Thrombosis patients face greater risks than previously believed

Deep venous thrombosis (DVT), the formation of blood clots in the lower limbs, is the third-most common vascular disease in North America after heart attack and stroke, and is a frequent complication in hospitalized patients.

DVT is a potentially serious condition that can lead to rapid death from pulmonary embolism if untreated, and has become such a serious health concern that the U.S. Surgeon General and the Canadian Safer Healthcare Now! coalition both recently issued highly publicized calls to action to reduce the number of cases of DVT in high risk groups, in part by improving the adoption of preventative measures like the early administration of blood thinners.

However, researchers at McGill University and the affiliated Jewish General Hospital – along with colleagues from Université de Montréal, McMaster University and other institutions – warn that, beyond the well-known risks of pulmonary embolism, DVT patients also face postthrombotic syndrome (PTS), a poorly understood, long-term complication not addressed by traditional treatment approaches like blood thinners. Their conclusions, derived from a large, multicentre Canadian study, were published in the November issue of the Annals of Internal Medicine.

The study followed 387 patients at eight hospital centres in Quebec and Ontario for two years, the researchers said, the first multicentre study of PTS ever undertaken in North America.

"Incredibly, we found as many as 43 per cent of the patients developed postthrombotic syndrome, and one-third of those had moderate to severe cases," said McGill's Dr. Susan R. Kahn, lead author of the study. "The syndrome is characterized by persistent leg pain and swelling, and in severe cases, patients can develop painful leg ulcers which are very difficult to treat.

"Contrary to popular belief, DVT doesn't just affect older people, it can affect adults of all ages," explained Kahn, an associate professor at McGill's Faculty of Medicine and Director of the Thrombosis Program and Associate Director of the Centre for Clinical Epidemiology & Community Studies at the JGH. "Developing postthrombotic syndrome and similar complications have been shown to lead to significant disability, lost workdays and very poor quality of life."

In addition to simply documenting the incidence of PTS, Kahn and her colleagues also attempted to identify risk factors that made certain patients more likely than others to develop it. They discovered that older patients, patients who had suffered a previous bout of DVT and patients with larger blood clots at the time of diagnosis faced a greater risk of developing PTS. Moreover, they also discovered that the risk of developing PTS was far higher in patients still experiencing leg symptoms one month after DVT was first diagnosed and treated.

"This suggests that physicians can predict if a patient is likely to develop chronic PTS as early as one month after DVT diagnosis," Kahn said. "Our results show that current modalities to treat acute DVT are not effective in preventing chronic complications of DVT, and emphasize the need for additional research in the prevention and treatment of PTS."