Summary

A three year follow up of patients who have had a blood clot in their leg or lungs shows that they remain at risk. Those who had a clot in the leg had an increased chance of recurrence, or of developing a clot in the lung. Patients with clots in the lung had a worse outcome, with their death rate being higher at one month, one year, and three years. Therefore, there is a need for better preventive treatment for those at risk of blood clots.

Introduction

Development of a blood clot in the leg (deep vein thrombosis, DVT) or in the lung (pulmonary embolism, PE) are generally considered to be two forms of the same disease, known clinically as venous thromboembolism (VTE). Patients at risk of VTE can be treated by anticoagulants which 'thin' the blood and help prevent it clotting when it should not.

Some studies have pointed to a risk of recurrence among patients with VTE, but the research involved small numbers of patients, or took place some years ago. There is a need for fresh, large-scale data on outcomes for patients suffering from this common medical problem. The Worcester Venous Thromboembolism Study is being carried out to find out more about VTE in the community. In the current study, researchers from McMaster University, Ontario, and Massachusetts Medical School, Worcester, present data on the three year outcomes for a group of patients who had had an episode of VTE.

What was done

The researchers examined medical records of 1,691 Worcester residents of whom 54 percent were women and of average age 65, all of whom had been diagnosed with VTE in 1999, 2001 or 2003. Of these, 549 had had PE and the rest DVT. They were followed up for a minimum of one year and a maximum of three years, with episodes of recurrent VTE being recorded, along with any major bleeding episodes (needing a transfusion). Information on patient characteristics and medical history was also collected to see if specific risk factors could be identified for DVT as opposed to PE.

What was found

The patients who had had PE were more likely to be obese than those who had DVT and more likely to have been hospitalized recently, including being in intensive care or undergoing surgery. They were also more likely to have had their episode while in the hospital for something else.

When it came to outcomes, 5.7 percent of those with PE had a recurrence of this condition, 13.7 per cent had recurrent VTE, 14.9 percent had a major bleed and 41.7 percent died during follow up. Of those who had DVT, 5.6 percent then had an episode of PE, 19 percent had recurrent VTE, while 12.8 percent had a major bleed and 36 percent died during follow up. Individuals with PE were more likely to die at one month (13 percent versus 5.4 percent), one year (26 percent versus 20.3 percent) and at three years (35.3 percent versus 29.6 percent) compared to those with DVT. Those with a major bleed seemed to be more at risk of death or recurrence, the researchers note.

What this means

The researchers comment that the rates of recurrence of VTE and fatality after an initial episode of clotting in the leg or in the lung are unacceptably high. There is room for improvement in the way patients at high risk are identified and managed with anticoagulant therapy.