Myocardial intra- and extracellular calcium changes following cardioplegic cardiac arrest

To study the behavior of myocardial cellular calcium during the course of myocardial ischemia following cardiac arrest induced by the chemical cardioplegia, LK352, transmural biopsies were made from the apex of the left ventricle of nine patients undergoing electric cardiac surgery. The biopsies were made before the onset of extracorporeal circulation, at the end of ischemia, and after the discontinuation of cardiopulmonary bypass following reperfusion and cardiac resuscitation. Ultrastructural studies focused on the pattern of distribution in the interstitial space of a certain combination of elements forming microcrystals, together with a quantitative intracellular calcium assay, based on electron probe X-ray microanalysis, presented the following results: In the course of ischemia, a highly significant depletion of intracellular calcium was associated with the pooling of calcium in the interstitial space. An intracellular calcium assay following coronary reperfusion with systemic blood demonstrated intracellular calcium replenishment in association with the depletion of the calcium which had accumulated in the interstitial space during ischemia. The intracellular concentration of calcium after reperfusion approximated the control value. Based on our results, we consider the intracellular calcium depletion a mechanism which keeps the heart arrested in the diastole.