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Reply To: Same Same but Different: Viscoelastic Hemostatic Assays in Cardiac Surgery

Published:August 26, 2021DOI:https://doi.org/10.1053/j.jvca.2021.08.039
      WE READ with interest the editorial by Bolliger et al. accompanying our publication comparing two different viscoelastic hemostatic assays.
      • Bolliger D
      • Kamber F
      • Mauermann E.
      Same same but different: Viscoelastic hemostatic assays in cardiac surgery.
      ,
      • DeAnda A
      • Levy G
      • Kinsky M
      • et al.
      Comparison of the Quantra QPlus System with thromboelastography in cardiac surgery.
      We applaud the authors’ efforts in detailing viscoelastic hemostatic assays and their use in perioperative monitoring of hemostasis. However, we would like to provide some clarification regarding the differences in testing methodologies used by various viscoelastic testing platforms.
      The authors incorrectly stated that the Quantra and TEG 6S use the same ultrasound technology. Although the TEG 6S uses sound (20-500 Hz), it does not use ultrasound to generate a visible wave pattern on the blood meniscus that is then photo optically read. As reported in a recent study by Pham et al., within each of the TEG 6S instruments microfluidic channels, a blood meniscus forms, which partially blocks the transmittance of light to a photodiode.
      • Pham HP
      • Azad A
      • Gounlong J
      • et al.
      Comparison of viscoelastic testing by rotational torsion and harmonic resonance methods: Two-center comparison of TEG 5000 and TEG 6S instruments [e-pub ahead of print].
      This channel subsequently is exposed to sound frequencies ranging from 20-to-500 Hz. An optical detector then senses the motion of the blood meniscus, and the clot's resonant frequency is identified by Fourier transformation as the frequency associated with the highest meniscal displacement.
      Conversely, the cup and pin technologies used by the TEG 5000 and ROTEM devices are descendants of Hartert's initial implementation of thromboelastography from the 1940s.
      • Hartert H.
      [Blood clotting studies with thrombus stressography; a new investigation procedure].
      Hartert's setup, recently described by Hochleitner et al., employees a mirror to reflect a light source into a photographic film graded in units of millimeters.
      • Hochleitner G
      • Sutor K
      • Levett C
      • et al.
      Revisiting Hartert's 1962 calculation of the physical constants of thrombelastography.
      The output tracing represents the evolution of clot amplitude versus time and the effects of both the elastic and viscous components of the forming clot, and is nonlinearly related to the actual shear modulus of elasticity. Consequently, both the TEG and ROTEM devices represent indirect measurements of a clot's viscoelastic properties and shear modulus.
      The measurement of resonance provides a direct quantitative assessment and the ability to directly report a clot's absolute viscoelastic properties. The sonic estimation of elasticity via resonance (SEER) sonorheometry technology implemented in the Quantra enables the analysis of the resonance signal and separates the elastic versus the viscous component of the viscoelastic response. Derivation of output parameters and the trace generated by the Quantra device depict only the elastic component (ie, the shear modulus of elasticity). The ability to directly measure shear modulus allows the Quantra to accurately compute the platelet contribution to clot stiffness, which the authors correctly mention in their editorial.

      Acknowledgments

      Dr. Sean G. Yates declares that this project was sponsored by a research grant from HemoSonics to the University of Texas Medical Branch in support of the research.

      Conflict of Interest

      All remaining authors have no conflict of interest to declare.

      References

        • Bolliger D
        • Kamber F
        • Mauermann E.
        Same same but different: Viscoelastic hemostatic assays in cardiac surgery.
        J Cardiothorac Vasc Anesth. 2021; 35: 1037-1039
        • DeAnda A
        • Levy G
        • Kinsky M
        • et al.
        Comparison of the Quantra QPlus System with thromboelastography in cardiac surgery.
        J Cardiothorac Vasc Anesth. 2021; 35: 1030-1036
        • Pham HP
        • Azad A
        • Gounlong J
        • et al.
        Comparison of viscoelastic testing by rotational torsion and harmonic resonance methods: Two-center comparison of TEG 5000 and TEG 6S instruments [e-pub ahead of print].
        Am J Clin Pathol. 2021; (Accessed August 24, 2021)https://doi.org/10.1093/ajcp/aqab028
        • Hartert H.
        [Blood clotting studies with thrombus stressography; a new investigation procedure].
        Klin Wochenschr. 1948; 26 ([in German]): 577-583
        • Hochleitner G
        • Sutor K
        • Levett C
        • et al.
        Revisiting Hartert's 1962 calculation of the physical constants of thrombelastography.
        Clin Appl Thromb. 2017; 23: 201-210

      Linked Article

      • Same Same but Different: Viscoelastic Hemostatic Assays in Cardiac Surgery
        Journal of Cardiothoracic and Vascular AnesthesiaVol. 35Issue 4
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          VISCOELASTIC hemostatic assays (VHA) have become increasingly popular for monitoring perioperative coagulation status and guiding timely hemostatic therapy in cardiac surgery.1,2 VHA can be performed as point-of-care tests and might track perioperative coagulation disorders more accurately than standard coagulation tests.3,4 Implementation of VHA results in transfusion algorithms that have reduced the requirements of allogeneic blood products efficaciously in several studies and meta-analyses.5-7 Accordingly, the use of VHA is recommended by recent clinical guidelines in patient blood management and perioperative coagulation therapy in cardiac surgery.
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