Abstract
Myocardial protection preserved by the topical hypothermia and crystalloid potassium cardioplegia was studied experimentally in 55 mongrel dogs. The animals were divided into nine groups according to the myocardial protective methods and then the changes in myocardial ultrastructure were compared in each group. Group I : Continuous aortic cross clamping for 30 minutes under systemic normothermia. Group II : Continuous aortic cross clamping for 60 minutes with topical myocardial cooling under mild systemic hypothermia. Group III : The same as group II combined with cardioplegia. Group IV : The same as group II. with continuous aortic cross clamping for 90 minutes. Group V : The same as group IV combined with cardioplegia every 60 minutes. Group VI : The same as group II with continuous aortic cross clamping for 120 minutes, Group VII : The same as group VI combined with cardioplegia only once soon after aortic cross clamping. Group VIII: The same as group II with continuous aortic cross clamping for 240 minutes. Group LX : The same as group VIII combined with cardioplegia every 60 minutes. Myocardial biopsies for electron microscope were performed from the left ventricle before the release from aortic cross clamping. Mitochon-drial score reported by Flameng et al. was evaluated in each group and the results were as follows : Group I, 2.27 ± 0.052; Group II, 1.725 ± 0.036; Group III, 1.44 ± 0.035; Group IV, 1.925 ± 0.028; Group V, 1.935 ± 0.002; Group VI, 2.07 ± 0.022; Group VII, 1.415 ± 0.035; Group VII, 2.185 ± 0.027; Group IX, 1.865 ± 0.029. Cardiac function after resuscitation was studied. Good cardiac function was obtained in group II, III, IV, V and group VII, however, cardiac function was very poor in group I, VIII and group IX. Continuous aortic oculusion for 120 minutes preserved by hypothermic cardioplegia and topical myocardial cooling under mild systemic hypothermia was performed safely in this experiment. However, the effectiveness of cardioplegic solution was not lasted when the infusion interval of cardioplegic solution was prolonged for 90 minutes (group VII) . In conclusion it can be deduced that hypothermic potassium cardioplegia was effective method for myocardial protection during aortic cross clamping.
