Nuclear stress test is fine but "perfusion is mildly nonuniform but appears preserved throughout myocardium."what does this mean? should i be worried?

Don't worry: There is often a difference between true perfusion (circulation of blood) and the APPEARANCE of perfusion on a nuclear stress test. Variations in the thickness of the chest wall, caused by breast tissue or other factors, could explain the findings on your test. Most important, however is your doctor's overall assessment based on all known information.