Platelet induced aggravation of acute ischaemia in an isolated rabbit heart model

In isolated coronary ligated rabbit hearts the effects of washed human platelets on the size of the epicardial ischaemic area and on recovery from ischaemia during 60 min of reperfusion was evaluated by endogenous NADH-surface-fluorescence photography. Infusion of washed human platelets to non-ischaemic control hearts produced a decrease in left ventricular pressure to 64(3)% of control (n = 4), no change in global coronary flow rate, no retention of platelets (recovery 108(9)%), and no alteration in basal NADH-fluorescence. When platelets were infused into coronary ligated hearts, however, the size of the epicardial ischaemic area was significantly enhanced to 127(8)% (n = 5) of control. Moreover, this increase in size was negatively correlated with the recovery of platelets in the coronary effluent: the lower the recovery rate the larger the ischaemic area (y = 253-1.44x, r = -0.855, n = 15, p less than 0.001). When platelet infusion was stopped after 30 min the enlargement of the ischaemic area seemed to be reversible. When the coronary ligature was released, however, and the ischaemic myocardium reperfused the recovery from ischaemia was retarded in the platelet treated hearts as shown by functional (left ventricular pressure and flow) and metabolic (NADH-fluorescence) indices. Thus it is directly shown for the first time in an isolated in vitro heart preparation that platelets aggravate myocardial ischaemia.