Researchers are particularly interested in studying patients with defects in the valves of the heart, especially aortic regurgitation and mitral regurgitation. Patients with these defects in the heart valves tend to develop abnormalities in the size and function of the left ventricle. The left ventricle is one of the four chambers of the heart responsible for ejecting blood out of the heart into the circulation. Researchers believe that by identifying changes in the function of heart muscle, they may be able to predict the occurrence of muscle damage due to the diseased valves.