pet scan

I am confused with IV drugs used during the scan.If the study uses two radiotracers,the first one,ammonium which measures blood perfusion into the heart muscle and the second tracer, flurodeoxyglucose which measures metabolism,why would one use adenosine or doubatime if ammonia can tell,at least at rest,if there are blockages in the coronary arteries? 2.Would heart PET scan test with ammonia and FDG (without heart rate inducing drugs,like adenosine doubatimee etc) detect blockages in the coronary arteries better than stress-echo? 3.Is ammonia safer(less pac,pvc,chest pain,sob) than adenosine and what's the differece between them? 4.If a 49 year old male had a normal stress echo two years ago and wants this year to have a heart PET scan (because of better accuracy),would you recomend a PET scan with heart rate inducing drugs(adenosine) or only rest part of the test with ammonia and FDG?5.Do ammonia and FDG causes arrhythmia,pac,pvc plus any other serious side effects?Thanks

[CCF-M.D.-RCJ]

Zk,

Thanks for the post.  I reviewed your last question regarding PET scans.

(1) Ammonia is a tracer that shows perfusion of the muscle.  The only way to detect a blockage is to see a difference between perfusion at rest and perfusion during stress.  There is not a reference standard to which a doctor can compare a given person's rest image to see if the perfusion is more or less than the reference standard.

(2) No one knows, but probably not.

(3) Ammonia is a flow agent.  Adenosine is a stress agent.  They are not used to do the same thing, like say dobutamine and adenosine, which are both "stress agents".

(4) I would probably not recommend a stress test at all, unless the clinical situation was now different.  A rest PET scan will not answer whether or not the 49 yr old man has blockages.  If he wants to know, then a stress portion will have to be completed.

(5) No.

Hope that helps.