Perioperative onset of acquired von Willebrand syndrome: Comparison between HVAD, HeartMate II and on-pump coronary bypass surgery

Objectives Acquired von Willebrand syndrome (AvWS) is associated with postoperative bleeding complications in patients with continuous flow left ventricular assist devices (CF-LVADs). The aim of this study is to analyze the perioperative vWF profile comparing an axial pump (HMII) to a centrifugal pump (HVAD) regarding the correlation between perioperative occurrence of AvWS, early-and late-postoperative bleeding events. Methods From July 2013 until March 2015 blood samples of 33 patients (12 HMII/8 HVAD/13 controls) were prospectively collected at 12 different time points and analyzed for the vWF antigen (vWF: Ag), its activity (vWF: Ac) and the vWF: Ac/vWF: Ag-ratio (vWF: ratio). The follow up period for postoperative bleeding events was from July 2013 until July 2016. Results Postoperatively, there was no difference in the vWF-profile between HVAD and HMII groups. However, a subgroup of patients already had significantly lower vWF: ratios preoperatively. Postoperatively, both CF-LVAD groups presented significantly lower vWF: ratios compared to the control group. Bleeding events per patient-year did not differ between the two groups (HMII vs. HVAD: 0.67 vs. 0.85, p = 0.685). We detected a correlation between vWF: ratio < 0.7at LVAD-start (r = -0.583, p = 0.006) or at the end of surgery (r = -0.461, p = 0.035) and the occurrence of pericardial tamponade. In the control group, the drop in both vWF: Ag and vWF: Ac recovered immediately postoperatively above preoperative values. Conclusion A subgroup of patients with end-stage heart failure already suffers AvWS preoperatively. In both CF-LVAD groups, AvWS begins immediately after surgery. Intraoperative vWF: ratios < 0.7 correlate with higher incidences of pericardial tamponade and re-operation. The presumably dilutive effect of the heart lung machine on vWF vanishes immediately at the end of surgery, possibly as part of an acute-phase response.