Mechanical circulatory support is associated with loss of platelet receptors glycoprotein Ibα and glycoprotein VI

Essentials Relationship of acquired von Willebrand disease (VWD) and platelet dysfunction is explored. Patients with ventricular assist devices and on extracorporeal membrane oxygenation are investigated. Acquired VWD and platelet receptor shedding is demonstrated in the majority of patients. Loss of platelet adhesion receptors glycoprotein (GP) Ibα and GPVI may increase bleeding risk.

SUMMARY

Background Ventricular assist devices (VADs) and extracorporeal membrane oxygenation (ECMO) are associated with bleeding that is not fully explained by anticoagulant or antiplatelet use. Exposure of platelets to elevated shear in vitro leads to increased shedding. Objectives To investigate whether loss of platelet receptors occurs in vivo, and the relationship with acquired von Willebrand syndrome (AVWS). Methods Platelet counts, coagulation tests and von Willebrand factor (VWF) analyses were performed on samples from 21 continuous flow VAD (CF-VAD), 20 ECMO, 12 heart failure and seven aortic stenosis patients. Levels of platelet receptors were measured by flow cytometry or ELISA. Results The loss of high molecular weight VWF multimers was observed in 18 of 19 CF-VAD and 14 of 20 ECMO patients, consistent with AVWS. Platelet receptor shedding was demonstrated by elevated soluble glycoprotein (GP) VI levels in plasma and significantly reduced surface GPIbα and GPVI levels in CF-VAD and ECMO patients as compared with healthy donors. Platelet receptor levels were also significantly reduced in heart failure patients. Conclusions These data link AVWS and increased platelet receptor shedding in patients with CF-VADs or ECMO for the first time. Loss of the platelet surface receptors GPIbα and GPVI in heart failure, CF-VAD and ECMO patients may contribute to ablated platelet adhesion/activation, and limit thrombus formation under high/pathologic shear conditions.

Laboratory testing, diagnosis, and management of von Willebrand disease. Current practice in Australasia. RCPA Quality Assurance Program in Haematology Scientific Haemostasis Advisory Panel

We report an evaluation of current laboratory and clinical practice for the diagnosis and management of von Willebrand disease (VWD) for a wide geographic area including Australia, New Zealand, and parts of Southeast Asia. This assessment has been undertaken in conjunction with the RCPA Quality Assurance Program (QAP) in Haematology. This external QAP currently comprises around 550 participating laboratories, of which some 450 perform coagulation testing, and from which 32 laboratories were identified to be actively involved in testing for VWD. These laboratories were targeted and their current laboratory and clinical practice evaluated by using various questionnaires. Our overall findings indicate a wide variation in laboratory test practice for VWD-based investigations. There was considerable variation among laboratories in the tests and test methods used, the control and calibration material used, the reported test reference intervals and units used, and the composite test panels used to diagnose VWD. However, substantial consensus in the clinical evaluation process, as undertaken by hematologists, also was identified. Despite the observed variations, most laboratory professionals seemed to understand the complexities involved in the diagnosis and subclassification of VWD, and the laboratories can provide an effective diagnostic service.