IMPROVED PRESERVATION OF ENDOTHELIAL FUNCTION AT 4-DEGREES-C

Hypothermia combined with chemical cardioplegia is routinely used clinically for perioperative myocardial protection and for donor heart preservation. Profound hypothermia can have an adverse influence on post-preservation endothelial and myocardial functions. In this study, we investigated the effect of temperature on endothelial and myocardial functions following global cardiac ischaemia in the isolated rat heart. A 5-hydroxytryptamine (5-HT)-induced increase in coronary flow was used as a selective probe to assess endothelial function, while myocardial function was measured by a working rat heart model. After recording control observations for endothelial and myocardial functions, hearts were kept ischaemic for 30 or 60 min without cardioplegia (groups 1 and 2, respectively) and for 60, 90 or 120 min following a single infusion of St. Thomas' Hospital solution (groups 3, 4 and 5, respectively). In each group, hearts were kept ischaemic at 20-degrees-C or at 4-degrees-C (n = 12 in each group). Endothelial and myocardial functions were reevaluated and compared with control values. The percentage recovery of the 5-HT response was significantly better in all groups at 4-degrees-C compared with 20-degrees-C (group 1, 4-degrees-C, 93.2 -/+ 3.5, 20-degrees-C, 22.9 -/+ 8.4; group 2, 4-degrees-C, 52.5 -/+ 7.6, 20-degrees-C, 3.2 -/+ 3.1; group 3, 4-degrees-C, 90.7 -/+ 2.1, 20-degrees-C, 65.5 -/+ 2.9; group 4, 4-degrees-C, 56.6 -/+ 4.8, 20-degrees-C, - 0.3 -/+ 12.0; group 5, 4-degrees-C, 49.9 -/+ 6.2, 20-degrees-C, - 33.9 -/+ 6.2; p < 0.01 in group 4, p < 0.001 in all other groups). Similarly, myocardial function as assessed by percentage recovery of aortic flow, coronary flow, cardiac output and dP/dt was better preserved at 4-degrees-C compared with 20-degrees-C. We conclude that in the isolated rat heart both endothelial and myocardial functions are better preserved at 4-degrees-C compared with at 20-degrees-C.