that occurred when taurine precursors were limited in the diets.18
A group of five related golden retrievers with DCM were found to have decreased plasma taurine levels.19 All of the dogs’ echocardiographic findings improved within 3 to 6 months of starting taurine supplementation, and four were eventually weaned off all cardiac medications. These findings provided further evidence of a secondary nutritional DCM in dogs.19 In a study of 19 Newfoundland dogs that were interrelated by environment, diet, or breeding to a Newfoundland with DCM and low taurine levels, 12 were found to have low plasma (<40 nmol/mL) and blood taurine levels.20 None of the Newfoundlands had clinical (n=12) or echocardiographic (n=6) evidence of DCM.20
All of the above reports suggest there are many possible causes of taurine-deficient DCM in dogs. One potential cause is insufficient synthesis of taurine from a lack of amino acid precursors in the diet or from the animal’s inability to synthesize taurine. Other causes may include impaired absorption, increased metabolic need, altered taurine-conjugated bile acid circulation, and increased urinary excretion of taurine or its precursors.3
Taurine Supplementation
To document taurine deficiency as the cause of DCM in dogs, both blood and plasma taurine levels should be tested. Documented improvement of cardiac function following taurine supplementation confirms the diagnosis. It has been suggested that all dogs with DCM receive taurine supplementation, as it is inexpensive and easy, until the results of blood and plasma assays are received. If these levels are normal, the taurine can be discontinued.18 Any dog with DCM that has low plasma taurine (i.e., <40 nmol/mL) and low blood taurine (i.e., <150 nmol/mL) should receive taurine supplementation [Table 1]. Supplements that are labeled as USP certified have been checked to ensure they contain the amount of supplement listed on the label.
More scientific studies are needed to further define the role of taurine and carnitine in normal and diseased hearts. Prospective, randomized, double-blind studies in different breeds of dogs and cats are also needed to evaluate the effectiveness of taurine and carnitine in diseased hearts.
Role of Herbal Therapies
Natural medicines have been used for years in people, but the benefits and side effects of these therapies for animals are not well understood. Only a few studies have been performed to evaluate herbs in animals, and the number of study subjects has usually been small, so results have been of limited value. The use of most herbs is based on extrapolation of the benefits found in humans and on personal observations.
Common sense must be used when prescribing different therapies for any disease. The veterinarian must avoid giving combinations of medications and herbs that have pharmacological interactions or have the same effect. Also, interactions between herbs and drugs may decrease the beneficial effects or increase the toxicity of one or both agents.21 Unfortunately, the active agents and potential drug interactions are unknown for many herbal and nutraceutical remedies. When using supplemental therapies such as herbs, strict attention must be given to the standards of Chinese and Western herbal medicine. In order to use herbs effectively, veterinarians must research the herb in depth and educate themselves to a level comparable to any other therapy they might choose for an animal. It would also be wise to consult with a veterinarian who is certified as a veterinary herbalist before any herbal remedies are considered for animals with heart disease.
As use of the Internet becomes widespread, owners research their animals’ diseases and discover many testimonials about drugs and herbs. Herbal medicines can have significant effects on the cardiovascular system, and many herbal preparations have additive effects or toxic interactions with other herbs or medicines.22 The following discussion summarizes the herbs most commonly used for heart disease, both from Eastern and Western herbalism, including their potential benefits, side effects, and drug interactions. The actions of herbs on other medical problems are not discussed. An overview of the use of herbal medicines in small animals has been written by Remillard and Wynn, and a more in-depth discussion can be found in the book by Wynn and Marsend.23,24 Detailed discussions regarding the mechanism of action, safety and toxicity, quality, and efficacy of herbs in humans are provided by Huang and Blumenthal, et al.25,26 Table 2 lists the herbs that may benefit dogs and cats with cardiac disease. The possible benefits, side effects, and known drug interactions of these herbs are also listed. Notations are provided as to whether or not the herb has been tried in animals or only in humans.
Specific Herbal Remedies
Artichoke (Cynara scolymus) is a vegetable found in the northern United States and Europe. Its flower heads, leaves, and roots are used for medicinal purposes. The active substances found in artichokes are cynarin, sesquiterpene lactones, flavonoids scolymoside, inulin, cynaropictin, and taraxasterol.27 Cynarin has been shown to lower cholesterol and triglyceride levels in humans. It has some diuretic action in people, but it is only used for kidney problems and proteinuria. It has not been used to treat congestive heart failure. Cynarin has no known toxicity in humans, and its actions are enhanced by turmeric, milk thistle, and licorice root.27 This herb has not been used in animals and appears to be of limited value in animals.
Astragalus (Astragalus membranaceus) is also called milk vetch, locoweed, yellow vetch, poison vetch, and huang ch’i. The active substances found in its roots are isoflavone, triterpenoid saponins (including astragalosides I to VIII), astramembrannins, soya-sapogenols, polysaccharides, choline, betaine, and kumatakenin.27 This herb is used in humans to treat peripheral vascular disease and ischemia and to restore peripheral circulation. It may reduce hypertension. It has no known toxicity in people but has not been studied in dogs or cats.27 Potential uses in animals include the treatment of hypertension.
Barberry’s (Berberis vulgaris) active ingredient is berberine, which acts like a class III antiarrhythmic (i.e., same class as sotalol and amiodarone).24 It may slow a rapid heart rate. Antiarrhythmic drugs in the same class should never be used together, as their therapeutic and adverse effects may be increased (e.g., marked bradycardia, heart block, and enhancement of arrhythmias). Barberry has no known toxicities or interactions. It has been used in animals and may be investigated further for controlling both supraventricular and ventricular arrhythmias.24
Bilberry (Vaccinium myrtillus) is also called huckleberry and whortleberry. The fresh fruit contains the active ingredients of anthocyanosides and flavonoids.27 This herb helps to maintain the integrity of capillaries and is a potent antioxidant in humans. It is used primarily for circulatory disorders of both the arteries and veins.27 It also decreases platelet adherence to endothelial surfaces, thereby preventing some clots from forming. It has no known toxicities.27 Bilberry has not been studied in animals yet, but it may be investigated as a possible anticoagulant.
The active substances in butcher’s broom (Ruscus aculeatus) are found in the rhizome and are saponin glycosides, which are used in people for venous circulatory problems.27 Butcher’s broom causes constriction of the veins, is an antiinflammatory agent, and decreases the fragility and permeability of capillaries. Its side effects in humans include an occasional allergy-induced nausea or gastritis. Its activities are enhanced by bilberry, Centella, ginkgo biloba, ginger root, and horse chestnut.27 Butcher’s broom has not yet been studied in animals and appears to be of limited benefit in animals.
Cayenne (Capsicum nanum) initially causes peripheral vasoconstriction and then dilatation in anesthetized dogs when it is given intravenously (IV).28 It decreases cardiac afterload in dogs by cholinergic mechanisms. Cayenne also strengthens the pulse of hypothermic, weak patients and slows the heart rate of other animals (described as those that are hot in the upper body and cold in the lower body).24 It has been used in animals, but its effects when given orally must be investigated further to determine whether it is a good arteriolar dilator in dogs.24 Cayenne has been used to deter dogs from coprophagy, but dogs resist ingesting it in high doses unless it is placed in a capsule to disguise the flavor.
Clerodendron trichotomum has been given IV and has decreased blood pressure in hypertensive rats.29 It has also increased renal blood flow in anesthetized dogs, so it may be a vasodilator. Clerodendron trichotomum has not been investigated as an oral product; therefore, its general effects are unknown.24
Coleus (Coleus forskalii) contains an extract called forskolin that increases cardiac contractility and also causes peripheral vasodilatation, thereby decreasing both preload and afterload.30 The mechanism of action of coleus may be the activation of adenylate cyclase.30 Coleus has no known toxicities and may be beneficial in animals with DCM or other cardiac diseases with decreased contractility.24
The active ingredient of coptis (Coptis chinensis) is berberine, which decreases heart rate and acts like a class III antiarrhythmic drug.24 It should not be used with other class III drugs (e.g., sotalol and amiodarone), as it may result in profound bradycardia, heart block, or may enhance arrhythmias. Coptis has no known toxicities and has been used in animals. It may be investigated further for control of supraventricular and ventricular tachycardias.24
Dandelion (Taraxacum officinalis) has been used as a potassium-sparing diuretic, but it has had disappointing results when used for ascites secondary to liver disease.24 Spironolactone is a similar potassium-sparing diuretic that has been used for many years. Spironolactone is a weak diuretic and is always used in combination with furosemide or a thiazide drug for congestive heart failure. Because dandelion is also a weak diuretic, it probably should be used in combination with other diuretics to clear cardiac-induced congestion. Dandelion has no known side effects or toxicities and has been used in animals.24
Dong quai or Chinese angelica (Angelica sinensis) contains the active substances of ligustilide, butyl phthalide, butylenes phthalide, ferulic acid, and polysaccharides in its dried root.27 It is used to promote peripheral blood flow. Side effects are rare but include diarrhea. Dong quai is contraindicated in people with hemorrhagic diseases, early pregnancy, and severe influenza. Its activities are enhanced by licorice root, black cohosh, red raspberry, peony, Rehmannia, ginger root, and wild yam. It has not been used in animals and may have only limited value in animals.27
Ephedra is also known as ma huang, Chinese ephedra, Mormon tea, and Shaw tea (Ephedra [E.] sinica, E. gerardiana, E. equisetina, E. dystachia). It contains ephedrine, pseudoephedrine, norephedrine, methylephedrine, tannins, saponin, flavone, catechins, and terpenolin in its stems and leaves.27 Ephedrine and pseudoephedrine alter blood pressure and reduce heart rate while relaxing smooth muscle. The whole plant is often used in people so that the side effects of the ephedrine (i.e., elevated blood pressure) are counteracted. It is contraindicated in people with hypertension, as well as in people taking other central nervous system stimulants or heart medications such as digitalis or beta blockers.27 The latter combinations may cause marked bradycardia or heart block. Single large doses of this herb can also cause arrhythmias (e.g., ventricular or supraventricular premature beats) in people.27 Clinical signs may occur with high levels of ephedrine from its stimulation of the sympathetic nervous system and may include hypertension, restlessness, hyperexcitability, and tachycardia in animals.31 A review of 47 dogs that ingested an herbal supplement containing guarana and ma huang showed that 17% of the dogs died or were euthanized. The other dogs developed vomiting, tachycardia, and hyperthermia that resolved with symptomatic therapy. Based on this documented toxicity, the herb should not be used in dogs and cats.32
Evodia (Evodia rutaecarpa) or wu zhu yu is used in combination with other herbs to achieve maximum benefits. Its extracts have a negative chronotropic effect (i.e., slow the heart rate), cause vasodilatation, and increase contractility (i.e., positive inotrope). Evodia should not be used with other vasodilators, because hypotension can result. In cats, Evodia has not been shown to affect the cardiovascular system, but it has improved cerebral blood flow.24
Foxglove (Digitalis purpurea) is the source of digoxin. Both digoxin and foxglove have very low therapeutic indices. Toxicity can occur with mildly elevated doses. Signs of toxicity include vomiting, diarrhea, anorexia, arrhythmias, and death.1,2,24 These two products should never be used together. Because variability exists between over-the-counter products and between batches of foxglove, it is better to use a pharmaceutical grade of digoxin in animals than to use an herbal remedy.24
Garlic (Allium sativum) contains the active ingredients alliin, alliinase, allicin, and vitamins A, B, and C.27 Garlic cloves are used primarily in humans to decrease blood cholesterol. Garlic decreases diastolic blood pressure, heart rate, and platelet aggregation, and prolongs blood clotting in dogs.24 One study of garlic in anesthetized dogs found that it suppressed both ventricular premature beats and ventricular tachycardia in ouabain-intoxicated dogs.33 However, it may or may not suppress ventricular arrhythmias from other causes. Experimentally in the cat, allicin was found to be a vasodilator of the pulmonary and systemic vasculature, but it was markedly less potent than sodium nitroprusside and isoproterenol, so it appears to have limited value in cats.34 Allicin can cause increased oxidative damage at high levels, and toxicity has occurred in cats given onion powder. Ingestion of high levels of allicin has also caused hemolytic anemia and intravascular hemolysis in dogs.35–37
Ginger (Zingiber officinale) contains phenyl-alkylketones (e.g., gingerols, shogaols, zingerone) and volatile oils (e.g., zingiberone, bisabolene, camphene, geraniol, linalool, borneol).27 It has been used in humans to suppress coughs (i.e., antitussive), and it is a strong antioxidant and anticoagulant. Ginger increases circulation and lowers blood cholesterol. It has no known toxicity, but it has only been studied in people.27 Ginger may have potential use as an anticoagulant in small animals.
Ginkgo biloba (Ginkgo biloba) or Maidenhair tree contains ginkgo-flavoglycosides (e.g., kaempferol, quercetin, isorhamnetin, and pronthocyanidins) and terpenes (e.g., ginkgolides, bilobalides).27 It has antioxidant and free radical properties that decrease inflammation.27 Ginkgo biloba reduces platelet adherence by inhibiting binding of platelet-activating factor to platelet membranes.38 These actions have been beneficial in people with peripheral vascular disease. Ginkgo may rarely cause gastric upsets or headaches in people and should not be used with anticoagulants or nonsteroidal antiinflammatory drugs (NSAIDs).24,27 Its actions can be enhanced by administration with bilberry, Butcher’s broom, Centella, milk thistle, vitamin B complex, magnesium, choline, and inositol.27 In people, ginkgo appears to be a cytochrome P450 inducer and enhances the metabolism of diazepam, imipramine, and omeprazole, which subsequently decreases the therapeutic blood levels of these drugs.27 In rats, ginkgo has increased the plasma levels and activity of diltiazem.38 Ginkgo biloba may have a potential use in cats with hypertrophic cardiomyopathy, particularly in preventing thrombosis.
Korean ginseng (Panax ginseng) is also known as Asian ginseng, Asiatic ginger, Chinese ginseng, Wonder-of-the-World, and ren shen.27 Its active substances are glycosides, saponins, and phytosterol, which are found in the roots.27 Korean ginseng is an antioxidant and may lower blood cholesterol in man. Its activity can be enhanced by licorice.27 Ginseng is used alone or in combination with other herbs in humans. It may inhibit platelet aggregation and may cause vaginal bleeding in women from its estrogenic effects.27 It should not be used with NSAIDs, warfarin, or heparin. Ginseng may interfere with the assay for digoxin and result in falsely elevated digoxin blood levels.38 It can increase the heart rate (i.e., positive chronotrope), prolong the time of contraction (an action similar to calcium channel blockers), and act as a vasoconstrictor in small doses and a vasodilator in large doses in dogs.39 In cats, the saponins have been found to cause moderate mental depression and altered electroencephalograms.40
Siberian ginseng (Eleutherococcus senticosus) or ciwujia, Devil’s shrub, Touch-Me-Not, or Urssurian thorny pepper bush contains glycosides (e.g., eleutherosides), resins, anthocyanin, and pectin in its rhizome and roots.27 It is used in people to help restore memory, concentration, and cognitive abilities that have been impaired by poor circulation from cardiac problems.27 It has no known side effects in people, and its actions are enhanced by ginkgo biloba. It has only been used in people and may have limited value in animals.27
Grape seed extract (Vitis vinifera) contains the active ingredient proanthocyanidin, which fights free radicals and maintains capillary integrity in humans.27 It also helps the microcirculation of the heart and brain and improves chronic arterial and venous congestion in the extremities of humans.27 Grape seed extract interferes with platelet aggregation in capillaries. It has only been used in people and may have limited value in animals.27 Grape seed extract is available as a veterinary product to be used as an antioxidant. Although it appears to be safe, it should be used cautiously in dogs because grapes, grape seeds, and raisins have caused renal toxicity in this species.41
The active ingredients in green tea extract (Camellia sinensis) are catechins, contained in the leaves.27 Green tea extract is rich in bioflavonoids and is used mainly to fight free radials that attack lipids in the brain. Higher quantities may help protect against the effects of high cholesterol, especially low-density lipoproteins in humans.27 Green tea extract lowers blood pressure in hypertensive rats by suppressing angiotensin K converting enzyme.27 It also reduces platelet aggregation as effectively as aspirin. Green tea extract has no known toxicities in people, even at high, short-term or long-term doses. Its activities are enhanced by vitamin E and C, as well as citric, malic, and tartaric acids.27 Green tea extract has only been used as an oral supplement in humans, but it may be beneficial in hypertensive animals and in cats with hypertrophic cardiomyopathy to prevent thromboembolism.27 It is added to a variety of veterinary supplements and to some commercial dog foods as an antioxidant.
Hawthorne (Crataegus oxyacantha), also called May blossom and white thorn, contains flavonoid glycosides, saponins, procyanidins, trimethylamine, and tannins in its berries.27 In humans, it dilates the peripheral and coronary blood vessels, thereby reducing hypertension, blood pressure, and angina.27 It has also been used for arrhythmias in people.27 In animals, it may increase contractility of the heart and decrease peripheral vascular resistance. Its greatest effects are seen after 6 to 8 weeks of use in animals.24 Hawthorne has no known toxicity but may potentiate the effects of digoxin.24 Its effects are enhanced by valerian root and motherwort.27 It may help cats with hypertrophic cardiomyopathy, because it increases coronary blood flow, removes free radicals, and increases cardiac contractility (which is not a problem in these cats until significant fibrosis has occurred from severe hypertrophy).24 Hawthorne may also be helpful in dogs with DCM or advanced mitral valve regurgitation.24
Lily of the valley (Convallaria majalis) contains cardiac glycosides and increases cardiac contractility.24 In high doses, it can cause death.24 It should not be used with digoxin, as it potentiates digoxin toxicity. It has not been used in animals, because the plant is very toxic, difficult to dose, and commercial preparations of digoxin are more reliable and easier to use.24
Lobelia (Lobelia inflata) is used in combination with other herbs, such as motherwort, bugleweed, passion flower, valerian, and lily of the valley to improve circulation in humans with heart failure.27 Lobelia increases the effects of the other herbs. It also reduces pulmonary edema by causing expectoration.27 Its use in animals has been limited.24
Oregon grape (Mahonia aquifolium) contains berberine, which slows the heart rate and may act like a class III antiarrhythmic.39 It may be beneficial to control supraventricular or ventricular arrhythmia, especially tachycardia. Oregon grape should not be used with other class III drugs, such as sotalol or amiodarone, as these combinations may produce profound bradycardia, heart block, or promote tachyarrhythmias.1,2
Parsley (Petroselinum crispum) is a diuretic that is commonly used for congestive heart failure in Western herbalism.24 It has also been used to treat ascites secondary to liver disease and may help relieve ascites secondary to right-sided heart failure. Long-term usage can lead to nerve damage, so the herb has limited application in the control of chronic heart disease.24 Its use in animals has been limited.24
Passion flower (Passiflora incarnate) contains glycosides, flavonoids, harmine and harmine alkaloids (e.g., passiflorine, aribine, loturine, yageine), and maltol.27 The harmine alkaloids lower blood pressure and dilate coronary arteries in humans. Passion flower has no known toxicity, and its activity is enhanced by hops, chamomile, skullcap, wood betony, valerian, L-tryptophan, and gamma-aminobutyric acid. It has not been evaluated in animals.24
Reishi mushroom extract (Ganoderma lucidum) is also called ling chi, ling chi mushroom, ling-zhi, mannentake, and Ganoderma. Its active parts are ganoderic acids (e.g., triterpenes), polysaccharides, and ergosterols.27 This mushroom lowers cholesterol, hyperlipidemia, and high blood pressure in humans. High doses of the powder may cause diarrhea, dry mouth, skin rash, or gastrointestinal upsets in man, especially early in its usage.27 It requires evaluation as an antihypertensive agent in animals.
Salvia (Salvia miltiorrhiza) is also called dan shen or tan seng. It may dilate coronary arteries, cause peripheral vasodilatation (a dose-related effect), and have anticoagulant activities.25 It is an important drug in Chinese medicine and is used for ischemic heart disease. Salvia has been used to reduce ischemic damage to the heart in rats and to induce dose-related hypotension in dogs.42,43 It may be of value in reducing hypertension in dogs and in treating cats with hypertrophic cardiomyopathy.24 The benefits in affected cats may include improved coronary artery circulation to the hypertrophied cardiac muscle, improved tissue regeneration and repair, and decreased development of thrombi by enhancing fibrinolysis.24
Scilla (Scilla maritime) is a cardiac glycoside that increases the contractility of the heart.24 It may be useful in dogs with DCM. Scilla is a very toxic herb, however, and must be used with caution. It has not been used extensively in animals, because commercially available digoxin is easier to use. Scilla should never be used with digoxin, as the two substances together cause vomiting, diarrhea, anorexia, arrhythmias, and possibly death.24
Stephania (Stephania tetrandra), also known as fang ji, is used in combination with other herbs to potentiate their effects.24 It acts as a calcium channel blocker and may slow supraventricular tachycardias.44 It may be beneficial in cats with hypertrophic cardiomyopathy.24 If the herb is labeled as mu tong, then a toxic herb may have been substituted, and that herb has caused renal failure and cancer in man. Stephania does not have many side effects in humans, but it has only been used on a limited basis in animals.24
Terminalia arjuna has been beneficial in humans to reduce cholesterol levels and treat coronary artery disease, but it has no current indications in animals.24 Uncaria (Uncaria rhynchophylla), also called gou teng, causes vasodilatation in hypertensive rats by contributing to endothelial-dependent relaxation.45 It has caused vasodilatation when given IV in anesthetized dogs, but it has not been tested as an oral product in this species.45
Additional Supplements
Table 3 lists some additional nutritional supplements that have been used in humans and animals. Most of these substances have not been thoroughly tested via double-blind, controlled studies; therefore, their benefits in animals with heart disease are as yet undetermined.
Coenzyme Q10 is an antioxidant that also catalyses adenosine triphosphate (ATP) production and supports energy metabolism.24 Its major indication is ischemic coronary artery disease in humans, and it may take months for any beneficial effects to be seen.24 Glandular or raw heart fed to animals with heart disease has had little benefit.24 Omega-3 fatty acids from marine sources may help to combat cachexia in dogs with stable chronic congestive heart failure.46 By modulating cytokines that adversely affect diseased hearts, omega-3 fatty acids may also extend the life span of cardiac patients.46 In several studies in humans, dogs, and rats, omega-3 fatty acids reduced the electrical excitability of the heart and increased the refractory period, which reduced the potential for arrhythmias and sudden death.47–49 These fatty acids also reduced calcium availability and release in the myocardium, which may have helped to prevent arrhythmias and decrease contractility.47–49
Selenium is an antioxidant mineral that helps reduce oxidative stress in the body and indirectly helps the diseased heart.24 It enhances the effects of vitamin E and is a component of glutathione peroxidase. Selenium is also involved in the production of prostanoids via arachidonic acid metabolism.24 The therapeutic window for selenium is small, and toxicity occurs with high doses. Vitamin E may be decreased in dogs with DCM and in cats with both DCM and hypertrophic cardiomyopathy.50,51 Vitamin E may counteract the rising levels of free radicals that can occur with oxidative stress. These free radicals may contribute to heart failure through mechanisms not fully understood. More work is required to investigate the use of vitamin E in the treatment of heart disease in animals.
Herbal Supplementation
As in conventional veterinary medicine where combinations of drugs are used to achieve maximum control of heart disease, herbal medicines may also be used in combinations to provide better results in the treatment of cardiac problems. Chinese and Western herbal medicines often have numerous herbal formulations to choose from for cardiac problems. Each formulation is different, and the veterinarian must be aware of which herbs are present and in what quantity. Veterinarians must also be educated as to why each herb is included in a particular formulation and what the overall effects and side effects are of that product.24 When combinations of drugs and herbs are used, the side effects of each need to be compared and considered so that adverse reactions do not occur. For example, using more than one vasodilator at a time makes hypotension much more likely. Also, combining antiarrhythmic drugs with the same properties may enhance rather than control arrhythmias. A good understanding of both drugs and herbs is necessary before they can be used safely in combination. It is advisable to consult a veterinarian certified in herbal medicine before using unknown or unfamiliar substances.
Conclusion
Carnitine and taurine are the two nutritional supplements that have been investigated more than other supplements or herbs in dogs and cats, and they have been found to be beneficial in treating certain cardiac diseases. The exact mechanism of action and benefits of these two supplements are not fully understood and require further investigation. The use of herbs in veterinary medicine is based on information regarding their actions and side effects in humans. Little information is available on their benefits or side effects in animals, so herbs must be used with care, especially in cats. Controlled, double-blind studies must be conducted using herbal remedies in animals with cardiac diseases before herbs can be routinely recommended.
Canine u/d; Hill’s Pet Nutrition, Topeka, KS 66601
Mighty Dog beef dinner; Nestle Purina PetCare Company, St. Louis, MO 63164
Hill’s Pet Nutrition, Topeka, KS 66601
