But be aware that dogs can also pant as a symptom for something more serious as well. They may excessively pant when under various forms of stress. They can also do so as a symptom of a medical illness, an injury or from heat stroke. Panting can also be symptomatic of fever, congestive heart failure, respiratory disease, infections, anemia, or even heartworms. It can even mean an obstruction in the throat. Check the gums.