I. Historical
II. Instrumentation
III. Echocardiographic Examination
V. Research Implications
VI. New Frontiers

GLOSSARY
heart failure failure of the heart muscle to pump sufficient
blood from the chambers into the aorta; inadequate supply of
blood reaches organs and tissues. hypokinesis decreased myocardial contraction usually caused by
damage and weakness of the heart muscle due to coronary
artery disease and cardiomyopathies. ischemia temporary lack of blood and oxygen to an area of
cells, for example, the heart muscle, usually due to severe
obstruction of the artery supplying blood to this area of cells. mitral regurgitation the mitral valve remains open when it
should be completely shut; blood rushes backwards from the
left ventricle into the left atrium. myocardial infarction death of an area of heart muscle due to
blockage of a coronary artery by blood clot and atheroma;
medical term for a heart attack or coronary thrombosis.

• I. HISTORICAL
  The Titanic disaster of 1912 lead the impetus for detect¬ing structures under the sea. In 1940 during World War II ultrasonic floor detectors were developed for tracking enemy submarines. In 1945 with the end of the war, attention was turned to imaging of body parts instead of tracking submarines and technologic developments advanced.
• II. INSTRUMENTATION
  Ultrasound is sonic energy with a frequency higher than the audible range of 20,000 Hz. The development of piezoelectric transducers made the application of ultra¬sound possible. A piezoelectric (pressure electric) element is the primary component of an ultrasonic transducer. The shape of a quartz crystal varies with its polarity when an electric current is impressed through the crystal. The expansion and contraction of the crystal produces compres¬sions and rarefactions or sound waves. Most important, when the crystal is struck by reflected ultrasound waves, the crystal creates ultrasound energy and then produces an electric impulse or signal.
• III. ECHOCARDIOGRAPHIC EXAMINATION
  A. Echocardiographic Window
• IV. CLINICAL APPLICATIONS
  Echocardiographic evaluation of heart disease is used extensively to verify many clinical diagnoses and assists with the formulation and timing of treatment strategies. The following are some of these clinical entities.
• V. RESEARCH IMPLICATIONS
  The very important role of echocardiography in the prac¬tice of cardiology has been outlined above. There is one important diagnosis, however, that the echocardiogram is not able to resolve adequately. The obstruction of coronary arteries by atheroma, which causes angina and fatal and nonfatal heart attacks and accounts for more than 90% of deaths from coronary artery disease cannot be visualized with this technology. Intravascular ultrasound done at the time of interventional procedures is improv¬ing our knowledge of the atherosclerotic process and its complications, but this technique cannot be applied in clinical practice.
• VI. NEW FRONTIERS
  A. Transthoracic Visualization of the Coronary Artery
• BIBLIOGRAPHY
  DeMaria, A. N., and Blanchard, D. G. The echocardiogram. In Hurst’s