Isosorbide dinitrate inhibits platelet adhesion and aggregation in nonthrombolyzed patients with acute myocardial infarction

Background: Apart from their vasodilatatory properties, nitrates have been shown to inhibit platelet aggregation. The effects of nitrates on platelet adhesion have not been studied. Nonselected patients with acute myocardial infarction (AMI) have been suggested to gain no benefit from administration of nitrates. However, the importance of nitrates may be greater in a subgr oup of nonthrombolyzed patients with AMI. Hypothesis: Isosorbide dinitrate (ISDN) decreases platelet adhesion and agg reation in nonthrombolyzed patients with AMI. Methods: Consecutive 48 men with AMI, not eligible for thrombolytic therapy because of late presentation (> 12 h), were prospectively randomized 2:1 t o double-blind ISDN (mean dose 2.4 +/- 0.9 mg/h) (n = 33) or placebo (0.9% sodium chloride) (n = 15) infusion. All patients received aspirin. Blood sa mples were taken at baseline (no study medication) and 3 h into ISDN or pla cebo infusion. Platelet adhesion to collagen was measured in the ethylene d iamine tetraacetic acid (EDTA)-platelet rich plasma by recording changes in light transmission with an optical aggregometer. Platelet aggregation was measured using the Born's method. Results: Isosorbide dinitrate significantly decreased both platelet adhesio n and aggregation. No effect was seen in the placebo group. Conclusions: in patients with AMI who do not receive thrombolytic therapy, ISDN effectively inhibits platelet adhesion and aggregation. These effects of nitrates may be of therapeutic and prognostic significance in this group of patients.