Pacers - I can't comment on aneurysms, as I have no experience there. I can, however, comment on second opinions, as I have a LOT of experience there. If a doctor seems to be resistant to me getting a second opinion, I fire him/her and go elsewhere. In this modern age, any doctor who feels that you don't warrant a second opinion on something as important as cardiology is not for me. My initial diagnosis was made, then confirmed by two other cardios. I then picked the one I liked, and stayed with him. The same is true with surgeons. I met with three surgeons, telling each of them that I had other consults planned. They were all fine with that.
In other serious medical issues, I've gotten two or three opinions on diagnosis and proposed treatment plans. It always works out best for me, the patient.
P.S. I have seen both of my parents and both of my in-laws' experiences in the "my doctor knows best" mode. None of these ended well for the patient. None.