Key result
Cyanide increases canine heart work despite reduced aerobic metabolism, demonstrating anaerobic energy converts to mechanical work.
This preclinical study demonstrates that the intact dog heart can utilize anaerobic metabolism to produce mechanical work when aerobic metabolism is inhibited.
Anaerobic metabolism may support cardiac work during aerobic inhibition; leaves open relevance to human ischemia or heart failure.
Energy liberated from substrates of heart muscle metabolism appears as mechanical work and heat. External mechanical work and heat production of the left ventricle were compared with its oxygen consumption in intact dogs. Under control conditions, within the range of accuracy possible, the sum of work and heat was equal to energy from oxidative metabolism. Intravascular administration of cyanide increased heart work but reduced its rate of aerobic metabolism. During the cyanide effect, work plus heat exceeded the energy available from oxidative metabolism. The difference represents myocardial anaerobic metabolism. Since the energy of mechanical work output alone was greater than the myocardial aerobic energy source, a portion of the anaerobic energy liberated must have been converted to mechanical work.
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Neill et al. (1963) studied this question. Intravascular administration of cyanide vs. Control conditions was evaluated on Myocardial anaerobic metabolism (difference between work plus heat and energy from oxidative metabolism). Intravascular administration of cyanide in intact dogs increased heart work while reducing aerobic metabolism, demonstrating that a portion of anaerobic energy is converted to mechanical work.
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