Endovenous Thrombectomy and Thrombolysis

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Chapter 14 Endovenous Thrombectomy and Thrombolysis

Rafael D. Malgor, Antonios P. Gasparis, Nicos Labropoulos

Historical Background

After the first episode of deep venous thrombosis (DVT), affected patients may develop pulmonary embolism (PE), recurrent DVT, or postthrombotic syndrome (PTS), and all carry significant morbidity and negative socioeconomic impact.¹ Important concepts in the natural history of the disease are recurrence, propagation, and recanalization with anatomic and/or hemodynamic changes following an episode of DVT. Spontaneous resolution of the DVT leaving intact the affected segment is rarely found, occurring only in one-third of patients.² Frequently, the segment affected by thrombosis develops reflux due to venous valve injury or some degree of residual obstruction.³ Patients who develop a combination of reflux and venous obstruction following an episode of DVT have the highest risk of developing PTS.^3,⁴ A combination of reflux and obstruction is found in up to 86% of the patients, while occlusion alone is found in less than 10%.⁵

Patients with extensive proximal DVT, such as iliocaval or iliofemoral occlusions, have a worse prognosis compared with patients with infrainguinal thrombosis.^6,⁷ The resolution of venous obstruction with iliac thrombosis is often incomplete, and the incidence of PTS is higher.⁴ Recurrent DVT is a very important factor in the natural history of the disease because other than exposing the patient to PE, it also increases significantly the risk for developing PTS.⁸ In fact, it has been shown that a recurrent ipsilateral DVT is the strongest predictor for developing skin damage.⁹ The risk of recurrent DVT was 40% (95% confidence interval [CI], 35.4% to 44.4%) after 10 years, being 53% (95% CI, 45.6% to 59.5%) in patients with unprovoked DVT and 22% in those with secondary DVT (95% CI, 17.2% to 27.8%).¹⁰ Other important risk factors to develop recurrent DVT are age older than 65 years, incomplete thrombus resolution, and iliofemoral thrombosis.^6,^9,¹¹^–¹³

Treatment Options

To improve the long-term natural history of DVT, it is important to preserve venous function and outflow. Overall, the first line of treatment for DVT remains anticoagulation using either low-weight-molecular heparin (LMWH) or unfractionated heparin (UFH). Nonetheless, a review of 13 studies of proximal DVT showed total and partial resolution in only 4% and 14% of patients, respectively, who were treated with anticoagulation.¹⁴

Venous thrombectomy was first attempted in extreme cases of extensive DVT with impending venous gangrene aiming for limb salvage.^15,¹⁶ Indications for surgical thrombectomy are extensive proximal (iliofemoral) DVT when thrombolytic agents are contraindicated.¹⁷ Therefore surgical thrombectomy has still not gained popularity, being performed in only a few specialized centers.¹⁸ More recently, local thrombolysis and venous thrombectomy have been used together with very good outcomes.¹⁹ Conversely, development of dedicated devises and safer use of thrombolytic agents has expanded percutaneous procedures. The goal with thrombolysis is to provide early thrombus removal with a minimally invasive procedure and low complications. By restoring venous flow, the objective is to prevent valve damage, venous hypertension, and recurrent thrombosis in an attempt to prevent PTS.

Patient Selection

Recommendations and patient’s eligibility criteria for endovenous thrombectomy and thrombolysis via catheter-directed thrombolysis (CDT) or pharmacomechanical thrombectomy (PMT) have been defined as follows ^17,²⁰:

• Extensive acute proximal (ileofemoral) DVT

• Less than 14 days from onset of symptoms or acute findings on duplex ultrasound

• Life expectancy of more than 1 year with good functional status

• Low risk of bleeding

While these are the most common recommendations for thrombolysis, deviations have been successfully reported, such as treatment of femoropopliteal DVT, thrombus longer than 14 days, and use of PMT in patients with higher risk of bleeding.

Modalities of Thrombolysis and Thrombectomy

Systemic Thrombolysis

Over the past 50 years, variable outcomes were reported with systemic thrombolysis. Analysis of 13 contemporary studies including 591 patients found that the success rate of anticoagulation with heparin only showed total dissolution, partial lysis, and no improvement of the thrombus in 4%, 14%, and 82%, respectively.¹⁴ Improvement with systemic thrombolysis was found in 45% of the patients in the same review.

Advantages of systemic infusion of thrombolytic agents were faster resolution of the clot load and less venous valve dysfunction compared with anticoagulation alone.¹⁴ Nonetheless, the disadvantages of the technique include variable outcomes with potential serious complications such as increased risk of intracranial hemorrhage due to higher doses required to dissolve a distant thrombus.²¹ In light of the variable success rate, systemic complications, and current advances in minimally invasive endovenous techniques such as CDT and PMT, systemic thrombolysis has been abandoned and now belongs to historical reports.

Catheter-Directed Thrombolysis

The higher risk of bleeding complications of systemic thrombolysis secondary to administration of high doses of thrombolytic agents via peripheral veins led to studies on devices to deliver intrathrombus thrombolytic agents.²¹^–²³ In general, the technique consists of a multi–side-hole catheter that is positioned in the thrombus and remains parked in position to deliver localized thrombolytics and lysing the thrombus over time (Fig. 14-1).

Fig 14–1 Thrombolysis in a 49-year-old man who presented with right lower extremity swelling. He was found to have iliofemoral thrombosis extending to the hypoplastic segment of the perihepatic inferior vena cava. A 50-cm infusion catheter was placed via the popliteal vein. The tip of the catheter was positioned in the suprarenal portion of the interior vena cava (arrow). The infusion segment extended down to the common femoral vein.

Initial experience using CDT was reported by Semba and Dake using urokinase in 21 consecutive patients with iliofemoral DVT.²⁴ Total thrombus lysis was achieved in 72% of the limbs with overall angioplasty or angioplasty with stents required in 64%.²⁴ Subsequently, several series were published comparing anticoagulation alone with CDT.^14,^23,²⁵ The impact on quality of life (QoL) in 68 patients who underwent CDT and 30 patients treated with anticoagulation alone was assessed by Comerota and colleagues.²² Notably, patients who underwent CDT reported better overall physical functioning, less stigma, and less health distress. Furthermore, health distress and symptoms were reduced in patients who had a successful versus a failed CDT treatment.

The caveats of initial studies related to a small number of patients and single-center observation were addressed by a multicenter registry study with urokinase in 473 patients that showed complete lysis of the thrombus in 31% and partial lysis in 52% of the limbs with better results in patients with acute symptoms of DVT.²⁶ Patients with iliofemoral DVT had higher patency rates at 1-year follow-up than those patients treated for femoropopliteal DVT (64% versus 47%, p < .01), and the mean intensive care unit stay for monitoring thrombolytic therapy was 48 hours.²⁶ One patient had fatal intracranial bleeding and another required surgical evacuation of a subdural hematoma.

Two prospective randomized clinical trials (RCTs) have been reported. The first RCT enrolled 35 patients comparing CDT with streptokinase versus anticoagulation alone; it showed 72% of the limbs in the CDT group with no obstruction or reflux versus only 12% in the anticoagulant group at 6-month follow-up.²⁵ No major bleeding or mortality was reported. The second RCT, the CaVEnT (Catheter-directed Venous Thrombolysis) trial, enrolled 118 patients to assess the long-term functional efficacy with frequency of PTS after 24 months and descriptive efficacy at 6 months’ evaluation for patency rates.²³ Patency of the iliofemoral vein segment was 64% in the CDT group and 36% in the control group. In addition, lysis greater than50% was achieved in 88% of the patients who underwent CDT.²³

The long interval of CDT treatment course remains problematic because of institutional requirements of an intensive care unit setting for monitoring. A longer infusion interval that is needed also raises concern of potential risk of major bleeding found in up to 11% of the patients.²⁶ In addition, the use of fluoroscopy for multiple follow-up venograms has directed efforts to accomplish thrombus removal in a more expeditious fashion than has currently been performed by PMT devices.^17,²⁷

Percutaneous Mechanical Thrombectomy

The advances of endovenous therapy are noticeable over the past two decades. The conception of PMT is a device that provides mechanical maceration of thrombus along with the ability to deliver local thrombolytics. This allows improved penetration of the thrombolytics into the thrombus by increasing the surface area, thereby theoretically decreasing treatment time and amount of thrombolytics delivered.

Two commercially available PMT devices are approved for treatment of DVT by the U.S. Food and Drug Administration (FDA): the Angiojet Thrombectomy system (Medrad/Possis Inc. Minneapolis, MN, and the Trellis-8 Peripheral Infusion System (Covidien, Mansfield, MA).²⁸ In addition, a brief discussion about the Ekos Endowave system (Ekos Medical, Bothell, WA) is pertinent due to distinct mechanism combining ultrasound waves to facilitate chemical thrombolysis.

The mechanisms of PMT elicited by the Angiojet and Trellis device system are distinct. The Angiojet system is based on the Bernoulli-Venturi principle that states that high speed of a flow decreases the fluid pressure and creates a zone of vacuum (Fig. 14-2). Therefore the high-speed saline injections cause dissolution of the thrombus into small particles that are aspirated and eliminated through an effluent port. Theoretically, the advantages of the system are less endothelial damage and valve dysfunction. The device can also be used in combination with thrombolytics. Drug is delivered into the thrombus with the catheter, allowed to immerse in the thrombus, and then aspirated with the effluent port opened.

Fig 14–2 Angiojet thrombectomy system. A, Catheter with saline infusion and aspiration port to retrieve thrombus. B, Pulse-suction Angiojet generator device.

Initial experience was reported by Kasijaran et al. in 17 patients showing 59% of overall (>50%) thrombus removal.²⁸ Bush et al. used the system in 23 limbs and reported complete and partial thrombus resolution in 65% and 35%, respectively.²⁹ A comparison between the Angiojet versus CDT using only urokinase showed reduced treatment duration and lower costs with the Angiojet pulse system.³⁰ Another study of 93 patients treated for symptomatic proximal DVT showed lower mean intensive care unit stays and overall length of hospital stays and lower total hospital costs with Angiojet compared with CDT only.²⁷ One of the shortcomings of the system is a larger amount of fluid used to dissolve the thrombus, which can be impeditive in patients under fluid restriction, suggesting that precautions be used in cases of renal failure and decompensated congestive heart failure. Provoked hemolysis with increased bilirubin release in patients with liver failure may be another contraindication.

The Trellis-8 Peripheral Infusion System uses a dispersion spiral wire at higher spinning motion to macerated the thrombus in an isolated venous segment between a proximal and distal end balloon (Fig. 14-3). Initial experience with the device showed overall thrombus resolution in greater than 95% of limbs treated.^31,³² No major complications including PE or major bleeding were reported. Trabal et al. reported a series of 25 limbs treated with the Trellis system showing greater than 50% thrombus resolution in 92% of the limbs with significant shorter treatment time and reduced thrombolytic agent used compared with CDT.³³ In addition to thrombus burden resolution, the advantages of the Trellis system are its safety in patients with contraindications to thrombolytic agents and potentially less distal embolization due to isolation of a venous segment between two balloons.

Fig 14–3 The Trellis-8 Peripheral Infusion System. A, Catheter advanced through the thrombus in the right iliac vein with distal balloon inflation. B, Pulse-spray injection of thrombolytic (purple strikes) after inflation of the proximal balloon, isolating the segment of thrombosis. C, Initiation of the sinusoidal-shaped catheter macerating the thrombus (hand-held power generator showed in the uppermost portion of the picture). D, Dramatic reduction of the thrombus burden secondary to fragmentation caused by high-frequency wave shock. The distal balloon is deflated and the lysed thrombus is aspirated.

The Ekos endowave functions by emitting high-frequency ultrasound waves that cause disaggregation of the fibrin in the thrombus, increasing permeability to the thrombolytic agents (Fig. 14-4).³⁴ The catheter consists of four lumens from 6 to 50 cm of functional area containing an ultrasound wire and three other ports for thrombolytic agents and saline infusion. Initial experience in a study of 53 limbs with acute, chronic, and acute-on-chronic DVT showed complete thrombus removal in 70% and overall (complete and partial) lyses rate of 91%.³⁵ There was no intracranial or retroperitoneal hematoma reported throughout the study. Further prospective, randomized studies on the use of the ultrasound-assisted thrombolysis are still expected.

Fig 14–4 Ekos Endowave system. A, Ultrasound (US) source generator with monitor. B, Ultrasonic catheter

with emission probe. C, Disarrangement and lysis of the thrombus by ultrasonic waves and continuous lytic

infusion. D, Detail of ultrasonic wave being emitted from distal probe.

An ongoing randomized multicenter trial, the ATTRACT trial, is designed to enroll 692 candidates to either PMT with anticoagulation versus anticoagulation alone in patients with symptomatic proximal DVT to assess the occurrence of PTS at 24-month follow-up.³⁶ The impacts on QoL, safety, and cost analysis are expected to be addressed.

Imaging Assessment

• Ultrasound to guide percutaneous access

• C-arm or wall-mounted fluoroscopy for contrast venography

• Intravascular ultrasound (IVUS) in some cases if iliac vein stenting is indicated

Operative Steps

Obtaining Access

The patient is taken to the angiography or dedicated operating room suite, prepped, and draped in the prone position. Please note that local anesthetic with 1% lidocaine is used to infiltrate the skin in the popliteal region. A direct popliteal vein stick under ultrasound guidance is performed with a micropuncture kit (Fig. 14-5). A 3- or 4-Fr micropuncture catheter is inserted and its position is checked with gentle hand injections of dilute contrast. Often, the injection reveals filling defects throughout the proximal popliteal, distal, and middle femoral vein. The 3-Fr catheter is exchanged over a wire to a 5-Fr sheath. One may choose access of posterior tibial vein for cases where extensive infrapopliteal involvement is of concern in providing adequate inflow, or for isolated iliac vein thrombosis the patient can be placed in the supine position and access can be obtained in the ipsilateral femoral vein. Other access sites described include the contralateral femoral vein and jugular vein. Our preferred access site is ipsilateral popliteal vein.

Fig 14–5 A, Ultrasound-guided popliteal vein access with the patient in the prone position. Access is obtained with a micropuncture set. The vein is accessed above or below the popliteal fossa. B, Needle being inserted in the popliteal vein (arrow). C, Transverse view confirming good position of the guidewire inside the popliteal vein (arrow).

Inferior Vena Cava Filter Placement

A retrievable filter when considered is placed via the right internal jugular (Fig. 14-6). Use of an IVC filter during thrombolysis is controversial. The risks and benefits of the filter placement must be explained to the patient. The right side of the neck is prepped and draped in the usual sterile fashion. Under continuous ultrasound guidance the right internal jugular vein is cannulated with the 22-gauge needle using a micropuncture kit. Subsequently, the 3-Fr sheath is exchanged for a 5-Fr sheath over a wire, which is passed into the infrarenal vena cava. Through the sheath and over the wire a pigtail marking catheter is positioned in the distal IVC, its position is confirmed with gentle hand injections with dilute contrast media, and then a cavogram is obtained with a power injection. Measurements are taken and the IVC filter is chosen based on operator’s preference. After IVC filter placement, hand injections through the sheath confirm the position of the filter and the opposition to the wall of the cava.

Fig 14–6 Selective placement of inferior vena cava filter via a jugular approach.

Catheter-Directed Thrombolysis

After access is obtained in the popliteal vein, a wire is advanced using a combination of an angled glidewire and glide catheter negotiating the iliofemoral segment to reach the IVC. Subsequently, the position of the catheter and patency of the IVC are confirmed with a venogram (Fig. 14-7, A–D).

Fig 14–7 A 49-year-old woman with bilateral lower extremity swelling and acute thrombosis of inferior vena cava (IVC), bilateral iliac, and right femoropopliteal veins. A, Initial venogram showing thrombosis extending from bilateral iliac veins into the IVC. B, Right femoral vein with proximal occlusion and patent deep femoral vein with collateral to the midportion of the femoral vein. C, Distal third of the femoral vein with partial reconstitution via a collateral from the deep femoral vein. D, Placement of bilateral thrombolysis catheters positioned in the IVC confluence. E, Venogram 12 hours after CDT of the IVC with complete resolution of IVC thrombus. F, Residual thrombus in the right iliac vein (arrow). G, Left iliofemoral veins partial resolution (arrow). H, Completion venogram showing proximal resolution of thrombosis in the right femoral vein after 24 hours of CDT. I, Patent distal portion of the femoral and popliteal veins.

A 5-Fr, 40- or 50-cm-long infusion catheter and the ball-tipped occluding wire are then placed through the catheter. This occludes the end-hole of the catheter and directs delivery of the thrombolytics through the infusion holes. In the case when a valved infusion catheter is used, the occlusion wire is not necessary because there is a occluding one-way valve at the end of the catheter. The infusion length of catheter is chosen based on the length of thrombus present that needs to be treated. The infusion portion of the multi–side-hole catheter is parked in the lowest part of the thrombus and positioned to cover the entire length of thrombus. The catheter is then connected to the infusion pump with an initial dose of 1 mg/hr of rt-PA, and 400 to 600 U of heparin runs through the sheath. Our preference is to use larger volumes of diluted rt-PA to improve lytic therapy if it is not contraindicated. This is theoretical and has never been studied. The catheter and sheath are both wrapped sterilely in the usual manner. The venogram of the more proximal iliac system is not necessarily performed if it is significant filling defect throughout the iliofemoral vein is present in a preprocedure imaging. At the end of the procedure, the patient is transferred to an intensive care unit for close monitoring throughout the thrombolysis course. A sequential treatment of an extensive iliofemoral and caval DVT using CDT is illustrated in Figure 14-7, E–I.

We advocate checking the complete blood cell count, serum chemistry, activated prothrombin time, and fibrinogen level every 4 to 6 hours while the thrombolytic agent is infused. The thrombolytic recheck is done every 12 hours to evaluate improvement.

Pharmacomechanical Thrombectomy

Trellis-8 Peripheral Infusion System. Access is obtained via popliteal vein as described earlier. An initial venogram is obtained as shown in Figure 14-8, A.

• The 5-Fr sheath is exchanged for an 8-Fr sheath to accommodate the Trellis catheter.

• The Trellis catheter is then advanced over a glidewire and parked in the segment of interest. Treatment is initiated in the most proximal segment (the segment closest to the heart) involved with the thrombus.

• The most common Trellis treatment length zone used is 30 cm. Specification of the sizes of the catheter is shown in Table 14-1. The specific length of the catheter encompasses the entire segment that is expected to be mechanically thrombectomized. If the treatment zone is longer than 30 cm, the venous segment is treated in serial segments starting from proximal to distal.

• The proximal end of the catheter is parked 1 to 2 cm above the proximal portion of the thrombus and the proximal balloon is inflated (Fig. 14-8, B and C). The glidewire is exchanged for the sinusoidal wire, and the distal balloon is inflated (Fig. 14-8, D).

• The motor is turned on at the highest rpm, and the direction of rotation is changed every 2 minute time interval. The combination of 5 mg of rt-PA mixed in 5 mL of heparinized saline is also infused at a rate of 1 mL/2 minutes (for a treatment time of about 20 minutes). This protocol of direction of rotation and drug infusion can be altered as per operator’s preference.

• After 20 minutes of treatment, the distal end balloon is deflated, and fragments of thrombus, residual rt-PA, and blood are aspirated via the aspiration port while flushing the infusion port.

• The proximal balloon is deflated and the catheter is pulled back to a more distal segment with residual thrombus and the previous steps are repeated (Fig. 14-8, E and F).

• Thus, the response is gauged with repeat hand injections of contrast after device removal (Fig. 14-8, G and H). If residual thrombus is present, several options exist:

• The Trellis catheter may be reinserted and additional PMT is performed in areas of residual thrombus.

• If iliac vein stenosis and/or residual thrombus is present preventing adequate outflow, angioplasty and/or stenting may be required (Fig. 14-8, I).

• Placement of the infusion catheter in areas of residual thrombus for CDT.

Fig 14–8 A 54-year-old man presented with a new onset of left lower extremity swelling and pain due to extensive iliofemoral and popliteal vein thrombosis. A, Initial venogram confirming femoropopliteal deep venous thrombolysis. B, Subsequently, a wire is advanced through the thrombus. C, A 30-cm Trellis catheter is parked proximally to the thrombus and the proximal balloon is inflated. D, Subsequently, the distal balloon is inflated into the femoral vein, isolating the segment to be treated. E, Upon treatment completion of the proximal segment, the catheter is positioned for treatment of the femoropopliteal segment. F, The distal balloon is again inflated, isolating the new segment to be treated. G, Venogram following PMT with most thrombi lysed in the femoropopliteal portion. H, Distal part of the treated segment. I, A 16 × 80-mm self-expanding stent was placed in the iliac vein to treat residual disease.

TABLE 14–1 FDA-Approved Commercially Available PMT Systems for Treatment of DVT

Angiojet Rheolytic System (MedRad; Warrendale, PA). After micropuncture access is obtained in the popliteal vein and changed to a 6-Fr sheath, a glidewire is advanced with an angled glide catheter crossing the thrombosed area into the IVC. A preintervention venogram is obtained. Fig. 14-9, A–C, depicts an extensive ileofemoropopliteal DVT.

• The catheter is removed over the wire and the Angiojet DVX catheter is advanced.

• The DVX catheter is connected to the drive unit and the machine is tuned on to initiate the high pressure (10,000 psi) saline jets; the debris generated is aspirated to the effluent port (see Fig. 14-2, A). The catheter is positioned at the most proximal vein segment involved with thrombus.

• The catheter is pulled back slowly 1 cm for every pump cycle, treating the entire length. Often, two or three passes are necessary to achieve maximal thrombus resolution.

• If “power-pulse” technique is performed, the effluent port is closed to allow delivery of drug and no aspiration.

• Drug is delivered from proximal to distal at a pullback rate of 1 cm every pump cycle. Once drug is delivered into the thrombus, it is allowed to bathe for 15 to 20 minutes.

• The effluent port is then opened and the Angiojet catheter is passed from proximal to distal to aspirate thrombus and excess thrombolytics.

• Following treatment, a venogram is performed, and the decision is made to complete treatment, continue further treatment with pharmacomechanical thrombolysis, or place an infusion catheter (Fig. 14-9, D and E, illustrates the results after pulse-spray and Angiojet thrombectomy).

• If an underlying iliac vein stenosis is uncovered, it should be treated with PTA and stenting (Fig. 14-9, F and G).

Fig 14–9 A 62-year-old female patient who presented with left lower extremity swelling associated with thigh and calf pain. A–C, She was found to have extensive iliofemoral and popliteal deep venous thrombosis as shown in the diagnostic venogram. D, Venogram of proximal femoropopliteal segment following “pulse-spray” thrombolysis with 10 mg of t-PA using the Angiojet. E, The distal femoropopliteal segment was successfully lysed as well. F, Completion venogram showing residual left iliac vein stenosis. G, Repeat venogram following deployment of 16 × 60-mm Wallstent.

EkoSonic Endovascular System (Ekos Medical, Bothell, WA). When the EkoSonic system is contemplated, a catheter must cross the thrombus over a .035-inch guidewire that is then exchanged with the ultrasonic (US) wire. The tip of the US wire exits the catheter, being parked at least 1 cm distal to the end of the catheter. Thrombolytic agent is delivered from the multi–side-hole catheter, and a mobile unit provides the temperature and US energy delivered. The patient is transferred to the unit and lytic re-recheck is performed every 4 to 6 hours or as per specific local protocols.

Venous Stenting and Angioplasty

The absolute indications for venous angioplasty and stenting are debatable. Angioplasty alone has not shown to be efficient to alleviate obstruction because of recoiling or persistent external compression. We advocate primary stenting whenever a significant residual stenosis is revealed. The presence of residual stenosis can be evaluated with venography or IVUS. Indirect signs of residual stenosis on venography include the presence of collaterals, intraluminal filling defects, or poor venous outflow. A direct evaluation of the residual obstruction can be obtained with IVUS. This also allows evaluation of the length needed to be treated and selection of the stent size. Most of the stents used are self-expandable and are 60 to 90 mm in length. The stent diameter for the common iliac should be 16 to 18 mm; for the external iliac, 14 to 16 mm; and for the common femoral vein, 12 to 14 mm. The key to venous stenting is to cover all diseased segments and obtain good inflow and good outflow. To achieve this, one may need to extend the stent into the IVC or below the inguinal ligament. Poststenting angioplasty with appropriately sized balloons is required to fully expand the stent. Completion venogram or IVUS is performed to evaluate flow and look for filling defects or residual stenosis.

Hemostasis and Anticoagulation

During thrombolysis, low-dose anticoagulation is achieved with UFH. Following completion of thrombolysis, therapeutic anticoagulation is accomplished with UFH or LMWH. The patient is subsequently bridged to warfarin sodium that is continued and tailored to the patient’s DVT presentation based on current guidelines.¹⁷

Puncture site hemostasis is effectively accomplished with manual compression or mechanical devices following completion of venography in the last lytic recheck.³⁷ In our experience, manual compression is appropriate with no need to use external mechanical compression devices.

Internal jugular and femoral vein access. Pressure is held manually for 10 to 15 minutes and a sterile dressing is applied to the puncture site. Application of heavy packs such as sandbags is not necessary.

Popliteal vein access. Manual compression for 10 to 15 minutes is applied, followed by the application of a mild to moderately tight Ace bandage wrapped around the venous puncture site right above and below the knee to confer hemostasis. A Coban bandage is then applied from foot to midthigh over a loose cotton layer to protect the skin. The patient is turned to the supine position after removal of the catheters, and the dressing is removed after 4 hours in the intensive care unit. Thereafter, the patient is encouraged to walk for 15 minutes.

Complications

Minor bleeding: Usually occurs from oozing and ecchymosis at the venous puncture site and does not require any treatment.

Major bleeding: Requires blood transfusion and usually occurs in the brain, retroperitoneum, muscles and gastrointestinal/genitourinary tract.

Venous wall injury: Wall damage during manipulation of catheters or rupture during balloon angioplasty.

Pulmonary embolism: Thrombus dislodgement into the pulmonary arteries during the procedure.

Comparative Effectiveness of Existing Treatments

Surgical thrombectomy was the first intervention attempted for limb salvage in cases of phlegmasia in patients with severe ischemia with impending venous gangrene. Contemporary results in a specialized center showed long-term patency of 80% at 5 years with no mortality.³⁸ Meticulous and technical refined operations require considerable efforts with a long learning curve. In light of advances in catheter technology and very good initial results with PMT devices, the surgical treatment is limited to cases of rapidly evolving massive DVT in patients with contraindications to thrombolytic agents and with impending limb loss.

Pearls and Pitfalls

Choosing the Access

The right choice of access site for CDT or PMT is critical for an appropriate treatment. In the majority of the series, the popliteal vein is the most commonly used puncture site followed by the contralateral femoral vein.³⁹

The advantages of the popliteal vein include a straight pathway for instrumentation in the iliofemoral segment via an antegrade approach, avoidance of crossing an IVC filter, and shorter catheters required. Conversely, thrombus involving the popliteal vein and reduced torque to negotiate catheters and stents for contralateral limb treatment are relative contraindications.

Some specialists advocate the use of the internal jugular vein for thrombectomy and thrombolysis. The rationale of using this access is to facilitate treatment of bilateral iliofemoral DVT. Disadvantages are longer catheters and limited approach to distal femoropopliteal DVT.

An additional access is often not necessary for CDT or PMT unless an intervention such as stenting is required in selected cases of bilateral iliac vein stenosis.⁴⁰ Regardless of the preference of access, the needs of each patient should be considered, tailoring the best approach to a specific scenario of DVT.

Angioplasty and Stenting Post-CDT and PMT Therapy

Often, an iliac vein stenosis is found after CDT or PMT, compromising venous outflow. Angioplasty and stenting are always recommended when underlying venous lesions are present following a successful thrombolysis and thrombectomy.¹⁷ We advocate the use of self-expanding stents over balloon-expandable stents. The stent diameter for the common iliac should be 16 to 18 mm; for the external iliac, 14 to 16 mm; and for the common femoral vein, 12 to 14 mm. Covering all venous segments with residual disease with stents and achieving good inflow and good outflow are very important to maintain patency. To accomplish this, one may need to use longer stents (60 to 90 mm) and extend the stents into the IVC or below the inguinal ligament. When stents are extended into the common femoral vein, patency of the femoral or deep femoral veins is essential. The use of IVUS appears attractive to better define anatomy and size the stents to attain precise apposition to the venous wall. However, the role of IVUS in procedures to treat acute DVT is not well defined.