Mitral regurgitation is associated with similar loss of von Willebrand factor large multimers but lower frequency of anemia compared with aortic stenosis.

Background: Various cardiovascular diseases cause acquired von Willebrand syndrome (AVWS), which is characterized by a decrease in high-molecular-weight (large) von Willebrand factor (VWF) multimers. Mitral regurgitation (MR) has been reported as a cause of AVWS. However, much remains unclear about AVWS associated with MR. Objectives: To evaluate VWF multimers in MR patients and examine their impact on clinical characteristics. Methods: Moderate or severe MR patients (n = 84) were enrolled. VWF parameters such as the VWF large multimer index (VWF-LMI), a quantitative value that represents the amount of VWF large multimers, and clinical data were prospectively analyzed. Results: At baseline, the mean hemoglobin level was 12.9 ± 1.9 g/dL and 58 patients (69.0%) showed loss of VWF large multimers defined as VWF-LMI < 80%. VWF-LMI in patients with degenerative MR was lower than in those with functional MR. VWF-LMI appeared to be restored the day after mitral valve intervention, and the improvement was maintained 1 month after the intervention. Seven patients (8.3%) had a history of bleeding, 6 (7.1%) of whom had gastrointestinal bleeding. Gastrointestinal endoscopy was performed in 23 patients (27.4%) to investigate overt gastrointestinal bleeding, anemia, etc. Angiodysplasia was detected in 2 of the 23 patients (8.7%). Conclusion: Moderate or severe MR is frequently associated with loss of VWF large multimers, and degenerative MR may cause more severe loss compared with functional MR. Mitral valve intervention corrects the loss of VWF large multimers. Gastrointestinal bleeding may be relatively less frequent and hemoglobin level remains stable in MR patients.

von Willebrand factor Ristocetin co-factor activity to von Willebrand factor antigen level ratio for diagnosis of acquired von Willebrand syndrome caused by aortic stenosis.

Background: Severe aortic stenosis (AS) causes acquired von Willebrand syndrome by the excessive shear stress-dependent cleavage of high molecular weight multimers of von Willebrand factor (VWF). While the current standard diagnostic method is so-called VWF multimer analysis that is western blotting under nonreducing conditions, it remains unclear whether a ratio of VWF Ristocetin co-factor activity (VWF:RCo) to VWF antigen levels (VWF:Ag) of <0.7, which can be measured with an automated coagulation analyzer in clinical laboratories and is used for the diagnosis of hereditary von Willebrand disease. Objectives: To evaluated whether the VWF:RCo/VWF:Ag is useful for the diagnosis of AS-induced acquired von Willebrand syndrome. Methods: VWF:RCo and VWF:Ag were evaluated with the VWF large multimer index as a reference, which represents the percentage of a patient's VWF high molecular weight multimer ratio to that of standard plasma in the VWF multimer analysis. Results: We analyzed 382 patients with AS having transaortic valve maximal pressure gradients of >30 mmHg, 27 patients with peripheral artery disease, and 46 control patients free of cardiovascular disease with osteoarthritis, diabetes, and so on. We assumed a large multimer index of <80% as loss of VWF large multimers since 59.0% of patients with severe AS had the indices of <80%, while no control patients or patients with peripheral artery disease, except for 2 patients, exhibited the indices of <80%. The VWF:RCo/VWF:Ag ratios, measured using an automated blood coagulation analyzer, were correlated with the indices (rs = 0.470, P < .001). When the ratio of <0.7 was used as a cut-off point, the sensitivity and specificity to VWF large multimer indices of <80% were 0.437 and 0.826, respectively. Conclusion: VWF:RCo/VWF:Ag ratios of <0.7 may indicate loss of VWF large multimers with high specificity, but low sensitivity. VWF:RCo/VWF:Ag ratios in patients with AS having a ratio of <0.7 may be useful for monitoring the loss of VWF large multimers during their clinical courses.

Impact of intraoperative use of venovenous extracorporeal membrane oxygenation on the status of von Willebrand factor large multimers during single lung transplantation.

Background: von Willebrand factors (vWFs), hemostatic factors, are produced as large multimers and are shear stress-dependently cleaved to become the appropriate size. A reduction in vWF large multimers develops in various conditions including the use of extracorporeal life support, which can cause excessive-high shear stress in the blood flow and result in hemostatic disorders. The objective of this prospective study was to investigate the impact of venovenous extracorporeal membrane oxygenation (VV ECMO) use on the status of vWF large multimers and hemostatic disorders during single lung transplantation (SLT). Methods: We prospectively enrolled 12 patients who underwent SLT at our center. Among them, seven patients were supported by VV ECMO intraoperatively (ECMO group) and the remaining five patients underwent SLT without ECMO support (control group). The vWF large multimer index (%) was defined as the ratio of the large multimer proportion in total vWF (vWF large multimer ratio) derived from a patient's plasma to that from standard human plasma. Results: The vWF large multimer index at the end of the surgery was significantly lower in the ECMO group than in the control group (112.6% vs. 75.8%, respectively; P<0.05). The intraoperative blood loss and the amounts of intraoperative transfusion products in the ECMO group tended to be greater than those in the control group; however, the differences were not significant. Conclusions: During SLT, the use of VV ECMO caused a decrease in the vWF large multimer index. The short duration of time of VV ECMO use in our study did not significantly affect the intra- and postoperative outcomes including blood loss, blood transfusion, and re-exploration thoracotomy for bleeding. Nevertheless, to comprehensively evaluate the actual influence of this decrease in the vWF large multimer index on intra- and postoperative outcomes, a multicenter larger-scale study is warranted.

Heat-Induced Dolomitization of Amorphous Calcium Magnesium Carbonate in a CO2-Filled Closed System.

We report a method to synthesize dolomite [CaMg(CO3)2] from amorphous calcium magnesium carbonate (ACMC) via solid-state transformation. When ACMC is heated in air, it does not crystallize into dolomite but decomposes into Mg calcite, magnesium oxide, and CO2. Hence, we heated ACMC in a closed system filled with CO2 gas (pCO2 >1.2 bar at 420 °C) and produced submicron-sized dolomite. Single-phase dolomite was obtained after dissolving impurities in the run products, such as northupite [Na3Mg(CO3)2Cl] and eitelite [Na2Mg(CO3)2], in water. Also, we investigated the crystallization process of dolomite by changing the heating temperature and heating time. Despite crystallization by solid-state transformation, the heated samples crystallized to dolomite via Ca-rich protodolomite with no ordering reflection of X-ray diffraction as previously observed for hydrothermal synthesis. The results demonstrated that this crystallization pathway is kinetically favored even in solid-state transformation and that the Ca-rich protodolomite phase preferentially crystallizes during heating, leading to phase separation from the amorphous phase. Therefore, the crystallization process via protodolomite as a precursor is a common mechanism in dolomite crystallization, suggesting the presence of kinetic barriers other than hydration of cations.