Use of Lexiscan for Myocardial Stress Perfusion Computed Tomography With a 3rd Generation Dual Source CT System

Inclusion Criteria: 1. Subject must present with symptoms (e.g. chest pain) suspicious for cardiac ischemia as determined by treating physician. 2. Subject must have been referred for cardiac CT angiography OR subject must have undergone clinically indicated SPECT with positive or equivocal findings OR subject must have undergone clinically indicated SPECT with prior cardiac CT angiography that showed moderate or severe stenosis. 3. Subject must be 18 - 85 years of age. 4. Subject must provide written informed consent prior to any study-related procedures being performed. 5. Subject must be willing to comply with all clinical study procedures. Exclusion Criteria: 1. Subject is a pregnant or nursing female. Exclude the possibility of pregnancy: * By testing (serum or urine beta HCG) within 24 hours before study agent administration, or * By surgical sterilization, or * Post menopausal, with minimum one (1) year history without menses. 2. Subject has severe asthma or COPD requiring frequent inhaler use. 3. Subject has prior diagnosis of obstructive CAD that has not been revascularized. 4. Subject with implanted rhythm devices (pacemaker, defibrillator). 5. Subject has significant arrhythmia. 6. Subject has high grade heart block. 7. Subject has resting heart rate \< 45 bpm, systolic blood pressure \<90 mm Hg, or has consumed caffeine within the last 12 hours. 8. Subject has an acute psychiatric disorder. 9. Subject is unwilling to comply with the requirements of the protocol. 10. Subject has previously entered this study. 11. Subject has an allergy against iodinated contrast agents or pharmaceutical stressors used in this study. 12. Subject suffers from claustrophobia. 13. Subject has impaired renal function (creatinine \> 1.5 mg/dl). 14. Subject is in unstable condition. 15. ST-elevations, new transient ST changes greater than 0.05mV or T- wave inversions with symptoms 16. Subject cannot safely be administered Lexiscan™ per prescribing information as determined by investigator 17. Subject has received interventional (PCI, stenting) or surgical (CABG) treatment that may alter the cardiac condition regarding myocardial perfusion status and/or stenosis degree between cardiac CTA, SPECT, and/or CT stress perfusion studies.