The effect of betamethasone on myocardial viability during cold cardioplegia in canine donor heart preservation.

This study examined the effect of betamethasone on myocardial viability of reperfused isolated canine hearts following a 6-h hypothermic cardioplegia. The dogs were divided into two groups: group I (n = 9) received nondepolarizing cardioplegia containing betamethasone 250 mg/l while group II (n = 7) was administered cardioplegia without betamethasone. The myocardial concentrations of calcium, ATP, ADP, total adenine nucleotide, cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) were identical in the two groups throughout the experiment. The coronary sinus plasma concentrations of MB fraction of creatine kinase (MB-CK), cAMP and cGMP after 2h of reperfusion were significantly lower in group I than in group II. The myocardial mitochondrial ultrastructure, as assessed by semiquantitative morphometry, was found to be significantly better preserved in group I than in group II at the end of both preservation and reperfusion. In addition, the left ventricular end-systolic pressure volume relation (ESPVR) showed a higher slope and lower intercept in group I than in group II. These results suggest that the addition of betamethasone to nondepolarizing cold cardioplegia enhances myocardial protection via membrane stabilization without affecting the adenine nucleotide metabolism.