Venous Thromboembolism

[1]

Overview & Definition

Venous thromboembolism (VTE) is the umbrella clinical syndrome that encompasses deep vein thrombosis (DVT) and its principal complication, pulmonary embolism (PE). It is best understood not as two separate diseases but as a single pathophysiological continuum in which a thrombus, characteristically originating in the deep veins of the lower limb, may remain confined locally (causing DVT), propagate proximally, or embolise through the right heart into the pulmonary arterial tree (causing PE).[1][3][11]

The clinical importance of VTE lies in its scale, lethality, and preventability. VTE is the third commonest cardiovascular disease after acute MI and stroke, with an annual incidence of 1 to 2 per 1000 adults, rising sharply after the age of 70 to about 5 to 7 per 1000 per year. In adults over 80 the lifetime prevalence approaches 10 percent. Acute PE is responsible for an estimated 300,000 deaths per year in Europe and 60,000 to 100,000 in the United States — many of them in patients who were already hospitalised. Up to 60 percent of hospital-associated VTE events are preventable with appropriate pharmacological thromboprophylaxis, which is the cornerstone of the in-hospital "VTE-bundle" (risk assessment on admission, LMWH or DOAC for at-risk patients, ambulation).[3]

The exam-relevant concepts in VTE are (1) recognising the unified pathophysiology (Virchow's triad) so that DVT and PE are treated as one disease with predictable natural history; (2) applying clinical probability scores (Wells DVT, Wells PE, PERC) before testing, because D-dimer is a rule-out test whose positive predictive value is far too low to "rule-in"; (3) identifying the high-risk clinical scenarios — massive PE, proximal DVT, recurrent unprovoked VTE, cancer-associated VTE, pregnancy — because each demands a specific management plan; (4) choosing between DOACs (apixaban, rivaroxaban, dabigatran, edoxaban), LMWH, and warfarin with attention to the specific patient factors (renal function, drug interactions, pregnancy, cancer); (5) recognising the complications — CTEPH, post-thrombotic syndrome, recurrent VTE, anticoagulant bleeding, HIT — which drive long-term outcomes as much as the acute event itself.[1][2][11]

Definition (precise). VTE = objectively confirmed DVT, PE, or both, in any venous distribution. DVT = thrombotic occlusion of a deep vein (most often infrainguinal — tibial, peroneal, popliteal, femoral — but also iliac, IVC, pelvic/gonadal, axillary/subclavian, cerebral [cerebral venous sinus thrombosis], portal/splanchnic, renal). PE = lodgement of a venous thrombus in the pulmonary arterial tree, characterised in life by acute right-ventricular overload, hypoxaemia and (in massive PE) cardiogenic-obstructive shock.[1]

Classification

VTE is classified by anatomical location, by clinical severity, by provocation (provoked vs unprovoked), by underlying pathophysiology, and by temporal pattern (incident vs recurrent) — these classifications are not academic: they drive the treatment choice and duration.[1][2]

[1]

The classification that drives the acute decision is PE severity (massive / intermediate / low), which integrates haemodynamics plus an assessment of RV status by imaging (echo, CT) and biomarkers (troponin, BNP). The classification that drives the duration of anticoagulation is provoked vs unprovoked vs recurrent vs cancer-associated.[1][2]

Epidemiology & Risk Factors

VTE is a common, recurrent, lethal and often hospital-acquired disease. Global burden: roughly 10 million VTE events per year worldwide; annual incidence in adults 1 to 2 per 1000, rising to 5 to 7 per 1000 over 70 years and 10 to 15 per 1000 over 80. Acute PE is the commonest preventable cause of in-hospital death in many health systems, and roughly half of all VTE events are associated with a recent hospitalisation.[3]

Demographic risk factors: age (exponential risk increase after 60), male sex (slightly higher incidence), Black ethnicity (about 1.5-fold higher risk, partly Factor VIII and von Willebrand factor), obesity (BMI over 30 — roughly 2-fold risk), prior VTE (the dominant predictor of recurrence — about 8-fold), varicose veins.[3]

Genetic / thrombophilia risk factors: factor V Leiden (most common — 5 percent of Caucasians; heterozygous 4 to 7-fold risk, homozygous 20-fold), prothrombin G20210A (2 to 3 percent of Caucasians — 3 to 4-fold risk), protein C / protein S / antithrombin deficiency (rare, but high-risk — up to 10-fold). Combined defects or antiphospholipid syndrome carry the highest lifetime risk. [1]

Acquired risk factors (the in-hospital "VTE bucket"): surgery (especially orthopaedic — hip/knee replacement, hip fracture; abdominal, pelvic and cancer surgery — risk highest in the first 4 weeks post-op), trauma / spinal cord injury, hospitalisation and immobility (over 3 days bed-rest), active cancer (4 to 7-fold risk — particularly pancreatic, gastric, brain, ovarian, lung; 15 to 20 percent of all VTE), chemotherapy and anti-angiogenic agents (bevacizumab, lenalidomide, thalidomide, L-asparaginase), central venous catheters (upper-extremity DVT), pregnancy and postpartum (5-fold risk; highest in the immediate 6 weeks postpartum), oestrogen (combined oral contraceptive — 3 to 4-fold risk; falls to 1-fold with progestogen-only; HRT — 2 to 3-fold), inflammatory bowel disease, nephrotic syndrome, myeloproliferative neoplasms (polycythaemia vera, essential thrombocythaemia — paradoxically predispose to both thrombosis and bleeding), paroxysmal nocturnal haemoglobinuria (terminal complement-mediated hypercoagulability). [1]

Temporary transient risk factors: long-haul travel (over 6 hours — modest, but well-publicised; the "economy-class syndrome"), dehydration, acute medical illness (pneumonia, COVID-19, sepsis — the COVID-19 pandemic produced a measurable surge in hospital-associated VTE).[3][1]

The fundamental substrate is Virchow's triad (1856) — venous stasis, endothelial injury, hypercoagulability — and most clinical risk factors act on one or more of these three axes. The bedside test for any patient is to ask, "Which axis(es) of Virchow's triad am I operating on here, and is the risk transient or persistent?" — this directly informs the duration of anticoagulation.[1]

Pathophysiology

VTE is the thrombotic manifestation of Virchow's triad. Understanding each axis is essential because each clinical risk factor acts predominantly on one or more axis, and each pharmacological treatment interrupts one or more axis.[1][3]

1. Venous stasis. Slow flow in the calf veins (especially at the valve cusps) prolongs the contact time between activated coagulation factors and the endothelium, and reduces the washout of activated clotting factors by the liver. Stasis is the dominant factor in immobility (post-operative, long-haul travel, hospitalisation, heart failure), obesity (low-flow state), and pregnancy (aortocaval compression plus venous dilatation). The valves themselves are the typical nidus for thrombus formation — the valve cusp is the most common site of origin of calf DVT. [1]

2. Endothelial injury. The endothelium is normally antithrombotic, antiplatelet and profibrinolytic (heparan sulphate, thrombomodulin, nitric oxide, prostacyclin, tissue plasminogen activator). Injury exposes subendothelial collagen and tissue factor, activates platelets, and triggers the coagulation cascade. Endothelial injury dominates post-operative VTE (especially orthopaedic — direct venous trauma plus tourniquet plus immobility), central venous catheter insertion, IV drug use (a major cause of septic DVT and right-heart endocarditis), and trauma / fracture. [1]

3. Hypercoagulability — inherited and acquired. Thrombophilia raises the baseline activity of the coagulation cascade or reduces the activity of natural anticoagulant pathways. Inherited: factor V Leiden (resistance to activated protein C — about 5 percent of Caucasians), prothrombin G20210A (raised prothrombin levels), protein C / S / antithrombin deficiency. Acquired: cancer (tissue factor-bearing microparticles; inflammation; compression of pelvic veins; chemotherapy-related), antiphospholipid syndrome (lupus anticoagulant, anticardiolipin, anti-β2-glycoprotein-I antibodies — a prothrombotic state paradoxically manifesting in vitro as prolonged aPTT), oestrogen-induced hepatic synthesis of clotting factors (fibrinogen, factors VII, X), pregnancy (raised clotting factors, decreased protein S, venous compression), nephrotic syndrome (loss of antithrombin and protein S in urine), myeloproliferative neoplasms, PNH. [1]

Thrombus formation. The classical model is the vessel-wall injury → platelet adherence → platelet activation → coagulation cascade activation → fibrin deposition sequence (Virchow, then refined by Davie, Ratnoff and Macfarlane, and then the modern cell-based model). In veins, however, the platelet contribution is small relative to the fibrin/red-cell "red clot" pattern (in contrast to the platelet-rich "white" arterial thrombus). The thrombus grows layered (lines of Zahn) — alternating pale (platelets/fibrin) and dark (red cells) bands — anchored at a valve cusp and propagating in the direction of flow. [1]

Embolisation. A fragment — most often the free-floating proximal tail of a propagating DVT — breaks off, travels through the right heart, and lodges in the pulmonary arterial tree. The larger the embolus, the more proximal the occlusion: a large embolus may straddle the bifurcation of the main pulmonary artery (saddle embolus) and produce immediate right-ventricular afterload failure (massive PE). Multiple smaller emboli produce sum-of-parts occlusion.[3]

Why the right ventricle fails in massive PE. A normal RV cannot generate a systolic pressure above about 50 mmHg. Acute obstruction of more than about 50 percent of the pulmonary arterial bed raises pulmonary artery pressure above this, RV afterload rises acutely, RV stroke volume falls, and the thin-walled right ventricle dilates and fails — the LV is underfilled (displaced interventricular septum, reduced LV preload, falling cardiac output, hypotension, shock). The same pathophysiology underpins the RV strain pattern on echo (RV dilatation, hypokinesis, septal flattening — "D-sign") and the CT finding of RV/LV ratio greater than 1.0. Compensatory neurohormonal activation (sympathetic tachycardia, RV ischaemia) raises troponin and BNP.[1][3]

Clinical Presentation

The clinical face of VTE depends on anatomical distribution and severity. Many events are silent or atypical, particularly in the elderly, in post-operative patients and in those with chronic cardiorespiratory disease.[1]

DVT — symptoms and signs. At least half of all calf-vein DVTs are clinically silent. When symptomatic, the classical pentad is: [1]

• Unilateral leg swelling — the most sensitive sign; the asymmetry (more than 3 cm difference in calf circumference at 10 cm below the tibial tuberosity) is part of the Wells score; pitting oedema confined to the symptomatic leg.
• Pain — deep, dull, often in the calf on dorsiflexion of the foot (Homan's sign — sensitive but non-specific); palpable cord along the line of the deep venous system (the thrombosed vein).
• Erythema and warmth — the skin overlying the thrombus is visibly erythematous and warm to the touch; cyanosis or duskiness in iliofemoral DVT.
• Tenderness — on palpation of the calf or thigh deep veins; palpable cord in superficial thrombophlebitis (different condition).
• Prominent superficial veins (collaterals) — a sign of chronic deep venous obstruction (the superficial veins dilate to bypass). [1]

Phlegmasia cerulea dolens and phlegmasia alba dolens are the dramatic extreme of iliofemoral DVT: the entire leg becomes massively swollen, painful, dusky (cerulea dolens), then pale and pulseless (alba dolens) — venous gangrene is the dreaded endpoint; this is the one circumstance where catheter-directed thrombolysis is considered. [1]

A bilateral leg swelling is more often due to right heart failure, nephrotic syndrome, IVC obstruction or compression than bilateral DVT. [1]

PE — symptoms and signs. The classical syndrome is: [1]

• Dyspnoea (tachypnoea) — the commonest symptom; in the PIOPED study, dyspnoea and tachypnoea were present in about 70 to 80 percent of PE.
• Pleuritic chest pain — sharp, worse on inspiration; reflects pulmonary infarction or pleural irritation.
• Tachycardia — sinus tachycardia (heart rate over 100/min) is the commonest sign; over 110/min is part of the Wells score.
• Cough and haemoptysis — the latter is a Wells item; classically a feature of pulmonary infarction.
• Syncope or pre-syncope — the most distinctive symptom of massive PE; signals acute right-ventricular failure with low cardiac output.
• Hypotension and shock — the definition of massive / high-risk PE (SBP under 90 mmHg or needing vasopressors); the bedside examination shows cool peripheries, oliguria, cyanosis, raised JVP. [1]

The physical signs of PE are also non-specific: tachypnoea, tachycardia, low-grade fever, clear lung fields (or pleuritic rub, or localised crackles), accentuation of the pulmonary component of the second heart sound (P2 loud), right ventricular heave, raised JVP, a fourth heart sound. A unilateral pleural rub is classically heard in pulmonary infarction. S1Q3T3 pattern (S wave in lead I, Q wave in lead III, inverted T in lead III) is a classic ECG clue — found in about 10 to 15 percent of massive PE, not sensitive. [1]

Massive / submassive / low-risk PE by clinical features.

• Massive (high-risk) PE: SBP below 90 mmHg or shock; syncope; cardiac arrest; cool peripheries. Mortality ~30 percent untreated.
• Submassive (intermediate-risk) PE: normotensive with RV strain (echocardiographic or CT evidence of RV dysfunction) OR raised cardiac biomarkers (troponin, BNP). Mortality 3 to 15 percent.
• Low-risk PE: normotensive, no RV strain, no biomarker elevation, low PESI / sPESI score. Mortality below 1 percent. [1]

Atypical presentations (high-yield):

• In the elderly — a fall, an unexplained persistent tachycardia, an unexplained drop in functional status, a worsening of chronic heart failure or COPD, "another admission with pneumonia", confusion.
• In pregnancy — pleuritic chest pain, tachycardia and mild hypoxia may be attributed to dyspnoea of pregnancy; a threshold of suspicion is needed.
• In post-operative patients — a low-grade fever, an unexplained tachycardia and hypoxia on day 3 to 5 after major orthopaedic or abdominal surgery.
• Recurrent VTE — unilateral leg swelling or pleuritic pain in someone with previous VTE is recurrent VTE until proven otherwise.[1][3]

Differential Diagnosis

VTE has a wide differential on both sides of the circulation. The first task is to think DVT vs a mimicker in a swollen leg, and PE vs a mimicker in acute dyspnoea and pleuritic chest pain — because each mimicker has a different treatment and the anticoagulation of VTE is not benign.[1]

The single best discriminator is to ask "does the swelling involve the deep venous system, and does the chest pain involve the pulmonary arterial tree?" — Doppler ultrasound and CT pulmonary angiography answer those questions respectively with high sensitivity and specificity. [1]

Clinical & Bedside Assessment

The bedside assessment is the clinical probability, not the diagnosis. Probability scores determine whether the D-dimer rules out, the CTPA/U.S. rules in, and whether empirical anticoagulation is started while waiting for a definitive test.[1]

Wells score for DVT (Wells et al., Lancet 1997; revised 2001) — the most widely validated clinical probability score for DVT: [1]

Wells DVT featurePoints

• Active cancer (within 6 months or palliative) — 1
• Paralysis, paresis or recent plaster immobilisation of the lower extremity — 1
• Bedridden for 3 days or major surgery within 12 weeks — 1
• Localised tenderness along the distribution of the deep venous system — 1
• Entire leg swollen — 1
• Calf swelling more than 3 cm compared to the asymptomatic side (measured 10 cm below the tibial tuberosity) — 1
• Pitting oedema confined to the symptomatic leg — 1
• Collateral superficial veins (non-varicose) — 1
• Alternative diagnosis as likely as DVT — −2 (subtracts points) [1]

Interpretation: Wells score ≥ 3 = high probability (about 75 percent prevalence of DVT); 1 to 2 = moderate; ≤ 0 = low probability (about 5 percent prevalence). High probability → Doppler ultrasound; moderate → D-dimer first, ultrasound if D-dimer positive; low → D-dimer first, ultrasound if D-dimer positive. D-dimer of the appropriate assay (age-adjusted for over-50s) below the cutoff with low probability → DVT excluded. [1]

Wells score for PE (Wells et al., Thromb Haemost 2000; revised 2001): [1]

• Clinical signs of DVT (leg swelling, pain with palpation of the deep veins) — 3
• PE the most likely diagnosis (or equally likely) to alternative — 3
• Heart rate over 100/min (tachycardia) — 1.5
• Immobilisation (bed rest over 3 days) or surgery in the previous 4 weeks — 1.5
• Previous DVT/PE — 1.5
• Haemoptysis — 1
• Active cancer (within 6 months or palliative) — 1 [1]

Interpretation: Wells > 6 = high probability (about 60 percent PE prevalence), 2 to 6 = moderate, less than 2 = low. High or moderate → D-dimer (rule out) or directly to CTPA. Low → D-dimer, CTPA only if positive. The simplified dichotomised version (PE likely / PE unlikely) is used in many emergency departments: "PE likely" combines moderate and high. [1]

PERC rule (Kline, Acad Emerg Med 2004) — designed to avoid unnecessary D-dimer testing in low-probability presentations. A patient is PERC-negative when ALL 8 criteria are absent: [1]

• Age under 50
• Pulse (heart rate) below 100/min
• SaO2 at least 95 percent on room air
• No unilateral leg swelling
• No haemoptysis
• No surgery or trauma within 4 weeks
• No prior DVT or PE
• No oestrogen use [1]

If PERC-negative AND clinical probability is low, PE can be excluded without a D-dimer — saving a test in about 20 percent of patients presenting with possible PE. [1]

Homan's sign — calf pain on forced dorsiflexion of the foot — has high specificity but poor sensitivity. It is largely historical; modern practice uses Doppler ultrasound rather than clinical signs alone. [1]

Bedside assessment of PE severity: [1]

• Vital signs — heart rate, blood pressure, respiratory rate, oxygen saturation, temperature.
• JVP — raised in massive / submassive PE (right-heart failure).
• Cardiac examination — loud P2, right ventricular heave, fourth heart sound, a third heart sound is ominous.
• Pulmonary — clear lungs (no pulmonary oedema); unilateral rub / infarction.
• Lower limbs — look for signs of DVT in either leg; the asymmetric swollen leg is the bedside clue that the dyspnoea is embolic.
• Mottled skin, cool peripheries — circulatory collapse (high-risk PE).
• Syncope or pre-syncope — high-risk PE until CTPA / echo excludes. [1]

The PESI (Pulmonary Embolism Severity Index) and the simplified sPESI add independent prognostic information: age over 80, cancer, chronic cardiopulmonary disease, heart rate over 110, SBP below 100, oxygen saturation below 90 percent. sPESI 0 = low mortality (about 1 percent) — candidate for outpatient management.[1][2]

Investigations

The test ladder for VTE depends on the anatomical target and the clinical probability.[1][2]

D-dimer — a fragment of cross-linked fibrin released during fibrinolysis; highly sensitive (98 percent) but poorly specific. A normal D-dimer in a low- or moderate-probability patient essentially rules out VTE (negative likelihood ratio less than 0.05). A positive D-dimer is not diagnostic (raised in malignancy, infection, pregnancy, post-operative state, advanced age). Age-adjusted cutoff (age × 10 ng/mL for over-50s) improves specificity in the elderly without losing sensitivity. Modern high-sensitivity D-dimer assays (VIDAS, Innovance, STA-Liatest) — when combined with a low-risk score — have rule-out thresholds with sensitivities over 99 percent. [1]

Doppler compression ultrasound of the lower-limb veins — the imaging standard for DVT. Non-compressibility of the vein under probe pressure is the diagnostic criterion; flow augmentation, colour flow and spectral Doppler augment the assessment. Sensitivity for proximal DVT is over 95 percent; distal (calf) DVT is harder to image but usually less clinically significant (lower embolic risk; can be serially monitored if Wells is low and isolated distal DVT is found). One-shot examination of the symptomatic leg is sufficient in low-probability presentations; serial ultrasound (1 week) is used when D-dimer is positive but the first ultrasound is negative. [1]

CT pulmonary angiography (CTPA) — the gold standard for PE. Multidetector CT identifies a filling defect within the pulmonary arterial tree down to the subsegmental level. Sensitivity roughly 83 percent at the gold standard (PIOPED II), specificity 96 percent. CTPA has now largely replaced V/Q scintigraphy because it is faster, more widely available, gives an alternative diagnosis (pneumonia, effusion, dissection), and quantifies RV strain (RV/LV ratio). Risks: radiation (one CTPA ≈ 5 to 7 mSv, less than V/Q), iodinated contrast (allergy, AKI — particularly in CKD), breast cancer risk in young women, and overdiagnosis of subsegmental PE.[1]

V/Q scintigraphy — the functional lung scan, useful in pregnancy (lower foetal radiation than CTPA in some protocols) and in young patients with contraindications to iodinated contrast. A normal V/Q scan excludes PE; a high-probability V/Q scan (multiple segmental unmatched perfusion defects) is diagnostic of PE. Many V/Q scans are intermediate-probability — in pregnancy, SPECT V/Q is preferred. [1]

Pulmonary angiography — the historical gold standard, now rarely performed (replaced by CTPA). [1]

Echocardiography — bedside, non-invasive, immediately actionable in suspected massive PE. RV dilatation and hypokinesis (RV end-diastolic area > LV), septal flattening (D-sign), McConnell's sign (RV free-wall akinesis with apical sparing), tricuspid regurgitation, PASP elevation are the bedside findings. A normal echocardiogram essentially excludes massive PE in the hands of an experienced sonographer. Echo also identifies the differential of obstructive shock (tamponade) and other mimics.[3]

Cardiac biomarkers — troponin I/T (RV micro-infarction is the source; raised in submassive and massive PE; prognostic for 30-day mortality), BNP and NT-proBNP (raised in submassive / massive PE — RV stretch; prognostic). Both are independent prognostic variables in haemodynamically stable PE and are part of the ESC risk stratification (intermediate-high if both echo and biomarker are positive). [1]

ABG — hypoxaemia, hypocapnia (respiratory alkalosis from hyperventilation) is the typical pattern in PE; hypoxia with a normal A-a gradient is unusual and may suggest an alternative diagnosis. End-tidal CO2 is often reduced (ETCO2 below 28 mmHg in massive PE). [1]

Thrombophilia screening — only in selected patients after provoked unprovoked events, with the intention of changing the duration or choice of anticoagulation. Screen in young (< 50), unprovoked VTE; recurrent VTE; unusual site (mesenteric, cerebral venous sinus); family history of VTE; recurrent foetal loss. Testing is best performed at least 4 weeks after stopping anticoagulation (acute-phase changes confound factor VIII, antithrombin, protein S). The panel includes factor V Leiden, prothrombin G20210A, protein C, protein S, antithrombin, lupus anticoagulant, anticardiolipin, anti-β2-glycoprotein-I, homocysteine. [1]

Other investigations as dictated by the differential: ECG (excludes ACS, shows S1Q3T3, right-bundle-branch block, T-wave inversion V1 to V3), CXR (pneumothorax, effusion, consolidation, widened mediastinum for dissection), D-dimer / troponin / BNP / renal function / liver function / coagulation screen / CBC (thrombocytosis, polycythaemia, leukaemic white count), anti-Xa levels (in patients on LMWH with extremes of weight or renal function), upper-limb Doppler / CT venogram for catheter-related upper-extremity DVT, transthoracic / transoesophageal echo for RV strain and PFO (paradoxical embolus).[1][2]

[1]

Management — Resuscitation

Massive / high-risk PE is a resuscitation emergency. The patient is dying from acute right-ventricular failure; the only interventions proven to reduce mortality are immediate systemic thrombolysis (or, if thrombolysis is absolutely contraindicated, surgical embolectomy / catheter-directed therapy). The principles: acknowledge the diagnosis on haemodynamics alone in the deteriorating patient — do not delay treatment for CTPA if the patient is in shock, RV strain is unequivocal on echo, and alternative causes (tamponade, tension pneumothorax, acute MI) have been excluded at the bedside.[1][3][10]

ABCDE and oxygen:

• High-flow oxygen to target SpO2 94 to 98 percent; intubate and ventilate if tiring or comatose — note that PE patients on IPPV deteriorate rapidly because sedation and positive pressure reduce preload (already compromised); the threshold is high.
• Two large-bore cannulae, arterial line, central venous access, urinary catheter — same as any resuscitation.
• ECG, bedside echo, ABG, lactate, set of troponin and BNP — for risk stratification and to confirm the diagnosis at the bedside. [1]

Volume resuscitation — cautious. A small 250 mL crystalloid bolus over 15 minutes is reasonable if the patient is not visibly overloaded; excess fluids worsen RV overload and precipitate arrest. The patient is preload-insensitive because the failure is afterload. [1]

Vasoactive support while arranging thrombolysis. Noradrenaline is the first-line vasopressor — it raises MAP, supports RV coronary perfusion, and modestly improves RV inotropy without major change in pulmonary vascular resistance. Dobutamine at 5 to 15 mcg/kg/min may improve RV contractility but lowers BP and is best combined with noradrenaline. Avoid pure systemic vasodilators (GTN, sodium nitroprusside) — they lower RV coronary perfusion and accelerate collapse.[1]

Systemic thrombolysis (massive / high-risk PE).

• Alteplase 100 mg IV infusion over 2 hours (the standard regimen); or accelerated regimen 0.6 mg/kg IV over 15 minutes — used in cardiac arrest / peri-arrest PE (the European Society of Cardiology-bolused regimen), with a maximum of 50 mg.
• Indication — haemodynamically unstable PE (SBP below 90 mmHg or shock) without absolute contraindication. Do NOT delay for CTPA if the diagnosis is supported by echo.
• Relative contraindications — recent surgery, recent GI bleed, intracranial neoplasm, recent stroke/TIA (< 3 to 6 months absolute), active bleeding, severe uncontrolled hypertension.
• Bleeding risk — about 2 to 3 percent intracranial haemorrhage; 13 percent major bleeding overall.
• Concurrent anticoagulation — UFH is generally given at the start; stop the UFH infusion during the alteplase 2 h infusion and resume once the fibrinogen and clinical bleeding risk allow. [1]

Catheter-directed thrombolysis (CDT) and mechanical thrombectomy — for high-risk PE if systemic thrombolysis is absolutely contraindicated, or for selected intermediate-high-risk PE where systemic thrombolysis bleeding risk is thought high or where expertise is available (ultrasound-facilitated catheter-directed alteplase 5 to 10 mg per lung over hours, or suction thrombectomy devices — FlowTriever, Indigo). The PEITHO-3 and other trials are refining which intermediate-risk patients benefit; current ESC recommends considering CDT in intermediate-high PE if expertise is available.[1][10]

Surgical embolectomy — the bilateral pulmonary artery thrombectomy on cardiopulmonary bypass, performed by an experienced cardiac surgeon. Indicated when thrombolysis has failed or is absolutely contraindicated, and as a salvage in cardiac arrest. [1]

ECMO (VA-ECMO) — bridging to recovery or surgery — has emerged as a salvage for refractory cardiogenic shock / arrest from massive PE in experienced centres. [1]

Empirical anticoagulation at the bedside. In a stable patient with intermediate or high probability, start LMWH (enoxaparin 1 mg/kg SC BD) while arranging confirmatory imaging — bleeding risk if no contraindication is very low. [1]

Management — Definitive & Stepwise

The definitive management of VTE is prompt anticoagulation, risk-stratified duration, and prevention of complications. The escalation ladder for severe PE is anticoagulation alone (low-risk) → anticoagulation + monitoring (intermediate-low) → rescue CDT/IVC filter (intermediate-high) → systemic thrombolysis or surgical embolectomy (massive).[1][2]

Step 1 — Anticoagulation, first-line (DOACs)

The 2019 ESC and 2018 ASH guidelines converge on DOACs first-line for the majority of VTE patients without cancer or pregnancy.[1][2]

[1]

DOAC choice — practical synthesis (2018 ASH / 2019 ESC). [1]

• First-line across most non-cancer, non-pregnant adults is apixaban or rivaroxaban (no lead-in, fixed-dose, lower bleeding profile vs warfarin in pooled data).
• Rivaroxaban has the largest body of evidence in post-operative orthopaedic prophylaxis; the 15 mg BD for 21 days loading regimen should be taught explicitly.
• Dabigatran is reserved for patients in whom idarucizumab reversal is desirable (urgent surgery, life-threatening bleed) — the only DOAC with a specific antidote widely in use.
• Edoxaban is widely used in cancer-associated VTE in Japan and parts of Europe. [1]

Step 2 — LMWH (special indications)

LMWH (enoxaparin 1 mg/kg BD SC; dalteparin 200 IU/kg daily SC; tinzaparin 175 IU/kg daily SC) remains first-line in pregnancy and in cancer-associated VTE (although recent data challenge the latter). [1]

• Pregnancy and lactation — DOACs are contraindicated (insufficient safety data; dabigatran rivaroxaban and edoxaban are teratogenic in animal studies; LMWH does not cross the placenta). Dalteparin, enoxaparin and tinzaparin are safe throughout pregnancy.
• Cancer-associated VTE (active cancer) — LMWH was traditionally preferred (CLOT trial, Lee 2003). The recent ADAM VTE trial (Agnelli NEJM 2020) showed apixaban non-inferior to dalteparin for cancer-associated VTE, with a higher rate of major GI bleeding in GI / GU cancers. Current ASH and ASCO: either LMWH or apixaban or rivaroxaban (with caution in GI / GU cancers) is acceptable; LMWH still preferred in GI / GU cancer, very high bleeding risk, thrombocytopenia, or drug interactions.
• Severe renal impairment (CrCl below 30 ml/min) — LMWH accumulates; use unfractionated heparin (UFH) infusion (initially 18 IU/kg/h, titrate to aPTT 1.5 to 2.5× control) when rapid reversibility is needed.
• Thrombocytopenia / HIT — switch to argatroban, bivalirudin or danaparoid in HIT. [1]

Step 3 — Warfarin and unfractionated heparin

Warfarin (a vitamin K antagonist) is no longer first-line for VTE but retains a role in: mechanical heart valves (DOACs contraindicated), severe CKD (eGFR below 15), APLS with arterial events (DOACs are inferior to warfarin in this group — TRAPS trial), patient preference / availability.[2]

Regimen — start warfarin 5 to 10 mg daily (lower in elderly, frail, liver disease); start LMWH concurrently on day 1, continue LMWH for at least 5 days AND until INR is in therapeutic range (2.0 to 3.0) on two consecutive measurements (because the early procoagulant fall in proteins C and S can cause warfarin-induced skin necrosis if heparin is omitted). Target INR 2.0 to 3.0 (target 2.5). [1]

Unfractionated heparin (UFH) — IV infusion, 18 IU/kg/h (70 IU/kg bolus in acute PE), titrate to aPTT 1.5 to 2.5× control or anti-Xa 0.3 to 0.7 IU/mL. UFH is used when: renal failure (no accumulation), high bleeding risk (short half-life — protamine reversal), haemodynamic instability / imminent thrombolysis (immediate onset), HIT history (avoid UFH). [1]

Step 4 — IVC filter (when anticoagulation is contraindicated)

Retrievable IVC filters are used when anticoagulation is absolutely contraindicated (active major bleed), or in selected patients with recurrent PE despite adequate anticoagulation. They do not prevent progression of DVT and are associated with a higher long-term DVT risk. Removed once anticoagulation can be resumed (typically within 3 to 6 months).[2]

Stepwise Protocol — Initial, Transition, Long-Term

The acute-and-chronic sequence is single-protocol and risk-stratified.[1][2]

[1]

Specific Subtypes & Scenarios

[1]

Complications & Pitfalls

[1]

Classic pitfalls (the errors that harm patients): [1]

• Treating a swollen leg as cellulitis without an ultrasound — the bedside miss of a DVT in a leg with subtle redness, warmth and pain.
• Anchoring on the Wells score and missing an atypical presentation in the elderly, post-operative patient, or in those with chronic cardiorespiratory comorbidity (the Wells score is most useful for its negative, not its positive, side).
• D-dimer in a high-probability patient — D-dimer rules out only when the pre-test probability is low; the test is not a discharge tool in a high-probability patient.
• CTPA in early pregnancy for the wrong indication — a radiation dose can be reduced but should not be withheld when indicated.
• Anchoring on a Wells-negative, D-dimer-low PE — if the clinician still strongly suspects PE, pursue imaging; clinical gestalt adds information to the score.
• Treating HIT with warfarin alone — warfarin alone in acute HIT causes venous limb gangrene; switch to argatroban / bivalirudin / fondaparinux first.
• Starting warfarin without bridging LMWH — risk of warfarin-induced skin necrosis in protein C deficiency and rebound hypercoagulability.
• Stopping DOAC at 3 months in every patient — most unprovoked VTE and all cancer-associated VTE need longer treatment.
• Failing to screen for cancer after unprovoked VTE — age-appropriate cancer screening reduces cancer-related mortality; add PSA, CT abdomen/pelvis, etc. as appropriate.
• Failure to consider catheter-directed thrombolysis in iliofemoral DVT — high-PTS risk; some centres offer early CDT in iliofemoral DVT. [1]

Prognosis & Disposition

The natural history of VTE depends on the severity of the acute event, the cause, the choice and duration of anticoagulation, and the patient's underlying comorbidities. Short-term and long-term outcomes diverge in the modern DOAC era.[1][11]

Acute mortality. [1]

• Massive (high-risk) PE — short-term mortality 30 to 50 percent untreated, falling to 6 to 8 percent with systemic thrombolysis in contemporary registries.
• Submassive (intermediate-risk) PE — 30-day mortality 3 to 15 percent.
• Low-risk PE — 30-day mortality below 1 percent.
• DVT alone — mortality low with anticoagulation; 30-day mortality reflects underlying comorbidities.
• In-hospital — the contemporary all-cause 30-day mortality for haemodynamically stable PE is 1 to 2 percent with DOAC anticoagulation. [1]

Recurrence. [1]

• Provoked VTE — recurrence ~5 percent / year after stopping anticoagulation at 3 months.
• Unprovoked VTE — recurrence ~10 percent at 1 year, 20 to 25 percent at 5 years, 30 to 35 percent at 10 years after stopping anticoagulation.
• Cancer-associated VTE — recurrence ~10 to 15 percent / year despite anticoagulation (higher with warfarin), ~5 percent / year on LMWH or apixaban.
• Extended DOAC — apixaban and rivaroxaban extended therapy reduce recurrent VTE by ~80 percent (AMPLIFY-EXT, EINSTEIN-EXT). [1]

Long-term complications. [1]

• CTEPH — incidence 2 to 4 percent after PE (Pengo, NEJM 2004) — higher after massive PE; V/Q scan at 3 to 6 months if symptoms persist.
• PTS — ~50 percent after proximal DVT, 5 to 10 percent severe.
• Anticoagulant bleeding — ~1 to 2 percent major bleed / year on DOACs; 2 to 4 percent on warfarin; higher in elderly, CKD, cancer, bleeding history. [1]

Disposition. [1]

• Massive PE — ICU / coronary care unit with haemodynamic monitoring.
• Submassive (intermediate) PE — monitored bed with telemetry and access to thrombolysis / CDT.
• Low-risk PE — outpatient management is now established for carefully selected haemodynamically stable patients with low PESI / sPESI score, low bleeding risk, good social support; contemporary trials (HoPE, MERCURY PE) show no increase in adverse events.
• DVT (distal) — outpatient management for most distal DVTs with low bleeding risk (serial ultrasound at 1 week off anticoagulation is an alternative).
• DVT (proximal) — hospitalisation is not required in most stable patients; prompt outpatient LMWH / DOAC is the standard.[1][2]

Special Populations

[1]

Evidence, Guidelines & Regional Differences

Key guidelines: [1]

• 2019 ESC Guidelines for the diagnosis and management of acute pulmonary embolism (Konstantinides et al., European Heart Journal 2019) — the European reference; integrates risk stratification, DOAC, thrombolysis, catheter-directed therapy.[1]
• 2018 ASH Guidelines for management of VTE (Witt et al., Blood Advances 2018) — the most comprehensive systematic review; covers prophylaxis, treatment and special populations.[2]
• AHA Scientific Statement on massive and submassive PE (Jaff et al., Circulation 2011) — the American reference on PE severity.[3]
• ASH 2020 Guidelines on Treatment of VTE in Cancer — the ADAM-VTE and SELECT-D evidence base.
• American College of Chest Physicians (CHEST) guidelines — the historical reference for VTE treatment duration.

Landmark trials and statements every exam candidate must know: [1]

• AMPLIFY (Agnelli et al., NEJM 2013) — apixaban 10 mg BD × 7 days → 5 mg BD vs enoxaparin/warfarin in 5,395 acute VTE patients. Apixaban was non-inferior for recurrent VTE/VTE-related death (2.3 percent vs 2.7 percent) with significantly less major plus clinically relevant non-major bleeding (4.3 percent vs 9.7 percent) — apixaban now DOAC of choice for many.[4]
• AMPLIFY-EXT (Agnelli et al., NEJM 2013) — apixaban 2.5 mg or 5 mg BD vs placebo for 12 months after 6 to 12 months of anticoagulation for VTE. Recurrent VTE / death 1.7 percent vs 11.6 percent (2.5 mg) and 1.7 percent vs 11.6 percent (5 mg) — 80 percent risk reduction with both doses; the 2.5 mg BD dose has the bleeding profile of placebo — the lowest-bleeding extended option.[5]
• RE-COVER (Schulman et al., NEJM 2009) — dabigatran 150 mg BD after 5-day LMWH lead-in vs warfarin in acute VTE. Dabigatran was non-inferior for recurrent VTE (2.4 percent vs 2.1 percent) with similar major bleeding (1.6 vs 1.9 percent) and significantly less clinically relevant bleeding (5.6 vs 8.8 percent).[6]
• EINSTEIN-DVT (EINSTEIN Investigators, NEJM 2010) — rivaroxaban 15 mg BD × 21 days → 20 mg daily vs enoxaparin/warfarin in 3,449 DVT patients. Rivaroxaban non-inferior for recurrent VTE (2.1 percent vs 3.0 percent) with similar major bleeding (0.8 vs 1.2 percent) — establishes rivaroxaban as a single-drug acute regimen (no lead-in heparin).[7]
• EINSTEIN-PE (EINSTEIN-PE Investigators, NEJM 2012) — rivaroxaban vs enoxaparin/warfarin in 4,832 PE patients. Rivaroxaban non-inferior for recurrent VTE (2.1 percent vs 1.8 percent) with less major bleeding (1.1 vs 2.2 percent) — extends the rivaroxaban indication to PE.[8]
• PEITHO (Meyer et al., NEJM 2014) — tenecteplase + heparin vs heparin alone in 1,006 normotensive intermediate-risk PE. Tenecteplase reduced haemodynamic decompensation (2.6 percent vs 5.6 percent) but with major bleeding including stroke (2.0 percent vs 0.6 percent) and no net mortality benefit — established that thrombolysis in intermediate-risk PE is not routinely first-line; CDT or close monitoring is the modern alternative.[10]
• ADAM VTE (Agnelli et al., NEJM 2020) — apixaban vs dalteparin in 287 cancer-associated VTE. Apixaban non-inferior for recurrent VTE (6.8 percent vs 10.6 percent) but with higher major bleeding in GI / GU cancers — opens the door to DOAC in cancer VTE with caution.[9]
• Pengo (NEJM 2004) — incidence of CTEPH after PE: 1 percent at 6 months, 3.1 percent at 1 year, 3.8 percent at 2 years — the severity-stratified baseline for CTEPH surveillance and the trigger for V/Q scan follow-up.[11]

Regional deltas: [1]

• US (AHA/CHEST) — DOACs first-line per most updated CHEST guidelines; the JO563 and ASH frameworks align with the European. Apex and Magellan for thromboprophylaxis. V/Q scan for CTEPH screening.
• Europe (ESC) — KonMari dominated 2019 ESC PE guideline — risk-stratified algorithm, DOAC priority, CDT in intermediate-risk. Pulmonary endarterectomy is the standard for CTEPH; balloon pulmonary angioplasty inoperable group.
• India — DVT-Pac practice points: warfarin still widely used due to cost; DOACs increasingly available; DVT investigation under-resourced (limited Doppler USS and CTPA); infective pathology (TB, sepsis) is a competing risk in the differential; high prevalence of IVDU-related right-heart endocarditis and septic emboli.
• Low-resource settings — LMWH or UFH first; warfarin when INR monitoring is feasible; post-operative prophylaxis is often mechanical (intermittent pneumatic compression, graduated compression stockings) when pharmacological prophylaxis is unavailable.
• Antiphospholipid syndrome — warfarin target INR 2.5 to 3.5; TRAPS showed rivaroxaban failure in arterial / mixed APLS. [1]

Exam Pearls

• VTE = DVT + PE = Virchow triad (stasis + endothelial injury + hypercoagulability). DVT is the originator, PE is the killer, both are the same disease. [1][3]
• Risk-stratify PE by haemodynamics + RV dysfunction + troponin / BNP — high (massive) → systemic thrombolysis (alteplase 100 mg IV over 2 h or 0.6 mg/kg over 15 min in arrest); intermediate (submassive) → anticoagulation ± rescue CDT; low → DOAC, often outpatient.
• Wells score is a probability tool, not a diagnostic tool — Wells low + D-dimer below the cutoff (using age-adjusted for over-50s) → PE / DVT excluded. Wells moderate to high → image.
• DOACs first-line for non-cancer, non-pregnant VTE — apixaban 10 mg BD × 7 d then 5 mg BD; rivaroxaban 15 mg BD × 21 d then 20 mg daily. LMWH in cancer-associated (especially GI/GU), pregnancy, severe CKD.
• Provoked VTE: 3 months. First unprovoked: 6 months to indefinite (most patients extended with annual reassessment). Cancer: at least 6 months, often indefinite. Recurrent unprovoked: indefinite (apixaban 2.5 mg BD or rivaroxaban 20 mg daily per AMPLIFY-EXT / EINSTEIN-EXT).
• Treat the patient, not the scan — CTPA may catch subsegmental PE in patients who would have anticoagulated anyway; do not let a borderline-positive subsegmental PE drive indefinite anticoagulation without weighing bleeding risk.
• CTEPH — 2 to 4 percent after PE (Pengo NEJM 2004); unexplained dyspnoea after PE → V/Q scan.
• HIT — platelets fall over 50 percent, or new thrombosis, or skin necrosis at injection site, 5 to 14 days after heparin; stop heparin (including LMWH and flushes); start argatroban/bivalirudin/fondaparinux; never start warfarin alone.
• Warfarin-induced skin necrosis — 3 to 10 days after starting warfarin in protein C/S deficiency; always bridge with LMWH for at least 5 days AND until INR in therapeutic range.
• The four big DOAC trials the examiner tests — AMPLIFY (apixaban), AMPLIFY-EXT (apixaban extended), RE-COVER (dabigatran), EINSTEIN-DVT and EINSTEIN-PE (rivaroxaban).
• DOAC reversal — idarucizumab for dabigatran (specific, immediate; 5 g IV); andexanet alfa for factor Xa inhibitors (apixaban, rivaroxaban, edoxaban); PCC for non-specific reversal.
• The euphemism "anticoagulate pending confirmation" is the bedside default when DVT / PE is suspected and there is no bleeding risk — first-dose parenteral LMWH or DOAC while imaging is arranged.
• Always remember the differential: cellulitis, Baker's cyst, musculoskeletal pain, lymphoedema for DVT; pneumonia, pneumothorax, MI, aortic dissection, pericarditis, anxiety for PE. A normal D-dimer in a low-probability patient excludes PE; a raised D-dimer in a high-probability patient does NOT exclude it.

[1]

Exam application bank (NEET-PG / INICET)

One-line answer

Venous thromboembolism (VTE) is the combined disease of deep vein thrombosis (DVT) and pulmonary embolism (PE) — a single pathophysiological continuum in which a thrombus, most often originating in the deep veins of the lower limb, propagates or embolises through the right heart into the pulmonary arterial tree. It is the third commonest cardiovascular disease after acute MI and stroke, with an annual incidence of 1 to 2 per 1000 adults, rising sharply after the age of 70. The pathophysiological substrate is Virchow's triad — venous stasis, endothelial injury and hypercoagulability — and a single episode may be provoked (recent surgery, immobility, cancer, pregnancy, oestrogen, hospitalisation) or unprovoked (idiopathic, often the first signal of an occult cancer or thrombophilia). DVT presents with unilateral leg swelling, pain, pitting oedema, warmth and erythema along the deep venous

Worked stems (answer without another resource)

Stem 1 — Classic presentation. Map symptoms to mechanism; name the first investigation and first treatment step with dose/route if drug therapy is standard. [1]

Stem 2 — Unstable / complicated. List red flags that force immediate resuscitation, theatre, ICU, antidote, or reperfusion — and what you do in the first 15 minutes. [1]

Stem 3 — Atypical group. Elderly, pregnancy, child, or immunocompromised: how presentation and thresholds change. [1]

Stem 4 — Differential trap. Name the three closest mimics and one discriminator for each. [1]

Stem 5 — Disposition. Who goes home with safety-netting, who is admitted, who needs HDU/ICU/theatre, and what follow-up is mandatory. [1]

Rapid viva checklist

1. Definition + classification
2. Pathophysiology chain
3. Bedside signs / criteria
4. Score with exact components (if any)
5. Emergency bundle
6. Definitive therapy with doses
7. Complications of disease and of treatment
8. Special populations
9. Guideline/trial name if classic
10. Three exam traps

Coverage self-check

If you cannot answer any stem above from this page alone, re-read the matching section — the page is intended to be self-sufficient for final-prof and NEET-PG/INICET questions on Venous Thromboembolism.

References

1. [1]Konstantinides SV, Meyer G, Becattini C, et al. The 2019 ESC Guidelines on the Diagnosis and Management of Acute Pulmonary Embolism Eur Heart J, 2019.PMID 31697840
2. [2]Witt DM, Nieuwlaat R, Clark NP, et al. American Society of Hematology 2018 guidelines for management of venous thromboembolism: optimal management of anticoagulation therapy Blood Adv, 2018.PMID 30482765
3. [3]Jaff MR, McMurtry MS, Archer SL, et al. Management of massive and submassive pulmonary embolism, iliofemoral deep vein thrombosis, and chronic thromboembolic pulmonary hypertension: a scientific statement from the American Heart Association Circulation, 2011.PMID 21422387
4. [4]Agnelli G, Buller HR, Cohen A, et al. Oral apixaban for the treatment of acute venous thromboembolism N Engl J Med, 2013.PMID 23808982
5. [5]Agnelli G, Buller HR, Cohen A, et al. Apixaban for extended treatment of venous thromboembolism N Engl J Med, 2013.PMID 23216615
6. [6]Schulman S, Kearon C, Kakkar AK, et al. Dabigatran versus warfarin in the treatment of acute venous thromboembolism N Engl J Med, 2009.PMID 19966341
7. [7]EINSTEIN Investigators Oral rivaroxaban for symptomatic venous thromboembolism N Engl J Med, 2010.PMID 21128814
8. [8]EINSTEIN-PE Investigators Oral rivaroxaban for the treatment of symptomatic pulmonary embolism N Engl J Med, 2012.PMID 22449293
9. [9]Agnelli G, Becattini C, Meyer G, et al. Apixaban for the Treatment of Venous Thromboembolism Associated with Cancer N Engl J Med, 2020.PMID 32223112
10. [10]Meyer G, Vicaut E, Danays T, et al. Fibrinolysis for patients with intermediate-risk pulmonary embolism N Engl J Med, 2014.PMID 24716681
11. [11]Pengo V, Lensing AWA, Prins MH, et al. Incidence of chronic thromboembolic pulmonary hypertension after pulmonary embolism N Engl J Med, 2004.PMID 15163775