Nuclear Stress test for PVC?

Hi, I'm 51 year old man.  I was told today I had PVCs after wearing a halter monitor for 24hrs.  I had a echo stress test 3 months ago which was fine.  My cholesterol is good.  The doctor now wants to do a Nuclear Stress test to see if there was some blockage that was missed.  All my blood work is good.  

The flutter sensation started suddenly a over a week ago.  It seems to happen only when I'm walking, or getting up, etc.  At rest I feel nothing.  Also when strenuously exercising I feel fine too.  The sensation feels almost like it's coming from my diaphragm area.  

I'm wondering what could be the cause, what will this stress test show and how much radiation will I be exposed to?? (I just had an upper GI series done last week which I know had much radiation exposure)

[Jerry_NJ]

A nuclear stress test is much more accurate/sensitive in searching for artery blockage to the heart muscles, than is a "regular" stress test.  The nuclear material is injected into the blood stream, not "radiated" at you.  I think the level is very minimal and it has been widely used for years...so there are many, myself included, who have survived .. I had my first nuclear (call thalium back then, the name of the agent I think) about 15 years ago.  I have had two since.  But, the nuclear stress test, and the regular stress test can give false positives for blockage.  I had such a result about 3 years ago and underwent a cardio catheter examination, the "gold standard".  I did not have any blocks.