It has been demonstrated that implantation of inferior vena cava filter was safe and effective in the prevention or reduction of fatal pulmonary thromboembolism in numerous clinical researches. When acute deep venous thrombosis need transcatheter thrombolysis, transfemoral Günther Tulip Filter implantation could avoid catheter across the Günther Tulip Filter. Although incidence of significant filter tilting (>10°) is not high (13%-16%), severe tilting of the Günther Tulip Filter may be associated with difficulty or sometimes impossibility of retrieval. It has been reported that a simple technique of keeping tension of the delivery system may prevent significant tilting of the transjugular Günther Tulip Filter in an in-vitro study. But no clinical study of prevention transfemoral Günther Tulip Filter from tilting has been reported. The investigators conducted a randomized, controlled study to test whether the introducer curving technique is useful to decrease the extent of tilting of transfemoral Günther Tulip Filter.

The study was designed as a double-blind randomized controlled trial, with research assessors and patients intended to be blind to the intervention status. The staff members performing the assessment were not involved in implementing any aspect of the intervention. 108 patients were randomized to accept curving introducer Günther Tulip Filter and transcatheter thrombolysis or straight introducer Günther Tulip Filter and transcatheter thrombolysis. The assessments include the tilting angle between the axes of inferior vena cava and Günther Tulip Filter after implantation; the tilting angle between the axes of inferior vena cava and Günther Tulip Filter before retrieval; the fluoroscopy time of Günther Tulip Filter retrieval; the rate of retrieval hook adhering vascular wall; the success rate of retrieval.

Inclusion Criteria:

• acute lower extremity deep vein thrombosis, diagnosed by vascular ultrasound and clinical history

Exclusion Criteria:

• both lower extremities deep vein thrombosis
• Inferior Vena Cava thrombosis
• refractory hypertension (blood pressure > 180/110mmHg)
• contraindication of thrombolysis
• the diameter of Inferior Vena Cava > 35mm or < 14mm
• Inferior Vena Cava venous anomalies