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Today’s Annals of Internal Medicine includes new results for the CLOTS (Clots in Legs Or sTockings after Stroke) Trial. Not-quite acronyms aside, it’s an interesting study with implications for many patients at risk for deep venous thrombosis (DVT).

compression stockings - NIH image (Medline Plus)

This U.K.-based study, involving 3114 patients in 112 hospitals in 9 countries, used ultrasound to evaluate possible DVTs in legs of people after they’d been immobilized upon suffering strokes. Patients were randomized to receive either thigh-length or below-the-knee compression stockings while recovering in the hospital. The main result was that 98 of 1552 (6.3 %) of patients who received thigh-length stocking and 138 of 1562 (8.8%) of patients with below-the-knee stockings developed DVT. This difference is highly significant (p = 0.008).

The twist is this: in a separate, extensive recent Cochrane review the investigators compiled data from multiple randomized studies of stockings in stroke patients and established that thigh-length stockings were inferior to no stockings, i.e. stroke patients who wore thigh-high compression stockings were more likely to develop DVTs than those who didn’t wear any stockings at all. The authors reconcile these separate results by suggesting that below-knee stockings might increase the risk for DVT after stroke.

Confusing? Yes. The bottom line is that thigh-high compression stockings may not help, based on the Cochrane analysis; below-the knee stockings may hurt.

Why this matters is that the results have implications for other hospitalized patients at risk for DVT, like people who’ve had hip replacements, pelvic or spine surgery. ”Unfortunately, no randomized trials have compared below-knee stockings with no stockings,” the authors write.

An accompanying editorial in the Annals considers the “puzzling” findings of the CLOTS trials and addresses how clinicians might prevent DVT in patients with stroke:

…The unexpected findings that thigh-length stockings are not very effective at preventing venous thromboembolism and that below-knee stockings might increase incidence of thrombosis in patients with stroke should prompt a reevaluation of the role of graduated compression stockings in other groups of patients….Clinicians need to realize that despite the ubiquity of graduated compression stockings in many settings, the net benefits and risks of this seemingly innocuous intervention remain uncertain.

As a hematologist, I see this as a low-tech, big deal because DVTs are a huge source of morbidity and mortality.

In the U.S., the number of clots per year runs in the hundreds of thousands. DVTs tend to arise in people who are immobilized after surgery, with neurological impairment and during travel. The elderly are particularly susceptible, as are pregnant women and people with inherited clotting dispositions. The National Blood Clot Alliance provides an interactive map of the incidence of DVTs, state by state, on its website.

Personally, I love it when the doctors allow me to take off the boots when I wake up after a procedure, so I can kick my feet around and, I hope, reduce my risk of DVT by movement and exercise. Compression stockings feel like corsets on my calves; they’re warm and constraining. On planes, too; I find stockings restrictive.

My own experience aside – the data supporting the use of compression stockings are limited, and this new study suggests they can be damaging.

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