Pulmonary Embolism/ DVT

Question 1

What is the pathophysiology behind PE/DVT?

Answer 1

• Venous thrombi can form in the deep veins of the legs or pelvis (DVT). Most form in the calf, with around 10% progressing to the proximal leg and becoming (more) symptomatic.
  
  • 50% of untreated proximal thrombi progress to pulmonary embolism (PE), the commonest type of venous thromboembolism (VTE).
  • Less commonly, PEs are caused by fat, fluid, or infective emboli.
  • Annual incidence of DVT: 1/1000.

Question 2

What are the signs/symptoms seen in PE/DVT?

Answer 2

• Symptoms:
  
  • Leg pain, which may be along the vein.
  • Respiratory: acute SOB, pleuritic chest pain, haemoptysis, cough.
  • Systemic: dizziness, fever.
• Signs:
  
  • Cyanosis
  • Swollen, tender, red leg.
  • Cardiac: ↑HR, AF, ↑JVP.
  • Chest: ↑RR, pleural rub, pleural effusion.
  • Pulsus paradoxus.

Question 3

What are the risk factors for PE/DVT?

Answer 3

• DICE:
  
  • DVT or PE past medical history, or thrombophilia
  • Immobility, leading to venous stasis. May be due to recent surgery or travel. Surgery (and trauma) may also directly cause thrombi, especially when affecting the lower leg.
  • Cancer, which activates thrombin. Prostate and ovarian are particularly associated.
  • Estrogen, which increases fibrinogen, prothrombin, and clotting factor levels. Causes: pregnancy, postpartum, contraceptive pill, HRT, and obesity.
• Others:
  
  • Age
  • Other conditions: HF, IBD, nephrotic syndrome, polycythaemia rubra vera.

Question 4

Which investigations should be carried out in suspected PE/DVT?

Answer 4

• Diagnosis
Screening:
  
  • Screen with 2-level Wells DVT score (≥2 is +ve) or 2-level Wells PE score (≥4 is +ve). D-dimer if Wells -ve.
  • CXR in suspected PE: may show wedge-shaped infarct (rare), but more for ruling out other conditions.
• Confirmation:
  
  • Imaging if either Wells or D-dimer is +ve.
  • Suspected DVT: proximal leg (above knee) compression US within 4 hours. If US not immediately available, give LMWH and get US within 24 hours. If US -ve, get D-dimer (if not done yet), and repeat US in 1 week if D-dimer +ve.
  • Suspected PE: CTPA or V/Q SPECT. If not immediately available, give LMWH. If scan -ve, proximal leg US if you suspect DVT.
• Other investigations
  
  • ABG in PE: ↓O2, ↓CO2, ↑pH.
  • ECG in PE: most commonly, sinus tachycardia (50%). Less commonly (20-30% each), RV strain (T inversion in V1-3), S1Q3T3 (prominent S in lead I, and Q wave and inverted T in lead III), RBBB, and right axis deviation.
  • Unprovoked VTE → consider thrombophilia screen. Look for underlying cancer only if suggested by history, exam, and basic bloods.
  • Baseline aPTT before heparin, and baseline INR before warfarin.

Question 5

How is PE/DVT managed?

Answer 5

• Acute
  
  • ABCDE
  • Therapeutic dose LMWH or fondaparinux SC for 5 days or until INR >2 for >24 hours. The goal of treatment is to prevent recurrent short-term VTE. Rivaroxaban PO is an alternative.
  • Consider thrombolysis with alteplase if hemodynamically unstable (SBP <90, ‘massive PE’).
• Preventing complications
Long-term anticoagulation:
  
  • Start during admission, overlapping with LMWH for 72 hours (or until INR >2 for 2 days).
  • Continue for 3 months if provoked, or 6 months if unprovoked. Take permanently if second VTE.
  • Options are warfarin, dabigatran, apixaban, or rivaroxaban (can also be used acutely).
  • 6 months LMWH in active cancer.
• Below-knee compression stocking(s):
  
  • Wear on affected leg(s) in patients with proximal DVT.
  • Start 1 week after diagnosis (or when swelling settles), and continue for 2 years.
  • Replace every 6 months.
• Thrombectomy:
  
  • Consider for symptomatic iliofemoral DVT if symptoms <2 weeks, patient well, life expectancy >1 year, and low bleeding risk.
  • Reduces risk of post-thrombotic syndrome.
• Distal DVTs
  
  • NICE do not discuss/recommend treating distal DVTs (below knee, infrapopliteal ‘calf clots’) – about 1/4 DVTs – as there is limited evidence of benefit and a low risk of progression to serious pathology. Hence they only recommend proximal leg US in suspected DVT, not whole leg US.
  • However, some guidelines and researchers say that these should be treated. Consider serial US if asymptomatic – to look for proximal propagation – or anticoagulation for 6-12 weeks if symptomatic and/or high risk.

Question 6

Which complications may occur in PE/DVT?

Answer 6

• Recurrent VTE:
  
  • 1/3 in 10 years after unprovoked VTE.
  • Low risk if post-surgical VTE.
  • Recurrent DVT can be hard to diagnose as residual US abnormalities remain for 6-12 months.
• DVT complications:
  
  • Cellulitis/thrombophlebitis: can resemble, cause, or follow DVT.
  • Post-thrombotic syndrome.

Question 7

How is post-surgical / longterm VTE prevention approached?

Answer 7

• All inpatients should be assessed for VTE risk (e.g. using Department of Health VTE risk assessement tool), and most will have prophylaxis prescribed if VTE risk outweighs bleeding risk.
Pharmacological VTE prophylaxis
In-hospital:
  
  • Offered to medical and surgical patients.
  • LWMH 1st line, fondaparinux 2nd line. UF heparin is another option in CKD.
  • It should be avoided in those with risk factors for major bleeding: active bleeding, anticoagulant use, bleeding disorder, acute stroke (unless very high risk e.g. thrombophilia, prior VTE), lumbar puncture or spinal anaesthesia planned, BP >230/120, platelets <75.
  • Start at admission – unless surgery within 12-24 hours – and continue until discharge.
  • Give up to 12 hours pre-op (LMWH half-life is 4 hours), re-start 6 hours post-op, except spinal and cranial surgery where gap must be 24 hours pre- and post-op.
• Treatment may continue at home in surgical patients discharged before completing recommended durations:
  
  • LMWH continued for 7 days after most major surgery, or even 28 days after adominal cancer surgery.
  • LMWH or DOAC continued for 2-4 weeks after most major lower limb orthopedic surgery, and up to 6 weeks if prolonged immobilization and has other risk factors.
• Mechanical VTE prophylaxis
  
  • Offered to surgical patients in addition to pharmacological prophylaxis.
  • Options: compression stockings, intermittent pneumatic compression (IPC) devices, foot impulse devices.
  • In medical patients, it is used when pharmacological prophylaxis is contraindicated, except stroke where IPC is 1st line given the high bleeding risk from anticoagulation.
  • Contraindications: PVD or peripheral bypass grafts, peripheral neuropathy, severe peripheral oedema, skin problems on legs.
• Other medications
  
  • Advise surgical patients to stop taking any estrogen-containing contraceptive or HRT 4 weeks before surgery.
  • Consider stopping antiplatelets 1 week before surgery.
  • Minimize other risk factors, most importantly immobility and dehydration.
  • If there is a high risk of bleeding, most patients on warfarin (e.g. AF) should stop 5 days before surgery and be switched to LMWH, with an INR target of <1.5. Very high risk patients (e.g. metallic heart valve) should get IV heparin, which has a 2 hour half life so can be continued until 4 hours before surgery.
  • Stop DOACs 24h before surgery.