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Biomedical subjects

H Schwarzenberg

Publications and source records attributed to H Schwarzenberg.

At least 19 recordsLinked to original sources
PubMed2000

Intravascular ultrasound evaluation of peripheral arterial stent-grafts.

RATIONALE AND OBJECTIVES: To evaluate neointimal hyperplasia, plaque distribution, and morphologic features of peripheral arterial stent-grafts with intravascular ultrasound (IVUS). METHODS: Twenty-three patients with stenoses or occlusions of the pelvic or femoral arteries were treated with 31 stent-grafts. Angiography and IVUS of the stented artery were performed 13.9 +/- 9.7 months after stent implantation. Maximum in-stent restenosis was measured by IVUS. Plaque composition and lesion topography were also assessed. RESULTS: The maximum in-stent restenosis was 53.2 +/- 26.5% for the femoral and 14.2 +/- 10.1 for pelvic arterial stent-grafts. Predilection sites of maximum neointimal tissue accumulation were the edges of the femoral stent-grafts. Only small amounts of neointimal hyperplasia were found in the stent-graft edges. No predilection site for maximum in-stent restenosis was found for the pelvic arterial stent-grafts. CONCLUSIONS: Predilection sites of maximum in-stent restenosis were the edges of femoral stent-grafts in contrast to pelvic stent-grafts. Femoral stent-grafts showed significantly higher graded stenoses with IVUS than iliac stent-grafts. The authors' findings at IVUS did not change the treatment plan in these patients treated with stent-grafts.

Arterial Occlusive Diseases↗
PubMed1999

[In vitro comparison of a size 6F and 8F high-speed rotational catheter for mechanical thrombus fragmentation].

PURPOSE: In vitro comparison of the 6F and 8F Amplatz thrombectomy device (ATD) for treatment of thrombotically occluded vessels in a flow-model. MATERIALS AND METHODS: Thrombectomy of clots from porcine blood was performed with either a 6F or an 8F Amplatz thrombectomy device (ATD) in a flow-model simulating a superficial femoral artery circuit (n = 40; 7.5 g: 7 mm diameter; 4.5 g: 5 mm diameter). Emboli caused during thrombectomy were determined in a three-step filter array (10 microns-1000 microns). RESULTS: Thrombectomy was successful in all cases. In 5 mm/7 mm lumen time for thrombectomy was measured from 47 s/56s (8F) to 86 s/107 s (p < 0.01) (6F). Remaining thrombus weighted in 5 mm/7 mm lumen 0.04 g/-0.02 g (8F) and 0.05 g/-0.02 g (6F). Overall weight emboli determined for 1000 microns, 100 microns and 10 microns size and percentage of emboli related to original thrombus weight measured 0.23 g/4.96% (8F, 5 mm), 0.2 g/4.36% (6F, 5 mm), 0.08 g/1.13% (8F, 7 mm). and 0.09 g/1.18% (6F, 7 mm). CONCLUSIONS: In vitro, the 6F ATD is in "vessels" with 5 mm and 7 mm diameter as effective as the 8F version. Particle embolization in flow-circuit was similar with both devices, although the 6F ATD requires a longer time for thrombectomy in vessel with larger diameter.

Animals↗
PubMed1999

In vitro effectiveness study for hydrodynamic thrombectomy devices of the second generation.

RATIONALE AND OBJECTIVES: To determine the efficacy of clot removal and the amount of applied saline and aspirated fluid and to compare procedure-related particle embolization for the hydrodynamic thrombectomy devices the LF 140 Angiojet (LF 140), the double-lumen Hydrolyser (double HL), and the triple-lumen Hydrolyser (triple HL) in an in vitro flow model. METHODS: Thrombectomy of clots (n = 42) from 7-day-old porcine blood (9.8 g) was performed with the LF 140, the double HL, and the triple HL in a flow model (flow 1 L/min) made of silicone tubes (7 mm inner tube diameter). All catheters were used according to the manufacturer's recommendations. RESULTS: Mean time of thrombectomy ranged from 20 seconds (triple HL) to 58 seconds (LF 140, P < 0.05). Only for the triple HL was remaining thrombus found within the tubes (41 mg). None of the tested devices worked isovolumetrically: the mean ratio of applied saline and aspirated fluid for the devices ranged from 0.79 (triple HL) to 0.89 (double HL, P < 0.05). Mean embolus weight and percentage of embolism from original thrombus were 675 mg/6.7% (LF 140, P < 0.05), 38 mg/0.4% (double HL), and 26 mg/0.3% (triple HL). CONCLUSIONS: Thrombectomy time and embolus weight depend on the device chosen. The ratio of applied to aspirated fluid, indicating the capability to work nearly isovolumetrically, is acceptable for all tested devices. In vitro, the triple HL seems to be the most appropriate device for rapid mechanical, hydrodynamic thrombectomy. Because of the high in vitro particle embolization rate, the LF 140 seems to be strictly limited to small-caliber vessels.

Animals↗
PubMed1999

In vitro effectiveness study of three hydrodynamic thrombectomy devices.

PURPOSE: To determine the in vitro efficacy of three hydrodynamic thrombectomy devices. MATERIALS AND METHODS: Thrombectomy of clots was performed with three thrombectomy devices (Angiojet [AJ], Possis Medical, Minneapolis, Minn; Hydrolyser [HL] Cordis Europe, Roden, the Netherlands; and the Shredding Embolectomy Thrombectomy [SET] catheter, HP-Medica, Augsburg, Germany) in a flow model. RESULTS: Mean thrombectomy time ranged from 10.22 seconds (HL) to 37.73 seconds (AJ with guide wire). For the AJ and HL, the use of guide wires prolonged thrombectomy time (P < .01). The AJ with and without a guide wire and the HL with a 0.018-inch guide wire worked isovolumetrically, whereas the mean ratio of applied saline and aspirated fluid for the other devices was different from 1, ranging from 0.54 to 0.72. Mean embolus weight with the AJ alone (56.44 mg) was significantly higher than that with the SET catheter alone (3.15 mg) and with a guide wire (1.31 mg, P < .01 for both) and the HL alone (3.9 mg, P < .05), as was the embolus weight with the HL with a 0.018-inch guide wire (66.5 mg) compared with the SET catheter with and without a guide wire (P < .01), AJ with a guide wire (22.33 mg, P < .05), the HL alone (P < .01), and the HL with a 0.025-inch guide wire (24.86 mg, P < .05). CONCLUSION: The devices showed performance differences. The SET catheter alone and with a guide wire and the HL may bear an increased risk of procedure-related anemia. In clinical applications, hydrodynamic thrombectomy might substantially reduce the need for thrombolytic therapy.

Equipment Design↗
PubMed1998

[Local fibrinolysis of peripheral arterial occlusions].

PURPOSE: Since their discovery more than 60 years ago fibrinolytic agents have shown their therapeutical efficiency in myocardial infarction and other thromboembolic disorders in clinical studies. Local catheter fibrinolysis as an alternative to surgical embolectomy was established in the mid eighties. Fibrin-specific agents such as rt-PA and pulse-spray fibrinolysis as a new catheter technology were developed in order to improve the efficiency of local fibrinolysis and to minimize complications such as bleeding. The purpose of this paper is to review the historical and recent developments of fibrinolytic agents and catheter technologies, and to describe the methods, indications, and complications of local fibrinolysis.

Arterial Occlusive Diseases↗
PubMed1998

[Suction pump-supported aspiration thrombectomy: an in-vitro comparison with a thrombus fragmentation procedure].

PURPOSE: To compare the efficacy of vacuum pump controlled aspiration thrombectomy (VPCAT) with the Amplatz thrombectomy device (ATD) for treatment of thrombotic occlusions. MATERIALS AND METHODS: In a flow-model a superficial femoral artery is simulated. VPCAT provides the connection either of an aspiration catheter (AC, 8 F) or a multipurpose catheter (MPC, 8 F) with a vacuum pump (-110 mbar underpressure). 7 day old porcine blood (n = 30; 7.4 g +/- 0.1g) was treated with AC and MPC (VPCAT technique) and with the ATD. RESULTS: Complete thrombectomy was achieved with all techniques. Thrombectomy time was short for ATD (8.8 +/- 0.94 s; p < 0.01). MPC caused the least overall weight of emboli related to thrombus weight (5.14 0/100; p < 0.01). ATD caused the least embolisms at 1000 microns (3.27 mg; p < 0.05), and the most embolisms at 100 microns and at 10 microns (26.5 mg and 26.9 mg; p < 0.01). The aspirated volume of the MPC (33 +/- 17 ml) was half the volume of the AC (65 +/- 25 ml). CONCLUSIONS: In-vitro, VPCAT proves to be an alternative procedure to ATD. The use of a wide lumen multipurpose catheter is advantageous. In vitro, embolism rates of all methods are sufficiently low.

Analysis of Variance↗
PubMed1998

[Treatment of arterial femoropopliteal obstructions with Palmaz midsize stents].

PURPOSE: To evaluate effectiveness, success and patency rates after endovascular treatment with mid-size Palmaz stents in high-grade stenoses or short-distance occlusions of femoral arteries. MATERIALS AND METHODS: 27 patients with 10 occlusions (average length 3.2 +/- 1.4 cm) and 17 severe stenoses of the superficial femoral artery were treated with 33 mid-size Palmaz stents. The follow-up included Doppler ultrasound at one, three, 6 and 12 months and an angiography at 6 months. Mean follow-up was 6.5 months. RESULTS: Technical success was 100%. The ankle-brachial index improved from 0.57 +/- 0.28 pretreatment to 0.87 +/- 0.13 within 24 hours. Acute stent thrombosis occurred in two patients (< 3 weeks). Angiography at 6 months revealed restenosis rates of 7.4% (> 50%, n = 2). Life-table analysis according to Kaplan-Meier revealed 6-month primary and secondary patency rates of 84% and 91%. CONCLUSION: With regard to our limited data, the implantation of mid-size Palmaz stents in femoral arteries seems promising in treatment of short-distance occlusions and stenoses of the femoral artery.

Aged↗
PubMed1998

Visualization of flow patterns from stents and stent-grafts in an in vitro flow-model.

RATIONALE AND OBJECTIVES: The authors determine flow characteristics and pressure gradients of different stents and stent grafts in an in vitro flow-model. METHODS: Five vascular stents (Memotherm, Cragg, two Palmaz P308, Strecker, and Wall) and one stent graft (Cragg EndoPro System 1), equal in length (60 mm) and diameter (10 mm), were deployed in a closed flow-model. The inner diameter of the tube measured 9 mm. Flow at 1.5 L/min, 6 L/min, and 10 L/min was simulated. Flow patterns were visualized by anionic particles illuminated with two Helium-Neon lasers. Laminary flow characteristics and pre-/poststent pressure gradients were determined in either expanded stent, 25% stenosis, or 50% stenosis. RESULTS: Stent implantation induced a decrease of laminary flow compared with an unstented tube with and without concentric 25% stenosis (P < 0.01) at all flow rates and an increase of pressure gradients compared with an unstented tube for flow rates greater than 1.5 L/min (P < 0.01) (except for Cragg EndoPro System 1 stent, which revealed an increase of the pressure gradient at a flow rate of 1.5 L/min [P < 0.01]). Memotherm stent permitted maximum of laminary flow at all flow rates and stenoses (expanded: 79.50% at 1.5 L/min to 69.90% at 10 L/min; P < 0.01). Memotherm and Palmaz permitted lowest pressure gradients (P < 0.01). All of the endoprostheses demonstrated laminary flow at 50% stenosis. CONCLUSIONS: The investigated stents and stent grafts showed different severity of flow disturbances and pressure gradients at different graded stenoses. Inadequate stent depolyment bears the risk of creating less laminary flow and pathologic pressure gradients. Because flow disturbances and pressure gradients may influence neointimal hyperplasia, stent design and completeness of stent unfolding are important regarding the appearance of postinterventional restenoses.

Analysis of Variance↗
PubMed1998

Percutaneous placement of a self-expandable stent for treatment of a malignant pulmonary artery stenosis.

Venous stent placement is widely accepted as the treatment of stenoses caused by external tumour compression to reduced clinical sequelae. We report percutaneous stent placement into a severely obstructed right pulmonary artery in a 73-year-old female patient. The underlying disease was a medistinal tumour mass of unknown aetiology. Pulmonary perfusion was successfully but temporarily restored by the intervention.

Aged↗
PubMed1998

Restenosis of peripheral stents and stent grafts as revealed by intravascular sonography: in vivo comparison with angiography.

OBJECTIVE: Our objective was to compare intravascular sonography with digital subtraction angiography (DSA) in the assessment of luminal dimension and morphologic features of endovascular stents and stent grafts. MATERIALS AND METHODS: Thirty-seven pelvic and 24 femoral stents (12 Wall-stents; 27 covered and 22 uncovered nitinol stents) in 50 patients were evaluated 15 +/- 10 months after implantation by DSA and intravascular sonography. The degree of maximum instent restenosis as revealed by DSA and intravascular sonography was compared for each location. Morphologic features of the stents and stenoses were also assessed. RESULTS: Intravascular sonography and DSA correlated well (R2 = .96) in determining in-stent restenosis. In-stent restenosis was underestimated by 13% +/- 6% by DSA compared with intravascular sonography. Differences in determining in-stent restenosis with intravascular sonography and DSA were not associated with severity of stenosis or type of stent. Intravascular sonography revealed incomplete expansion of stents in 21 cases, whereas DSA revealed incomplete expansion of stents in seven cases. The intra- and interobserver variabilities in our study were 4% and 5%, respectively. CONCLUSION: In-stent restenoses are underestimated with DSA. Intravascular sonography is superior to DSA for detection of incomplete stent expansion.

Alloys↗
PubMed1998

Evaluation of maximum neointima proliferation and plaque morphology in iliac self-expanding nitinol stents with intravascular sonography.

OBJECTIVE: The purpose of this study was to use intravascular sonography to evaluate neointima formation, plaque location, and the performance of self-expanding nitinol (Memotherm) stents in iliac arteries. SUBJECTS AND METHODS: Seventeen patients (mean age, 64+/-9.4 years) with stenoses or occlusions of the common (n = 12) or external (n = 5) iliac artery were treated with 21 Memotherm stents (mean diameter +/- SD, 8.9+/-1.3 mm; mean length, 53+/-20.9 mm). Four patients had two stents each. Intravascular sonography was performed 13+/-6 months after stent implantation. Maximum thickness of neointima and maximum cross-sectional plaque area were measured. Qualitative analysis of plaque composition and lesion topography were also assessed. RESULTS: Intravascular sonography revealed 22.1%+/-17.3% maximum percentage of restenosis, and maximum plaque area was found to be 11.2+/-10 mm2. Only hypoechogenic in-stent lesions (soft plaques) were found. Seven (33%) incomplete stent expansions and two (10%) incomplete appositions of the stent to the vessel wall were revealed by intravascular sonography. CONCLUSION: Iliac artery Memotherm stents generally showed moderate in-stent restenosis with uniform neointima distribution. Incomplete stent expansion was detected in one third of all implanted stents.

Alloys↗
PubMed1997

[3D-CT angiography and duplex sonography compared to arteriography in carotid stenoses].

PURPOSE: To determine the value of 3D-CT angiography, duplex sonography in comparison to selective digital subtraction angiography for evaluation of carotid artery stenoses. METHODS: 30 patients with 51 stenoses of carotid artery underwent 3D-CT angiography, duplex sonography and angiography. Quantification of stenosis was determined according to the NASCET study and categorized into mild (0-29%), moderate (30-69%), severe (70-99%) and occluded (100%). RESULTS: The agreement of 3D-CT angiography with intraarterial digital subtraction angiography (DSA) was 62% (r = 0.89; p < 0.0001) and of duplex sonography with DSA was 77% (r = 0.94; p < 0.0001). Both modalities underestimated one occlusion as stenosed. In the evaluation of moderate and severe stenoses 3D-CT angiography showed an agreement with DSA in 50% (duplex: 88%) and 55% (duplex: 89%) respectively and was inferior to duplex sonography. CONCLUSION: 3D-CT angiography is inferior to duplex sonography in the evaluation of carotid stenosis and not useful as a screening or reference examination.

Aged↗
PubMed1997

MR imaging signal-intensity abnormalities after placement of arterial endoprostheses.

OBJECTIVE: Our objectives were to describe changes in T2-weighted MR images of patients who had undergone implantation of an endoluminal stent-graft and determine the rate of early reocclusion in patients with abnormal MR findings. SUBJECTS AND METHODS: Twenty-nine patients with 26 occlusions (average length, 8.7 +/- 5.6 cm) and three dissections of the superficial femoral artery were treated with 45 endoluminal stent-grafts. T2-weighted gradient-echo and T2-weighted turbo spin-echo MR images were obtained for all patients at 48 hr and at 4 weeks after stent-graft placement. We reviewed the MR imaging studies to assess the extent and severity of tissue alteration at the site of stent-graft implantation. RESULTS: Technical success rate of stent-graft placement was 100%. Three signal-intensity patterns were seen on MR images obtained at 48 hr: normal signal intensity (n = 8), subtle perivascular signal-intensity abnormalities at the site of stent-graft implantation (n = 11), and extensive signal-intensity abnormalities from the adductor canal to the subcutis (n = 10). Twenty of 21 patients with abnormal signal intensity on MR images had fevers and pain at the implantation site. Clinical signs of deep vein thrombosis, a diagnosis excluded on the basis of phlebography, were seen in the 10 patients with extensive signal-intensity abnormalities. In two of these 10 patients, the superficial femoral artery reoccluded within 4 weeks of implantation. MR images obtained at 4 weeks showed no signal-intensity abnormalities in any of the 29 patients. CONCLUSION: MR findings of perivascular signal-intensity abnormalities after implantation of endoluminal stent-grafts are associated with clinical complications such as local pain and fever. Care should be taken to avoid confusing the clinical signs of the postimplantation syndrome at 48 hr with deep vein thrombosis.

Aged↗
PubMed1997

[Minimal invasive therapy of aneurysms of the superficial femoral artery and the popliteal artery].

Percutaneous stent placement has been described for treatment of aneurysms as an alternative to surgical therapy. Literature reports of percutaneous minimal invasive therapy of peripheral aneurysms shall be reviewed and compared with our own results. Six male patients (51-69 years) with femoropopliteal occlusions related to aneurysms were treated percutaneously. In two cases Wallstents and in four cases polyester-covered nitinol stents were applicated. A clinical investigation including doppler-ultrasound was performed 24 hrs, 1, 3, 6, 12 and 24 months after the intervention. Stent placement succeeded in all cases. No adjunctive surgical treatment was necessary. Ankle-brachial-index (ABI) improved from 0.22 +/- 0.2 before to 0.74 +/- 0.2 24 hours after the intervention. One patient was lost for follow-up (Wallstent). A decrease of ABI and additional intraarterial angiography revealed stent-graft occlusion within one month (n = 2) and within three months (n = 1). One of these cases was successfully recanalized with local fibrinolysis therapy. In three patients patency of the stent persisted for 24 (+/- 2) months follow-up with three-vessel-supply of the calf. These results warrant further investigations for this minimal invasive method of percutaneous stent deployment as an alternative to surgical bypass treatment of femoropopliteal aneurysms. Time of hospitalization was reduced. At this time, surgical treatment of peripheral vascular aneurysms is gold standard.

Aged↗
PubMed1996

[Therapy of venous stenosis using wall stents].

OBJECTIVE: To evaluate the patency of Wallstents implanted for the treatment of venous stenoses in patients with benign or malignant disease. PATIENTS AND METHODS: 22 Wallstents (20 central venous; two peripheral) were implanted during a period of two years in 12 patients (nine men, three women; mean age 57.8 [26-76] years) with malignant venous stenoses (n = 9) or stenosed dialysis shunts (n = 3). Stent diameter ranged from 8-16 mm, length from 32-91 mm. Introduction of the stents were by percutaneous transfemoral catheterisation, in six patients with simultaneous wire placement from a cubital to the femoral vein. The superior vena cava was the involved vessel in six patients (in two each also the subclavian or brachiocephalic veins), in three only the subclavian vein, twice only the inferior vena cava and once the cephalic vein. RESULTS: The patency of the stents was checked after 4.7 +/- 3.6 (1-14) months, in seven patients clinically, by digital subtraction phlebography in three, by computed tomography in two. In nine patients there was no evidence of obstruction to flow or flow was normal. Stent occlusion had occurred in three patients, 4, 9 and 14 months after placement. There were no complications. Five patients died after a mean period of 4.8 +/- 3.6 (1-6.5) months from the underlying disease, without symptoms of obstruction to flow. CONCLUSION: Stent placement should be considered early, as it is a well-tolerated and effective palliative procedure for central venous stenoses associated with malignant disease or stenosis of dialysis shunts.

Adult↗
PubMed1996

[Technical modification of the rheolytic thrombectomy].

A 48-year-old male patient with acute occlusion (5 cm) of a leg artery was treated with the rheolytic thrombectomy (RT). As recommended the catheter is applied via a single coaxial running guide wire, which is removed later. If an additional wire has been placed in the occluded vessel segment, the occlusion can be passed repeatedly. A 30 degrees bent catheter tip improves the removal of wall-adherent thrombotic material. The occluded segment was successfully recanalized with the RTC, 270 ml of heparinised saline had been injected. The blood examinations showed mild haemolysis.

Arterial Occlusive Diseases↗