Eptifibatide-induced thrombocytopenia and coronary bypass operation

Acute Severe Thrombocytopenia Occurring After Administration of Eptifibatide Postpones Emergent Coronary Artery Surgery

Introduction

Eptifibatide is a platelet glycoprotein IIb/IIIa (GP IIb/IIIa) receptor antagonist that inhibits fibrinogen binding to the activated GP IIb/IIIa site and prevents platelet-platelet interaction and clot formation. GP IIb/IIIa inhibitors improve outcome in patients undergoing percutaneous coronary intervention for acute coronary syndrome. Thrombocytopenia is a complication of GP IIb/IIIa inhibitors, but severe thrombocytopenia is unusual. Most reported cases of severe thrombocytopenia after eptifibatide occurred in patients with acute coronary syndrome. The authors describe a patient who developed acute profound thrombocytopenia after receiving eptifibatide before emergent coronary artery bypass graft surgery.

Case Presentation

A 67-year-old man with a normal platelet count (220 K/uL) developed atrial fibrillation, left bundle branch block, and respiratory insufficiency consistent with acute coronary syndrome two days after colectomy. He received eptifibatide during cardiac catheterization, where three-vessel coronary artery disease was encountered. Emergent coronary artery surgery was planned, but the platelet count before surgery was 2 K/uL. Eptifibatide was discontinued, surgery was postponed, and acute coronary syndrome was treated with intraaortic balloon counterpulsation.

Conclusions

The authors describe the second reported case of eptifibatide-induced severe thrombocytopenia associated with cardiac surgery. In this case, discontinuation of eptifibatide and transfusion of apheresis platelets increased the platelet count (137 K/uL) the following day, and the patient subsequently underwent successful coronary artery surgery using cardiopulmonary bypass.

Eptifibatide-induced thrombocytopenia and thrombosis in humans require FcgammaRIIa and the integrin beta3 cytoplasmic domain

Thrombocytopenia and thrombosis following treatment with the integrin alphaIIbbeta3 antagonist eptifibatide are rare complications caused by patient antibodies specific for ligand-occupied alphaIIbbeta3. Whether such antibodies induce platelet clearance by simple opsonization, by inducing mild platelet activation, or both is poorly understood. To gain insight into the mechanism by which eptifibatide-dependent antibodies initiate platelet clearance, we incubated normal human platelets with patient serum containing an alphaIIbbeta3-specific, eptifibatide-dependent antibody. We observed that in the presence of eptifibatide, patient IgG induced platelet secretion and aggregation as well as tyrosine phosphorylation of the integrin beta3 cytoplasmic domain, the platelet FcgammaRIIa Fc receptor, the protein-tyrosine kinase Syk, and phospholipase Cgamma2. Each activation event was inhibited by preincubation of the platelets with Fab fragments of the FcgammaRIIa-specific mAb IV.3 or with the Src family kinase inhibitor PP2. Patient serum plus eptifibatide did not, however, activate platelets from a patient with a variant form of Glanzmann thrombasthenia that expressed normal levels of FcgammaRIIa and the alphaIIbbeta3 complex but lacked most of the beta3 cytoplasmic domain. Taken together, these data suggest a novel mechanism whereby eptifibatide-dependent antibodies engage the integrin beta3 subunit such that FcgammaRIIa and its downstream signaling components become activated, resulting in thrombocytopenia and a predisposition to thrombosis.

Glycoprotein IIb/IIIa inhibitor-induced thrombocytopenia

Thrombocyte glycoprotein IIb/IIIa inhibitors prevent fibrinogen binding and thereby thrombocyte aggregation. The inhibition of thrombocyte activation at the damaged coronary plaque is the target of the new therapeutic strategies in treating acute coronary syndrome. This reduces the ischemic complications associated with the non-STelevation myocardial infarction (NSTEMI) and percutaneous coronary intervention (PCI). Thrombocytopenia is a known complication of glycoprotein (GP) IIb/IIIa inhibitors. Although, in general, GP IIb/IIIa inhibitor-induced thrombocytopenia is a harmless side effect which responds readily to thrombocyte transfusion, it can occasionally be a very serious complication associated with serious bleeding. In addition patients developing thrombocytopenia have unfavorable outcome (e.g., death, myocardial infarction, bypass surgery or additional PCI) in comparison to patients without thrombocytopenia. Advanced age (> 65 years), low BMI and a low initial thrombocyte count (<180,000/microl) are independent risk factors of thrombocytopenia. The risk of bleeding is higher with this form of thrombocytopenia not only due to the low thrombocyte count but also to the impaired function of the remaining thrombocytes. It is important to closely monitor platelet count during GP IIb/IIIa antagonist treatment. Platelet count monitoring two, six, twelve and 24 hour after starting the treatment reveals most cases of acute thrombocytopenia. Side effects can be avoided by the early discontinuation of the GP IIb/IIIa antagonist treatment. This article reviews the diagnosis and treatment of glycoprotein IIb/IIIa inhibitor-induced thrombocytopenia and summarizes the differential diagnosis from heparin-induced thrombocytopenia and laboratory-related pseudothrombocytopenia.

Eptifibatide-induced thrombocytopenia and thrombosis

Glycoprotein (GP) IIb/IIIa inhibitors have been shown to reduce morbidity and mortality in patients with acute coronary syndromes undergoing percutaneous coronary interventions (PCI). With their widespread use, there is a growing body of literature describing adverse outcomes, including severe thrombocytopenia. Here we report a case of a 75-year-old man who presented with an ST-elevation myocardial infarction, underwent primary PCI and stenting, and subsequently developed profound thrombocytopenia and thrombosis after eptifibatide administration. This report adds to the literature regarding eptifibatide-induced thrombocytopenia and also raises the possibility of a new syndrome of eptifibatide-induced thrombosis. A case is made to examine available databases for thrombosis after administration of eptifibatide and other GPIIb/IIIa inhibitors.

Clopidogrel (Plavix) and cardiac surgical patients: implications for platelet function monitoring and postoperative bleeding

The use of clopidogrel (Plavix), an inhibitor of adenosine diphosphate (ADP)-induced platelet aggregation, has been proven to reduce ischemic events in cardiovascular patients, but little information is available for optimal monitoring of platelet function in patients receiving the drug preoperatively. In the first part of the study we compared different testing modalities (thrombelastography (TEG), platelet aggregometry, and whole blood aggregation) to assess platelet ADP receptor inhibition. Because clopidogrel is a pro-drug, we used an in vitro model of ADP inhibition with 5'-p-fluorosulfonylbenzoyladenosine (FSBA). FSBA at final concentration of 80 microM completely inhibited platelet aggregation but had no effect on TEG maximum amplitude (MA). In the second part of the study, antiplatelet effects of clopidogrel were clinically assessed and correlated to postoperative bleeding in 18 coronary bypass surgery patients. Preoperative TEG results were normal or hypercoagulable in clopidogrel-treated patients, although platelet aggregation responses to ADP were inhibited. Clopidogrel-treated patients who underwent cardiopulmonary bypass had a high incidence (84.6%) of platelet transfusion therapy due to increased chest tube drainage. In conclusion, we have demonstrated that normal preoperative TEG-MA does not preclude clopidogrel-induced ADP receptor blockade; however, TEG can be a reliable monitor for CPB-induced platelet dysfunction related to GPIIb/IIIa. For monitoring clopidogrel, it is necessary to perform more specific platelet function tests (aggregometry or platelet count ratio) using ADP as an activator.

Eptifibatide-associated acute, profound thrombocytopenia

OBJECTIVE

To describe 3 cases of eptifibatide-associated acute, profound thrombocytopenia.

CASE SUMMARIES

A 40-year-old black female received eptifibatide 180-microg/kg double bolus followed by a continuous infusion of 2 microg/kg/min for percutaneous coronary intervention (PCI). The platelet count decreased from 308 x 10(3)/mm3 to 2 x10(3)/mm3 4 hours after initiation of eptifibatide. Eptifibatide was discontinued and platelets were transfused. The patient developed a hematoma and petechiae. A 67-year-old white female received the same dosage regimen of eptifibatide for PCI with no serious adverse effects, with the treatment repeated one month later. At that time, she developed chest and back pain, dyspnea, wheezing, and hypotension after the first bolus. Her platelet count decreased from 334 x10(3)/mm3 to 6 x10(3)/mm3 24 hours after initiation. Eptifibatide was discontinued and platelets were transfused. The patient died due to shock. A 72-year-old white male received eptifibatide 180-microg/kg double bolus followed by a continuous infusion of 2 microg/kg/min for acute coronary syndrome. His platelet count decreased from 189 x10(3)/mm3 to 17 x10(3)/mm3, and eptifibatide was discontinued. Eptifibatide was readministered with bivalirudin for PCI once the platelet count increased to 94 x10(3)/mm3. Sixteen hours later, the platelet count decreased to 1 x 10(3)/mm3. Eptifibatide was discontinued and platelets were transfused. The patient developed a hematoma.

DISCUSSION

Acute, profound thrombocytopenia is a rare complication of glycoprotein IIb/IIIa inhibitor therapy characterized by a precipitous decline in platelet count to <20 x10(3)/mm3 within 24 hours of therapy. An objective causality assessment revealed that the adverse drug event was probable in 2 cases and possible in the other.

CONCLUSIONS

Increasing use of the glycoprotein IIb/IIIa inhibitors and enhanced recognition of the potential for acute, profound thrombocytopenia reinforce the need for more vigilant monitoring and alternative management strategies.

In vivo platelet redistribution and acute transient thrombocytopenia after eptifibatide injection in baboons

BACKGROUND

The occurrence of thrombocytopenia has been reported during clinical eptifibatide (Integrilin) therapy, but the exact mechanism is not yet established to explain the varied duration and severity of thrombocytopenia associated with glycoprotein (GP) IIb/IIIa inhibitors. We assessed the redistribution of platelets in juvenile baboons during acute transient thrombocytopenia that was observed after eptifibatide injection.

METHODS

Eptifibatide was administered intravenously to eight baboons by infusion at 20 microg/kg/min or a bolus injection of 10 mg. Platelet distribution was measured with a gamma scintillation camera using 111In-labeled autologous platelets. Platelet function and GP IIb/IIIa receptor inhibition were evaluated using the Plateletworks system. The effects of pretreatment with abciximab (0.4 mg/kg) or human immunoglobulin concentrate (0.75 g/kg) were also investigated.

RESULTS

Eptifibatide, administered as an infusion or a bolus, caused transient thrombocytopenia with uptake of platelets predominantly by the liver. The recovery of platelet aggregation was associated with the re-entry of platelets from the liver into the systemic circulation. Pretreatment with either abciximab (0.4 mg/kg) or human intravenous immunoglobulin (IVIG, 0.75 g/kg) attenuated eptifibatide-induced thrombocytopenia and the hepatic uptake of radiolabeled platelets.

CONCLUSION

Acute thrombocytopenia after eptifibatide injection was caused by the transient redistribution of platelets to the liver. Attenuation of the decrease in platelet count and hepatic sequestration by abciximab and IVIG suggests that thrombocytopenia may have been caused by ligand-induced binding site antigen induction and recognition by the reticuloendothelial system.

A novel method to assess platelet inhibition by eptifibatide with thrombelastograph

We examined a novel method to detect platelet inhibition with thrombelastography (TEG). We hypothesized that this method would be suitable for monitoring the antiplatelet effects of eptifibatide (Integrilin). Whole blood from healthy volunteers was anticoagulated with 3.2% citrate or unfractionated heparin (7 IU/mL). For the platelet aggregation test, both citrate and heparinized samples were spiked with increasing concentrations of eptifibatide (0, 0.2, 0.4, 0.8, 1.6, and 4 microg/mL). Conventional kaolin TEG was performed with citrated samples, and batroxobin-modified TEG was performed with heparinized samples, which were spiked with eptifibatide at concentrations of 0, 0.4, 0.8, 1.6, 4, 8, and 24 microg/mL. Adenosine 5'-diphosphate-induced platelet aggregation was reduced to 6.4% +/- 2.9% (citrate) and 10.3% +/- 4.8% (heparin) with eptifibatide at the concentration of 4 mug/mL. The kaolin TEG showed a decrease in maximum amplitude (MA) only at the eptifibatide concentration of 24 mug/mL and no change in alpha angle, whereas with the batroxobin-based TEG, the difference in MA and alpha angle was observed at concentrations >/=0.8 microg/mL. Additionally, the time to achieve maximum MA was much shorter for batroxobin TEG than for kaolin TEG. We conclude that the batroxobin-modified TEG is a sensitive method that detects platelet inhibition induced by eptifibatide.