Abstract 2461: Low Thromboembolism and Pump Thrombosis Potential of the HeartMate II (HM) LVAD
Introduction: The HM continuous flow LVAD has been shown to have good reliability and an excellent safety profile when used as a bridge to transplantation (BTT). Initially, there were concerns that the continuous flow and design of the HM might pre-dispose patients to thromboembolic events or pump thrombosis and therefore oral anticoagulation with coumadin was recommended. Our study evaluates the risk of thromboembolism and pump thrombosis related to the degree of anticoagulation as reflected by the International Normalized Ratio (INR).
Methods: We evaluated all patients enrolled in the HM BTT pivotal trial from 1 to 6 months post-implant in order to eliminate perioperative events unrelated to anticoagulation. All patients were on aspirin and some also on persantine. An INR was measured monthly per protocol. Each individual INR sample from each time interval was assigned to ranges of INR values. Adverse events analyzed were ischemic (I) and hemorrhagic (H) stroke, pump thrombosis (T), and GI bleeding (G). Patients with adverse events were associated with the most recent INR at the start of the time interval.
Results: The median duration of support for 189 patients was 132 days (range: 1–672 days) (cumulative: 96.9 patient years). There were 7 (3.7 %) patients with thrombotic events and 11 (5.8 %) patients with hemorrhagic events. The only pump thrombosis occurred with an INR > 2.5 (0.5 %).
Conclusions: The rates of thromboembolism, including stroke and pump thrombosis appear to be low with the HM as BTT. The thrombotic events appear to be offset by an equivalent number of hemorrhagic events. There appears to be no correlation between the degree of anticoagulation with warfarin, as reflected by the INR, and the frequency of thrombotic or hemorrhagic events. Therefore, particularly in patients having recurrent episodes of bleeding, the risk of lowering the target INR appears to be small.