The metabolism of the preserved heart. I. Does lactate properly reflect the functional state of the preserved heart? Part one.

Since there are controversial data and opinions on the use of lactate as a viability test for preserved hearts, investigations were carried out of the variations of lactate and pyruvate amounts in the perfusion fluid during hypothermic preservation of canine hearts by means of a perfusion fluid containing amino acids in "cytoplasmic" concentrations. These variations were interpreted in connection with the changes in the coronary perfusion flow during storage and the functional performances of the preserved hearts during long periods of subsequent ex vivo functional testing. Likewise, investigations of the ability of the myocardial mitochondria to oxidize in vitro lactate and pyruvate at low temperature levels were performed in order to explain the nature of the impairment in using these metabolic substrates during preservation and of the functional cardiac disturbances after resuscitation. The investigations have led to the conclusion that lactate should not be used as the sole index of heart storage efficiency and that it gains in significance only when a high myocardial lactate production is associated with a progressively increasing resistance in the coronary vasculature during preservation. The possible metabolic significance of the results obtained in these investigations are amply discussed.