Effects of on pump surgery and warm blood versus cold cristalloid cardioplegia on myocardial behaviour and the intracellular calcium metabolism

Aim: Arrhythmias are a common complication and a source of morbidity after cardiac surgery. Several observations pointed out that calcium overload is an important factor in the initiation of postoperative arrhythmias. The present study was designed to investigate, whether differences of intracellular calcium [Ca 2+ i ] levels were present, when myocardium was analyzed before (group A) or after (group B+C) extracorporal circulation. It was further examined, whether these differences are dependent on the use of warm blood (group B) or cold crystalloid cardioplegia (group C). Methods: Myocardial trabeculae (right atrial appendage) were loaded with the calcium-binding fluorescence dye FURA-2/AM, and adjusted to the length with optimal isometric force output (optimal length, L max ) at constant electrical stimulation frequency (1Hz, amplitude 10% above threshold). Systolic [sCa i ] and diastolic [dCa i ] intracellular calcium concentrations were simultaneously monitored. Results: DCa i was significantly higher in B (p=0.028) and C (p=0.003) than in A. There was no difference in the Ca 2+ i between B and C (p=0.574). sCa i did not differ between any of the groups (p=0.749). Retardation of the time course of intracellular calcium transient appeared in B compared to A (75% rising slope point: p=0.028; 75% decreasing slope point: p=0.007), and compared to C (75% rising slope point: p=0.05). Fig. 1 dCa Conclusion: The data indicate that postoperative arrhythmias are related to the type of cardioplegia. Especially the retardation of the time course of the intracellular calcium transient in myocardium protected with blood cardioplegia indicates a less effective myocardial protection in this group.