Comparative Analysis of von Willebrand Factor Profiles in Pulsatile and Continuous Left Ventricular Assist Device Recipients

A higher rate of nonsurgical bleeding has been observed in nonpulsatile left ventricular assist device (LVAD) recipients. von Willebrand factor (vWF) profiles were compared for nonpulsatile and pulsatile LVAD recipients to explore mechanisms that may contribute to the development of postimplant nonsurgical bleeding. The nonpulsatile mechanism may impair vWF function by creating a deficiency in vWF high molecular weight multimers (HMWMs), essential for hemostasis. High molecular weight multimer deficiency should result in low ristocetin cofactor (RCo) to vWF antigen ratios (vWF:RCo/vWF:Ag) because of impaired platelet (plt)-binding ability. von Willebrand factor profiles and HMWM were measured pre- and post-LVAD placement in 11 nonpulsatile (HeartMate II [HM II[) and 3 pulsatile (HeartMate XVE [HM XVE]) recipients. All the nonpulsatile LVAD recipients exhibited loss of HMWM 30 days postimplant. The vWF:RCo/vWF:Ag ratio was significantly lower after LVAD placement in the nonpulsatile group when compared with the pulsatile group. In addition, the vWF:RCo/vWF:Ag ratio decreased significantly from baseline 30 days postimplant within the nonpulsatile recipients. All nonpulsatile LVAD recipients had low vWF:RCo/vWF:Ag ratios 30 days post-LVAD even if the values were normal at baseline. These data suggest that nonpulsatile HM II recipients develop HMWM loss and impaired vWF platelet (plt)-binding ability after LVAD placement. Similar results were not observed in our small series of pulsatile HM XVE recipients. This finding could suggest a contributing factor to the increase in nonsurgical bleeding observed in nonpulsatile LVAD patients. Further investigation is ongoing to identify specific causes of vWF impairment. ASAIO Journal 2010; 56:441-445.