Infections can trigger serious blood clots

Infections are associated with an increase risk of developing deep vein thrombosis, a condition in which a blood clot forms, usually in the leg, which can lead to a heart attack or strode. Also increased is the risk of pulmonary embolism, a life-threatening condition in which a blood clot travels to the lungs, according to a report by UK researchers

Previous reports have linked infections with a higher risk of cardiovascular disease involving the arteries, but it was unclear if the same held true for thromboembolic disease affecting the veins.

To investigate, Dr. Liam Smeeth, from the London School of Hygiene and Tropical Medicine, and colleagues analyzed data from 7,278 deep vein thrombosis patients and 3,755 pulmonary embolism patients who were registered in a UK general practice database from 1987 to 2004.

In the two weeks after a urinary tract infection, the risks of deep vein thrombosis and pulmonary embolism increased by more than two-fold, the report indicates. It took longer than one year for the risk to return to normal levels.

Respiratory infections were also associated with an increased risk of deep vein thrombosis, but the effect on pulmonary embolism risk was less clear, the authors note in their report, published in the April 1st issue of The Lancet, a British medical journal.

"Our finding that two infectious processes in different organ systems are associated with a substantial, reversible increase in the risk of venous thromboembolism suggest that acute infections may have a causal role in triggering events," the researchers conclude. "We now need to uncover the mechanism that underlies the risk."

SOURCE: The Lancet, April 1. 2006.