Summary

Second update to the CHEST 9th edition guidelines on antithrombotic therapy for VTE, providing 29 guidance statements (13 strong recommendations) across 17 PICO questions. Major changes from prior versions include a strong recommendation for DOACs over VKA as first-line treatment-phase therapy, a strong recommendation for oral Xa inhibitors over LMWH in cancer-associated thrombosis, new guidance on antiphospholipid syndrome favoring VKA over DOACs, and endorsement of reduced-dose DOACs for extended-phase therapy. Anticoagulation phases are formally defined as initiation (5-21 days), treatment (3 months), and extended (no preplanned stop date).

Key Recommendations

Treat acute VTE (DVT or PE) with apixaban, dabigatran, edoxaban, or rivaroxaban over VKA for the treatment phase (strong, moderate-certainty).
For cancer-associated thrombosis, use an oral Xa inhibitor (apixaban, edoxaban, or rivaroxaban) over LMWH; prefer apixaban or LMWH if luminal GI malignancy (strong, moderate-certainty).
In confirmed antiphospholipid syndrome, use adjusted-dose VKA (INR 2.5) over DOACs (weak, low-certainty).
Treat low-risk PE as outpatient over hospitalization if access to medications, follow-up, and home circumstances are adequate (strong, low-certainty).
Do NOT use systemic thrombolytic therapy in most acute PE without hypotension; reserve for hemodynamic deterioration or hypotension (SBP <90 mm Hg for ≥15 min) without high bleeding risk.
Anticoagulate cerebral vein/venous sinus thrombosis for at least 3 months (strong, low-certainty), even in presence of intracranial hemorrhage.
For acute isolated distal DVT without severe symptoms or extension risk factors, perform serial ultrasound for 2 weeks rather than anticoagulating; anticoagulate if severe symptoms or risk factors present.
For isolated subsegmental PE without proximal DVT and low recurrence risk, perform clinical surveillance over anticoagulation.
Treat all acute VTE for a 3-month treatment phase; then reassess every patient for extended-phase therapy (strong, moderate-certainty).
Do NOT offer extended-phase anticoagulation after VTE provoked by a major transient risk factor (strong, moderate-certainty); offer extended-phase DOAC for unprovoked VTE or persistent risk factor (strong, moderate-certainty).
For extended-phase therapy, use reduced-dose apixaban (2.5 mg BID) or rivaroxaban (10 mg daily) over full dose, and over aspirin or no therapy.
Do NOT use IVC filter in addition to anticoagulation for acute VTE; reserve filters for patients with contraindications to anticoagulation, and remove promptly when anticoagulation can begin.
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 if parenteral therapy refused.
Do NOT routinely use graduated compression stockings to prevent post-thrombotic syndrome after acute DVT (weak, low-certainty).

Thresholds & Doses

Treatment phase duration: 3 months (12 weeks) for all acute VTE.
Initiation phase: 5-21 days of parenteral or high-dose oral anticoagulation depending on agent.
Extended-phase reduced doses: apixaban 2.5 mg twice daily; rivaroxaban 10 mg once daily.
Superficial vein thrombosis: fondaparinux 2.5 mg daily for 45 days (alternative rivaroxaban 10 mg daily).
Systemic thrombolysis trigger for PE: SBP <90 mm Hg for ≥15 minutes (hypotension).
VKA target INR in antiphospholipid syndrome: 2.5.
SVT eligible for treatment: ≥5 cm in length, >7 mm diameter, or near saphenofemoral junction.
Serial ultrasound for isolated distal DVT: repeat weekly for 2 weeks (or sooner if symptoms worsen).
Major transient risk factor window: provoking event within 3 months before VTE (e.g., surgery with GA >30 min, ≥3 days inpatient bedrest, major trauma, cesarean).
Minor transient risk factor window: within 2 months (e.g., surgery with GA <30 min, estrogen, pregnancy/puerperium, ≥3 days reduced mobility, prolonged travel).
Bleeding risk categories (AT9 framework): 0 factors = 0.8%/yr, 1 factor = 1.6%/yr, ≥2 factors = 6.5%/yr annualized major bleeding.
5-year VTE recurrence after stopping anticoagulation: ~3% surgical provoked, ~15% nonsurgical transient, ~30% unprovoked.

Citations

Summary of Recommendations #1-2 — isolated distal DVT management (serial imaging vs anticoagulation).
Summary of Recommendations #3 — isolated subsegmental PE management based on recurrence risk.
Summary of Recommendations #5 — cerebral vein/venous sinus thrombosis anticoagulation for ≥3 months.
Summary of Recommendations #8-9 — systemic thrombolytic therapy in acute PE.
Summary of Recommendations #14 — outpatient treatment for low-risk PE.
Summary of Recommendations #15-16 — DOACs over VKA; oral Xa inhibitor over LMWH in cancer.
Summary of Recommendations #17 — VKA (INR 2.5) over DOAC in antiphospholipid syndrome.
Summary of Recommendations #18-20 — superficial vein thrombosis treatment with fondaparinux/rivaroxaban.
Summary of Recommendations #21-27 — duration of therapy and extended-phase anticoagulation.
Summary of Recommendations #29 — compression stockings not routinely recommended for PTS prevention.
Terminology section — definition of initiation, treatment, and extended phases of anticoagulation.
Precipitating Factors section — classification of major transient, minor transient, persistent risk factors.