title: Platelet dysfunction in outpatients with left ventricular assist devices.
abstract: BACKGROUND
  Thromboembolic and bleeding complications in outpatients with a left ventricular assist device are common and can be detrimental. A meticulous balance between anticoagulant and procoagulant factors is therefore crucial. However, in contrast to routinely performed plasmatic coagulation tests, platelet function is hardly ever monitored although recent reports indicated platelet dysfunction. We therefore differentially evaluated platelet function with four commonly used point-of-care devices.
  
  
  METHODS
  In a cross-sectional design platelet function was assessed in 12 outpatients and 12 healthy matched volunteers using thrombelastography platelet mapping, thromboelastometry, platelet function analyzer, and a new whole blood aggregometer (Multiplate).
  
  
  RESULTS
  Phenprocoumon produced an international normalized ratio of 3.5. It was associated with a twofold prolongation in the thromboelastometry clotting time (p < 0.001). Platelet function under high shear was severely compromised: collagen adenosine diphosphate closure times were 2.5-fold longer in patients than in volunteers (p < 0.001), and 50% of patients had maximal collagen adenosine diphosphate closure time values. Although antigen levels of von Willebrand factor were 80% higher in patients (p < 0.001), von Willebrand factor-ristocetin was subnormal in 5 of 12 patients. Ristocetin-induced aggregation was also threefold higher in volunteers (p < 0.001), indicating an additional functional defect of platelets affecting the glycoprotein Ib-von Willebrand factor axis. The von Willebrand factor multimer pattern in patients also appeared abnormal.
  
  
  CONCLUSIONS
  Multimodal antiplatelet monitoring showed markedly impaired platelet function in patients with a left ventricular assist device. Platelet dysfunction under high shear rates and abnormal ristocetin-induced aggregation is only partly attributable to low von Willebrand factor activity. These findings resemble the acquired von Willebrand syndrome that is associated with microaggregate formation and enhanced bleeding.
authors.affiliation: Division of Cardiothoracic and Vascular Anesthesia and Intensive Care, Medical University of Vienna, Vienna, Austria. barbara.steinlechner@meduniwien.ac.at
authors.forename: Barbara
authors.initials: B
authors.lastname: Steinlechner
authors.forename: Martin
authors.initials: M
authors.lastname: Dworschak
authors.forename: Beatrice
authors.initials: B
authors.lastname: Birkenberg
authors.forename: Monika
authors.initials: M
authors.lastname: Duris
authors.forename: Petra
authors.initials: P
authors.lastname: Zeidler
authors.forename: Henrik
authors.initials: H
authors.lastname: Fischer
authors.forename: Ljubisa
authors.initials: L
authors.lastname: Milosevic
authors.forename: Georg
authors.initials: G
authors.lastname: Wieselthaler
authors.forename: Ernst
authors.initials: E
authors.lastname: Wolner
authors.forename: Peter
authors.initials: P
authors.lastname: Quehenberger
authors.forename: Bernd
authors.initials: B
authors.lastname: Jilma
mesh_terms: D000328:Adult; D000553:Ambulatory Care; D001780:Blood Coagulation Tests; D001791:Blood Platelet Disorders / Q000175:diagnosis* / Q000453:epidemiology / Q000209:etiology*; D003430:Cross-Sectional Studies; D005260:Female; D005500:Follow-Up Studies; D006353:Heart-Assist Devices / Q000009:adverse effects*; D006801:Humans; D015994:Incidence; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D010045:Outpatients / Q000706:statistics & numerical data; D010976:Platelet Count; D010979:Platelet Function Tests; D019106:Postoperative Hemorrhage / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology*; D011336:Probability; D012016:Reference Values; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D013916:Thrombelastography / Q000379:methods; D014914:Whole Blood Coagulation Time; D014841:von Willebrand Factor / Q000378:metabolism*
chemical_list: D014841:von Willebrand Factor