Comparison of Cardiac Computed Tomography and Vasodilator Stress Magnetic Resonance Imaging Perfusion in Patients With Prior Equivocal Stress Test for Detection of Coronary Artery Disease

Background: * Noninvasive cardiac stress testing is imperfect. Inconclusive test results generate further expensive testing. * In patients with known or suspected coronary artery disease, both computed tomography (CT) and magnetic resonance imaging (MRI) have been shown to provide suitable results for detecting the disease. However, both types of scans have limitations in their usefulness, and it is not known whether one is preferable in either accuracy or cost-effectiveness. Objectives: \- To determine the accuracy and cost-effectiveness of CT and MRI in subjects with a prior inconclusive heart stress test. Eligibility: \- Patients 18 years of age and older who have had an inconclusive heart stress test within the past 90 days. Design: * A blood test will be obtained prior to both heart tests. This will require less than a teaspoon of blood. * A CT scan will be performed, accompanied by beta blocker medications (to slow heart rate) or nitroglycerin (to enlarge blood vessels) to improve picture quality, as needed. * An MRI scan will be performed. Scans will be taken before, during, and after the patient receives vasodilators (to increase blood flow to the coronary arteries and detect blockages in heart blood vessels). * Heart rate and function will be monitored with an electrocardiogram.