A nuclear stress test lets doctors see pictures of your heart while you are resting and shortly after you have exercised. The test can give information about the size of the heart's chambers, how well the heart is pumping blood, and whether the heart has any damaged or dead muscle. Nuclear stress tests can also give doctors information about your arteries and whether they might be narrowed or blocked because of coronary artery disease.
An echo will take images of the heart at rest only, and does not include a perfusion test. Perfusion (blood flow) test can/will observe any occlusions with exertion, an echo can not show any vessel occlusions, but it will show any wall movement inpairment from a prior heart attack, etc.