ASPIRIN DOES NOT PREVENT THE ATTENUATION OF MYOCARDIAL STUNNING BY THE ACE-INHIBITOR RAMIPRILAT

The attenuation of myocardial stunning by the ACE inhibitor ramiprilat is prevented by cyclooxygenase inhibition with indomethacin. In the c linical setting of ischemia/reperfusion, however, the cyclooxygenase i nhibitor aspirin is widely used to prevent platelet aggregation. The p resent study therefore investigated whether aspirin, in dosages suffic ient to inhibit platelet aggregation, interferes with the attenuation of myocardial stunning by ramiprilat. Fifteen dogs received either 1 m g/(kg . day) (group I, n = 7) or 10 mg/(kg . day) (group II, n = 8) as pirin orally for 1 week. Both dosages of aspirin inhibited ADP-induced platelet aggregation. The dogs were then anesthetized, thoracotomized and subjected to 15 min LCx-occlusion and 4 h reperfusion. Before LCx -occlusion, groups I and II received ramiprilat (20 mu g/kg, i.v.). Sy stemic hemodynamics, posterior myocardial blood flow (PMBF, colored mi crospheres) and wall thickening (PWT, sonomicrometry) of these groups were measured and data compared to placebo-controls (group III, n = 11 ) and dogs receiving only ramiprilat before LCx-occlusion (group IV, n = 11). Four dogs received 10 mg/(kg . day) aspirin without ramiprilat (group V). Mean aortic pressure was kept constant by an intra-aortic balloon, and heart rate did not change, PMBF was not different between the five groups. Under control conditions and during myocardial ische mia, PWT was also not different. At 4 h reperfusion, PWT was still dep ressed in group III (-5 +/- 20% of control) and group V (-23 +/- 6%), whereas PWT recovered to the same extent in groups I (46 +/- 23%), II (50 +/- 15%) and IV (58 +/- 18%) (all P<0.05 v groups III and V). The attenuation of myocardial stunning by the ACE inhibitor ramiprilat is not prevented by aspirin in dosages which are nevertheless sufficient to inhibit platelet aggregation. (C) 1996 Academic Press Limited