Successful use of bivalirudin for cardiopulmonary bypass in a patient with heparin-induced thrombocytopenia

Bivalirudin in acute coronary syndromes

INTRODUCTION

Bivalirudin, a bivalent direct thrombin inhibitor, has been developed to reduce bleeding without any trade-off in thrombotic events in acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI).

AREAS COVERED

Despite showing a superior safety profile compared with unfractionated heparin (UFH), bivalirudin is not considered the anticoagulant of choice in ACS patients undergoing PCI, mainly because of an increased rate of acute stent thrombosis (ST) shown by several randomized controlled trials (RCTs), in addition to limited availability in certain countries and increased costs. However, RCTs on bivalirudin have been characterized by several confounding factors hindering the interpretation of its safety and efficacy compared with UFH among the spectrum of ACS patients. Furthermore, a significant body of evidence has demonstrated that the risk of acute ST can be mitigated by a full-dose infusion regimen following PCI, without compromising the favorable safety profile compared to UFH.

EXPERT OPINION

In light of the increased understanding of the prognostic relevance of bleeding events and the excellent safety profile of bivalirudin, recent trial evidence may allow for this anticoagulant agent to reemerge and have a more prominent role in the management of ACS patients undergoing PCI.

Bivalirudin during percutaneous coronary intervention in acute coronary syndromes

INTRODUCTION

Anticoagulant therapy is critical to prevent ischemic recurrences and complications in acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI). Unfractionated heparin (UFH), an injectable anticoagulant has several limitations: lack of predictability of its biological efficacy, platelets activation, heparin-induced thrombopenia and bleedings. Bivalirudin, a synthetic direct thrombin inhibitor has biological properties that promised better clinical outcome in ACS patients undergoing PCI.

AREAS COVERED

The present review aimed to summarize two decades of randomized clinical trials that compared bivalirudin to UFH in ACS patients treated with PCI. Early trials highlighted a reduction of bleedings with bivalirudin compared to UFH in combination with glycoprotein inhibitors (GPI). Recent studies questioned this reduction given that GPI are less and less used during PCI. Further, trials raised concerns about the risk of stent thrombosis in patients treated with bivalirudin. In light of this data, bivalirudin has been downgraded in international guidelines and appears as a second line anticoagulant agent after UFH.

EXPERT OPINION

The highly questioned reduction of bleedings under bivalirudin and the potential risk of stent thrombosis are unwarranted. Based on clinical trials, UFH has no equivalent in terms of anticoagulation in ACS patients undergoing PCI.

Anticoagulation with bivalirudin during deep hypothermic circulatory arrest in a patient with heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia is a well-recognized complication of anticoagulation with heparin. We present the case of a patient with recent heparin-induced thrombocytopenia who subsequently needed surgery on an emergency basis for acute type A aortic dissection. This article reports the successful use of bivalirudin, a direct thrombin inhibitor, as an alternative to heparin throughout cardiopulmonary bypass and deep hypothermic circulatory arrest. We contend that bivalirudin is a safe alternative to heparin when performing surgery for aortic dissection and should be considered as an option for use in patients who present with heparin-induced thrombocytopenia.

Antiphospholipid syndrome; its implication in cardiovascular diseases: a review

Antiphospholipid syndrome (APLS) is a rare syndrome mainly characterized by several hyper-coagulable complications and therefore, implicated in the operated cardiac surgery patient. APLS comprises clinical features such as arterial or venous thromboses, valve disease, coronary artery disease, intracardiac thrombus formation, pulmonary hypertension and dilated cardiomyopathy. The most commonly affected valve is the mitral, followed by the aortic and tricuspid valve. For APLS diagnosis essential is the detection of so-called antiphospholipid antibodies (aPL) as anticardiolipin antibodies (aCL) or lupus anticoagulant (LA). Minor alterations in the anticoagulation, infection, and surgical stress may trigger widespread thrombosis. The incidence of thrombosis is highest during the following perioperative periods: preoperatively during the withdrawal of warfarin, postoperatively during the period of hypercoagulability despite warfarin or heparin therapy, or postoperatively before adequate anticoagulation achievement. Cardiac valvular pathology includes irregular thickening of the valve leaflets due to deposition of immune complexes that may lead to vegetations and valve dysfunction; a significant risk factor for stroke. Patients with APLS are at increased risk for thrombosis and adequate anticoagulation is of vital importance during cardiopulmonary bypass (CPB). A successful outcome requires multidisciplinary management in order to prevent thrombotic or bleeding complications and to manage perioperative anticoagulation. More work and reporting on anticoagulation management and adjuvant therapy in patients with APLS during extracorporeal circulation are necessary.

Bivalirudin for patients with heparin-induced thrombocytopenia undergoing cardiovascular surgery

OBJECTIVE

To evaluate the use of bivalirudin in patients with heparin-induced thrombocytopenia (HIT) undergoing cardiovascular surgery.

DATA SOURCES

Relevant information was identified through a search of MEDLINE (1966-April 2008), International Pharmaceutical Abstracts (1960-April 2008), and Cochrane Databases (publications archived until April 2008) using the terms bivalirudin, heparin-induced thrombocytopenia, and cardiovascular surgery.

STUDY SELECTION AND DATA EXTRACTION

Prospective and retrospective studies, case reports, and case series in adults were eligible for inclusion if bivalirudin had been used in a patient with known HIT undergoing any cardiovascular surgical procedure other than percutaneous coronary intervention.

DATA SYNTHESIS

Two small, open-label, multicenter clinical trials were identified that evaluated treatment with bivalirudin in patients with HIT undergoing coronary artery bypass graft surgery. One looked at on-pump cardiopulmonary bypass (CPB), while the other looked at off-pump CPB. Procedural success was achieved at day 7 in 94% (n = 46) of patients in the on-pump CPB study and in 92% (n = 47) of patients in the off-pump CPB study. Dosing strategies varied between the 2 trials, with the on-pump study using a 1-mg/kg bivalirudin bolus followed by a 2.5-mg/kg/h infusion; the off-pump study used a 0.75-mg/kg bolus followed by a 1.75-mg/kg/h infusion. In addition, 10 case reports met the criteria to be included in the review and are summarized. In these cases, procedural success was reported using various bivalirudin doses in valve repair and replacement, right ventricular assist device implantation, and heart transplantation.

CONCLUSIONS

Growing data demonstrate procedural success with bivalirudin in patients with HIT undergoing cardiovascular surgery. However, bivalirudin dosing and goal-activated clotting times varied between the studies and case reports. Bivalirudin represents a viable alternative to heparin in patients with HIT undergoing cardiovascular surgery; however, further trials are warranted to identify optimal dosing and monitoring parameters.

Heparin-Induced Thrombocytopenia: Treatment Options and Special Considerations

Heparin-induced thrombocytopenia (HIT) is an immune-mediated adverse effect that typically manifests several days after the start of heparin therapy, although both rapid- and delayed-onset HIT have been described. Its most serious complication is thrombosis. Although not all patients develop thrombosis, it can be life threatening. The risk of developing HIT is related to many factors, including the type of heparin product administered, route of administration, duration of therapy, patient population, and previous exposure to heparin. The diagnosis of HIT is typically based on clinical presentation, exposure to heparin, and presence of thrombocytopenia with or without thrombosis. Antigen and activation laboratory assays are available to support the diagnosis of HIT. However, because of the limited sensitivity and specificity of these assays, bedside probability scales for HIT were developed. When HIT is suspected, prompt cessation of all heparin therapy is necessary, along with initiation of alternative anticoagulant therapy. Two direct thrombin inhibitors--argatroban and lepirudin--are approved for the management of HIT in the United States, and bivalirudin is approved for use in patients with HIT who are undergoing percutaneous coronary intervention. Other agents, although not approved to manage HIT, have also been used; however, their role in therapy requires further evaluation. A comprehensive HIT management strategy involves the evaluation of numerous factors. Many patients, including those undergoing coronary artery bypass surgery, those with acute coronary syndromes, those with hepatic or renal insufficiency, and children, require special attention. Clinicians must become familiar with the available information on this serious adverse effect and its treatment so that optimum patient management strategies may be formulated.

Deep Hypothermic Circulatory Arrest and Bivalirudin Use in a Patient With Heparin-Induced Thrombocytopenia and Antiphospholipid Syndrome

BACKGROUND

Patients with heparin-induced thrombocytopenia II (HIT II) need an alternative nonheparin-based method of anticoagulation for cardiopulmonary bypass (CPB) to prevent thrombosis and thrombosis related complications.

METHODS

Bivalirudin was used during CPB and deep hypothermic circulatory arrest (DHCA) for resection of multiple right atrial masses in a patient with HIT II and antiphospholipid antibodies syndrome (APS). Anticoagulation was monitored with the activated clotting time (ACT) and a target ACT of 450 seconds or greater was maintained.

RESULTS

Surgical removal of multiple right atrial masses was successful and there was no evidence of thromboembolic events. Clot was noticed in the cardiotomy and venous reservoir after CPB was discontinued and the system flushed. The postoperative course was uneventful.

CONCLUSIONS

Anticoagulation was successfully managed with bivalirudin, a new short-acting, and direct thrombin inhibitor. Further studies are necessary to evaluate the safety of bivalirudin during DHCA.

Successful use of bivalirudin for cardiac transplantation in a child with heparin-induced thrombocytopenia

Bivalirudin, a direct thrombin inhibitor, has recently emerged as a promising option for anti-coagulation during cardiopulmonary bypass in patients who cannot receive heparin. There is limited experience with the use of bivalirudin in children. We present the case of a child with heparin-induced thrombocytopenia with thrombosis (HIT Type II) who underwent successful orthotopic cardiac transplantation using bivalirudin as the primary anti-coagulant for cardiopulmonary bypass.

Clinical presentation and laboratory diagnosis of heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) type II is an immune mediated reaction in which pathologic antibodies develop to a complex composed of heparin and the platelet-derived alpha granule protein, platelet factor 4 (PF4). HIT must be recognized quickly so as to eliminate all heparin exposure from a patient's clinical care. Thrombosis (HIT) may accompany thrombocytopenia resulting in limb and life-threatening complications. Despite a higher incidence of subclinically detectable heparin-PF4 antibody formation in the cardiac care setting, the development of the full clinicopathologic syndrome occurs in approximately 2% to 3% of patients, similar to the incidence in other clinical scenarios.

Bleeding in Cardiac Surgery: Its Prevention and Treatment—an Evidence-Based Review

Expected and unexpected bleeding occur frequently in patients undergoing cardiac surgery. Bleeding after cardiac surgery can be broadly divided into two groups: surgical (unrecognized bleeding vessel, anastomosis, or other suture line) or nonsurgical bleeding (caused by coagulopathy). Factors influencing both surgical and nonsurgical bleeding can be further broken down into those occurring preoperatively and those that occur intraoperatively and postoperatively. A thorough understanding of these factors is necessary to reduce bleeding. This is a desirable clinical goal, because excessive bleeding is associated with adverse outcomes.

Diagnosis and management of heparin-induced thrombocytopenia

Heparin use is ubiquitous, wherein 1 to 5% of patients exposed to standard unfractionated heparin develop thrombocytopenia due to antibodies to a complex of heparin and platelet factor 4. Classic features include onset of thrombocytopenia after 5 to 10 days of ongoing heparin exposure, a 50% fall in the platelet count from baseline, resolution of the thrombocytopenia 5 to 10 days after cessation of heparin and a high risk of thrombosis noted in 30 to 75% of patients with heparin-induced thrombocytopenia (HIT) in terms of every-other-day platelet-count monitoring in patients on standard unfractionated heparin. And those patients developing thrombocytopenia necessitate an accurate, readily accessible diagnostic test for HIT. Diagnosis has been recently facilitated by the development of an enzyme-linked immunosorbent assay (ELISA) test for the heparin-P4 antibody complex, although this test carries a relatively low specificity. Widespread use of the ELISA demonstrates a relatively high prevalence of the antibody in patients exposed to heparin in certain settings, such as cardiopulmonary bypass, wherein a quarter of patients have a positive ELISA of unclear significance. Once HIT is diagnosed, the high risk of thrombosis necessitates empiric anticoagulation with an antithrombin such as argatroban or lepirudin, or the heparinoid danaparoid. Additional agents under further study include the antithrombin bivalirudin and the pentasaccharide fondaparinux. Future issues in HIT include increasing awareness for HIT, improving the specificity of HIT testing and the development of new anticoagulants for HIT that will enable out-patient management.

An Update on the Diagnosis, Complications, and Treatment of Heparin-Induced Thrombocytopenia

This continuing feature will update readers on recent developments in cardiovascular pharmacotherapy. Cardiovascular disease remains the number one killer in the US, and more clinical outcome trials have been conducted in cardiology than in any other field of medicine. Given this rapidly expanding knowledge base, pharmacists can have a significant impact on prevention and treatment — if they keep current with developments in drug therapy.