Nuclear stress tests are not 100% accurate. Indeed there can be false positive and false negatives. The heart function is also reported on a nuclear stress test(ejection fraction). In your case, it seems based on what you are reporting, although your nuclear stress test showed ischemia in the anterior and inferior walls of the heart, your cardiac catheterization, which by the way is the gold standard test looking for coronary artery stenoses, was normal, so you do not need to repeat the stress test. One other finding that also would raise suspicion for coronary artery disease based on the stress test was the cavity dilatation with stress. The false positive stress test was most likely related to attenuation from the diaphragm and the breast tissue which can sometimes be read as an abnormal test but when a coronary angiogram is done, everything is normal. That is how we define false positive tests.
Therefore, one can say for sure that there is no obstructive coronary artery disease.
That being said, there is a condition called Prinzmetal's angina or variant angina, in which the coronary arteries can be relatively normal with no significant obstruction, but from time to time can undergo vasospasm, which basically means that they suddenly narrow transienty. This narrowing is often relieved by nitroglycerin. If your cardiologist feels this is a potential source of symptoms, one can try using long acting nitrates and calcium channel blockers which could improve symptoms. Alternatively, there is a test called an ergonivine challenge which can try to bring out coronary vasospasm in the cath lab, but this is an invasive test and should only be reserved for patients in which the diagnosis remains unclear. Hope this is useful.