PALM CITY, Fla. -- The FDA is investigating a potential dietary link between canine dilated cardiomyopathy (DCM) in dogs and certain grain-free dog foods.

The foods of concern are those containing legumes — like peas and lentils — or potatoes listed as primary ingredients.

That is information Laila Esmaeel and Russell Taylor wish they had known would have known. Last week, their 11-year-old Staffordshire terrier, Floyd, collapsed during a walk.

"We saw his legs give out, and he just fell over. Hit the ground like a ton of bricks," Esmaeel said.

"I thought he was having a seizure," Taylor said.

The next day, the vet broke the news: Floyd was suffering from dilated cardiomyopathy, which causes an enlarged heart.

Dr. Annette Sysel, a vet at Martin Downs Animal Hospital in Palm City, Florida, says if DCM is not caught early, it can be fatal. She is currently treating two dogs with DCM.

She says the FDA has been studying the potential link between canine heart disease and diet since 2014.

In June of this year, the FDA issued a warning about certain brands of grain-free pet food and their possible connection to dilated cardiomyopathy.

Sysel says that while there is no direct link between grain-free pet food and DCM, it should spark some concern for dog owners.

"When you look at all cases of DCM, especially in breeds of dogs not predisposed to the condition, a lot of those dogs, 90%, are on grain-free diets," she said.

Just walk down any pet food aisle, and it's clear grain-free is the hot new trend. The trend caught on as gluten-free diets did for humans.

But Sysel warns that while grain-free foods may seem healthier for pets, that's not always the case.

"Grain-free does not mean gluten-free, carb-free — it just means certain grains are eliminated from the diet," Sysel said.

Vets say dogs with allergies and gastrointestinal issues often need to go on a grain-free diet. Floyd was one of those dogs.

But the food Floyd was eating is one of the 16 brands on the FDA warning list.

Esmaeel said she had no idea the FDA had issued a warning about Floyd's food. A quick Google search made her realize they weren't alone.

"I found hundreds of reports from the FDA from other pet owners whose dogs had very similar symptoms and instances such as the fainting episode," she said.

Sysel says exercise intolerance, fatigue, lethargy, and weakness are other signs to look for in your pet.

"If we're worried, then the next step is a cardiac ultrasound to determine any changes to the heart," Sysel said.

Today, Floyd is doing well. He's off the grain-free food and responding to heart medicine.

"I don't want to start crying. He's just great. He's been our little guy, our best friend for all these years," Esmaeel said.

Sysel recommends that anyone who is confused about what pet food to buy should talk to their vet. She also says owners should avoid feeding their dogs "trendy" brands and should buy foods from well-known companies.

Pet owners and veterinarians are urged to report all cases of DCM to the FDA.

This story was originally published by Kelley Dunn on WPTV in West Palm Beach, Florida.

