[Platelet activation in the early phases of acute myocardial infarction].
Myocardial infarction and thrombolysis are proven to be associated with platelet activation. However, the time relationship of platelet activation with the onset of symptoms and with thrombolysis, and the response to aspirin are not well defined. In this study we measured platelet activity in the early phase of myocardial infarction treated with either streptokinase or recombinant tissue-type plasminogen activator (rt-PA) and evaluated whether and to what extent it may be counteracted by aspirin. Fourty-one patients (mean age 57 +/- 6 years) received thrombolytic therapy after coronary occlusion: 1.5 million units of streptokinase (Group 1; 21 patients) or 100 mg of rt-PA (Group 2; 20 patients). Ten randomly selected patients in either group were given 500 mg aspirin i.v. prior to infusion of the thrombolytic compound and, then, 325 mg/die of aspirin orally. Beta-thromboglobulin (BTG), a marker of platelet activity, was determined at admission, after thrombolysis and in the subsequent 48 hours. At admission, BTG plasma levels averaged 125 +/- 31 IU/ml in Group 1 and 134 +/- 35 IU/ml in Group 2 (NS). Thrombolysis produced a similar increase in platelet activity in both groups, and maximal values were reached at the third hour (196 +/- 43 IU/ml in Group 1 and 192 +/- 39 in Group 2, p < 0.001 vs baseline and NS between groups). Levels of BTG were higher in streptokinase-treated group starting from 24 hours (p < 0.05). Differences in BTG levels between aspirin-treated and aspirin-untreated patients became significant at 48 hours after thrombolysis in both groups. An inverse correlation was found between time elapsed from onset of symptoms and BTG value on admission (r = -0.86, p < 0.001); in patients admitted within 2 hours after the beginning of symptoms, and having the higher BTG levels, thrombolysis did not induce a significant increase in platelet activity; this, on the contrary, was observed in patients admitted later. Platelet activation is greater early after myocardial infarction and is differently influenced by thrombolytic treatment, depending on the delay of the patient's admission. Streptokinase and rt-PA induce a similar increase in platelet activity which is more persistent after streptokinase; cycloxygenase inhibition with aspirin seems to influence platelet activity only starting from the second day.
Salvioni
A
A
Istituto di Cardiologia, Università degli Studi, Centro di Studio per le Ricerche Cardiovascolari del CNR, IRCCS, Milano.
Giraldi
F
F
Assanelli
E
E
Lauri
G
G
Grazi
M
M
Pardea
S
S
Marenzi
G
G
D000328:Adult; D000368:Aged; D001241:Aspirin / Q000494:pharmacology / Q000627:therapeutic use; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology*; D003627:Data Interpretation, Statistical; D005260:Female; D005343:Fibrinolytic Agents / Q000494:pharmacology / Q000627:therapeutic use; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000097:blood / Q000188:drug therapy*; D010960:Plasminogen Activators / Q000494:pharmacology / Q000627:therapeutic use; D013300:Streptokinase / Q000494:pharmacology / Q000627:therapeutic use; D015912:Thrombolytic Therapy; D013997:Time Factors; D010959:Tissue Plasminogen Activator / Q000494:pharmacology / Q000627:therapeutic use; D001620:beta-Thromboglobulin / Q000032:analysis*
D005343:Fibrinolytic Agents; D001620:beta-Thromboglobulin; D013300:Streptokinase; D010960:Plasminogen Activators; D010959:Tissue Plasminogen Activator; D001241:Aspirin