ACUTE AND DELAYED OUTCOMES OF MECHANICAL THROMBECTOMY WITH USE OF THESTEERABLE AMPLATZ THROMBECTOMY DEVICE IN A MODEL OF SUBACUTE INFERIORVENA-CAVA THROMBOSIS

PURPOSE: To study the efficacy and delayed outcome of mechanical throm bectomy with the Amplatz thrombectomy device (ATD) in an experimental model of subacute inferior vena cava (IVC) thrombosis. MATERIALS AND M ETHODS: Mechanical thrombectomy was performed in 23 dogs with subacute infrarenal IVC thrombosis (6-15 days old), Heparin was administered d uring thrombectomy in all procedures (activated clotting time greater than or equal to 300 sec), Thirteen animals were killed immediately af ter thrombectomy, and the remaining 10 were allowed to survive for up to 1 month with no anticoagulation therapy. RESULTS: Venographic paten cy of the IVC was restored in all animals, although residual mural thr ombus remained in nine dogs (< 20% narrowing in seven, 20%-30% narrowi ng in two), No histopathologic evidence of mechanical wall disruption attributed to mechanical thrombectomy was seen, However, foci of organ izing residual thrombus with associated transmural phlebitic changes w ith round-cellular infiltration were present in all acute specimens, i ncluding those appearing clear at venography, Venography at 1 week or 1 month after thrombectomy showed IVC rethrombosis in eight dogs (80%) who were not receiving anticoagulants, During mechanical thrombectomy , a small increase in mean pulmonary artery pressure occurred, with a corresponding decrease in systemic arterial oxygen saturation, No acut e emboli were noted on the post-thrombectomy pulmonary angiograms, How ever, histopathologic examination of acutely explanted lungs in 11 ani mals showed arteriolar microemboli (100-500 mu m) in four. CONCLUSION: Mechanical thrombectomy with use of the ATD can effectively clear sub acute IVC thrombus, However, rethrombosis is common and may be due to the high prevalence of phlebitis and residual thrombus, Anticoagulatio n may need to be continued after successful thrombectomy to prevent pr ogression of residual thrombus and allow mural phlebitic changes to su bside.