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Morphometric evaluation of volume shifts between intra- and extra-cellular space before and during global ischemia
A Schmiedl1, G Haasis, P A Schnabel
1Department of Anatomy, University of Göttingen, Germany.
Background:
It is well known that all forms of cardiac arrest lead to global ischemia combined with alterations in cellular and interstitial volume. The aim of this study was to investigate the nature of these alterations with respect to different methods of cardiac arrest and establish the extent of their mutual influence at the onset as well as during the course of global ischemia.
Methods:
Three tested clinical methods were employed to induce cardiac arrest by a) aortic cross clamping, b) coronary perfusion with the cardioplegic solution St. Thomas, and c) coronary perfusion with the cardioplegic solution histidine-tryptophane-ketoglutarate (HTK). The arrested hearts were subjected to global ischemia at 25 degrees C. The size of the myocytes, as well as the interstitial space of myocytes, was determined morphometrically. The contraction state of myocytes was evaluated according to a score.
Results:
We found that the degree of contraction, as well as nature of alterations in the cellular and interstitial volumes, depended both on the form of cardiac arrest and on the duration of ischemia. The following relationships were established. High contraction at the onset of ischemia leads to expulsion of fluid from the interstitium between bundles of myocytes into the tissue clefts increasing their size. The decrease in contraction during ischemia leads to narrower tissue clefts. Cellular swelling at the onset of and during ischemia is caused by volume shifts between intracellular and interstitial space. An increase in cellular volume during global ischemia and/or additional contraction reduce the interstitium within bundles of myocytes. Sufficient relaxation and/or interstitial edema enlarge the interstitium.
Conclusions:
Cellular and interstitial alterations seen at the onset and during the course of ischemia are dependent upon the method of cardiac arrest. Furthermore, a considerable mutual influence is exerted by the alterations in cellular and interstitial spaces.