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Biomedical subjects

K Amplatz

Publications and source records attributed to K Amplatz.

At least 433 records · Page 24Linked to original sources
PubMedDate not supplied

Acute clot-trapping efficiency in dogs with compacted versus elongated wires in bird's nest filters.

PURPOSE: The clot-trapping efficiency of the Bird's Nest filter was studied in dogs with the stainless steel wires in a compacted versus fully elongated configuration. MATERIALS AND METHODS: Bird's Nest filters were placed infrarenally with the wires compacted in 10 dogs and with the wires elongated in an additional 10 dogs. The dogs were separated into two groups, five dogs with each wire configuration in each group. In group 1, 10 unlabeled 6 x 30-mm blood clots were injected into the inferior vena cava. In group 2, six 6 x 10-mm, four 6 x 15-mm, and four 6 x 30-mm labeled clots were introduced. RESULTS: In group 1, clot-trapping efficiencies were 82% for the compacted versus 86% for the elongated configuration, as seen on serial cavograms and pulmonary angiograms. In group 2, clot-trapping efficiencies were 90% for the compacted versus 97% for the elongated configuration, as seen at fluoroscopy. Clot size did not affect trapping efficiency. CONCLUSION: Acute clot-trapping efficiency of Bird's Nest filters did not differ when the wires were in a compacted versus elongated configuration. This study suggests that placement of a Bird's Nest filter in the elongated configuration may be satisfactory and may not indicate placement of a second filter.

Animals↗
PubMedDate not supplied

Hemolytic effect of the Amplatz thrombectomy device.

PURPOSE: The hemolytic effect of the Amplatz thrombectomy device (ATD) was evaluated in nine dogs and in nine patients. MATERIALS AND METHODS: The device was activated for 1-2 minutes in the abdominal aorta, inferior vena cava, or femoral artery of nine dogs. The device was activated for 1-4 minutes in the nine patients in occluded lower extremity bypass grafts (n = 5), native superficial femoral artery (n = 1), a pulmonary artery embolus (n = 1), a portocaval shunt (n = 1), and an iliac vein stent (n = 1). Patients were examined for laboratory evidence of hemolysis following mechanical thrombectomy. RESULTS: In all dogs haptoglobin level decreased, free hemoglobin level in the plasma increased, and hemoglobinuria was present. There was no change in renal function. The level of haptoglobin decreased and the level of plasma free hemoglobin increased in eight patients, with hemoglobinuria detected in one. More hemolysis was observed in the animals than in the patients. CONCLUSION: The ATD has a definite transient hemolytic effect. Until further studied, it should not be used in children and should be used with caution in patients who are anemic, hypoxemic, or have potentially reversible renal insufficiency. Activation time should be monitored closely because hemolysis probably increases with increasing activation time.

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PubMedDate not supplied

In vitro and in vivo experimental evaluation of a new vena caval filter.

PURPOSE: A new stainless steel (MP35N alloy) vena cava filter without a central stasis point was evaluated in vitro and in vivo. MATERIALS AND METHODS: The clot-trapping efficiency and hemodynamic flow pattern of the filter were assessed in a flow model and were compared with those of currently available commercial filters including the Vena Tech-LGM, Simon nitinol, Greenfield, and Bird's Nest filters. The new filter was placed in the inferior vena cava (IVC) of 31 dogs; 21 of the 31 dogs were followed up with cavography for up to 3 months. At the termination of the study, the filters and IVCs were examined grossly and histologically. An in vivo clot-trapping test was carried out in five dogs. RESULTS: The least turbulence was noted with the new filter and the titanium Greenfield filter. The stainless steel Greenfield and Simon nitinol filters caused major flow disturbances. Migration within 5 cm of initial placement occurred in two animals (9.5%). There were no IVC thromboses, perforations, or filter embolizations. An in vivo clot-trapping study showed an 80% efficiency for small thrombi (3 x 20 mm) and 100% efficiency for large thrombi (6 x 20 mm) with the new filter. The Simon and the new filter had the best clot-trapping capabilities. The Vena Tech-LGM and Bird's Nest filters were slightly inferior and the Greenfield filter demonstrated by far the lowest trapping capacity. CONCLUSION: The new vena cava filter is easily introduced percutaneously through a 12-F sheath and appears to be very promising due to its high filtering capability, low turbulence, nonmagnetic properties, good mechanical stability, and hypothrombogenicity. Clinical trials are warranted.

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PubMedDate not supplied

Mechanical thrombectomy with the Amplatz device: human experience.

PURPOSE: The authors present their early experience of mechanical arterial and graft thrombectomy with the Amplatz thrombectomy device. PATIENTS AND METHODS: Preliminary data are presented for 14 patients treated with the Amplatz thrombectomy catheter. The procedure was carried out in 10 arterial polytetrafluorethylene grafts, in two native arteries, and in two patients with venous thrombosis. RESULTS: The thrombectomy catheter completely removed the clot in 11 patients and partially removed clot in three patients. Mean thrombectomy time was 2 minutes 45 seconds. Despite distal blood pressure cuff occlusion, two instances of insignificant distal embolization occurred. Mechanical clot dissolution has consistently produced hemolysis without adverse clinical effects. The underlying causative factors such as stenoses were treated by means of angioplasty, atherectomy, or surgical endarterectomy. CONCLUSION: Mechanical thrombectomy with this device is a new, effective technique and can rapidly remove the thrombus. From preliminary results, the device seems most promising in clearing out thrombi in occluded synthetic femoral-to-popliteal bypass grafts. The device could have wider application if it were steerable and if it could be introduced from the contralateral approach.

Adult↗
PubMedDate not supplied

Chronic iliac artery occlusions: primary recanalization with endovascular stents.

PURPOSE: The authors describe treatment of chronic iliac artery occlusions with primary stent placement without prior thrombolysis or angioplasty. PATIENTS AND METHODS: Eight patients with chronic iliac artery occlusions (six men and two women) underwent primary stent placement without prior use of thrombolytic agents or angioplasty. Palmaz stents were placed in seven patients and a Wallstent device was placed in one. RESULTS: In all patients, revascularization was successful without residual stenoses or pressure gradients. There was no angiographic evidence of distal embolization. CONCLUSION: Primary stent placement for chronic iliac artery occlusions without prior thrombolysis or angioplasty appears to be safe and efficacious and is potentially cost effective.

Adult↗
PubMedDate not supplied

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.

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PubMedDate not supplied

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.

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PubMedDate not supplied

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.

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