MYOCARDIAL FUNCTIONAL PRESERVATION DURING ISCHEMIA - INFLUENCE OF BETA-BLOCKING-AGENTS

To determine whether prior acute Beta blockade protects the heart agai nst the deleterious effects of normothermic low flow global ischemia o n myocardial function, aortic pressure, developed pressure, dP/dt(max) and end diastolic pressure were monitored in isolated perfused rabbit hearts prior to, during and following 30 and 60 min ischemia, during which either Krebs-Henseleit (control) or Beta blocking agents, Bevant olol (cardioselective) or Propranolol (non-selective) were perfused th rough the heart. Control hearts made ischemic for 30 min and then repe rfused had significantly elevated end diastolic (p <.01) and aortic pr essures (p <.01) and reduced developed pressure relative to baseline ( p <.05). Hearts treated with Bevantolol or Propranolol (3 x 10(-5) m/l ) 5 min prior to and during 30 min ischemia recovered preischemic deve loped pressure and dP/dt(max) (p>0.05), while end diastolic pressure w as elevated (p <.01, p <.05 respectively). Aortic pressure was unchang ed relative to baseline (p <.05). Comparison of indices from hearts un der Beta blockade with controls showed that following 30 min ischemia and recovery, the Bevantolol treated group had reduced aortic pressure (p <.01) and end diastolic pressure (p <.05) and increased percent de veloped pressure and percent dP/dt(max) (p <.001) relative to control. In the propranolol treated group, end diastolic pressure was reduced and percent developed pressure (p <.01) and percent dP/dt(max) (p<.001 ) were increased relative to unblocked hearts. Following 60 min ischem ia and 30 min reperfusion, reduction in all functional indices occurre d, however dP/dt(max) was unchanged from baseline in the Propranolol a nd Bevantolol treated groups. Comparison between groups showed that th e Bevantolol treated group had significantly better dP/dt(max) and dev eloped pressure (p <.05), whereas the Propranolol group shows no signi ficant difference from baseline (p >.05) (K-H). We conclude that follo wing short periods of ischemia, Beta blockade protects the heart from deleterious function effects of ischemia but that the protective effec t is diminished in Bevantolol relative to Propranolol treatments follo wing prolonged ischemia. The data indicates that the beneficial effect s of Beta blockade in reducing ischemic induced damage occurs early du ring conditions of ischemia such as would be present in the setting of acute myocardial infarction.