Free-floating iliofemoral thrombus. A risk of pulmonary embolism.

We retrospectively evaluated the risk of pulmonary embolism in hospitalized patients with venographically proved iliofemoral deep vein thrombosis (DVT). Venograms and clinical records of 78 patients with iliofemoral DVT were reviewed and the proximal intraluminal thrombus was characterized as free-floating (greater than 5-cm nonadherent segment) or occlusive (no free-floating elements). The incidence of pulmonary embolism confirmed by high-probability radioisotope ventilation-perfusion lung scanning within ten days following venography was 9% (7/78) and was associated with 60% (3/5) free-floating and 5.5% (4/73) occlusive phlebographic criteria (P less than .05). All patients who experienced pulmonary embolism were given therapeutic heparin treatment (partial thromboplastin time, more than twice the control value). The mean (+/- SD) time from the diagnosis of DVT to pulmonary embolism was 104 +/- 60 hours, and 120 +/- 71 hours for patients with free-floating and occlusive thrombi, respectively (P greater than .05). Patients with iliofemoral DVT that met free-floating criteria are at significant risk for pulmonary embolism, despite the administration of heparin.