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The failing heart has impaired mechanical efficiency, unable to convert liberated energy into useful work as effectively as normal heart muscle.
The failing heart is found to liberate energy in contraction to the same extent at any fiber length as the normal heart muscle, but it is unable to convert as much of the energy into useful work. Its efficiency as a machine is impaired. In the light of these observations the word "tonus" as applied to heart muscle becomes synonymous with "efficiency." The implications of these findings in applied cardiology are discussed.
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Decherd et al. (1934) studied this question.
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