There is a good reason you have to have a nuclear scan, and a reason why is often results in normal findings even when something is clearly wrong. It is important to remember that each test looks at different things, I mean, what would be the point of 3 tests if they look for the same thing. When you have abnormal ECG and or stress test, a nuclear scan is important to establish whether you have any necrosis (dead heart muscle). If the nuclear scan revealed that a section of heart muscle has died, then bypass or stenting is a waste of time because the blood won't be of any benefit. It's great that your nuclear scan came out normal, it means that your heart muscle is in good shape, it's all using available oxygen. A nuclear scan can even look normal when there's a total blockage because the heart adapts by opening tiny vessels called collaterals which are a built in natural bypass system. In many cases this is not enough to stop symptoms under exertion, but perfusion will be seen during the nuclear scan, giving the appearance of being normal.
Each test is progressivly more accurate. An EKG is about 50% accurate, a normal stress test is about 65% accurate and a nuclear stress test is about 85% accurate overall but if you back out the false positives, it will find significant heart disease 97% of the time. Having said that, are you working with your doctor to find a cause other than heart disease? I would not rule out the possibility of heart disease should you have more chest pains, seek out medical attention if it returns until a proper evaluation can be made.
Hope this helps,
Jon