Summary

Second update to the 9th edition CHEST guideline on antithrombotic therapy for VTE, providing 29 guidance statements (13 strong) across 17 PICO questions covering initial management, treatment-phase anticoagulation, extended-phase secondary prevention, and PTS prevention. Major changes from 2016 include strong preference for DOACs over VKA for treatment phase, preference for oral Xa inhibitors over LMWH in cancer-associated thrombosis, new guidance on cerebral vein thrombosis, antiphospholipid syndrome, reduced-dose DOACs for extended phase, and superficial vein thrombosis. New nomenclature defines three phases: initiation (5-21 days), treatment (3 months), and extended (no preplanned stop date).

Key Recommendations

For acute isolated distal DVT without severe symptoms or risk factors for extension, use serial ultrasound imaging for 2 weeks over anticoagulation; anticoagulate if severe symptoms or risk factors for extension.
For isolated subsegmental PE without proximal DVT and low recurrence risk, use clinical surveillance over anticoagulation; anticoagulate if high recurrence risk.
Treat incidentally found asymptomatic PE the same as symptomatic PE.
Anticoagulate cerebral vein/venous sinus thrombosis for at least 3 months (strong recommendation despite low-certainty evidence).
Treat low-risk PE as outpatient rather than hospitalize when home circumstances permit (strong recommendation).
Do not give systemic thrombolytics for acute PE without hypotension; reserve for hypotensive PE (SBP <90 mmHg for ≥15 min) without high bleeding risk, or for deterioration after starting anticoagulation.
Use apixaban, dabigatran, edoxaban, or rivaroxaban over VKA for treatment-phase anticoagulation in DVT/PE (strong recommendation).
For cancer-associated thrombosis, use an oral Xa inhibitor (apixaban, edoxaban, rivaroxaban) over LMWH; prefer apixaban or LMWH in luminal GI malignancies due to GI bleeding risk with edoxaban/rivaroxaban.
For antiphospholipid syndrome, use adjusted-dose VKA (INR 2.5) over DOAC during the treatment phase.
For superficial vein thrombosis at increased risk of progression, anticoagulate for 45 days with fondaparinux 2.5 mg daily (preferred) or rivaroxaban 10 mg daily.
Treat acute VTE for a 3-month treatment phase, then reassess all patients for extended-phase therapy.
Do not offer extended anticoagulation for VTE provoked by a major or minor transient risk factor; do offer extended-phase DOAC for unprovoked VTE or VTE with persistent risk factor.
For extended-phase therapy, use reduced-dose apixaban (2.5 mg BID) or rivaroxaban (10 mg daily) over full-dose; use reduced-dose DOAC over aspirin or no therapy.
Insert IVC filter only when anticoagulation is contraindicated in acute VTE; remove promptly once anticoagulation can be started.
Do not routinely use compression stockings to prevent post-thrombotic syndrome after acute DVT.

Thresholds & Doses

Treatment phase duration: 3 months (12 weeks) for all acute VTE without contraindication
Initiation phase: 5–21 days of parenteral or high-dose oral anticoagulation
Serial imaging for isolated distal DVT: ultrasound weekly for 2 weeks
Cerebral vein thrombosis: anticoagulate for at least 3 months
Hypotension threshold for thrombolytics in PE: SBP <90 mmHg for ≥15 minutes
Superficial vein thrombosis treatment: 45 days of anticoagulation if at increased risk of progression
Fondaparinux dose for SVT: 2.5 mg daily
Rivaroxaban dose for SVT: 10 mg daily
Reduced-dose extended-phase apixaban: 2.5 mg twice daily
Reduced-dose extended-phase rivaroxaban: 10 mg once daily
VKA target INR in antiphospholipid syndrome: 2.5
Major transient risk factor window: within 3 months before VTE (e.g., surgery >30 min, hospital bed-rest ≥3 days, cesarean, major trauma)
Minor transient risk factor window: within 2 months before VTE (e.g., surgery <30 min, hospital <3 days, estrogen, pregnancy, leg injury with reduced mobility ≥3 days, prolonged travel)
SVT trigger threshold suggesting anticoagulation: greater saphenous vein involvement >5 cm in extent
PESI low-risk thresholds for outpatient PE care: original PESI <85 or simplified PESI = 0

Citations

Summary of Recommendations #1–2 — isolated distal DVT management
Summary of Recommendations #3–5 — subsegmental PE, incidental PE, cerebral vein thrombosis
Summary of Recommendations #8–9 — systemic thrombolytics in PE
Summary of Recommendations #14 — outpatient treatment of low-risk PE
Summary of Recommendations #15–17 — DOAC vs VKA, cancer-associated thrombosis, APS
Summary of Recommendations #18–20 — superficial vein thrombosis treatment
Summary of Recommendations #21–27 — duration and extended-phase anticoagulation
Summary of Recommendations #29 — compression stockings and PTS prevention