Heartworm disease causes damage to the pulmonary arteries which eventually leads to heart failure. If you have any acquaintances with chronic heart failure, ask them how much joy there is in their lives. Heart failure robs the dog of its ability to play comfortably. Eventually it becomes difficult to just participate in normal activities.
Serious damage begins to occur in other organ systems affected by the heart failure.
Some dogs do manage to live almost normal lifespans despite infection with heartworms but they are very lucky. Inc. Opinions expressed are those of Dr. Richards. 1997,1998,1999,2000,2001- TierCom, Inc.