This study is designed to compare two different echocardiographic techniques in the evaluation of heart disease (coronary artery disease). Both tests called Myocardial Contrast Echocardiography with Pharmacologic Stress and Stress Echocardiography with Dobutamine, are performed using a standard echocardiographic machine.

Myocardial Contrast Echocardiography (MCE) does not use radioactivity. It uses sound waves like standard echocardiography. However, with MCE patients receive an injection of a "contrast agent" directly into the blood stream through a vein. The contrast agent, called Optison, is made of tiny microbubbles smaller than red blood cells. The echocardiogram can detect these microbubbles in the small blood vessels of the heart muscle and allow researchers to find areas of the heart receiving less blood flow than others. It is important to observe the heart during exercise because there are changes in blood flow. Since MCE cannot be performed when the patient is exercising, researchers give medication (adenosine) that stimulates the heart and creates a situation similar to exercise.

Stress Echocardiography with Dobutamine does not use radioactivity. It uses sound waves like standard echocardiography. During this echocardiogram patients receive doses of a medication called dobutamine that stimulates the heart to beat stronger and faster.

The purpose of this study is to evaluate the accuracy of MCE compared to stress echocardiography at detecting coronary artery disease (CAD).