Dynamic Cardiac SPECT Imaging

Inclusion Criteria: * Patients who have had clinically indicated stress MPI with a low pre-test likelihood (0 - 15% ) of coronary disease based on the criteria of Diamond and Forrester. * Patients who have already had a clinically indicated stress MPI in the last three years with a low likelihood of having active coronary disease with no significantly narrowed coronary arteries. * Patients whose clinically indicated stress MPI demonstrates clear abnormalities and who are likely to go on to SCA for clinical indications. * If, after conventional and dynamic MPI some of these patients do not have SCA, they will still be followed for events for up to 3 years following participation in the protocol. To avoid delays and unnecessary procedures among patients in Group II who will have the dynamic imaging protocol studies after SCA, patients will be selected for protocol enlistment only if the decision is made by the patient's physician, based totally on clinical and social factors, that any considered revascularization intervention would not be performed on the day of diagnostic SCA and will be performed electively, at least 4 to 7 days later. * Patients found at SCA to have lesions of "borderline" clinical significance, preferably in the absence of other associated lesions. Exclusion Criteria: * Cannot give informed consent * Unable or unwilling to return for a second stress imaging study * Cannot cooperate for adequate SPECT or PET supine and/or prone imaging * Pregnant females * Patients under 21 years old * Active bronchospasm - No theophylline for 48 hours prior to study * Heart block more severe than Wenckebach block * Patients with uncomplicated infarction will not be included if they cannot have an exercise test later than 8 weeks of the event or a vasodilator pharmacologic stress test at least 24 hours or more after the event * Coronary bypass surgery within 8 weeks * Symptoms of congestive heart failure at rest * Has had an event or change in drug regimen since the initial stress test. * Has serious response to or side effect from initial clinical stress test induced ST elevation, hypotension, prolonged arrhythmia, bronchospasm. * Has had a clinical event since last coronary angiogram, angioplasty, or coronary surgery. * Has had 201Tl rest SPECT MPI prior to dynamic imaging