Heparin-Induced Thrombocytopenia in Cardiac Surgery Patients

Abstract

Heparin-induced thrombocytopenia (HIT) is a prothrombotic disorder mediated by platelet-activating antibodies that target complexes of platelet factor 4 (PF4) and heparin. Because nearly all patients undergoing cardiopulmonary bypass (CPB) are exposed to heparin and experience a postoperative platelet count fall, it is not surprising that HIT is commonly suspected in this population. However, the incidence of HIT in cardiac surgery patients who receive intraoperative and postoperative unfractionated heparin is much lower than the incidence of suspected HIT, being approximately 1 to 2%. Clinical diagnosis may therefore be particularly challenging because of the need to distinguish the common platelet count fall associated with CPB and surgery from the much less common platelet count fall associated with HIT. A biphasic platelet count pattern is characteristic of HIT in this setting. Laboratory diagnosis is also difficult because of the high frequency of anti-PF4/heparin antibody seropositivity after cardiac surgery in patients without HIT. A unique aspect of management in the cardiac surgery setting is selecting an anticoagulant for intraoperative use in patients with a history of HIT who require cardiac surgery. In this article, we review the epidemiology, clinical diagnosis, and laboratory diagnosis of HIT in cardiac surgery patients and present a conceptual framework for selecting intraoperative anticoagulation in patients with a history of HIT.

A Case Report of Heparin-Induced Thrombocytopenia in a Patient One Month after Coronary Artery Bypass Graft Surgery in the Era of Coronavirus Disease 2019

“…The optimal diagnosis of HIT based on both clinical parameters and functional assays but laboratory examination is reported as time-consuming and time is critical for immediate intervention to avoid morbidity and even mortality of HIT (9). In our case, we could not con rm the clinical diagnosis of HIT functional assays due to the limitations in our hospital and this might raise suspicions about a proper diagnosis.…”

“…But we believed that the increment of thrombocyte count just after the cessation of all heparin sources reinforced the diagnosis. Also, Pishko et al (9) reported that immune assay was (+) approximately 50% of patients after cardiac surgery while the clinical HIT was seen only in 1-2% of cases. So there was a risk of overdiagnosis with immune assays and rigorous clinical assessment was advised.…”

“…Generally, the Warkentin 4 T's score which consists of the degree of reduction in thrombocyte count, thrombotic incident or sequelae, timing, and the exclusion of another reason for thrombocytopenia, is used for the clinical diagnosis of HIT (8). The incidence of HIT was reported between 0.1% and 5.0% in general population and as 1 to 2% after cardiac surgery in which the patients received UFH intraoperatively and postoperatively for thromboprophylaxis (9). Yet in case of infection (like or major surgery, negatively charged bacterial nucleic acids, and hypersulfated chondroitin could induce spontaneous HIT, in the absence of proximate heparin exposure (2).…”

Antithrombotic therapy management of adult and pediatric cardiac surgery patients

“…Limiting exposure to UFH thromboprophylaxis has been shown to decrease the incidence of HIT . Diagnosis of HIT after cardiac surgery is challenging because thrombocytopenia after CPB is common and 22–52% of patients will have circulating anti‐PF4 heparin antibodies . Differences in patient inclusion and laboratory techniques have resulted in variable estimates of HIT frequency.…”

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“…14 Finally, the difficult task of anticoagulation in patients with previous HIT requiring future cardiac surgery is addressed. 14 In surgical patients, the focus has been on pharmacological prophylaxis to reduce the intra-and postoperative thromboembolic risk. Nonetheless, increasing attention is being paid to other modalities such as ischemic conditioning, which has been shown to attenuate ischemia-reperfusion injury.…”