Reflected Ultrasound as a Diagnostic Instrument in Study of Mitral Valve Disease*

The refinement of phonocardiography, apex cardiography, electrocardiography, vectorcardio-graphy, cardiac catheterization, and cine-angio-graphy in the post-war years has contributed considerably toward enhancing the clinical acumen of physicians. These techniques have become standardized and widely used as diagnostic aids, particularly in the study of valvular heart disease. In the evaluation of patients as candidates for surgical correction it is customary to employ as many diagnostic procedures as is feasible. But in many instances reliance on catheterization and cine-angio-cardiographic information has been necessary to establish the type and degree of abnormality. Unfortunately, the latter two techniques are not without complications, particularly in those who are seriously ill. The development of an ultrasound technique to evaluate mitral and tricuspid valve motion with some degree of precision has provided an important additional tool to this armamentarium. By definition, ultrasound is composed of sound waves with a frequency above 20,000 cycles per second exceeding the limits audible to the human ear. The physical characteristics of the transmis-sion of ultrasound through liquid or solid matter are similar to light in many respects, including the occurrence of reflection and refraction through medium having different acoustical impedance. Acoustical impedance is a value determined by the product of the velocity times the density of the medium. The portion of ultrasound that is reflec-ted at any interface is directly related to change i