If your dog coughs a lot, seems to gag, and/or no longer has the stamina to go on miles-long hikes, it could be due to heart problems.

After all, the heart is responsible for pumping blood (which contains oxygen and nutrients) throughout the body. This provides energy.

When your dog’s body doesn’t get enough oxygen, he feels fatigued and isn’t as playful. You might chalk it up to “old age” if your dog is getting older, but it could be something more. It could be heart problems.