Author: Indy Karpha / Codes: CC5, HAP6 / Published: 11/03/2015
Suspected VTE is a common presentation in the ED, yet investigation and management of these conditions remains a challenge due to uncertainty regarding diagnostic tests, a spectrum in clinical presentation, and probably an element of defensive practice from a medico-legal perspective.
Haematology Registrar Indy Karpha talks us through it.
What exactly is VTE?
A venous thromboembolism (VTE) is when a blood clot forms in a deep vein, commonly in the lower limbs or pelvis. This thrombus can embolise to the lungs, causing a blockage in the pulmonary arteries, causing a pulmonary embolism (PE). The term VTE therefore includes both deep vein thrombosis (DVT) and PE.
When should it be suspected?
We all probably know the answer to this one. The commonest presentations we will be coming across will be either lower limb DVT or PE.
DVT usually presents as a unilateral lower limb swelling with a hot, tender calf with pitting oedema, collateral superficial veins and possibly localised tenderness along the deep venous system. Typically the calf will be >3cm larger than the asymptomatic side.
PE classically presents with shortness of breath and pleuritic chest pain. ABG may reveal a respiratory alkalosis due to hyperventilation, with a type 1 respiratory failure. The commonest ECG finding is a sinus tachycardia, but there may be a RBBB, R axis deviation, or the textbook description of S1Q3T3 (actually fairly uncommon).
Remember in patients with a history of malignancy, thrombophilia traits or intra-vascular access, VTE may present in more unusual places like the upper limbs.
When VTE is a differential, it is useful to weigh up potential risk factors to support your diagnosis. Risk factors for a venous thromboembolism include:
- Active cancer
- Paralysis/limited mobility
- Recent plaster immobilisation of the lower limbs
- Recently bedridden for >3 days
- Major surgery in the preceding 12 weeks
- Recent long haul flights
- Oral contraceptive pill
- Previous history of VTE
The Wells score is also often used to weigh up the likelihood of VTE, and in fact in some trusts is used as part of the vetting process for radiology requesting.
The Wells score, youll probably remember from medical school, is a series of questions on the clinical presentation and presence of risk factors for VTE. NICE guidance suggests that every patient with suspected VTE, after thorough clinical assessment should have a documented Wells Score. The score differs slightly between DVT and PE see below.
Suspected DVTwhat to do:
So, you think your patient probably has a DVT. What is the best way to work this up?
- Do the Wells score. The rest of the management is actually very dependent on this.
- If the Wells score is unlikely (<2), get a D Dimer.
- If the Wells score is unlikely and the d dimer is negative, DVT can be effectively ruled out.
- If the Wells score is unlikely and the D Dimer is positive, get a doppler US of the lower limb. This can be done without anticoagulation if the doppler will happen within 4 hours of being requested. Otherwise, the patient should receive a shot of parenteral anticoagulation, normally a low molecular weight heparin like clexane or dalteparin (consult your trust policy).
- If the Wells score is likely, get a doppler within 4 hours of requesting, or anticoagulate and organise a doppler US if it cant be done within 4 hours.
BUT according to NICE guidance, you still need to get a d dimer because:
If the patient has a positive D Dimer was positive AND the doppler was negative, you still need to get an interval doppler US in 6-8 days. This is to rule out proximal extension of a superficial/distal thrombus which may present later.
If the D Dimer was negative AND the doppler was negative, DVT can be ruled out.
If the D Dimer was positive AND the doppler was positivethey have a DVT! Continue LMWH and organise longer term anticoagulation, such as a vitamin K antagonist (eg warfarin).
The process is similar for PE, but the Wells score slightly different.
So, if you think your patient has a PE
- Do the Wells score.
- If it is likely (>4 points), no need for d dimer. Instead get imaging either immediately, or anticoagulate whilst you await this. The NICE guidance is suggestive of CTPA as better than VQ, but service provision is likely to differ from trust to trust.
- If the Wells score is unlikely (4 points), get a d dimer. (Note that the score is different for PE compared to DVT).
- If the Wells score is unlikely and the d dimer negative, PE is unlikely here.
- If the Wells score is unlikely and the D Dimer positive, organise immediate imaging or anticoagulate whilst you wait.
NB If your CTPA is negative but you suspected DVT and PE, it might be worthwhile getting a doppler US of the leg as well.
Other Points to Consider
There are a number of other issues to bear in mind when assessing patients with VTE.
- Patients with confirmed DVT should be offered below knee graduated stockings (affected leg only) about a week after diagnosis or when swelling has reduced sufficienctly (in the absence of contraindications).
- TEDS should be worn on the affected leg for 2 years post DVT (get them changed 2-3 times a year).
- Anyone aged >45 with an UNPROVOKED VTE (ie, no risk factors), should get a CT chest/abdomen and pelvis, to rule out an underlying malignancy. Women should get a mammogram as well.
- Heparin is an animal based product, and patients should be advised of this, as some patients may have concerns or religious beliefs which can impact management.
This is often considered in patients presenting with recurrent unprovoked VTE or with a strong family history of VTE. However, in general it is rare that this should be investigated in the acute setting.
Essentially, the only alteration in management if there was an underlying thrombophilic state, would be with regard to duration of anticoagulation. So, in patients with unprovoked VTE, or with a first degree relative who has also had an unprovoked VTE, thrombophilia screening can be considered at the stage when anticoagulation is to be stopped.
The D Dimer
Current NICE guidance does encourage the use of the D Dimer alongside Wells scoring, essentially to aid ruling out a diagnosis of VTE, or to aid decision making regarding interval doppler scanning in 6-8 days time in DVT.
The D Dimer is essentially a marker of fibrin breakdown, and as such is used to aid diagnosis of VTE, as well as a marker of DIC. However, there is a high rate of false positive as it can be elevated in several other conditions, including:
- GI haemorrhage
And the list continues..! It should also be remembered that VTE CAN occur in the presence of a negative d dimer, so the whole clinical picture needs to be taken into account when assessing these patients.
Community DVT services
As a large proportion of patients are likely to require doppler US for suspected DVT, more and more trusts are now offering a home DVT service, in which the patient receives a parenteral anticoagulant, is discharged from the hospital and returns for a doppler US the next day. This prevents unnecessary inpatient stays whilst awaiting scans.
Newer Oral Anticoagulants (NOACS)
I thought it would be worthwhile briefly thinking about the use of NOACS in VTE. Currently, the only licenced NOAC for VTE is Rivaroxaban. The benefits of the NOACS is that the onset of therapeutic activity is quick (within a few hours), there is no drug level monitoring required, and the half life is fairly short, so effects stop rapidly after stopping treatment.
Rivaroxaban is a factor Xa-inhibitor, and at present there is no antidote (like octaplex for warfarin). This raises issues with regard to reversal in the presence of bleeding. Moreover, it should be remembered that Rivaroxoban should not be offered in patients with renal impairment, potential for drug interactions, or deranged LFTs. It does however offer a more convenient alternative than warfarin for longer-term anticoagulation.
VTE is common in the ED and proper investigation is needed for diagnosis. Always calculate the Wells score and use measure a d-Dimer if indicated, but dont forget to take the clinical picture into consideration when managing these patients.