Thrombophilia and VTE — Viva Defence

Long Case Viva Defence

The scenario

Mrs K is a 38-year-old marketing executive who presents to the emergency department with a three-day history of left calf pain and swelling. She has a background of metastatic breast cancer (diagnosed 18 months ago, currently on palliative palbociclib and letrozole) and a history of a right proximal DVT 8 months ago, treated with apixaban for 6 months then stopped by her oncologist. She also has a history of one fetal loss at 20 weeks gestation two years ago, attributed at the time to severe pre-eclampsia. She is a non-smoker, takes no regular medications apart from her cancer therapy, and lives with her husband and a 5-year-old son. ^[1]

On examination, the left calf is swollen and tender with 3 cm asymmetry. The Wells score is 2 (localised tenderness, entire leg swollen). Compression ultrasound confirms an extensive left proximal DVT from the popliteal to the common femoral vein. ^[1]

Laboratory results: haemoglobin 112, platelets 180, INR 1.0, aPTT 48 seconds (prolonged, does not correct on mixing study, corrects with excess phospholipid). Anticardiolipin IgG is 52 GPL. Anti-beta-2 glycoprotein I is positive. She is confirmed as triple-positive for antiphospholipid syndrome. ^[1]

Opening statement (SASPOP)

"This is Mrs K, a 38-year-old marketing executive presenting with a second unprovoked proximal DVT, in the context of metastatic breast cancer on palliative therapy and newly diagnosed triple-positive antiphospholipid syndrome. Her main problems are the acute DVT requiring immediate anticoagulation, the triple-positive APS which means she needs warfarin not a DOAC — the TRAPS trial showed excess thrombosis with rivaroxaban in this subgroup, the metastatic breast cancer which makes this a cancer-associated VTE requiring indefinite anticoagulation, the history of fetal loss at 20 weeks which is part of the APS syndrome and has implications for future pregnancy planning, and the psychosocial impact of recurrent thrombosis in a young woman with metastatic cancer. My priorities are to establish immediate therapeutic anticoagulation with LMWH — because it is safe in cancer, effective in APS, and does not require a heparin lead-in — then transition to warfarin for long-term therapy, engage the haematology and oncology multidisciplinary team, and plan a shared decision on the duration and the future pregnancy approach." ^[1]

Problem list (numbered, prioritised)

1. Acute left proximal DVT — extensive, from popliteal to common femoral; requires immediate therapeutic anticoagulation.
2. Triple-positive antiphospholipid syndrome (APS) — confirmed by lupus anticoagulant, high-titre anticardiolipin and positive anti-beta-2 glycoprotein I, with both clinical criteria (vascular thrombosis and pregnancy morbidity).
3. Metastatic breast cancer on palliative therapy — a second independent prothrombotic state; makes this a cancer-associated VTE requiring indefinite anticoagulation.
4. History of fetal loss at 20 weeks — obstetric APS component; has implications for future pregnancy planning.
5. Psychosocial impact — a young woman with metastatic cancer and now a second thrombosis; needs honest communication and support. ^[1]

Integrated management plan

Pillar 1 — Immediate anticoagulation: ^[1]

"I would commence therapeutic low molecular weight heparin (enoxaparin 1 mg/kg subcutaneously twice daily or 1.5 mg/kg daily). The reasons for choosing LMWH rather than a DOAC upfront are twofold. First, this patient has triple-positive APS, and the TRAPS trial demonstrated excess thrombotic events with rivaroxaban compared with warfarin in this subgroup ^[1]. While the TRAPS trial tested rivaroxaban specifically, the principle is extrapolated across DOACs — warfarin is the preferred agent. Second, she has active cancer, and LMWH is a well-established option in cancer-associated VTE, especially in patients where a DOAC is contraindicated or undesired. I would NOT start a DOAC in this patient given her APS diagnosis."

Pillar 2 — Transition to warfarin for long-term therapy: ^[1]

"After the initial 5 to 10 days of LMWH, I would transition to warfarin with a target INR of 2.0 to 3.0, overlapping LMWH with warfarin for at least 5 days and until the INR is therapeutic for 2 consecutive days. The rationale is: warfarin is the standard of care for APS-associated VTE, supported by the TRAPS trial data ^[1]. I would avoid a loading dose of warfarin because APS patients may have concurrent protein C or S deficiency, and rapid depletion of these natural anticoagulants by warfarin can precipitate warfarin-induced skin necrosis."

Pillar 3 — Duration of anticoagulation: ^[1]

"This patient requires indefinite anticoagulation. She has three independent reasons: (1) APS-associated VTE carries a very high recurrence risk after stopping (20 to 30 per cent per year), (2) she has already had a recurrence after a 6-month course — her first DVT was treated and she has now clotted again, and (3) she has active metastatic cancer, which independently mandates indefinite anticoagulation. If she has a further recurrence despite a therapeutic INR on warfarin, the escalation is to increase the target INR to 3.0 to 4.0, and to consider adding low-dose aspirin for any arterial component." ^[1]

Pillar 4 — Cancer management coordination: ^[1]

"I would coordinate with her oncologist. The palbociclib and letrozole are her palliative therapy — I would check for drug interactions with warfarin (palbociclib is a CYP3A4 inhibitor and can potentiate warfarin, requiring closer INR monitoring). The cancer is metastatic, so treatment is palliative, but the cancer-associated VTE still requires full-dose anticoagulation. I would review her cancer prognosis with the oncologist to ensure that the anticoagulation plan is aligned with her overall goals of care." ^[1]

Pillar 5 — Future pregnancy planning: ^[1]

"If Mrs K wishes to consider future pregnancy, the plan would be: switch from warfarin to LMWH before conception (warfarin is teratogenic), continue LMWH throughout pregnancy with dose escalation as weight increases, add low-dose aspirin to reduce the risk of pregnancy loss, plan the delivery mode and timing with a maternal-fetal medicine specialist, and switch to warfarin postpartum for at least 6 weeks (safe in breastfeeding). The combination of aspirin and LMWH in pregnancy reduces the risk of fetal loss from about 60 per cent to under 20 per cent in APS. However, this discussion must be had in the context of her metastatic cancer prognosis, and the pregnancy option may not be realistic." ^[1]

Pillar 6 — Communication and shared decision-making: ^[1]

"I would sit with Mrs K and her husband in a quiet room. I would explain the APS diagnosis in plain language — an acquired condition in which antibodies increase clotting tendency — and explain that she now needs lifelong warfarin with regular INR monitoring. I would acknowledge the emotional impact of a second thrombosis in the setting of metastatic cancer. I would set out the plan honestly: immediate LMWH, transition to warfarin, indefinite duration, coordination with her oncologist, and a specific plan if she wishes to consider pregnancy. I would give written information, a named contact, and arrange follow-up. I would document the shared decisions and review them as her circumstances evolve." ^[1]

Probing questions the examiner would ask

Q: You mentioned the TRAPS trial. Can you summarise its key findings and limitations? ^[1]

A: "The TRAPS trial — Trial of Rivaroxaban in Antiphospholipid Syndrome — was published by Pengo and colleagues in Blood in 2018 ^[1]. It randomised triple-positive APS patients (positive for lupus anticoagulant, anticardiolipin and anti-beta-2 glycoprotein I simultaneously) to rivaroxaban 20 mg daily versus warfarin with a target INR of 2.5. The trial was terminated early after enrolling only 120 of the planned 540 patients because of an excess of events in the rivaroxaban arm: 7 thromboembolic events in the rivaroxaban group versus 0 in the warfarin group, and 4 major bleeds versus 2 respectively. The key limitation is that it tested rivaroxaban specifically — apixaban, dabigatran and edoxaban were not tested in this high-risk subgroup. Another limitation is the small sample size due to early termination. However, the signal was strong enough that all major guidelines (BSH, ASH, EULAR) now recommend warfarin over DOACs in triple-positive APS. A further trial, the ASTH-2 study of apixaban in APS, is ongoing."

Q: How would your management change if the PF4 antibody comes back positive during her admission? ^[1]

A: "If she develops a platelet fall of 50 per cent or more 5 to 14 days after starting LMWH, and the 4T score is intermediate or high, I would suspect heparin-induced thrombocytopenia (HIT). I would stop ALL heparin products immediately — LMWH and unfractionated heparin, and even heparin flushes. I would switch to argatroban (a direct thrombin inhibitor given intravenously, hepatically cleared — preferred because she has cancer and may have renal impairment), and confirm with a PF4 ELISA and a serotonin release assay. I would NOT transfuse platelets unless she is actively bleeding. The transition to warfarin would be delayed until the platelet count has recovered to at least 150, with slow overlap. The practical issue is that warfarin is still the long-term agent of choice for her APS, but the bridging would need to be done from argatroban, not from heparin." ^[1]

Q: What if her breast cancer goes into remission? Would you still continue warfarin indefinitely? ^[1]

A: "Yes — even if the cancer goes into durable remission, her triple-positive APS independently mandates indefinite anticoagulation. APS-associated VTE has a recurrence rate of 20 to 30 per cent per year after stopping anticoagulation, and she has already had a recurrence. The APS does not remit. So the indication for lifelong warfarin persists regardless of the cancer trajectory." ^[1]

Q: How does the Caravaggio trial inform your choice of anticoagulant if she did NOT have APS? ^[1]

A: "If she did not have APS — pure cancer-associated VTE — apixaban would be a reasonable first choice. The Caravaggio trial, published by Agnelli et al in NEJM in 2020 ^[3], randomised cancer-associated VTE patients to apixaban versus dalteparin and showed non-inferiority for recurrent VTE (5.6 per cent apixaban vs 7.9 per cent dalteparin) with no significant increase in major bleeding (3.8 per cent vs 4.0 per cent). Unlike the Hokusai-CANVAS (edoxaban) and SELECT-D (rivaroxaban) trials, which showed a GI bleeding signal especially in GI cancers, Caravaggio did not show a significant bleeding excess with apixaban. So for most cancer-associated VTE without APS, apixaban is first-line. But the APS changes this — she needs warfarin."

Q: She asks whether her 5-year-old son should be tested for thrombophilia. How do you answer? ^[1]

A: "For APS specifically — no. APS is an acquired condition (antibodies, not genes), so it is not inherited and her son is not at risk of inheriting it. For the inherited thrombophilias (Factor V Leiden, prothrombin G20210A, antithrombin, protein C, protein S) — I would first determine whether she carries any of these by testing her when she is off anticoagulation. If she has a high-penetrance deficiency (antithrombin, protein C, or protein S), then testing her son after appropriate genetic counselling may be reasonable when he is older, particularly to inform decisions about contact sports, future surgery, and oestrogen avoidance if applicable. If she has only a low-penetrance thrombophilia (heterozygous Factor V Leiden or prothrombin G20210A), routine testing of asymptomatic children is not recommended by the ASH or BSH guidelines — the absolute risk is too low and the result does not change childhood management. I would reassure her that most people with a thrombophilia never have a thrombosis, and that the family history itself (a parent with VTE) is the more useful risk marker for counselling, regardless of genotype." ^[1]

Communication and shared decision-making

"I would frame Mrs K's situation as a convergence of three prothrombotic conditions — APS, metastatic cancer, and an acute clot — each of which independently requires careful anticoagulation. I would be honest that the combination makes her high-risk for further events and that the treatment is lifelong. I would explain the shift from a DOAC (which she took for her first DVT) to warfarin, in plain language: the specific antibodies she has make the new blood thinners less effective than the older warfarin, based on a clinical trial. I would address the practicalities of warfarin — regular blood tests, dose adjustment, dietary consistency with vitamin K — and arrange anticoagulation clinic support. I would acknowledge the emotional burden of recurrent illness and offer the social work and palliative care team for support, given her metastatic cancer. I would document the shared decision and review it as her clinical picture evolves." ^[1]