Regadenoson R-T Perfusion Imaging Trial

Inclusion Criteria: * Male or female. Age ≥30 years. * Resting Left Ventricular Ejection Fraction \> 40% using Simpson's biplane measurement. * Scheduled for coronary angiography within 30 days of the Regadenoson stress test. * Negative urine pregnancy test within 2 hours of ultrasound contrast administration required of females of childbearing age unless post-menopausal or with evidence of surgical sterilization. * Be conscious and coherent, and able to communicate effectively with trial personnel. * Agreeable to undergo the additional stress test and coronary angiography * Have at least an intermediate likelihood of coronary disease based on the following clinical profile * Good apical echo images with at least 50% of each coronary artery territory well visualized. Exclusion Criteria: * Known or suspected hypersensitivity to ultrasound contrast agent used for the study. * Pregnancy or lactation. * Complicated hemodynamic instability (i.e., New York Heart Association (NYHA) Class IV heart failure, unstable angina at rest despite medical therapy). * Life expectancy of less than two months or terminally ill. * Congestive (idiopathic) or hypertrophic cardiomyopathy. * Known left main disease. * Heart transplant recipient, hypertrophic cardiomyopathy, acute myo- or pericarditis. * Resting Left Ventricular Ejection Fraction \< 40% * Large inducible perfusion defects or wall motion abnormalities during prior stress imaging study associated with left ventricular cavity dilatation. * Early positive treadmill EKG within the first stage of the test. * History of \>1st degree heart block, sick sinus syndrome or high grade atrioventricular (AV) block without a pacemaker. * Dipyridamole use within 30 hours of stress test, or consumption of methylxanthines within 12 hours, or use of sublingual nitroglycerin within two hours. * Participation In another investigational study within one month of this study.