A diagnosis of CHF in a dog requires commitment to a daily medication regimen and changes to the patient’s diet, which can be difficult to adjust to. The author, seen here with her dog, experienced first-hand some of the challenges pet owners face when CHF is diagnosed. Photo courtesy Sarah M. Cavanaugh Soon after the diagnosis of congestive heart failure (CHF) comes a discussion with the patient’s family of treatment, which, in most cases, includes a relatively long list of oral medications. CHF therapy is typically lifelong, and most of the essential drugs to treat it need to be administered twice daily and more frequently in some cases. When my own dog developed CHF secondary to degenerative mitral valve disease (i.e. Stage C), I thought my training and experience as a veterinary cardiologist had me well prepared for the daily medication regimen; however, some days were truly a struggle. The thought of also having to alter my dog’s diet during this tough time seemed unrealistic initially. At this stage… Fortunately, the American College of Veterinary Internal Medicine (ACVIM) consensus guidelines for the diagnosis and treatment of degenerative (myxomatous) mitral valve disease provide succinct dietary recommendations for dogs at each stage: A, B1, B2, C, D (See the article on the opposite page). For Stage A and Stage B1 dogs, no dietary intervention is recommended. For Stage B2 dogs, the following dietary interventions are recommended: 1) Mild sodium restriction: - Generally, this means staying in the range of approximately 80 to 99 mg of sodium per 100 kcal (including treats/snacks). - It is important not to over-restrict dietary sodium at this stage in order to avoid excessive activation of the renin angiotensin aldosterone system (RAAS). In addition, some commercial diets with very low sodium content may be less palatable, which can result in reduced intake and weight loss. 2) Provision of a highly palatable diet with adequate protein and calories for maintaining optimal body condition: - Age and activity level of Stage B dogs are diverse, and these factors should be taken into account when calculating a patient’s maintenance energy requirement (MER). Readers are referred to veterinary nutrition resources for a more detailed discussion of MER calculation. - Clinicians should be aware that some sodium-restricted diets are also protein-restricted. These diets should be avoided due to the deleterious effects of protein restriction on muscle condition. For Stage C dogs, the following dietary interventions are recommended: 1) Moderate sodium restriction: - A target range of approximately 50 to 79 mg of sodium per 100 kcal (including treats/snacks) is appropriate in most patients at this stage. 2) Maintain adequate caloric intake and ensure adequate protein intake: - Maintenance of caloric intake in Stage C dogs should be approximately 60 kcal per kg of body weight per day. Keep in mind activity level and comorbidities affect MER; therefore, 60 kcal/kg may not be appropriate for all Stage C dogs. - Daily protein intake should be a minimum of 5 gm per 100 kcal. I typically aim for a range of 6 to 10 gm per 100 kcal in Stage C patients. Critical point: Low-protein diets (such as those prescribed for patients with chronic kidney disease [CKD]) should be avoided in patients with advanced heart disease unless severe concurrent renal failure is present. Further, the prerenal azotemia that develops in some dogs with CHF is not an indication to prescribe a low-protein diet. Cardiac cachexia (loss of muscle due to heart failure) is associated with shortened survival time in dogs, and protein restriction is likely to exacerbate this disorder. Cardiac cachexia also negatively impacts appetite and mobility in CHF patients. 3) Consider supplementing with omega-3 fatty acids (eicosapentaenoic acid [EPA] and docosahexaenoic acids [DHA]), especially in dogs with decreased appetite, muscle loss, or arrhythmia: - Target dose: 40 mg/kg of EPA and 25 mg/kg of DHA. Fish oil is an effective source of omega-3 fatty acids for dogs, and fish oil supplements are available over the counter. Cod liver oil should be avoided due to the high vitamin A and vitamin D content. Plant-based sources of omega-3 fatty acids for dogs require more research. Some commercially prepared dog foods contain EPA and DHA. Therefore, clinicians should take care to ensure a patient’s total daily intake of EPA and DHA does not exceed the doses mentioned here. - The benefit of omega-3 fatty acid supplementation in dogs with CHF is two-fold. First, EPA and DHA provide calories and essential fatty acids. Second, EPA and DHA reduce the production of inflammatory cytokines (e.g. IL-1, TNF-a) and reactive oxygen species. In CHF, inflammatory cytokines inhibit appetite, increase energy metabolism, and accelerate breakdown of muscle protein. In addition, EPA and DHA have an anti-arrhythmic effect in some dogs. For Stage D dogs, all the dietary interventions described for Stage C apply. Some patients with refractory pulmonary edema may benefit from more severe sodium restriction (i.e. <50 mg per 100 kcal). Monitor for muscle loss The detrimental effects of cardiac cachexia on quality and quantity of life in dogs and cats with CHF are significant and prevention of cachexia (with the strategies mentioned earlier) is not always possible; therefore, it is important clinicians diligently monitor for muscle loss in patients with cardiac disease. The simple addition of a muscle condition score (MCS) line to the physical examination form will help ensure cachexia is recognized early in the course of CHF, which will enable prompt intervention. It is extremely helpful to introduce to clients the concepts of sodium restriction, adequate calorie and protein intake, and cardiac cachexia in the pre-CHF stage (i.e. when the dog is in Stage B). This helps prepare clients mentally for lifestyle changes if/when their dog progresses to Stage C. Having the nutrition discussion early also helps reduce the amount of information presented to clients at the emotionally challenging (and sometimes overwhelming) time of CHF diagnosis. A REVIEW OF ACVIM’S CLASSIFICATION SYSTEM FOR MYXOMATOUS MITRAL VALVE DISEASE IN DOGS Stage A refers to dogs at high risk for developing heart disease, but that currently have no identifiable structural disorder of the heart (i.e. their echocardiogram is normal). Stage B1 refers to asymptomatic dogs with structural disease (e.g. mitral regurgitation, thickened leaflets) and either no chamber enlargement or mild chamber enlargement (i.e. enlargement not severe enough to meet clinical trial criteria that have been used to determine whether initiating specific drug therapy is warranted). Stage B2 refers to asymptomatic dogs that have more advanced mitral valve regurgitation that is hemodynamically severe and long-standing enough to have caused moderate or severe left atrial and ventricular enlargement (i.e. enlargement severe enough to meet clinical trial criteria used to identify dogs that clearly should benefit from initiating pharmacologic treatment to delay the onset of heart failure). Stage C denotes dogs with either current or past clinical signs of heart failure caused by myxomatous mitral valve disease. Stage D refers to dogs with end-stage myxomatous mitral valve disease in which clinical signs of heart failure are refractory to standard treatment. HELPFUL RESOURCES Pet food calculator: bit.ly/35VFPe0 Reduced sodium dog foods: bit.ly/2zzWFmB Homemade diets, recipe formulation by veterinary nutritionists: bit.ly/2Lm7Baf and bit.ly/2YYalCE Muscle condition score charts: bit.ly/2ztp26e and bit.ly/2Z8Vcif Sarah M. Cavanaugh, DVM, MS, DACVIM (cardiology), is assistant professor of small animal medicine at Ross University School of Veterinary Medicine. Dr. Cavanaugh received her bachelor of science from the University of Florida and earned her DVM from Ross University. After graduation, she completed an internship in small animal medicine and surgery at the Animal Medical Center in New York City before completing a residency in cardiology and master of science at Colorado State University. In 2010, Cavanaugh became a diplomate of the American College of Veterinary Internal Medicine Specialty (ACVIM) of cardiology. She has practiced small animal cardiology in Denver, Colo., and Fort Myers, Fla., and joined the faculty at RUSVM in 2017. Cavanaugh can be contacted via email at scavanaugh@rossvet.edu.kn. References Keene BW, Atkins CE, Bonagura JD, et al. ACVIM consensus guidelines for the diagnosis and treatment of myxomatous mitral valve disease in dogs. J Vet Intern Med. 2019;33:1127-1140. Ineson DL, Freeman LM, Rush JE. Clinical and laboratory findings and survival time associated with cardiac cachexia in dogs with congestive heart failure. J Vet Intern Med. 2019;33:1902-1908. Freeman L.M. Beneficial effects of omega-3 fatty acids in cardiovascular disease. J Small Anim Pract. 2010;51:462–470. Fascetti AJ, Delaney SJ. Applied Veterinary Clinical Nutrition. Ames, IA: Wiley-Blackwell;2012. Freeman LM, Rush JE, Kehavias JJ, et al. Nutritional alterations and the effect of fish oil supplementation in dogs with heart failure. J Vet Intern Med. 1998;12:440-448.
