Inconsistent effectiveness of myocardial preservation among cardiac chambers during hypothermic cardioplegia

The purpose of this study was to examine the selective and differential natures of ischemic injuries among three cardiac chambers (right atrium, right ventricle, and left ventricle) from the viewpoint of ultrastructural morphometric study. Twenty consecutive adult patients undergoing cardiac operations were studied. The duration of aortic crossclamp time varied from 36 to 142 minutes (mean 83.4 +/- 36.4 minutes). Two serial specimens (preischemic and ischemic) were obtained from the right atrium, the right ventricle, and the left ventricle, respectively. A total of 120 biopsy specimens was obtained from these 20 patients. The average mitochondrial surface area of the left ventricle was 0.308 +/- 0.062 micron 2 in the preischemic stage and 0.352 +/- 0.083 microns 2 in the ischemic stage. This represented a 14.3% increase in mitochondrial surface area after ischemic injury (p less than 0.01). The mitochondrial surface area of the right ventricle showed an average increase of 43.7%, from 0.252 +/- 0.036 micron 2 in the preischemic stage to 0.362 +/- 0.087 micron 2 in the ischemic stage (p less than 0.0005). With respect to the mitochondrial surface area of the right atrium, there was an increase of 88.0%, from 0.217 +/- 0.044 micron 2 in the preischemic stage to 0.408 +/- 0.084 micron 2 (p less than 0.0005). The difference of mitochondrial swelling among three chambers was statistically significant (right atrium versus right ventricle versus left ventricle, p less than 0.0005). Moreover, the differences of mitochondrial swelling between any two chambers were also highly significant (right atrium versus right ventricle, p less than 0.0005; right ventricle versus left ventricle, p less than 0.01; right atrium versus left ventricle, p less than 0.0005). In conclusion, our findings suggest that from the viewpoint of ultrastructural morphometric study myocardial injury after an average of 83 minutes of ischemic arrest is poorer in the right chambers of the heart than in the left ventricle, with the right atrium having the poorest preservation.