|Year : 2015 | Volume
| Issue : 2 | Page : 49-54
Thromboreductive Strategies in Acute Deep Vein Thrombosis
Arvind D Lee
Department of Vascular Surgery, Nepean Clinical School University of Sydney, Sydney, Australia
|Date of Web Publication||31-Jul-2015|
Dr. Arvind D Lee
Department of Vascular Surgery, Nepean Clinical School University of Sydney, Sydney
Source of Support: None, Conflict of Interest: None
This paper reviews the current rationale, methods and outcomes of interventions to reduce acute clot burden in deep vein thrombosis.
Keywords: Deep vein thrombosis, postthrombotic syndrome, thrombectomy, thrombolysis
|How to cite this article:|
Lee AD. Thromboreductive Strategies in Acute Deep Vein Thrombosis. Indian J Vasc Endovasc Surg 2015;2:49-54
| Introduction|| |
Deep vein thrombosis (DVT) has acute and chronic effects on the affected limb. Acute symptoms can range from minimal swelling and pain to profound venous obstruction leading to venous gangrene. Chronic symptoms in a postthrombotic limb can also range from no discernible effects to ulceration, pain, and a serious compromise on the quality of life. While anticoagulation remains the cornerstone of treatment, clinical outcomes of an anticoagulation-only strategy depend largely on the efficacy of physiological fibrinolysis in restoring venous outflow and limiting venous wall damage. The wide variation in patient outcomes following an episode of DVT suggests that restoration of normal venous outflow does not occur in all and additional therapeutic strategies to remove clot are required in some situations. This paper reviews the rationale, methods, and outcomes of such therapies in acute DVT.
| The Rationale for Reducing Clot Burden|| |
Acute massive deep vein thrombosis
Acute, massive venous thrombosis with severe outflow obstruction in a limb is a recognized presentation. Traditionally, the condition has been classified into three groups - phlegmasia alba dolens (PAD), phlegmasia cerulea dolens (PCD), and venous gangrene.
Phlegmasia alba dolens is manifested by massive swelling, pain and pallor of the affected limb and is believed to be due to extensive thrombosis of major outflow veins with sparing of collateral veins leading to subcutaneous edema but no features of cutaneous venous congestion. The term PAD is not commonly used in contemporary literature and is essentially a clinical description of an extensive, proximal iliofemoral DVT (IFDVT). While most patients with PAD can be managed with limb elevation, anticoagulation and compression with a low risk of limb loss, there are reasons to consider thromboreduction and these are discussed in more detail in the next section on postthrombotic syndrome (PTS).
Phlegmasia cerulea dolens is characterized by swelling, pain and cyanosis and is believed to be due to further thrombosis of collateral veins leading to cutaneous venous congestion. PAD and PCD are reversible. Venous gangrene is irreversible damage to skin, subcutaneous tissue, and muscle secondary to increased interstitial pressures compromising arterial perfusion at the capillary level. A review of 32 reports on a total of 62 patients with PCD showed a 57% mortality rate and 43% major amputation rate in patients with venous gangrene. Lesser forms of PCD still carried >20% mortality and major amputation rate. 
There are no randomized controlled trials or accepted treatment algorithms available on the management of this group of patients. However, there are numerous reports of successful limb salvage in cases of PCD with impending venous gangrene. This has been achieved by both open surgical thrombectomy  and catheter-directed thrombolysis (CDT). , It makes intuitive sense that clot removal by any means is the only chance of avoiding limb loss and death in a situation of progressive venous congestion of a limb.
Postthrombotic syndrome is a spectrum of symptoms and signs that can occur in a limb previously affected by a DVT. Symptoms typically include pain, swelling, heaviness, itching and cramps in the affected limb with visible signs of edema, venous ectasia, erythema, hyperpigmentation, eczema and ulceration. The condition can vary in severity and can occur as a continuation of symptoms associated with an acute DVT or can develop later. 
The risk of developing PTS after all episodes of acute DVT is reported varyingly between 20% and 50% and the risk of severe PTS with ulceration between 5% and 10%. , With the annual risk of DVT ranging from 0.1% to 0.3% of the general population, severe PTS is a significant health problem with impacts on health care costs and quality of life. Severe PTS has been shown to have generic quality of life scores worse than chronic lung disease and osteoarthritis.  The following factors have been shown to increase the risk of developing PTS following an episode of DVT:
- High body mass index ,
- Older age ,
- DVT affecting iliac and femoral veins ,
- Recurrent and residual DVT in the affected limb 
- Persistent symptoms of acute DVT at 1-month after diagnosis 
- Subtherapeutic INR after anticoagulation with warfarin. ,
Delayed and incomplete resolution of thrombus, especially through major outflow veins of the affected limb appears to play a major role in the development of PTS. It is hypothesized that the ongoing presence of thrombus and inflammation in the vein wall leads to an increased risk of valvular damage and fibrosis leading to venous reflux and obstruction. As early as 1948, Swedish phlebologist Gunnar Bauer, showed that most deep veins recanalized following a DVT, but the venous valves were destroyed during the process.  His suggestion to resect the popliteal vein to disrupt the reflux however never gained traction. Over the last 2 decades, the role of venous obstruction in the pathogenesis of chronic venous disease has increasingly been recognized particularly with the use of intravascular ultrasound.  In a large series of patients with chronic venous disease including 54% postthrombotic limbs, identification and correction of outflow obstruction alone resulted in significant improvements in clinical outcomes.  The American Heart Association (AHA) has proposed a pathophysiological model for the development of PTS consisting of both venous outflow obstruction and venous valvular reflux. 
The use of thromboreductive strategies aimed at rapidly eliminating the initial thrombotic burden is the logical choice when one follows the above line of thought. However, there is as yet insufficient evidence to support the universal use of these modalities in all patients with an acute DVT. There are numerous nonrandomized, single-center series that have shown a reduction in the incidence of PTS with the use of CDT and percutaneous mechanical thrombectomy (PMT). ,, The largest randomized clinical trial with the use of most contemporary modalities of treatment and robust design, the ATTRACT trial is expected to complete enrolment in 2016.  Two earlier randomized clinical trials - the CaVenT study , and TORPEDO trial  provide some insights into the use of CDT and PMT in preventing PTS. The Norwegian CaVenT trial studied 209 patients with acute, proximal DVT in a nonblinded fashion. The patients were randomized to CDT with anticoagulation versus standard anticoagulation alone. At the end of 2 years, the risk of PTS was 41% in the CDT arm as opposed to 55% in the anticoagulation arm (absolute risk reduction of 14.4% and a number needed to treat of 7). These underwhelming results were compromised by a lack of comparability in adequacy of anticoagulation and in the use of compression stockings between the two groups. Interestingly, a subsequent quality of life analysis at 24 months did not show any significant difference between the two groups.  The TORPEDO trial compared PMT with anticoagulation and standard anticoagulation in patients with symptomatic DVT. The overall risk of PTS was 30% in the anticoagulation arm and only 7% in the PMT group. This trial too was compromised by a nonstandard definition of PTS and bias associated with a nonblinded design.
It must not be forgotten that other strategies to prevent PTS exist and have only been incompletely studied. Inadequate anticoagulation with warfarin during treatment of an acute DVT has been shown to increase the risk of PTS. , The HOME-Lite study showed higher rate of recanalization and lower rates of venous ulceration in patients treated with prolonged use of low molecular weight heparin compared to warfarin.  The role of newer anticoagulants with more predictable activity has also not been studied in the context of PTS prevention. External compression stockings have long been held as useful in preventing PTS. While randomized trials carried out by Brandjes et al.  and Prandoni et al.  showed a reduction in PTS rates with the use of stockings, the larger SOX trial did not show any significant difference between the use of graduated compression stockings and placebo stockings. 
| Methods of Thromboreduction|| |
Open trans-femoral thrombectomy for IFDVT has been well described but not widely practiced. Comerota  has described a comprehensive, contemporary approach to open surgical thrombectomy that consists of the following key elements:
- Good preoperative imaging of the extent of the clot
- Use of intraoperative fluoroscopy
- Infra-inguinal and proximal thrombectomy using appropriately sized thrombectomy catheters
- Intraoperative use of recombinant tissue plasminogen activator (rTPA)
- Intra and postoperative use of catheter-directed heparin
- Creation of an arteriovenous fistula
- Postoperative use of intermittent pneumatic compression.
Individual series on open thrombectomy have reported iliac vein patency rates consistently over 80%. A randomized trial done by Plate and colleagues comparing surgical thrombectomy and anticoagulation alone showed significantly fewer postthrombotic symptoms in the surgical group with the difference in outcomes remaining even after 10 years.  Open thrombectomy has also been reported to successfully salvage patients with impending venous gangrene. There are no randomized trials comparing open thrombectomy and CDT or PMT.
It is fair to say that open venous thrombectomy, is an effective but under-utilized procedure in most centers, likely due to its invasive nature and lack of individual surgeons' experience. Changing patterns in vascular surgery training  is only likely to further diminish its role.
Systemic thrombolysis for DVT has only been infrequently reported. A study done by Schwieder et al. showed significant recanalization in only a 1/3 rd of patients who had systemic rTPA and anticoagulation. It also carried a risk of bleeding in 26.5% of patients. 
The AHA does not recommend systemic thrombolysis for reducing the clot burden in acute DVT. 
Catheter directed thrombolysis
Attempts at directing thrombolytic agents toward a vein affected by DVT using peripheral cannulas did not yield good results.  CDT refers to the infusion of thrombolytic agents directly into a venous thrombus via a catheter placed using fluoroscopic guidance. It came into vogue in the early to mid-1990s especially for the management of extensive, IFDVT. 
Data from a prospective, multi-center registry of CDT in lower limb DVT showed successful (>50%) lysis in 83% of patients.  Similar to data from arterial thrombolysis, successful lysis correlated with an acute presentation <14 days. Further analysis of a subset of patients with IFDVT, showed significantly reduced postthrombotic symptoms when compared to historical controls treated with anticoagulation alone.  There are other prospective studies that have shown objective evidence of improved venous function in patients with IFDVT after CDT when compared with standard therapy using anticoagulation alone. ,
The basic steps of CDT for IFDVT include:
- Accurate imaging of the extent of thrombus including computed tomography venography to identify involvement of the inferior vena cava (IVC)
- Safe intravenous access with a sheath in a vein proximal to the thrombus, preferably using ultrasound guidance. The popliteal vein is often used, but the superficial femoral vein can also be used. Contralateral femoral access is also an option
- Initial guidewire traversal across the thrombus
- There are no data comparing end-holed and multiple side-holed catheters. If an end-holed catheter is used, then the tip of the catheter is placed in the proximal aspect of the clot and may need to be repositioned frequently
- The thrombolytic infusion is then commenced
- Repeat venography is used at 12-24 h intervals to monitor progress.
| Choice of Thrombolytic Agent and Dosage|| |
Urokinase and alteplase are the most commonly used agents. Other agents such as reteplase and tenecteplase have also been used. , A retrospective analysis comparing urokinase, alteplase and reteplase showed a trend toward higher risk of bleeding with reteplase. 
The aforementioned, multi-center registry using urokinase CDT had 11.4% risk of major bleeding 18. The CaVenT trial reported a 3% risk of major bleeding and up to 20% overall bleeding in the CDT arm using rTPA (alteplase).  Other studies using alteplase have also shown a risk of major bleeding between 2% and 4%. ,
The AHA suggests CDT with alteplase at a dose of 0.01 mg/kg/h or urokinase at a dose of 12,000-18,000 units/h. They also recommend using "subtherapeutic" doses of heparin during alteplase infusion 5.
The mean duration of thrombolysis in the CaVenT trail was 2.4 days 20 with most studies reporting infusion times over 24 h.
Percutaneous mechanical thrombectomy
Devices to physically break down thrombus were developed in the late 1990s and early 2000s. These devices are used either in combination with thrombolytic infusion (pharmaco-mechanical thrombolysis) or as a stand-alone option in patients with contraindications to thrombolysis. The primary attraction of such devices over CDT is in reducing treatment time and hence reduces the risk of bleeding, need for monitored beds, and repeat angiography. PMT devices can be divided into three categories - rotational, rheolytic and ultrasound-assisted.
Rotational devices use high-speed rotating mechanical energy to break thrombus down. These devices carry a theoretical risk of endothelial and valvular damage. The Arrow-Trerotola percutaneous thrombolytic device (Arrow) uses a rotating basket that opens to a diameter of 9 mm when unsheathed to macerate thrombus. Fragments are likely to embolize distally but can be aspirated through a proximal sheath. In a series of 20 patients treated with the device as an adjunct to urokinase thrombolysis, 1 case of symptomatic pulmonary embolism (PE) was documented despite IVC filter use.  A recent retrospective study comparing the device with CDT showed no difference in patency rates but a reduction in procedure time and dose of urokinase in the PMT group. 
The Trellis thrombectomy-thrombolysis system (Covidien, Dublin, Ireland) is a rotational device that combines an oscillating, sinusoidal wire to mechanically disperse thrombus between 2 occlusive balloons to isolate the treated venous segment. Thrombolytic agents can be infused between the balloons and thrombus can also be aspirated. As the treated segment is isolated, the risk of PE is low. Retrospective studies using the device have shown excellent patency rates with very low doses of thrombolytic drugs and procedure times. 
Rheolytic devices such as the AngioJet (Boston Scientific Corporation (Natick, MA)) use high-speed jets of saline to break up the clot and allow it to be aspirated. They theoretically have less risk of endothelial and valve damage; however, no direct comparative studies exist. The AngioJet device is a dual-lumen catheter with high-speed saline jets directed retrograde from the catheter tip allowing thrombus to be fragmented and extracted through the effluent lumen. Unpublished information from the PEARL Registry which collects data on AngioJet usage in peripheral vessels shows up to 95% substantial lysis (>50% thrombus reduction) in lower limb DVT. Rheolytic devices do carry a risk of hemolysis with release of adenosine and potassium leading to bradyarrythmias and hemoglobinuria. Data from the PEARL Registry show a 1/332 (0.3%) risk of serious bradycardia with the use of the AngioJet catheter. Shorter catheter activation <5 s per pass may help avoid this complication. 
Ultrasound-assisted devices work on the principle that high-frequency, low-intensity ultrasound aids thrombolysis by breaking down the fibrin mesh and thereby exposing more of the thrombus to the thrombolytic drug. Ultrasound also aids in streaming the drug away from the infusion catheter toward more peripherally placed thrombus. The ability to break down the fibrin meshwork may allow such devices to treat more long-standing thrombus. The EkoSonic endovascular system (EKOS, Bothell, Washington) is the most widely used ultrasound accelerated thrombolytic device. A recent randomized trial comparing ultrasound-accelerated thrombolysis with the Ekos catheter to conventional CDT showed no difference in thrombus load reduction by adding ultrasound. 
| Inferior Vena Cava Filter Use|| |
The PREPIC trial remains the only randomized trial studying the addition of IVC filtration to standard anticoagulation in patients with proximal DVT.  While there was a reduction in the incidence of recurrent PE from 4.8% with anticoagulation alone to 1.1% with the use of a filter, this was offset somewhat by an increase in the incidence of recurrent DVT at 2 years from 11.6% to 20.8% in the filter group. The AHA recommends for the use of an IVC filter in all adult patients with a PE or proximal DVT with contraindications or complications from anticoagulation but recommends against the routine use of a filter in all patients with IFDVT.
The addition of thromboreduction procedures may theoretically increase the risk of PE; however, there is no evidence to support such a risk. Practice varies between routine uses of retrievable filters to selective use. In a systematic review of 16 studies on PMT, 10 studies reported using prophylactic IVC filters both selectively and routinely while in 4 studies no IVC filters were used. The risk of a symptomatic PE was <1% in all the studies.  However, it must be emphasized that all these studies were single-center, retrospective series and in the absence of prospective data definite recommendations either way cannot be made. It is reasonable to consider selectively placing an IVC filter in patients with free-floating IVC thrombus and in those with preexisting PE and reduced cardiopulmonary reserve.
| Adjuvant Venoplasty and Stenting|| |
Completion venography after CDT or PMT may show residual areas of stenosis and flow limitation characterized by sluggish flow and filling of collaterals. Such stenosis may be due to residual thrombus adherent to the vein wall or due to underlying lesions in the vein wall itself. Such underlying lesions can be due to fibrosis and scarring from previous episodes of DVT or due to nonthrombotic iliac vein obstruction (NTIVO) also known as May-Thurner or Cockett's syndrome. NTIVO can be seen on either side but is commoner on the left side where the right common iliac artery crosses over the left common iliac vein. Up to 80% of patients with IFDVT have been shown to have evidence of iliac vein compression on imaging.  Failure to correct such underlying lesions, risks re-thrombosis of the treated venous segment. Rapid flow with no filling of collaterals on venography is the desired end-point of intervention, and this can often only be achieved by adjuvant measures such as balloon angioplasty and stenting. The Cardiovascular and Interventional Radiology Society of Europe standards of practice guidelines states that "iliocaval stenting should always be considered as an adjunct to the interventional management of iliocaval thrombus."  In the CAVENT trial, 42% (38/90) of the patients in the CDT arm required adjuvant angioplasty or stenting.  Angioplasty was used in 68 of the 90 patients (75%) who had intervention in the TORPEDO trial. 
The Society for Vascular Surgery and American Venous Forum clinical practice guidelines strongly recommend placing stents in the iliac veins to treat obstructive lesions after surgical thrombectomy or CDT or PMT.  Stenting across the inguinal ligament and in the common femoral vein may be associated with stent fractures, and a trial of angioplasty alone is considered reasonable. Stents are not recommended in the femoropopliteal segments.
| Summary|| |
Interventions to remove clot from acutely thrombosed outflow veins of a limb have been shown to reduce the risk of long-term symptoms of pain and swelling of the affected limb. They are also indicated in limbs with PCD and impending venous gangrene to prevent limb loss. Open surgical thrombectomy while effective is invasive and labour intensive. Endovascular thrombolysis and mechanical thrombectomy are less invasive and highly successful alternatives and should be considered in all good risk patients with acute IFDVT. This conclusion is based on the increasing volume of data over the last 10-15 years and a logical extension from a better understanding of the pathogenesis of PTS. Higher quality evidence from well-designed, randomized trials like the ATTRACT trial should allow objective risk-benefit assessment and help in individual patient selection for intervention.
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Conflicts of interest
There are no conflicts of interest.
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