Detection of acquired von Willebrand syndrome after ventricular assist device by total thrombus-formation analysis system.

Aims: Bleeding is a serious complication in patients with continuous-flow left ventricular assist device (CF-LVAD). Acquired von Willebrand syndrome (AVWS; type 2A) develops because of high shear stress inside the pumps and is a cause of bleeding complication. Although von Willebrand factor (vWF) multimer analysis is useful for diagnosing AVWS, it is only performed in specialized research institutes. A novel microchip flow chamber system, the total thrombus-formation analysis system (T-TAS), is a point-of-care system to evaluate the thrombus-formation process and useful for monitoring platelet thrombus-formation capacity in patients receiving antiplatelet therapy and the diagnosis and evaluation of the clinical severity of von Willebrand disease type 1. However, little is known about the association between AVWS and platelet thrombus-formation capacity evaluated by T-TAS in patients with CF-LVAD. We aimed to evaluate the utility of T-TAS for easy detection of AVWS in patients with CF-LVAD.

Methods And Results: We simultaneously evaluated the vWF large multimers and T-TAS parameters in four consecutive patients with axial-type CF-LVAD and eight control patients treated with aspirin and warfarin. vWF large multimer index was defined as the proportion of large multimers in total vWF derived from a normal control plasma. T-TAS analyses different thrombus-formation processes using two microchips with different thrombogenic surfaces. PL -AUC levels in the platelet (PL) chip are highly sensitive for platelet functions, while AR -AUC levels in the atheroma (AR) chip allow the assessment of the overall haemostatic ability. vWF large multimer index and T-TAS parameters were decreased in all patients with CF-LVAD. The mean PL -AUC level (5.4 ± 2.9 vs. 219 ± 67; P < 0.01), AR -AUC level (338 ± 460 vs. 1604 ± 160; P < 0.01) and vWF large multimer index (49 ± 11% vs. 112 ± 27%; P < 0.01) were significantly lower in the patients with CF-LVAD than in control patients. One patient showed changes in T-TAS levels before and after implantation of CF-LVAD. PL -AUC and AR -AUC levels decreased from 438.1 to 5.0 and from 1667.9 to 1134.3, respectively.

Conclusions: In patients with CF-LVAD, the platelet thrombus-formation capacity was extremely impaired because of AVWS, and T-TAS parameters could detect the presence of AVWS. T-TAS can be used for easy detection of AVWS as a point-of-care testing. Further studies with a large sample size are needed to validate our results in several LVAD models and evaluate the prognostic value of bleeding complications and thromboembolism in patients with LVAD.