title: Role of thromboelastography and rapid thromboelastography to assess the pharmacodynamic effects of vitamin K antagonists.
abstract: Thromboelastography (TEG) measures the effects of antithrombotic agents by assessing global functional clotting status by evaluating the viscoelastic properties of in vitro clot formation. Recently, rapid TEG (r-TEG), which uses tissue factor in addition to standard kaolin to accelerate activation of the clotting cascade, has been proposed to obtain more immediate results. The correlation between results of TEG or r-TEG with international normalized ratio (INR) in patients on vitamin K antagonist (VKA) therapy has not been explored and represents the aim of this study. Patients on chronic therapy with VKAs (n = 100) were included in an observational prospective pharmacodynamic study. The correlation between TEG parameters, in particular markers of thrombus generation [Reaction time (R), maximum rate of thrombus generation (MRTG), and time to maximum rate of thrombus generation (TMRTG)], and INR values as well as the concordance between these parameters and therapeutic INR ranges were evaluated. In addition, in a subgroup of subjects (n = 17), the correlation of r-TEG parameters with TEG parameters and INR values was also assessed. No correlation was found between INR and TEG parameters of thrombus generation, in particular between INR and R (r = 0.189, p = 0.06), MRTG (r = -0.027, p = 0.79), and TMRTG (r = 0.188, p = 0.06). Further, no concordance was found between these parameters and recommended INR ranges. Significant Spearman correlations were found between INR and activated clotting time (rS = 0.546, p < 0.001), r-R (rS = 0.572, p = 0.017), and r-TMRTG (rS = 0.510, p = 0.037), but not r-MRTG (rS = 0.131, p = 0.617). Results were obtained in 24 ± 6 versus 12 ± 4 min with TEG and r-TEG, respectively (p < 0.001). In patients on chronic VKA therapy, TEG is not a useful tool to evaluate VKA anticoagulant effect, compared with standard INR measurements. However, r-TEG parameters of thrombus generation correlate with INR levels, suggesting a possible role of this assay for measuring more expeditiously anticoagulant treatment effects.
authors.affiliation: University of Florida College of Medicine-Jacksonville, 655 West 8th Street, Jacksonville, FL, 32209, USA.
authors.forename: Francesco
authors.initials: F
authors.lastname: Franchi
authors.forename: Jafri Syed
authors.initials: JS
authors.lastname: Hammad
authors.forename: Fabiana
authors.initials: F
authors.lastname: Rollini
authors.forename: Antonio
authors.initials: A
authors.lastname: Tello-Montoliu
authors.forename: Ronakkumar
authors.initials: R
authors.lastname: Patel
authors.forename: Andrew
authors.initials: A
authors.lastname: Darlington
authors.forename: Dale F
authors.initials: DF
authors.lastname: Kraemer
authors.forename: Jung Rae
authors.initials: JR
authors.lastname: Cho
authors.forename: Christopher
authors.initials: C
authors.lastname: DeGroat
authors.forename: Mona
authors.initials: M
authors.lastname: Bhatti
authors.forename: Mohamad
authors.initials: M
authors.lastname: Taha
authors.forename: Dominick J
authors.initials: DJ
authors.lastname: Angiolillo
mesh_terms: D000328:Adult; D000368:Aged; D000925:Anticoagulants / Q000494:pharmacology*; D001777:Blood Coagulation / Q000187:drug effects* / Q000502:physiology; D005260:Female; D005343:Fibrinolytic Agents / Q000494:pharmacology; D006801:Humans; D019934:International Normalized Ratio / Q000379:methods; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D011446:Prospective Studies; D013916:Thrombelastography / Q000379:methods; D013997:Time Factors; D016896:Treatment Outcome; D014812:Vitamin K / Q000037:antagonists & inhibitors* / Q000097:blood
chemical_list: D000925:Anticoagulants; D005343:Fibrinolytic Agents; D014812:Vitamin K