Thrombosis in OC Recipients Favors the Left


WASHINGTON — When women develop deep vein thrombosis while on oral contraceptives, the lower left side of the body is more likely to be affected than are the upper extremities or the lower right side, according to the results of a single-center, retrospective chart review.

The findings also suggest that a narrow left common iliac vein may predispose to thromboses in this location, and that this anatomical risk factor could be addressed with endovascular stenting, according to Dr. Grace A. Tye, who reported the results of the review at the annual meeting of the Society of Interventional Radiology.

Oral contraceptives are a well-described risk factor for lower extremity venous thromboembolic events, but there are few published studies on the anatomical distribution of these events in women taking OCs, Dr. Tye said.

Among 52 women who were younger than age 45 and were diagnosed with DVT at Stanford (Calif.) University Hospital in 2002–2006, 19 were on OCs at the time of their diagnosis, reported Dr. Tye, a radiology resident at Stanford. All 19 women on OCs had lower extremity DVTs; of these, 16 were in the left lower extremity and 3 were in the right lower extremity, a statistically significant difference.

Cross-sectional imaging was available for 11 of the 19 patients, and the findings indicated a left common iliac diameter (at the point of maximal narrowing) of 3.7 mm, compared with a right common iliac diameter of 13.1 mm, a highly significant difference.

Dr. Tye proposed that the lower left side predominance of the DVTs might be related to the “May-Thurner Syndrome,” which also is called iliac vein compression syndrome. Named after the two physicians who first described it more than 50 years ago (Angiology 1957;8:419–27), the syndrome describes the small diameter of the left common iliac vein as typically resulting from compression by the right common iliac artery.

The lower left side predominance of the DVTs suggests that women who develop DVT while on oral contraceptives might benefit from early endovascular stenting to relieve compression of the left common iliac vein, according to Dr. Tye, who said that conventional anticoagulation therapy may not address the risk for recurrent DVTs and postthrombotic syndrome in these women. They may benefit from endovascular stenting of the left common iliac vein to relieve compression at this location, which may subsequently result in a lower risk for recurrent DVTs and postthrombotic syndrome, she concluded.

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