DCM can be idiopathic, genetic, and/or primary. DCM can also occur secondary to infectious disease (eg, myocarditis, parvovirus in puppies, Chagas disease), toxicity (eg, doxorubicin-induced), or nutritional causes (eg, taurine or L-carnitine deficiency, diet-associated) or can be tachycardia-induced/mediated (eg, myocardial failure due to persistent tachyarrhythmias).3,9 Inherited DCM has been reported in large- and giant-breed dogs (eg, Doberman pinschers, Great Danes, Irish wolfhounds).2,3,10
In July 2018, the US FDA released a notice regarding reports from veterinary cardiologists of suspected diet-associated DCM in dogs not typically predisposed to DCM. Since then, the FDA has released an additional update on their investigation, reporting over 300 dogs with suspected diet-associated DCM as of November 2018.11 Diets of concern include pet foods containing peas, lentils, fava beans, tapioca, barley, chickpeas, other legume seeds, and potatoes as the main ingredient and/or exotic ingredients (eg, kangaroo, duck, buffalo, bison, venison).9,11 Pet food from boutique companies (ie, small manufacturers) that contain exotic ingredients (eg, nontraditional protein sources) and/or are grain-free are also suspected to be linked to diet-associated DCM.9,12-14 See Suggested Reading for a resource providing additional information and updates on these diets and their association with DCM.12,13 It is important to note that diets that meet minimum nutrient standards and that are formulated based on Association of American Feed Control Officials recommendations do not necessarily ensure a balanced or regulated diet. There have been no documented cases of diet-associated DCM in dogs eating a commercial diet from an established major pet food company. Pet foods should ideally undergo feeding trials to verify complete and balanced nutrition.15
DCM has also reportedly been diagnosed in a few subsets of dogs, including primary DCM in predisposed breeds (unrelated to diet), diet-associated DCM in dogs with normal taurine levels, and diet-associated DCM in dogs with taurine deficiency (eg, golden retrievers).5,9,11,13 A previous study demonstrated that dogs with DCM that were fed a grain-free diet had a greater magnitude of LV dilation on echocardiography as compared with dogs with DCM that were fed a nongrain-free diet.14 The exact mechanism for the development of DCM in dogs fed these diets is not completely understood and may be multifactorial.9,11-14,16 Theorized causes under investigation include reduced bioavailability of nutrients due to interactions with other ingredients, nutrient deficiencies, and potential for cardiotoxic ingredients.9
Recommendations for treatment and additional diagnostics vary by patient but may include obtaining a detailed dietary history,9,11-13,15 evaluating whole blood and plasma taurine levels,4 providing taurine supplementation, screening for DCM via echocardiography, initiating cardiac medications as indicated,5,9,11-13 and transitioning the patient to a nonboutique, nonexotic protein, nongrain-free diet with standard ingredients and manufactured by an established company (see Take-Home Messages and Suggested Reading).9,15 Additional diagnostics (eg, ECG, 24-hour Holter monitoring, thoracic radiography, N-terminal prohormone of brain natriuretic peptide, troponin levels) may be suggested based on cardiac evaluation. The specific diet of patients with suspected diet-associated DCM should be reported to the FDA.9,11 Owners of dogs with diet-associated DCM should be questioned if other pets in the household are eating the same diet.
The subclinical occult phase of DCM can last up to 2 to 4 years, whereas median survival time in dogs with development of CHF secondary to primary DCM is reportedly 6 to 12 months.3,17,18 Follow-up echocardiography should be recommended every 3 to 6 months to monitor for improvement. Reverse remodeling may be visualized in some patients in this timeframe, whereas others may take longer (ie, 6-9 months) or show no improvement.9,11,13 For example, a study has shown golden retrievers with taurine deficiency and DCM to have slow and steady improvement over a 6- to 12-month period after diet was changed and taurine supplementation was initiated. Of the 11 dogs with CHF in this study, 9 had resolution of congestion, and 5 were tapered off diuretics completely.5