Acute and delayed outcomes of mechanical thrombectomy with use of the steerable Amplatz thrombectomy device in a model of subacute inferior vena cava thrombosis.

PURPOSE: To study the efficacy and delayed outcome of mechanical thrombectomy with the Amplatz thrombectomy device (ATD) in an experimental model of subacute inferior vena cava (IVC) thrombosis. MATERIALS AND METHODS: Mechanical thrombectomy was performed in 23 dogs with subacute infrarenal IVC thrombosis (6-15 days old). Heparin was administered during thrombectomy in all procedures (activated clotting time > or = 300 sec). Thirteen animals were killed immediately after thrombectomy, and the remaining 10 were allowed to survive for up to 1 month with no anticoagulation therapy. RESULTS: Venographic patency of the IVC was restored in all animals, although residual mural thrombus remained in nine dogs (< 20% narrowing in seven, 20%-30% narrowing in two). No histopathologic evidence of mechanical wall disruption attributed to mechanical thrombectomy was seen. However, foci of organizing residual thrombus with associated transmural phlebitic changes with round-cellular infiltration were present in all acute specimens, including 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 acute emboli were noted on the post-thrombectomy pulmonary angiograms. However, histopathologic examination of acutely explanted lungs in 11 animals showed arteriolar microemboli (100-500 microm) in four. CONCLUSION: Mechanical thrombectomy with use of the ATD can effectively clear subacute IVC thrombus. However, rethrombosis is common and may be due to the high prevalence of phlebitis and residual thrombus. Anticoagulation may need to be continued after successful thrombectomy to prevent progression of residual thrombus and allow mural phlebitic changes to subside.

Transvenous closure of secundum atrial septal defects: preliminary results with a new self-expanding nitinol prosthesis in a swine model.

BACKGROUND: Our purpose was to evaluate a new prosthesis for percutaneous closure of secundum atrial septal defects (ASDs). METHODS AND RESULTS: Percutaneous closure of surgically created fossa ovalis ASD was attempted in 15 minipigs. The mean balloon-stretched ASD diameter was 12.3+/-2.3 mm (range, 10 to 16 mm). The self-expanding prosthesis was braided from 0.005-in Nitinol wires in the shape of two flat buttons with a short connecting waist with a diameter corresponding to that of the defect to be closed. Polyester filling was added to enhance thrombogenicity. Pulmonary arteriography with levo-phase was obtained before placement; immediately after placement; and at 1-week, 1-month, and 3-month follow-ups. Four animals were killed at 1 week, 1 month, and 3 months for histopathological correlation. Three deaths resulted from ventricular fibrillation (one during anesthesia and two during the placement procedure). Successful placement of the prosthesis was achieved in the remaining 12 animals. Overall immediate ASD closure on angiography occurred in 7 of 12 animals (all polyester-filled prostheses). Absent or trace shunt by angiography was present in 11 of 12 devices at 1 week, with the remaining one demonstrating a small shunt. All septal defects were completely closed at 1 month with the exception of one case in which delayed partial dislodgment of an undersized prosthesis into the right atrium had developed. Closure rate at 3 months was 100%. Neoendothelialization and fibrous incorporation of the prosthesis were completed within 1 to 3 months. CONCLUSIONS: Effective and permanent occlusion of secundum ASDs is feasible with a device that offers the advantages of easy placement, self-centering, and repositionability.

Experimental evaluation of a new self-expanding patent ductus arteriosus occluder in a canine model.

PURPOSE: A new self-expanding patent ductus arteriosus (PDA) occluder was designed. MATERIALS AND METHODS: Percutaneous closure of surgically created aortopulmonary shunts was attempted in 19 dogs. The occlusion device consisted of a nitinol wire frame tightly woven into a cylinder with a flat retention disc. A polyester-filled frame was used in the last six procedures. A 6-F introducing sheath was advanced across the aortopulmonary conduit into the descending thoracic aorta. The prosthesis (attached on a stiff delivery cable) was advanced through the introducing sheath. The retention disc was first released in the descending thoracic aorta, then the cylindrical device frame was expanded within the conduit by withdrawing the sheath. RESULTS: Subtotal misplacement into the descending aorta occurred in one procedure (overall technical success rate, 95%), and one animal died before the 1-week follow-up. Complete angiographic shunt closure was achieved in seven of 18 (39%) animals at 30 minutes, 12 of 17 (71%) animals at 1 week, 14 of 17 (82%) animals at 1 month, and 11 of 12 (92%) animals at 3 months. Significantly higher 30-minute closure rates occurred with polyester-filled occluders compared with nonfilled occluders (five of five [100%] vs one of 13 [15%]; P = .002). Persistent shunt at 3 months occurred in only one nonfilled device (6%). In the remaining 16 animals, both orifices of the shunt were covered by a smooth glistening neoendothelium at postmortem examination. CONCLUSION: This device combines the advantages of small delivery system, easy placement, self-centering, and repositionability. Immediate shunt closure can be reliably accomplished with the polyester-filled prosthesis.

Repositionable vascular occluder: experimental comparison with standard Gianturco coils.

PURPOSE: To evaluate the efficacy and recanalization rates of a newly designed vascular occlusion device. MATERIALS AND METHODS: The self-expanding vascular occluder was braided from fine nitinol wires and filled with polyester fibers. The device was delivered through a 6-F polyethylene introducing sheath with use of a delivery cable with a microscrew adaptor. Comparison was made between one occlusion plug and two Gianturco coils placed in the corresponding contralateral arterial segment in nine dogs and six pigs. The mean diameter of the targeted vessels was 4.8 mm +/- 0.8. Two animals were killed immediately after occlusion, and the remaining 13 animals underwent follow-up angiography at 1 week and/or 1 month, after which the animals were killed and the vessels were explanted for gross and histopathologic examination. RESULTS: Significantly shorter time-to-occlusion was achieved with the nitinol plug compared with two Gianturco coils (1.73 minutes +/- 1.28 vs 5.73 minutes +/- 6.18; P = .021). The recanalization rate at 1 month was also significantly lower (36.4% vs 81.8%, P = .027). The occlusion time was strongly dependent on the target artery diameter with Gianturco coils (R = .79, P = .0007), and not with the nitinol plug. CONCLUSION: The nitinol vascular occluder appears highly effective and reliable, with one plug resulting in significantly faster and longer lasting occlusions compared with two Gianturco coils. The new device can be repositioned prior to release, therefore allowing optimal positioning.