Role of aspirin with thrombolytic therapy in acute myocardial infarction

Glycoprotein IIb/IIIa receptor antagonist (2S)-2-[(2-Naphthyl-sulfonyl)amino]-3-[[2-([4-(4-piperidinyl)-2-[2-(4-piperidinyl)ethyl] butanoyl]amino)acetyl]amino]propanoic acid dihydrochloride (CRL42796), in combination with aspirin and/or enoxaparin, prevents coronary artery rethrombosis after successful thrombolytic treatment by recombinant tissue plasminogen activator

The antithrombotic effect of the glycoprotein IIb/IIIa (GPIIb/IIIa) antagonist (2S)-2-[(2-naphthyl-sulfonyl)amino]-3-[[2-([4-(4-piperidinyl)-2-[2-(4-piperidinyl)ethyl] butanoyl]amino)acetyl]amino] propanoic acid dihydrochloride (CRL42796), administered alone, or in combination with aspirin, and/or enoxaparin, was examined in a canine left circumflex (LCX) coronary artery rethrombosis model. The electrolytic induction of arterial thrombosis was followed by intracoronary recombinant tissue plasminogen activator administration to achieve thrombolysis, and the adjunctive therapy was initiated 15 min earlier and maintained for 4 h. Thirty-five purpose-bred beagle dogs were randomized to receive one of the following treatments: group 0 (n = 6, placebo); group 1 (n = 6, CRL42796 15 microg/kg i.v. loading dose followed by 0.31 microg/kg/min i.v. infusion), group 2 (n = 6, aspirin 7 mg/kg, administered orally, at -47, -23, -17 h before entry into the experimental protocol); group 3 (n = 6, aspirin + CRL42796); group 4 (n = 6, aspirin + enoxaparin 0.6 microg/kg i.v. loading dose followed by 6.0 microg/kg/min i.v. infusion); and group 5 (n = 5, aspirin + CRL42796 + enoxaparin). The incidence of LCX reocclusion was as follows: group 0, 6/6; group 1, 3/6; group 2, 5/6; group 3, 2/6; group 4, 2/6; and group 5, 0/5. Aspirin pretreatment increased the tongue-bleeding time, whereas the addition of CRL42796 or enoxaparin did not prolong bleeding time to a further degree. However, the combination of the three drugs did increase bleeding time significantly, from 173.9 +/- 19.8 to 620.0 +/- 98.7 s. In conclusion, low-dose CRL42796 together with aspirin and enoxaparin prevented coronary artery rethrombosis, although bleeding time was prolonged. The latter may be of concern in the clinical use of combination therapy.

Evaluation of a GPIIb/IIIa antagonist YM337 in a primate model of middle cerebral artery thrombosis

We compared the antithrombotic effect of anti-GPIIb/IIIa antibody Fab fragment YM337 with that of a thromboxane A2 synthetase inhibitor, sodium ozagrel. With the monkeys under halothane anesthesia, the right middle cerebral artery was observed via a transorbital approach without cutting the dura mater. Photoillumination (wavelength 540 nm) was applied to the middle cerebral artery, and then rose bengal (20 mg kg(-1)) was administered intravenously. The experimental drugs were intravenously injected 15 min before rose bengal injection and followed by continuous infusion for 3 h after dye injection. The thrombotic occlusion induced by this photochemical reaction in monkey middle cerebral artery was reproducible. YM337 significantly prolonged the time to first occlusion and the total time of arterial patency during the 3-h observation period after dye injection. In contrast, sodium ozagrel had no significant effect. YM337 but not sodium ozagrel significantly inhibited ex vivo ADP-induced platelet aggregation. However, while sodium ozagrel significantly inhibited the thromboxane B2 generation accompanying arachidonic acid-induced platelet aggregation, YM337 had no effect on this variable. Neurological deficit in the YM337-treated animals was significantly milder than that in the control group. The area of infarct in the YM337 treatment animals was smaller than that in the control group. The novel selective GPIIb/IIIa antagonist YM337 was effective in ameliorating the decrease in patency of the middle cerebral artery and reducing the area of cerebral infarction in monkeys.

Chimeric 7E3 prevents carotid artery thrombosis in cynomolgus monkeys

BACKGROUND AND PURPOSE

We compared the current antithrombotic strategy of antiplatelet therapy with aspirin, and anticoagulant therapy with heparin, with a specific genetically engineered chimeric antibody (c7E3 Fab) directed against the human glycoprotein IIb/IIIa receptor in an animal model of arterial thrombosis.

METHODS

Anesthetized cynomolgus monkeys (Macaca fascicularis) were instrumented for monitoring of arterial blood pressure, heart rate, and carotid artery flow velocity. Animals were treated with saline (n = 6), aspirin (25 mg PO daily for 3 days; n = 6), heparin (100 U/kg i.v. plus infusion adjusted to maintain activated partial thromboplastin time at 2 to 3 times baseline; n = 6), aspirin plus heparin (as administered separately, n = 6), or c7E3 Fab (0.10 mg/kg i.v., n = 7; 0.15 mg/kg i.v., n = 6; 0.20 mg/kg i.v., n = 6; 0.25 mg/kg i.v., n = 6). Thrombus formation via anodal electrolytic stimulation (100 microA) to the intimal surface of the right carotid artery was initiated 15 minutes after drug administration and continued for 180 minutes. Electrolytic injury to the left carotid artery began 210 minutes after drug administration and continued for 180 minutes. Whole blood cell counts, glycoprotein IIb/IIIa receptor blockade, ex vivo platelet aggregation, template bleeding time, and activated partial thromboplastin time were assessed at various time points throughout the experimental protocol.

RESULTS

Hemodynamic and hematologic parameters were comparable among groups at baseline. Treatment with c7E3 Fab inhibited ex vivo platelet aggregation, increased bleeding time, decreased thrombus weight, and increased time to occlusion in a dose-dependent manner in both vessels. Treatment with aspirin, heparin, or the combination of aspirin plus heparin was ineffective for the prevention of carotid artery thrombosis in this model.

CONCLUSIONS

Inhibition of the platelet glycoprotein IIb/IIIa receptor with c7E3 Fab was found to be safe and effective for the prevention of primary thrombus formation, whereas treatment with either aspirin or heparin or the combination of the two agents failed to protect against occlusive thrombus formation in cynomolgus monkeys.

Blood conservation in cardiac surgery

We reviewed current blood conservation techniques and their use in cardiac surgery. Avoidance of aspirin preoperatively is an important blood conservation measure. Patients scheduled for an elective operation should participate in autologous predonation programs. With careful monitoring, patients with major coronary artery disease can safely donate blood preoperatively. Intraoperative processing of blood withdrawn before cardiopulmonary bypass provides autologous platelet-rich plasma for infusion after reversal of heparin sodium. Blood collected from the field during operation and blood remaining in the oxygenator after bypass can also be processed to yield washed and concentrated red blood cells for reinfusion. Randomized, prospective studies document that postoperative autotransfusion is both safe and effective in reducing homologous blood use. Aprotinin reduces plasma protein activation and platelet damage during bypass. The integration of available blood conservation techniques into a comprehensive program combined with careful consideration of the indications for transfusion may allow more patients to avoid transfusion entirely.