What is Dilated Cardiomyopathy?

Dilated cardiomyopathy (DCM) is a common heart disease in dogs. Cats can also develop DCM, though it is no longer very common in this species. In DCM, the heart chambers become dilated, while the walls of the heart become thin. These thinner heart walls are weak and cannot perform the heart’s normal work, including pushing blood to the rest of the body. Pets with DCM commonly develop congestive heart failure (fluid build-up in the lungs or belly) or irregular heartbeats.

There are two main categories of DCM:

1. Primary DCM: This form has a genetic cause and occurs in certain large- and giant-breed dogs, such as Doberman Pinschers, Boxers, and Great Danes. This is typically a serious, progressive disease with no cure. (More information can be found here).

2. Secondary DCM: This form can occur as the result of infections, certain drugs, or nutritional causes (diet-associated DCM).

What is Diet-Associated Dilated Cardiomyopathy?

It has long been known that deficiencies of certain nutrients, such as vitamin B1, vitamin E, or taurine, can cause secondary diet-associated DCM. Pets that are eating an unconventional diet could be at risk for DCM caused by a nutritional deficiency. Diets of concern include homemade diets (unless formulated by a Board Certified Veterinary Nutritionist and the recipe is strictly followed), vegetarian/vegan diets, or over-the-counter diets not designed to be complete and balanced (the label will read “for intermittent or supplemental use”).

In 2018, the United States Food and Drug Administration (FDA) published an alert on its investigation of a potential connection between diet and DCM in pets eating diets containing high levels of pulses (pulses include peas, lentils, chickpeas, and dried beans) and, to a lesser degree, potatoes and sweet potatoes. Many of the diets associated with this problem are labeled as “grain-free.” However, pulses have become popular ingredients in grain-inclusive diets as well. Unlike primary (genetic) DCM, diet-associated DCM can occur in dogs of any breed, from Chihuahuas to Great Danes. Another big difference is that dogs with diet-associated DCM can have major improvements in heart function or even reversal of heart disease after medical treatment and diet change.

Deficiencies of nutrients are uncommon in dogs with diet-associated DCM (except one study of Golden Retrievers in which taurine deficiency was present). Thus, the exact cause of this unusual form of DCM is not yet known. However, this disease continues to affect some dogs eating high-pulse diets. Diet-associated DCM may also affect cats, although cats appear to be less sensitive to it than dogs. Cats are very sensitive to DCM caused by taurine deficiency, as this species is unique in requiring this amino acid in their diets (compared to dogs, humans, and most other species). Therefore, taurine deficiency is always a concern in cats with DCM. However, most cats with DCM in recent years do not have taurine deficiency.

What are the Symptoms of Diet-Associated DCM?

The symptoms of diet-associated DCM are similar to those seen with primary DCM. One big difference is that while primary DCM is a disease of certain large- and giant-breed dogs, diet-associated DCM can occur in dogs of any breed.

The symptoms of DCM can be severe, such as coughing, difficulty breathing, fainting, or even sudden death. However, some pets have no symptoms, and the disease is only identified when a veterinarian hears a heart murmur, identifies an irregular heartbeat, or finds high levels of a heart biomarker in the blood (NT-proBNP) on routing laboratory testing. Heart problems associated with high-pulse diets may be even more subtle: several recent studies in outwardly healthy dogs eating high-pulse diets have shown changes in heart size and function that improve after diet change.

How is Diet-Associated DCM Diagnosed?

A physical examination, electrocardiogram (ECG), chest x-rays, ultrasound of the heart (echocardiography), and blood tests can all be important in the diagnosis of DCM. Since diet-associated DCM is seen in pets eating diets high in pulses or potatoes/sweet potatoes, or those eating nutritionally unbalanced diets, pet owners play a crucial role by providing detailed information on their pet’s diet. It is important to give the exact brand, product, and flavor of all your pet’s foods (or the exact recipe if you feed a homemade diet) since this can help determine whether the DCM could be diet-associated. It is impossible to determine the presence or absence of pulses in diets based only on the diet’s name or whether it contains grains because many grain-inclusive diets also contain pulses. Therefore, the diet’s full ingredient list must be reviewed. If the diet contains pulses in the top 10 ingredients (or multiple pulses anywhere on the ingredient list), it might put some pets at risk for DCM. The full name of the product and variety is important, since sometimes the exact same product can contain peas in one flavor and not in another flavor. Although potatoes and sweet potatoes are also common in many of the diets reported to the FDA, their role remains unclear. A diet history form is helpful to ensure you are providing all the important diet details to help your veterinarian or cardiologist make this diagnosis.

What are the Treatment Options?

Treatment is tailored to each individual patient based on symptoms, laboratory values, and other clinical findings. Typically, treatment includes one or more heart medications (multiple medications are often needed in severe cases). If DCM is diagnosed (or early changes, such as heart enlargement, reduced contraction of the heart, or irregular heartbeats), the diet should be changed to one without pulses or potatoes/sweet potatoes that is reduced in sodium. Depending on the individual patient, adjustments in other nutrients such as fat, fiber, or phosphorus are also needed. A diet that meets the guidelines of the World Small Animal Veterinary Association’s Global Nutrition Committee is recommended. Despite the low likelihood of taurine deficiency in dogs with diet-associated DCM, until more is known, measuring plasma and whole blood taurine levels in both dogs and cats with DCM is ideal (especially in cats). In addition to heart medications, your cardiologist may also recommend dietary supplements, such as taurine, carnitine, coenzyme Q10, or omega-3 fatty acids from fish oil. However, there is not much evidence for benefits of these supplements in diet-associated DCM (except for taurine supplements when taurine deficiency is present). 

What is the Outcome after Treatment?

Dogs with diet-associated DCM, especially if caught early, can have major improvements in their hearts after medical treatment and diet change. This is different from dogs with primary DCM, where improvement typically does not occur. Improvement can take months to years, and most dogs’ hearts do not return to normal unless the disease is detected early. In diet-associated DCM, even breeds predisposed to primary DCM can have improvement in their heart size and function. However, sudden death can occur in diet-associated DCM, and pets with severely affected hearts can be challenging to care for. Therefore, working with a veterinary cardiologist and careful monitoring are very important.

Additional Reading/Websites

1. Tufts HeartSmart website, including low sodium diet and treat lists: http://vet.tufts.edu/heartsmart/
2. Tufts Petfoodology website 2023 post on diet-associated DCM (plus several previous posts): https://vetnutrition.tufts.edu/2023/02/diet-associated-dilated-cardiomyopathy-the-cause-is-not-yet-known-but-it-hasnt-gone-away/
3. United States FDA’s June 2019 investigation update: https://www.fda.gov/animal-veterinary/outbreaks-and-advisories/fda-investigation-potential-link-between-certain-diets-and-canine-dilated-cardiomyopathy- WSAVA Global Nutrition Committee. Nutrition Toolkit, including a Diet History Form and Guidelines on Selecting Pet foods. https://wsava.org/global-guidelines/global-nutrition-guidelines