EXPERT ANALYSIS FROM NORTHWESTERN VASCULAR SYMPOSIUM
CHICAGO (FRONTLINE MEDICAL NEWS) – The use of therapeutic-dose anticoagulation in hospitalized patients with calf vein thrombosis significantly reduces the risk of venous thromboembolic complications, compared with lower-dose prophylactic anticoagulation or surveillance alone, Heron E. Rodriguez, MD , said at a symposium on vascular surgery sponsored by Northwestern University.
Moreover, placement of an inferior vena cava filter in patients with calf vein thrombosis when anticoagulation is contraindicated accomplishes nothing beneficial and had a 10% complication rate in a large retrospective single-center study, added Dr. Rodriguez of Northwestern University, Chicago.
“In our population – patients that are in the hospital with risk factors for venous thromboembolic complications – we think that anticoagulation is a good idea. Low-risk patients or patients in whom anticoagulation is contraindicated should not be getting a filter. There’s really not any advantage in putting in a filter,” the vascular surgeon said.
Deep vein thrombosis (DVT) remains a significant source of morbidity and mortality despite worldwide awareness of the problem.
“Specifically, calf vein thrombosis [CVT] is very common, and we know that in some series up to 30% of patients end up propagating proximally if they’re not treated, and a good number of them develop chronic venous insufficiency, with long-term consequences,” he noted.
“Unfortunately there is no consensus regarding treatment. The guidelines are very vague. For example, there is no mention [in current American College of Chest Physicians guidelines] of how to manage muscular vein thrombosis and much ambiguity on how to treat calf vein thrombosis,” he continued.
Dr. Rodriguez cited as an indication of the lack of consensus on management of CVT a single-institution survey by other investigators of the practices of physicians in various specialties. Forty-nine percent of respondents indicated they anticoagulate patients with CVT; 51% don’t. Of those who did, 62% prescribed low-molecular-weight heparin and 11% intravenous heparin. Fifty-eight percent of physicians who anticoagulated did so for 3 months, 30% for 6. And 46% of physicians used an inferior vena cava (IVC) filter when anticoagulation was contraindicated (Vascular. 2014 Apr;22[2]:93-7 ).
That rate of IVC placement “seemed really high” given the paucity of supporting evidence for safety and efficacy of filter placement in the setting of CVT, so Dr. Rodriguez and coinvestigators decided to conduct a retrospective review of practices at Northwestern Memorial Hospital. He explained the study hypothesis: “Our thinking was that these kinds of thrombi are associated with low risk of propagation and pulmonary embolism, and they can and should be managed conservatively.”
Of 647 patients with isolated thrombosis of the anterior and posterior tibial, soleal, peroneal, or gastrocnemius veins, 44% received an IVC filter, and the rest got medical treatment alone. Of the 362 patients managed medically, 49% received therapeutic anticoagulation, 12% got low-dose prophylactic anticoagulation, and 39% underwent surveillance without anticoagulation.
The primary outcome was the incidence of venous thromboembolic complications – that is, propagation of DVT or pulmonary embolism. The incidence was 35% in the surveillance-only group, 30% with prophylactic anticoagulation, and 10% in patients who got therapeutic anticoagulation.
Of note, the rate of the most feared complication, pulmonary embolism, was low and similar in the filter recipients and medically managed group: 2.5% in the IVC group, 3.3% with medical management.
“Distal vein thromboses have low rates of pulmonary embolism, regardless of whether or not they are so-called protected with a filter. On the other hand, a filter was associated with a 10% rate of complications. I have to make clear that these were radiographic abnormalities – tilting, migration, caval perforation – that didn’t have clinical consequences, but we were very aggressive in removing the IVC filters, and I’m guessing if they’d been left inside they would create problems in the long term,” Dr. Rodriguez said.
An important point about this study is that these were all sick patients, and most were hospitalized. The filter recipients and medical groups differed in key ways. For example, 49% of the filter patients had a malignancy, and 56% had a baseline history of venous thromboembolic events, compared with 26% and 16%, respectively, of the medical group. For that reason, the investigators performed propensity score matching and came up with 157 closely matched patient pairs. The outcomes remained unchanged.
Of course, this was a retrospective study, with its inherent limitations, but Dr. Rodriguez characterized the published randomized trials on management of CVT as “small and limited.” The most frequently quoted study is the double-blind multicenter CACTUS trial, which randomized 252 outpatients with symptomatic CVT to 6 weeks of low-molecular-weight heparin or placebo and found no difference in the rates of proximal extension of venous thromboembolic events (Lancet Haematol. 2016 Dec;3[12]:e556-62 ). But these were all low-risk patients. Prior DVT or malignancy were exclusion criteria, so this was a very different population than treated at Northwestern.
Based upon the results of the retrospective study at Northwestern, which have been published (J Vasc Surg Venous Lymphat Disord. 2017 Jan;5[1]:25-32 ), the vascular surgery service has developed a management algorithm for DVT management based upon the lesion site. For acute isolated lower extremity DVT, the algorithm calls for 3 months of therapeutic anticoagulation. If a patient is unable to undergo anticoagulation, venous duplex ultrasound is repeated at 1 week. If the imaging shows propagation into the popliteal vein and anticoagulation remains contraindicated, only then is placement of an IVC filter warranted.
Dr. Rodriguez reported serving as a paid speaker for Abbott, Endologix, and W.L. Gore.
