Believe it or not, the majority of heart disease in dogs and cats is caused by dental problems. Animals on a diet of soft food don't get the chewing exercise they need. This can lead to gum infections which enter the blood stream and eventually make their way to the heart. If you feed your pet dry food and dry, chewy treats, as well as brushing its teeth regularly, there shouldn't be problems. The other major cardiac concern is heartworms. Heartworms are usually found in dogs, but cats can become infected, too. They are transmitted by mosquitoes. Make a heartworm test a regular part of your pet's annual checkup. If the veterinarian detects signs of heartworm, there's medication available to keep it under control.