Norwegian researchers are the first to show that a little-used supplementary treatment can help to prevent such complications.
Pain, swelling, itching, eczema and venous ulcers are characteristic signs of post-thrombotic syndrome, a condition developed by roughly half the patients who have experienced serious deep vein thrombosis, or blood clots in the leg.
In a study carried out in a group of Norwegian hospitals it has been demonstrated for the first time that a treatment to dissolve blood clots prevented such complications in a substantial number of patients. The treatment is called catheter-directed thrombolytic therapy.
Based at Oslo University Hospital, the project is a collaboration between the Department of Haematology and the Department of Radiology. All the hospitals in the South-Eastern Norway Health Region have participated. The study has received funding under the Research Programme on Clinical Research (KLINISKFORSKNING), administered by the Research Council of Norway.
No longer experimental
Catheter-directed thrombolytic therapy has been in modest use in Norway since the early 1990s and is known in other countries as well. But it is a costly treatment and until now its effect had not been documented.
“In our study we have shown for the first time that catheter-directed thrombolysis truly can reduce the long-term complications of blood clots in the legs,” says project manager Per Morten Sandset, a professor at Oslo University Hospital’s Department of Haematology. “This means it is no longer considered an experimental treatment and will likely be offered on a far larger scale.”
Per Morten Sandset (Photo: Birgit S. Kjelvik)
Dissolves blood clots
Roughly half of the study’s 209 blood-clot patients were randomly selected to receive standard treatment with blood-thinning medicine. The other half received thrombolysis in addition, administered via catheter and intended to dissolve blood clots.
The effects of the treatments were measured after six months and after two years, and will be measured again after five years. After two years, 41 per cent of patients who received both thrombolysis and conventional therapy had developed post-thrombotic syndrome (PTS) compared to 55 per cent of patients receiving conventional therapy only.
The findings were recently presented at a conference organised by the American Society of Hematology and have been published in the electronic version of the medical journal The Lancet.
In their commentary in The Lancet, radiologists Lawrence V. Hofmann and William T. Kuo of the Stanford University School of Medicine in the US hail the Norwegian study as a very important contribution to the literature on treating blood clots in the legs. They conclude that the findings should lead to the adoption of thrombolytic therapy for patients with blood clots in the legs.
The two US radiologists point out, however, that although the results are promising, the PTS rate among the thrombolysis group is still too high. Professor Sandset concurs, but believes that refinements in the therapy will be able to substantially increase the rate of patients avoiding complications.
Must work out the best method
In the study, only one treatment regime was tested. Professor Sandset also points out that the health care personnel involved had relatively little experience with the therapy.
“It is to be expected that more experience with the actual procedure would yield better results. It is also reasonable to presume there are more effective ways of administering the therapy. This is a vital topic for further research,” asserts Professor Sandset, who believes the gap between the two patient groups will widen with the follow-up after five years.
Open veins lower the risks
The study’s researchers observed a clear correlation between thrombolytic therapy, unobstructed veins and lower risk of developing PTS.
“Patients with unobstructed veins had a far lower risk of developing PTS,” explains Professor Sandset. “It is crucial to open up the veins and get the blood flowing properly again.”
In thrombolytic therapy, patients receive medication through a catheter in the blood vessel and directly into the clot. This enables physicians to use a much lower dose than with conventional treatment, which is given intravenously.
The study also identified a drawback to thrombolytic therapy: increased risk of haemorrhaging. The researchers therefore recommend not using the treatment on patients at high risk for haemorrhage.
Professor Sandset emphasises that more and larger studies are needed in this area. US researchers are now recruiting 700 patients for a similar study on thrombolysis. Those results, due in a few years, will be compared with those of Professor Sandset and his colleagues.