Critical Care / Emergency / Trauma

New minimally invasive technique treats acute DVT

In 2003, NBC correspondent David Bloom died from a pulmonary embolism (PE) after spending many hours immobile in an armored personnel carrier while covering the Iraq war. His widow has since led a nationwide education campaign to make the public aware that PEs stemming from deep vein thrombosis (DVT) are the leading cause of preventable deaths in U.S. hospitals, killing an estimated 300,000 Americans each year.

Healthcare professionals have long known DVT is a significant threat to bedridden patients. Research shows patients who are recovering from joint replacement surgery or undergoing cancer treatment are particularly vulnerable because they may be relatively immobile for long periods. Yet recent studies in the United Kingdom (UK) found a higher-than-expected DVT risk in far less stationary populations—active teenagers with recent injuries, prostate cancer patients, and even top-class athletes.

Recognizing a developing DVT can be a challenge for medical professionals unfamiliar with the syndrome. In hospital settings, the vast majority of cases are first recognized by nurses—commonly in emergency departments and on surgical and oncology wards. Nurses’ close daily contact with patients makes it easier for them to rapidly detect signs and symptoms of a developing thrombus—swelling of an extremity and soreness or a burning sensation that may quickly evolve into severe pain. More often than not, a nurse is the one who first alerts the attending physician (and the patient) to the possibility of an incipient DVT.

Limitations of anticoagulants

Clinical examination and ultrasound confirm the diagnosis of DVT. The standard first step in DVT treatment—systemic anticoagulation using such drugs as heparin or warfarin—is based on 2008 guidelines from the American College of Chest Physicians (AACP).

But while systemic anticoagulants alone can prevent a clot from breaking loose and becoming a pulmonary embolism, they generally don’t relieve DVT symptoms. Nor do they remove the clot, so the vein remains blocked and the limb may continue to be swollen and painful. What’s more, post-thrombotic syndrome (PTS) may develop. (See the box below.)

What is post-thrombotic syndrome?

Over several months, up to 60% of patients who receive anticoagulant drugs to treat deep vein thrombosis develop a series of complications known collectively as post-thrombotic syndrome (PTS). Signs and symptoms include venous reflux, significant leg pain and swelling, varicose veins, and even venous-stasis skin ulcers. In extreme cases, a rare complication known as phlegmasia arises, which may impair blood flow and eventually cause venous gangrene and necessitate limb amputation. Diagnosed and categorized with a tool called the Villalta PTS scale, PTS can occur in patients of any age and may prevent even young, previously active people from returning to the workforce and leading normal lives.

Thrombolysis: Attacking the clot directly

In acute DVT, marked by signs and symptoms less than 14 days old, a preferred alternative to anticoagulants is to attack the clot directly through the occluded vein using a minimally invasive technique called catheter-directed thrombolysis. A catheter delivers the clot-busting thrombolytic known as tissue plasminogen activator (tPA) directly to the DVT. Thrombolysis is effective and endorsed by ACCP guidelines. But it takes hours or days to achieve optimal results and carries a significant risk of bleeding complications, which may necessitate a prolonged stay in an intensive care unit.


In open surgical thrombectomy, the thrombus is removed surgically. However, this procedure isn’t widely accepted in the U.S. medical community and has dubious value because of difficulty clearing all clot material from the vein. It also has an unacceptably high DVT recurrence rate in the same location.

A new approach: Pharmacomechanical thrombectomy

New medical technology is providing a fast, safe, and highly effective means of DVT removal using a minimally invasive procedure called pharmacomechanical thrombectomy (PMT). Using local anesthesia, the physician introduces a catheter-guided device into the occluded vein, where it delivers tPA directly to the thrombus, and mechanically fragments and aspirates the clot material to allow blood flow through the vessel to resume. PMT usually can be completed in 2 hours or less. With circulation restored, the patient almost immediately feels comfortable again. (See the box below for information on PMT devices.)

PMT devices

The two main devices available for performing pharmacomechanical thrombectomy (PMT) are the Trellis (made by Covidien) and the Possis AngioJet (made by Medrad). Each uses a slightly different approach. The Trellis isolates the thrombosed vein segment with inflatable balloons to limit embolization risk, and then fragments the clot by delivering a lytic agent through an oscillating wire. Thrombus fragments are vacuumed out through an aspiration port; the balloons are deflated and circulation is restored. The Possis AngioJet fragments and aspirates the clot with a jet of fluid agent. Both devices have produced excellent results.

Before PMT, clotting factors must be drawn to detect preexisting clotting conditions. The preoperative workup also includes venous duplex ultrasound imaging and a computed tomography scan of the chest, abdomen, and pelvis. After the procedure, the patient must be monitored for hematoma and bleeding at the catheter entry site, along with signs and symptoms of pulmonary embolism, intracranial bleeding, GI bleeding, and bleeding from orifices and I.V. sites. Patients with a recent history of GI or intracranial bleeding aren’t eligible for PMT.

Patients receive anticoagulant therapy both before PMT (usually via a heparin I.V. drip) and afterward (via oral warfarin). In those with a major reversible risk factor (for instance, if DVT developed after surgery or lengthy immobilization), warfarin usually is stopped after 3 months. Otherwise, anticoagulation typically continues for 6 to 9 months. Most patients with clotting disorders, such as antithrombin II deficiency, require lifelong anticoagulation therapy. For patients with unexplained DVTs, indefinite anticoagulant therapy generally is recommended and may need to continue lifelong.

Most patients are discharged the day after PMT with graduated compression stockings, which they should wear as long as swelling persists. Usually, patients recover quickly and completely, with return of full venous and valve function, no DVT recurrence, and no PTS symptoms. ACCP guidelines now recognize PMT as the preferred approach for acute DVT removal if the appropriate expertise is available locally.

PMT isn’t a universal solution to DVT. For one thing, the expertise required isn’t available in many areas. Also, the Possis AngioJet and the Trellis aren’t always successful in treating chronic DVT, and patients with a limited life expectancy or a high bleeding risk aren’t eligible. PMT isn’t appropriate for patients with recent major trauma, surgery, GI hemorrhage, obstetric delivery, coagulation disorders, or severe hepatic disease.

We currently are involved in a nationwide study of acute DVT treatment called the ATTRACT Trial (Acute Venous Thrombosis: Thrombus Removal with Adjunctive Catheter-Directed Thrombolysis). The study focuses on patients with newly developed proximal DVT in the iliac common femoral vein who have significant pain and swelling. A primary study goal is to increase awareness of the new PMT technology among first-line health professionals who may be unaware of anticoagulation alternatives. (We’ve chosen the Trellis device to treat our study subjects selected for PMT.)

Nurses’ educational role

Nurses can play a major rule by educating patients—and even physicians—about the benefits of PMT in treating acute DVT. We’ve seen positive results firsthand in two recent case referrals from nurses. In the first, the nurse’s friend was a postpartum patient who developed an extensive DVT unrelieved by anticoagulation alone. In the other case, a nurse’s neighbor was a young man who sought her advice after getting little relief from anticoagulants. Both patients underwent PMT successfully and have recovered fully.

For the millions who suffer acute DVTs every year—air travellers, recovering surgical patients, the bedridden chronically ill, postpartum women, and even highly fit young athletes—PMT can allow a return to normal function in an impressively short time. But this can happen only if healthcare professionals know about this remarkable technology. Those of us who see DVTs often and know how they can impair patients’ lives are driven to spread the word about PMT as quickly and widely as possible. Our hope is that everyone who develops DVTs can be seen by a provider who knows about all available treatment options.

Both authors work at the University of Pittsburgh Medical Center in Pittsburgh, Pennsulvania. Susan Tamburro is a vascular clinical research coordinator. Rabih A. Chaer is a vascular surgeon.

Selected references

Kearon C, Kahn SR, Agnelli G, Goldhaber SZ, Raskob GE, Comerota AJ. Antithrombotic therapy for venous thromboembolic disease: American College of Chest Physicians’ Evidence-Based Clinical Practice Guidelines (8th edition). Chest. 2008 Jun;133(6 Suppl):454S-545S.

Kim HS, Preece SR, Black JH, Pham LD, Streiff MB. Safety of catheter-directed thrombolysis for deep venous thrombosis in cancer patients. J Vasc Surg. 2008 Feb;47(2):388-94.

O’Sullivan GJ, Lohan DG, Gough N, Cronin CG, Kee ST. Pharmacomechanical thrombectomy of acute deep vein thrombosis with the Trellis-8 isolated thrombolysis catheter. J Vasc Interv Radiol. 2007 Jun;18(6):715-24.

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4 thoughts on “New minimally invasive technique treats acute DVT”

  1. JC says:

    Hello. How come there’s no mention of SCD sleeves to the lower extgremities, to prevent DVTs in long standing cases example VT or Afib ablations, is this still recommended or useless since heparin is given in a timely manner during the procedure in relation to the ACT results. What does the new DVT guidelines/protocol say about this. Thank you.

  2. Karen - Vascular Srugery NP says:

    To Terry – you can take your coumadin up until surgery and based on what your INR is will determine if the vascular surgeon stops it or not. If you are not therapeutic yet, no problem, if you are they still may proceed, if you are too high they will hold it.

  3. terry bouier says:

    I am going to have the procedure done on February 15th this year. My vascular surgeon has me on comadi and said I will stay on it even up to surgery. My home town doctor disagrees with the comadin up to surgery, this is confusing. Can you tell me what you think?

  4. Anonymous says:

    Very informative article. As a Acute Care NP in Pulmonary Medicine & Critical Care, a vast majority of my consults consist of patients admitted with DVTs. A hypercoaguable state is always permitted prior to beginning oral anticoagulation, however, PMT will definitely offer another alternative to prolong oral anticoagulation and length of hospital stay. Most patients diagnose with a DVT are inpatient for at least 5 days while on low molecular weight heparin & warfin.

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