The fine structure and the content in energy-rich
phosphate compounds,
glycogen, and metabolites of the Embden-Meyerhoff-pathway in rabbits hearts or human papillary muscles arrested by
magnesium aspartate-procaine are investigated in normothermia and mild or deep
hypothermia. In all experimental conditions the break-down of
adenine nucleotides and
glycogen was distinctly retarded in
cardioplegia compared to ischaemic arrest. While e.g. an
ATP-content of 3.6 mumole/g wet weight was found after 40 min. at 32 degrees C in the
magnesium asparate-
procaine arrested heart, it dropped down to 1.3 mumole/g in the ischaemically arrested heart. In
cardioplegia after 60 min at 15 degrees C the in vivo contents of
ATP and
glycogen were determined. The rate in metabolic changes in the
magnesium aspartate-procaine arrested human papillary muscle was in the range of that recorded in the arrested rabbit heart. The ultrastructural appearance of the cardioplegically arrested heart did not differ from that of the controls after 20 min at 32 degrees C or 120 min at 15 degrees C. In hearts arrested by
cardioplegia 40 min at 32 degrees C first signs of ischaemic lesions e.g. mild swelling of mitochondria and few rarefications in mitochondrial matrix were observed. Because of the significantly improved preservation of the fine structure of the heart and retardation of ischaemically provoked changes in cardiac metabolism, the method of inducing
heart arrest by
cardioplegia should also clinically be given preference to methods of arresting the heart by ischaemia.