OC 71.5 - Reasons for Anticoagulation Failure and Provider Management

Background: Failure of anticoagulation therapy is frequently mentioned in medical literature despite a limited understanding for failure mechanisms and the exact definition being unclear.

Aims: Describe reasons for anticoagulation failure in patients treated for venous-thromboembolism (VTE) and management strategies of VTE recurrence in the setting of failure.

Methods: Consecutive patients enrolled at Mayo Clinic VTE Registry between March 2013 to November 2022 with acute VTE were prospectively followed. Recurrence was defined as new diagnosis of VTE on anticoagulation or during a time of standard peri-procedural management.

Results: Of the 4,980 patients enrolled, 150 (3.0%) experienced anticoagulation failure. Among this group, there was not a significant difference between anticoagulant type (p = 0.07). Most patients with failure had underlying malignancy (71.3%) with hepatobiliary, gynecologic, and hematologic cancers being the most common (Table 1).

Factors associated with anticoagulation failure included new diagnosis of malignancy or malignancy progression (32.7%), reduced absorption (26.0%), under dosing (13.3%), or brief interruption due to recent bleed (8.7%) (Table 2). Other reasons for failure include anticoagulation interruption due to surgery, non-compliance, or medication interaction. Nearly 20% of failure events had multiple contributing factors, while only 17.3% did not have an identifiable cause.

After anticoagulation failure, most patients (60.1%) were transitioned to an alternative medication with the majority (60.0%) being enoxaparin. Nearly one fifth of patients remained on the same therapy after treatment failure when an underlying reason could be addressed (18.2%).

Conclusion(s): Failure of anticoagulation is uncommon. Most patients are transitioned to therapeutic enoxaparin after anticoagulation treatment failure. In some cases, failure was not preventable, occurring due to a profound hypercoagulable state or another inevitable clinical factor. However, in nearly 50%, risk for VTE recurrence could be reduced by appropriate patient selection and medication compliance, highlighting the necessity of clinician diligence when prescribing anticoagulation.