Nuclear stress testing evaluates whether the heart receives enough blood, by injection of a nuclear isotope during a stress on the heart that permits taking pictures of the heart muscle. A low-radiation-dose protocol for nuclear stress testing involves injecting less of the nuclear isotope than standard protocols, by utilizing a new, more efficient camera (called an Alcyone camera) which could decrease radiation dose to patients while still providing excellent clinical information. Subjects will undergo imaging under the Alcyone camera after undergoing stress testing with exercise or a standard medication simulating exercise, and then at rest if needed. Subjects will have follow-up to measure events occurring after the test, such as death, heart attack, unstable angina, repeat emergency department visit for chest pain evaluation, or repeat imaging needed to evaluation for coronary artery disease. Radiation doses and quality of the images from the imaging with the new protocol will be recorded to compare to those used in standard nuclear imaging protocols. The primary study hypothesis is that greater than 90% of patients who have a normal very low dose stress first myocardial perfusion scintigraphy (MPS) will be free at 3 months after study of death, nonfatal myocardial infarction, unstable angina, and repeat emergency department visit for chest pain evaluation or repeat anatomical or functional cardiac imaging.