The 2019 European Association for Cardio-Thoracic Surgery (EACTS) consensus statement on long-term mechanical circulatory support (LT-MCS) recommends withdrawal of dual antiplatelet therapy and/or vitamin K antagonists to reduce the risk of bleeding and to optimize preoperative organ function. It also supports the use of short-acting intravenous (IV) anticoagulation for bridging prior to implantation of LT-MCS. IV antithrombotics are specifically recommended for preoperative conditions. Postoperative early anticoagulation is mentioned as being mandatory, with IV unfractionated heparin (UFH) being a commonly used agent. Anticoagulation can be initiated 8 hours after surgery with all devices if bleeding is less than 50 mL/hour with an initial target activated partial thromboplastin time of 40 seconds. Target activated partial thromboplastin time is then increased to 55-60 seconds over the first 48-72 hours. The vitamin K antagonist can be initiated once the clinical condition is stable and oral administration is possible. The target INR varies from 2.0 to 3.0 depending on device recommendations. Aspirin (acetylsalicylic acid) is routinely used. This consensus statement does not currently recommend the use of direct oral anticoagulants (DOACs). [1]
The 2013 International Society for Heart and Lung Transplantation (ISHLT) guidelines for mechanical circulatory support recommend IV heparin or alternative anticoagulation if there is no evidence of bleeding on a postoperative day 1 to 2 for the management of HeartMate II patients. Heparin can be continued, or warfarin and aspirin (81 to 325 mg daily) can be started after the removal of chest tubes on a postoperative day 1 to 3. The same recommendations are made for patients receiving implantable centrifugal pumps or pulsatile mechanical circulatory support devices. [2] Consistently, American Heart Association (AHA) Scientific Statement discussed that the current generation of continuous-flow ventricular assist devices (CF-VADs) may require both systemic anticoagulation and antiplatelet therapy. [3]
Per institution-based practice guidelines specific to antithrombotic management of patients with left ventricular assist systems (LVAS), the standardized approach for comprehensive anticoagulation management of these patients is divided into 3 phases of care including: (1) perioperative anticoagulation management during the initial hospitalization for LVAS placement, (2) subsequent inpatient admissions, and (3) routine outpatient management. The postoperative inpatient management recommends antiplatelet and anticoagulation strategies for the early postoperative period which include initiation of warfarin based on risk factors for bleeding and warfarin sensitivity (e.g., age, liver dysfunction, nutritional status, history of warfarin dosing, drug-drug interactions). Once hemostasis is achieved, antiplatelet therapy (postoperative day [POD] 0) in conjunction with IV anticoagulation as a bridge to a therapeutic INR (typically PODs 1-3) should be considered. IV anticoagulation with direct thrombin inhibitor (bivalirudin) is reserved for those with a history of heparin-induced thrombocytopenia (HIT) or in bridge-to-transplant (BTT) status. For routine outpatient management, fondaparinux could be considered for patients with a history of HIT, or in BTT patients to decrease exposure to heparin products and possible development of HIT antibodies prior to transplant. Anticoagulation therapy should be individualized based on the patient’s history of bleeding or recurrence risk of thrombotic events. [4]
A comprehensive state-of-the-art review on antiplatelet and anticoagulation strategies for left ventricular assist devices (LVAD) discussed pre-implant, intraoperative, and perioperative anticoagulation management for patients undergoing LVAD. For pre-implant anticoagulation management, outpatients taking direct oral anticoagulants (DOACs) should be transitioned to coumadin or bridged with heparin/enoxaparin, and outpatients on coumadin should be bridged with unfractionated heparin (UFH). Subsequent discontinuation of low molecular weight heparin (LMWH) and fondaparinux should proceed 12 and 24 hours prior to the surgery, respectively. For intraoperative anticoagulation management during cardiopulmonary bypass (CPB), UFH is most commonly used given its short half-life and availability of a reversal agent. There is a lack of clear consensus on initial UFH dose calculations, but some options include a fixed, weight-based dose (e.g., 300 IU/kg) and the use of point-of-care tests that measure the whole blood sensitivity to heparin using an associated dose-response. For perioperative anticoagulation management, the manufacturer guidelines exist [Table 1], but there are variations between institutions. UFH bridging to a therapeutic vitamin K antagonist (VKA) is recommended after LVAD implantation. The potential of DOACs as viable alternatives to warfarin in LVAD patients was discussed; however, given the safety concerns, DOACs are not currently recommended as primary anticoagulation in LVADs. [5]
A 2017 retrospective analysis evaluated the proportion of time spent in target range (PTTR) for INR (estimated target range of 2.0 to 3.0) among adult patients (N= 115) with LVAD placed from 2006 to 2012. During 624.5 months of follow-up, LVAD patients remained in the INR target range for an average of 42.9% of the time. The finding is consistent with the result shown in the previous small case series (N= 16) which also demonstrated low rates of anticoagulation control despite the rigorous anticoagulation and VAD management. The authors noted that when compared to other chronically anticoagulated patients such as those with nonvalvular atrial fibrillation (proportion of time spent in target range [PTTR] 68%), the percent time in range appeared less in VAD patients. [6], [7]