DOAC Dilemmas in Hospitalized Patients with Dr. Jori May

Defining Anticoagulation Failure

• 🎯 Anticoagulation failure is defined as definitive evidence of a new thrombus despite adequate anticoagulation, with key considerations being what constitutes a 'new thrombus' and 'adequate anticoagulation'.
• 💡 It is extremely rare for anticoagulation to fail; the focus should be on proving adequate anticoagulation and a new thrombus.

Assessing Adequate Anticoagulation

• 💊 Verification of medication fill history is crucial, as patients may believe they are taking medication when they are not.
• 🍽️ Riveroxaban requires food for adequate absorption, and patients must be reminded of this.
• ⏰ Apixaban is taken twice daily, and patients often miss the evening dose, leading to inadequate anticoagulation.
• ⚖️ Ensure patients are on the correct dose for their indication, as some may be on a reduced dose for atrial fibrillation when VTE requires a full dose.

Identifying New Thrombus and Underlying Causes

• 🖼️ Old images for comparison are extremely valuable when assessing for a new thrombus.
• 🧪 A D-dimer can be helpful when unsure if a thrombus is new.
• 🧬 Hypercoagulable states (e.g., malignancy, antiphospholipid syndrome), endothelial injury, and stasis are key factors that can push anticoagulation beyond its limits.
• 💊 Certain chemotherapy agents, like bevicizumab, can increase thrombotic risk.

Navigating Specific Scenarios and Agents

• ❓ There is no definitive data on how many missed doses constitute failure; guidance is extrapolated from procedure holds (1-2 days off medication).
• 🔬 Anti-10a levels can be useful if calibrated for DOACs, but only indicate presence/absence, not historical levels.
• 🔄 Apixaban has significant colonic absorption, potentially making it less ideal for patients with colonic pathology, while Riveroxaban does not have this issue.
• 🤰 DOACs are not recommended during pregnancy or breastfeeding; oxiparin is preferred during pregnancy, and oxiparin or warfarin can be used during breastfeeding.
• 🧠 Extreme obesity (BMI 55-60) may warrant caution with DOACs due to lack of data, potentially favoring warfarin initially.
• 🩸 In patients with renal failure, apixaban is often preferred due to less renal clearance dependence, and dose reduction is not typically done unless on dialysis, where dose reduction is considered due to bleeding risk.

Managing Complex Cases and Agent Selection

• ⚠️ Anatomical issues like May-Thurner syndrome or post-thrombotic syndrome can disrupt flow and increase thrombosis risk, requiring broader evaluation beyond just anticoagulation.
• 📞 Consulting radiologists can provide crucial insights into whether a clot appears acute or chronic, beyond what's in the report.
• 📈 Asymptomatic propagation of a clot within the first month of anticoagulation is not uncommon and does not necessarily indicate treatment failure.
• ❓ For antiphospholipid syndrome, warfarin is generally preferred due to increased risk of arterial thrombosis with DOACs, though nuances exist.
• 💉 In cases of suspected DOAC failure without a clear explanation, oxaparin may be considered temporarily rather than immediately switching to warfarin.
• 🫀 For left ventricular thrombus, DOACs are now considered an acceptable alternative to warfarin, supported by evolving literature.
• 🔄 Reversal agents for DOACs exist (dexanate alpha for 10a inhibitors, idarucizumab for dabigatran), but their availability and efficacy, especially in severe bleeding, are debated; four-factor PCC is a common reversal agent for 10a inhibitors.