A 10-year review of iliofemoral deep vein thrombosis - are they more dangerous than their distal counterparts?

Iliofemoral deep vein thrombosis (IFDVT) is associated with potential for poor outcomes despite optimal anticoagulation therapy. To characterize the real-world management of IFDVT in an Australian population. Retrospective evaluation of IFDVT cases managed at Northern Health, Australia from January 2011 to December 2020 was performed and compared to non-iliofemoral lower limb DVTs (non-IFDVT) (n = 1793). 375 IFDVT episodes (median age 69 years; 54.7% female (n = 205)) were diagnosed with median follow-up 56 months. 61.6% (n = 231) were provoked events, including 100 episodes (26.7%) of cancer-associated thrombosis. 24.8% (n = 93) of patients had concomitant pulmonary embolism. Eleven cases underwent endovascular intervention including all seven patients with May-Thurner syndrome. Non-cancer patients with IFDVT received longer duration of anticoagulation (8 vs. 6 months, p < 0.001) or indefinite anticoagulation (28.7% vs. 16.0%, p < 0.001) compared to those with non-IFDVTs. Venous thromboembolism (VTE) recurrence (2.3/100PY, HR 0.839, 95% CI 0.562-1.255, p = 0.390) and major bleeding (2.7/100PY, HR 1.679, 95% CI: 0.876-3.220, p = 0.119) were comparable but the 30-day all-cause mortality (5.1% vs. 1.2%, p < 0.001) including thrombosis-related deaths (1.8% vs. 0.4%, p = 0.004) was more common in the non-cancer IFDVTs. In cancer patients, VTE recurrence rate (4.3/100PY, p = 0.421) was similar but major bleeding (12.4/100PY, p = 0.043) and 30-day mortality (23.0%, p = 0.026) was higher compared to IFDVT patients without active cancer. While the VTE recurrence and major bleeding were comparable between patients with IFDVT and non-IFDVTs, 30-day mortality (including thrombosis-related death) was higher in patients with IFDVT, suggesting a higher risk cohort that warrants careful assessment particularly during the acute period post diagnosis.