Low-dose Vitamin K can Improve Warfarin Control in Patients on LVAD Support

Background Anticoagulation with oral vitamin K antagonists (VKA) is very important in patients supported on a left ventricular assist device (LVAD) to prevent thromboembolic complications. Some patients tolerate VKAs poorly and have an unstable INR as a result. It is reported that low-dose vitamin K can improve INR control in patients with an unstable INR in other clinical settings. We evaluated its safety and effectiveness in patients on LVAD support. Methods The records of all patients supported on an implantable LVAD between January, 2013 and March, 2014 were reviewed retrospectively to identify those who had received low-dose vitamin K while on warfarin. INR values and warfarin doses before and after initiation of vitamin K supplementation were compared to evaluate its effectiveness. Results There were six LVAD patients who were on low-dose vitamin K due to an unstable INR out of a total of 59 VAD patients followed as an outpatient. The standard deviation (SD) of INR decreased significantly after starting vitamin K (p=0.04) while the SD of warfarin dose did not (p=0.22). Comparing divergence from target INR, INR became significantly closer to target INR after starting vitamin K. The number of bleeding complications tended to be fewer on vitamin K, but this did not reach statistical significance (p=0.09). Conclusions Daily low-dose vitamin K supplementation can improve INR control in LVAD patients with unstable INR without increasing thromboembolic complications.