heartworms?

Question
I have an older female mixed breed dog, spade, 10-12 lbs.  Her weight fluxuates and she is very active.  She has always been the healthiest and most active of my three dogs.  Lately she has been much less active and is tending to one side of her rib cage excessively.  She also has had one episode of fainting but seemed fine afterwards.  I love my Molly dearly, but have a very low income and cant afford to take her to the vet unless it is an exreme emergency.  I take very good care of her and provide her with vitamins and a high protein diet.  I am not familiar with heartworms but am afraid that she may have it.  I may be paranoid, but better safe than sorry.  Please help with information regarding her symptoms.   Thanks, Leisa

Answer
Fainting is NOT normal in a dog.  She could have heartworms which requires a blood test to determine, however, she may have a heart murmur or arrhythmia and heart disease.  To be safe, I would recommend getting her to the vet ASAP for a check up and then at the appointment it can be determined if she has a heart murmur or any evidence of heart disease.