Abstract 11397: Impact of Von Willebrand Factor Multimer Abnormalities on Blood Loss After Aortic Valve Replacement Using the Semi-Automated Hydragel 5 Multimer Assay

Abstract

Introduction: Acquired von Willebrand syndrome (aVWS) is common in patients with severe aortic stenosis (sAS), which is characterized by the loss of high-molecular-weight multimers (HMWM) of the von Willebrand factor (VWF). VWF abnormalities are improved after surgical aortic valve replacement (SAVR). While conventional multimer analysis is technically challenging, lengthy and non-standardized, recently a new semi-automated multimer assay, the Hydragel 5 VWF multimers (H5VWM) has become available. Therefore, the aim of our study was to analyze VWF abnormalities by H5VWM in patients undergoing SAVR in terms of echocardiography parameter and perioperative bleeding. Methods: We prospectively included 52 patients (age: 67.9±7.2 years; 53.8% male) undergoing SAVR. Patients were divided in two groups (A: abnormal VWF, n=24; B: normal VWF, n=28). Blood samples and echocardiographic data were collected at three time points (TP): day before SAVR (TP1), 7 days (TP2), and 3 months (TP3) after SAVR. Blood loss from chest drainage and the use of blood and haemostatic products were evaluated peri- and postoperatively. Results: Baseline characteristics were similar in both groups. Loss of HMWM was present in 38.5%. After SAVR the level of HMWM had increased significantly compared to baseline in group A. At TP3, we observed no loss of HMWM at all. Bleeding occurred in 15% (A: 17% vs. B: 14%; p>0.999) with need of re-thoracotomy in about 10% (A: 8% vs. B: 11%; p>0.999). There was no significant difference in postoperative bleeding in the first 24hrs (A: 491 ml vs. B: 701ml; p=0.255). Also, peri- and postoperative need of blood transfusion and haemostatic agents were similar between both groups. HMWM was inversely correlated with the peak aortic gradient (R=-0.557; p<0.001) and positively correlated with the aortic valve area (R=0.292; p=0.04). Conclusion: Loss of HMWM was not associated with increased postoperative bleeding in patients with sAS. Echocardiographic parameters could predict the loss of HMWM. The complete restoration of altered VWF at three months postoperatively, demonstrated by H5VWM, seems to be indicative for successful SVAR. Therefore, H5VWM, as a rapid and sensitive assay, could be included as diagnostic tool of suspected aVWS in AS patients.