Key differences in presentation, outcomes for distal versus proximal deep vein thrombosis uncovered

Deep vein thrombosis (DVT) occurs when a blood clot forms in a large (deep) vein. Proximal DVTs occur in deep veins above the knee and isolated, distal DVTs can occur when smaller blood clots form in the veins below the knee. But the differences between the clinical presentation, short-term and long-term outcomes for patients with isolated distal DVT (smaller thrombi in veins below the knee) versus proximal DVT have been unclear.

A new study led by investigators from Brigham and Women’s Hospital highlights key differences in clinical features and co-morbidities, as well as short-term and also long-term outcomes for patients with distal DVT versus proximal DVT. The team found that patients with isolated distal DVT had lower co-morbidity burden and a lower risk of 90-day mortality. They were also at lower risk of developing a pulmonary embolism or a new venous thromboembolism in one year.

The authors note that some of the differences in the outcomes are attributable to the risk profile of these patients. Patients with distal DVT were younger, more likely to have had DVT in the setting of transient provoking factors such as surgery or hormonal use but less likely to have serious co-morbidities such as cancer or anemia.

“Our findings may have implications for risk stratification and for practice,” said corresponding author Behnood Bikdeli, MD, MS, of the Brigham’s Division of Cardiovascular Medicine. “While we find less ominous outcomes for isolated, distal DVTs, they are not entirely benign. Even among patients who received initial anti-coagulation treatment, almost half had signs or symptoms of post thrombotic syndrome, a chronic manifestation of these clots. Randomized clinical trials are needed to assess the best long-term management for patients who have had isolated, distal DVT.”