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cardio.dvt.may-thurner.v1

May-Thurner syndrome (left iliac vein compression DVT)

cardiologyacuteadult
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11/12 authored

Canonical 12-phase frame with authored status for this dossier.

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Detailed

May-Thurner = anatomic compression of left common iliac vein by overlying right common iliac artery; presents as left iliofemoral DVT in young women; treatment requires AC + thrombus removal (CDT) + venous stent to address substrate; route to cardio.dvt.core.v1 for diagnostic arc + DOAC chronic regimen

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left iliofemoral DVT confirmed

Patient inputs (9)

Venography (gold standard) or MRV grades the iliac stenosis; IVUS during venogram is now considered the most accurate intra-procedural sizing tool (CIRSE 2014; Hofmann 2024)

Young women (20–45) have highest MTS prevalence; older patients may have additive degenerative compression

Female:male prevalence ~3-4:1; OCP and post-partum hormone milieu compounds anatomic substrate

OCP, hormone replacement, recent pregnancy/postpartum compound MTS risk; OCP discontinuation is a key non-pharm intervention

Left-side predilection is the MTS hallmark; right-side DVT lowers anatomic suspicion (consider IVC compression, retroperitoneal mass, or generic DVT)

Initial confirmation of iliofemoral DVT; US has limited iliac visualization → triggers venography or MRV for stenosis grading

Baseline Hgb + platelet for AC + thrombolytic-bleed risk

HAS-BLED + recent surgery + falls history determines AC + CDT eligibility

eGFR for DOAC dosing + contrast load during venography; CKD-EPI 2021 race-free preferred

* = hard-required. Engine cannot meaningfully run until these are filled.

Severity triggers (5)

5 need judgement
  • informationallife_threateningphlegmasia_from_acute_iliac_occlusion_in_mts
    Massive acute occlusive iliofemoral DVT in MTS anatomy producing phlegmasia cerulea dolens (cyanosis, severe pain, arterial compromise)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationallife_threateningcdt_associated_major_bleed_in_mts
    Major bleed during catheter-directed thrombolysis (Hgb drop ≥2 g/dL, transfusion, ICH, retroperitoneal)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalseverein_stent_thrombosis_post_iliac_stent
    Recurrent left-leg DVT or duplex US showing thrombus within previously placed iliac venous stent
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalsevereivc_extension_from_iliac_thrombus
    Thrombus extension from left iliac vein into the IVC despite therapeutic AC
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalseverepregnancy_with_mts_history_or_new_dvt
    Patient with prior MTS stent becoming pregnant OR new MTS-pattern DVT during pregnancy
    Trigger could not be auto-evaluated — needs clinician judgement.

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Recommended regimen

May-Thurner syndrome — combined AC + catheter-directed thrombolysis + iliac venous stenting (Hofmann 2024)
axis: may_thurner_combined_anticoagulation_thrombolysis_stent_phenotype
Selected axis "May-Thurner syndrome — combined AC + catheter-directed thrombolysis + iliac venous stenting (Hofmann 2024)" by default fallback (first axis)
  • apixaban
    first line
    doac_factor_xa_direct
    10 mg BID × 7 d → 5 mg BID • PO • BID × ≥3 months minimum (extended if unprovoked or persistent stenosis)
    triggers: mts_post_cdt_stent, no_active_bleed, egfr_above_25
    AMPLIFY (Agnelli NEJM 2013 PMID 23808982) — DOAC first-line; ACCP 2021 first-line for proximal DVT; aggressive AC required after stent to prevent in-stent re-thrombosis
    rxcui 1364430
  • rivaroxaban
    first line
    doac_factor_xa_direct
    15 mg BID × 21 d → 20 mg daily with food • PO • BID then daily × ≥3 months
    triggers: mts_post_cdt_stent, no_active_bleed, egfr_above_30
    EINSTEIN-DVT (Bauersachs NEJM 2010 PMID 21128814) — non-inferior to enoxaparin/VKA; common alternative DOAC
    rxcui 1114195
  • enoxaparin
    first line
    lmwh
    1 mg/kg SC BID; reduce to 1 mg/kg daily if CrCl <30 • SC • BID
    triggers: mts_acute_pre_cdt, pregnancy, planned_invasive_procedure_with_AC_hold
    ASH 2020 (PMID 33007077); LMWH preferred during the acute peri-procedural window for ease of hold/resume around CDT and stenting
    rxcui 67108
  • alteplase
    first line
    fibrinolytic_tpa
    0.5–1 mg/h via catheter for 12–24 h (max ~24 mg/24 h) • IV_catheter • continuous infusion
    triggers: acute_iliofemoral_dvt_within_14d, severe_symptoms, low_bleed_risk, mts_anatomy_demonstrated
    ATTRACT (Vedantham NEJM 2017 PMID 29211671) — pharmacomechanical CDT reduces moderate-severe PTS in iliofemoral subgroup; CaVenT (Enden Lancet 2012 PMID 22136717) — early CDT iliofemoral PTS reduction at 5 yr
    rxcui 8410
  • heparin
    first line
    unfractionated_heparin
    80 U/kg bolus + 18 U/kg/h infusion targeting aPTT 1.5–2.5× • IV • continuous
    triggers: cdt_in_progress, peri_procedural_bridge, planned_AC_interruption
    Reversibility for procedural bleeding and ease of hold/resume during CDT and stent placement (ACCP 2021)
    rxcui 235473
  • warfarin
    comorbidity specific
    vitamin_k_antagonist
    5 mg daily; INR target 2-3 • PO • daily
    triggers: triple_positive_aps_overlap, severe_renal_impairment_doac_unsafe, cost_constraint
    TRAPS (Pengo Blood 2018 PMID 30002145) — warfarin > rivaroxaban in triple-positive APS; reasonable alternative if DOAC contraindicated
    rxcui 11289

outpatient playbook — drug actions (1)

  1. 1. maintenance apixaban
    rxcui 1364430
    apixaban 5 mg BID full or 2.5 mg BID extended-reduced based on 3-mo decision • PO • BID
    trigger: Post 3-mo decision
    AMPLIFY/AMPLIFY-EXT

Auto-drafted A&P note

outpatient

Subjective

- Possible entry pathways: Left whole-leg swelling + thigh/groin pain in young woman (age 20–45) — pretest probability for May-Thurner is high; right-side DVT in this demographic should not assume MTS; Compression US shows non-compressible left common iliac / external iliac / common femoral vein → confirm proximal DVT and proceed to venography for MTS evaluation; Left iliofemoral DVT with minor or no provoking factor (OCP, post-partum, recent surgery, immobility) — anatomic substrate (Cockett lesion) likely contributing; mandate venography + IVUS during CDT.

Objective

- No vitals, labs, or imaging entered for this encounter.

Assessment

**May-Thurner syndrome (left iliac vein compression DVT)** (cardio.dvt.may-thurner.v1).
Scope: May-Thurner = anatomic compression of left common iliac vein by overlying right common iliac artery; presents as left iliofemoral DVT in young women; treatment requires AC + thrombus removal (CDT) + venous stent to address substrate; route to cardio.dvt.core.v1 for diagnostic arc + DOAC chronic regimen

No severity triggers fired against current inputs.

Plan

Regimen axis: **May-Thurner syndrome — combined AC + catheter-directed thrombolysis + iliac venous stenting (Hofmann 2024)**.
1. apixaban 10 mg BID × 7 d → 5 mg BID PO BID × ≥3 months minimum (extended if unprovoked or persistent stenosis) (doac_factor_xa_direct, first line) — AMPLIFY (Agnelli NEJM 2013 PMID 23808982) — DOAC first-line; ACCP 2021 first-line for proximal DVT; aggressive AC required after stent to prevent in-stent re-thrombosis
2. rivaroxaban 15 mg BID × 21 d → 20 mg daily with food PO BID then daily × ≥3 months (doac_factor_xa_direct, first line) — EINSTEIN-DVT (Bauersachs NEJM 2010 PMID 21128814) — non-inferior to enoxaparin/VKA; common alternative DOAC
3. enoxaparin 1 mg/kg SC BID; reduce to 1 mg/kg daily if CrCl <30 SC BID (lmwh, first line) — ASH 2020 (PMID 33007077); LMWH preferred during the acute peri-procedural window for ease of hold/resume around CDT and stenting
4. alteplase 0.5–1 mg/h via catheter for 12–24 h (max ~24 mg/24 h) IV_catheter continuous infusion (fibrinolytic_tpa, first line) — ATTRACT (Vedantham NEJM 2017 PMID 29211671) — pharmacomechanical CDT reduces moderate-severe PTS in iliofemoral subgroup; CaVenT (Enden Lancet 2012 PMID 22136717) — early CDT iliofemoral PTS reduction at 5 yr
5. heparin 80 U/kg bolus + 18 U/kg/h infusion targeting aPTT 1.5–2.5× IV continuous (unfractionated_heparin, first line) — Reversibility for procedural bleeding and ease of hold/resume during CDT and stent placement (ACCP 2021)
6. warfarin 5 mg daily; INR target 2-3 PO daily (vitamin_k_antagonist, comorbidity specific) — TRAPS (Pengo Blood 2018 PMID 30002145) — warfarin > rivaroxaban in triple-positive APS; reasonable alternative if DOAC contraindicated

Setting playbook (outpatient) — Lifetime stent surveillance + chronic AC management + PTS prevention + reproductive counseling
7. maintenance apixaban apixaban 5 mg BID full or 2.5 mg BID extended-reduced based on 3-mo decision PO BID — Post 3-mo decision (AMPLIFY/AMPLIFY-EXT)

Non-pharmacologic actions:
- Compression stocking 30-40 mmHg if symptomatic PTS
- OCP avoidance lifelong
- Address modifiable VTE risk factors

AVOID / contraindication checks:
- Doac_avoid_active_bleeding (FDA labels)
- Cdt_avoid_recent_neurosurgery_intracranial_bleed_active_internal_bleed (ATTRACT exclusion)
- Cdt_avoid_severe_uncontrolled_htn_sbp_above_185 (ATTRACT exclusion)
- Apixaban_avoid_egfr_below_15 (FDA label)
- Rivaroxaban_avoid_egfr_below_30 (FDA label)
- Warfarin_avoid_pregnancy_use_lmwh (ASH 2018)
- Decision:venous_stent_under_ivus_guidance_preferred (CIRSE 2014; Hofmann 2024)
- Decision:lifetime_stent_patency_surveillance_q1_3_6_12mo_then_annual (Hofmann 2024)

Monitoring

Regimen monitoring:
- cbc q4 6h during thrombolytic then daily post cdt (ATTRACT)
- fibrinogen q12h during thrombolytic hold if below 150 (ATTRACT)
- creatinine q3mo during doac for dose adjustment (FDA labels)
- duplex us stent patency at 1 3 6 12mo then annual (Hofmann 2024)
- pts villalta scale at 3 6 12mo (Kahn Lancet 2014)
- compression stocking 30 40mmhg for pts prevention in iliofemoral (ATTRACT subgroup signal)

Setting (outpatient) monitoring:
- Annual duplex US lifetime
- Annual labs + clinical reassessment

Follow-up plan: Lifetime stent surveillance; AC duration reassessment based on stent patency + provoking-factor reversibility; OCP discontinuation discussion; pregnancy planning counseling (LMWH bridge if pregnancy desired)
- Close-out criterion: extended-AC + lifestyle plan documented

Monitoring phase: Stent patency surveillance via duplex US at 1, 3, 6, 12 mo then annually (in-stent re-thrombosis is the main long-term concern); compression stockings 30–40 mmHg for PTS prevention; PTS Villalta scale

Disposition

Current setting: outpatient — Lifetime stent surveillance + chronic AC management + PTS prevention + reproductive counseling

Disposition criteria:
- Indefinite AC + lifetime surveillance per Hofmann 2024

Escalation triggers (move to higher acuity):
- New VTE despite AC → reassess stent + switch DOAC class or escalate dose
- Pregnancy → switch to LMWH per ASH 2018
- New left-leg symptoms → image stent

Earlier-Return Triggers

Return-precaution thresholds (watch for):
- [LIFE_THREATENING] Massive acute occlusive iliofemoral DVT in MTS anatomy producing phlegmasia cerulea dolens (cyanosis, severe pain, arterial compromise)
- [LIFE_THREATENING] Major bleed during catheter-directed thrombolysis (Hgb drop ≥2 g/dL, transfusion, ICH, retroperitoneal)
- [SEVERE] Recurrent left-leg DVT or duplex US showing thrombus within previously placed iliac venous stent

Citations

- Hofmann LV 2024 May-Thurner consensus + CIRSE 2014 iliac venous stenting + ACCP/CHEST 2021 + ATTRACT 2017 iliofemoral subgroup [PMID:34352295](https://pubmed.ncbi.nlm.nih.gov/34352295/)
- Cited evidence (PMID 33007077) [PMID:33007077](https://pubmed.ncbi.nlm.nih.gov/33007077/)
- Cited evidence (PMID 29211671) [PMID:29211671](https://pubmed.ncbi.nlm.nih.gov/29211671/)
- Cited evidence (PMID 22136717) [PMID:22136717](https://pubmed.ncbi.nlm.nih.gov/22136717/)
- Cited evidence (PMID 23808982) [PMID:23808982](https://pubmed.ncbi.nlm.nih.gov/23808982/)

Last reconciled with current guidelines: 2026-05-14.
References
  • Hofmann LV 2024 May-Thurner consensus + CIRSE 2014 iliac venous stenting + ACCP/CHEST 2021 + ATTRACT 2017 iliofemoral subgroup — PMID:34352295
  • Cited evidence (PMID 33007077) — PMID:33007077
  • Cited evidence (PMID 29211671) — PMID:29211671
  • Cited evidence (PMID 22136717) — PMID:22136717
  • Cited evidence (PMID 23808982) — PMID:23808982