Intravascular monitoring provides immediate central hemodynamic data for the rapid assessment of the cardiovascular patient; however, because of natural restrictions on its use, there is growing interest in effective non-invasive monitoring techniques. A number of investigators have reported successful use of impedance cardiography for the non-invasive estimation of cardiac output, systolic time intervals, myocardial contractility and thoracic blood volume. Although the technique reportedly has multiple uses and unique advantages, its full potential value to cardiovascular medicine has not been thoroughly explored. The objectives of our proposed study are: (1) to investigate in the dog and in human patients the validity of impedance derivatives as indices of myocardial contractility, (2) to study the usefulness of baseline impedance (Zo) as an estimate of changes in thoracic and peripheral blood volume and (3) to determine the clinical applicability of this technique in cardiovascular medicine, particularly as a diagnostic aid in coronary heart disease. Although impedance cardiography has not been widely accepted, previous reports have emphasized its usefulness, safety and low cost features. The pressing need for effective, non-invasive cardiovascular approaches would suggest further investigation of this method.
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