I guess the problem you have is that he could have both conditions. I would certainly want your first vet to explain what is meant by "heart issues", which is not a diagnosis. What heart issues? What illness? And what treatment is he suggesting? What follow-up (to see if treatment has been successful)?
A collapsing trachea is a symptom, not an illness as such. So, your second vet also needs to provide you with more details. Why is the trachea collapsing? Is it congenital or due to an illness? Can it be treated? What are the options?
Tony