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T Schmitz-Rode

Publications and source records attributed to T Schmitz-Rode.

83 records · Page 5Linked to original sources
PubMedDate not supplied

Effectiveness and safety of ultrasonic atherosclerotic plaque ablation: in vitro investigation.

Ultrasound energy was applied to 137 segments of human cadaver atherosclerotic arteries, 90 with calcified and 47 with noncalcified atheromatous plaque, and to 100 segments of healthy swine aorta. The average depth of penetration was dependent on the forward force of the ultrasonic probe, the duration of treatment, and the degree of atherosclerosis. There was one perforation of a fibrous plaque using a forward force of 2 Newton and 45 sec of application time. Injury of healthy intima was minimal. It is concluded that catheter-delivered ultrasound is effective and safe for the disintegration of atherosclerotic plaques. Presently, the main limitations of the system are the lack of flexibility and steerability.

Angioplasty, Balloon↗
PubMedDate not supplied

Oscillating probe aspiration thrombectomy: comparative in vitro evaluation of two concepts.

Aspiration thrombectomy supported by an oscillating metal probe within the catheter allows continuous aspiration of large thrombi without catheter obstruction. Thrombus aspiration assisted by an ultrasound-driven probe (frequency 26 kHz) and by an electric motor-driven probe (frequency 40 Hz) was compared in two different in vitro models: aspiration of large clots from a Petri dish and recanalization of thrombotic occlusions in a flow model. Comparable results were found for a 1 mm ultrasound-driven probe and a 0.5 mm motor-driven probe. The motor-driven device, however, seems to be more appealing for in vivo application because of its simplicity, probe flexibility, absence of thermal effects, and low cost.

Animals↗
PubMedDate not supplied

Ultrasound thrombolysis in hemodialysis access: in vitro investigation.

PURPOSE: To evaluate the effectiveness of ultrasound thrombolysis in occluded hemodialysis access shunts using an in vitro model. METHODS: Thrombosed hemodialysis accesses were simulated by clotted bovine blood in a flow model (silicone tubing; inner diameters 4, 6, and 9 mm). After retrograde and antegrade sheath placement (7 Fr), mechanical thrombolysis was performed using an ultrasound probe (Acolysis, Angiosonics, Morrisville, NC, USA). The tip of the device measured 2.2 mm in diameter. During sonication, the catheter was moved slowly back and forth using an over-the-wire system. Thirty complete occlusions [tubing diameters 4 mm (n = 12), 6 mm (n = 12), 9 mm (n = 6)] were treated. Initial thrombus weights were 3.5 (+/- 0.76) g, 7.7 (+/- 1.74) g, and 19.4 (+/- 2.27) g for the three diameters. Maximum sonication time was 15 min for each probe. RESULTS: With this device, we were able to restore a continuous lumen in all 12 occluded 4 approximately mm silicone tubes. No wall-adherent thrombi remained after sonication for 3.5--9.6 min. In hemodialysis access models with diameters of 6 mm, thrombus fragments persisted in 25% (3/12 accesses). These were located in the medial portion of the access loop and near to the puncture sites. However, flow was re-established after 5.0--13.0 min of treatment in all settings. Mechanical dissolution of thrombus material failed in five of six access models with diameters of 9 mm, even though ultrasound energy was applied for the maximum of 15 min. CONCLUSION: In a clotted hemodialysis shunt model, successful ultrasound thrombolysis was limited to small access diameters and small amounts of thrombus.

Equipment Design↗
PubMedDate not supplied

In vitro evaluation of a rheolytic thrombectomy system for clot removal from five different temporary vena cava filters.

PURPOSE: To evaluate the feasibility of thrombus removal from temporary vena cava filters using a rheolytic thrombectomy device and to assess the embolization rate of this procedure. METHODS: Five temporary vena cava filters together with porcine thrombi were placed in a vena cava flow model (semitranslucent silicone tube of 23 mm diameter, pulsatile flow at a mean flow rate of 4 L/min). A rheolytic thrombectomy system (Hydrolyser) was used with a 9 Fr guiding catheter to remove the clots. The effluent was passed through filters of different size and the amount of embolized particles as well as the remaining thrombus were measured. RESULTS: Thrombus removal rates ranged from 85% to 100%. Embolization rates between 47% and 60% were calculated for the different filters. CONCLUSION: The Hydrolyser is able to remove sufficiently high amounts of thrombus from temporary vena cava filters. However, the amount of embolized particles makes it impossible to utilize this method without special precautions against embolization.

Animals↗
PubMedDate not supplied

Simulated flow pattern in massive pulmonary embolism: significance for selective intrapulmonary thrombolysis.

PURPOSE: The flow pattern in the central pulmonary arteries proximal to large pulmonary emboli was studied experimentally. The currents to which thrombolytic agents are exposed when administered via an intrapulmonary catheter were visualized in order to explain the lack of benefit of local versus systemic administration. METHODS: By illumination of suspended microspheres, the flow pattern proximal to an obstructing embolus was visualized in an in vitro pulmonary arterial flow model. In six dogs massive pulmonary embolism was created. A pigtail catheter was positioned in the pulmonary artery immediately proximal to the central edge of the occluding embolus. To allow visualization of the local flow pattern, a small amount of contrast material (4 ml) was injected through the catheter at a high flow rate (25 ml/sec). The course of the radiopaque spot that emerged from the catheter tip within 160 msec was monitored with digital subtraction angiography at a frame rate of 12.5 frames/sec. In two dogs, the study was repeated after embolus fragmentation with the same catheter position. RESULTS: The flow model study revealed formation of a vortex proximal to the occluding embolus. In vivo experiments showed that the radiopaque spot was whirled by the vortex proximal to the embolus and made only evanescent contact with the edge of the embolus. Regardless of the embolus location, the contrast spot was washed into the non-occluded ipsilateral and contralateral pulmonary arteries within 0.40-0.64 sec. After embolus fragmentation, the contrast spot was carried completely into the formerly occluded artery. CONCLUSION: Flow studies explain why thrombolytic agents administered via a catheter positioned adjacent to the embolus may have no more effect than systemically administered agents. An enhanced local effect is precluded by the rapid washout into the non-occluded pulmonary arteries and subsequent systemic dilution. These results support the practice of direct intrathrombic injection of thrombolytics or local thrombolysis as an adjunct to embolus fragmentation.

Angiography, Digital Subtraction↗
PubMedDate not supplied

Experimental nonsurgical female sterilization: transcervical implantation of microspindles in fallopian tubes.

PURPOSE: A nonsurgical method of female sterilization was investigated in rabbits. MATERIALS AND METHODS: A self-expanding microspindle (length 9-18 mm, diameter 1.5-2.0 mm) made from tubular metal mesh was implanted in a single fallopian tube of 12 rabbits via catheterization of a single uterus. The contralateral fallopian tube and uterus served as controls. Each rabbit was scheduled to undergo three cycles of breeding. Before delivery, absence of pregnancy on the side with the microspindle was verified with hysterography. RESULTS: Eight rabbits completed three cycles of breeding and pregnancy. Two rabbits had one pregnancy. Two rabbits did not conceive. Spindles were placed correctly in 11 rabbits. Successful contraception was achieved in nine rabbits, who had 25 gestations on the nonspindle side and no gestation on the spindle side. One rabbit, which received the shortest spindle, was bilaterally pregnant, indicating a failure of contraception on the spindle side. No spindles dislocated. Histologic study showed all spindles firmly embedded in the tubal wall without signs of inflammation. CONCLUSION: Microspindles of a certain minimum length have potential as a transcervically implantable, permanent intratubal contraceptive device.

Animals↗
PubMedDate not supplied

Use of a temporary caval filter to assist percutaneous iliocaval thrombectomy: experimental results.

PURPOSE: To test a new filter design that allows coaxial insertion of thrombectomy devices and active clot removal. MATERIALS AND METHODS: A prototype filter system was used in animal experiments. It is a transjugularly inserted coaxial system with a 16-F outer sheath and an inner tube that is covered by a tulip-shaped meshwork with a 22-mm diameter at its inserted end. The inner tube allows insertion of instruments up to 8 F. The filter was developed to assist with percutaneous mechanical thrombectomy in the iliofemoral and caval veins. The filter has been used as an assisting tool in nine sheep and eight pigs. It was combined with an impeller system in nine sheep for caval thrombectomy and with a hydrodynamic catheter for iliac thrombectomy in eight pigs after artificial induction of iliac or caval thrombosis. RESULTS: The filters captured emboli from the intervention in six of nine sheep. The amount of captured emboli was reduced within the filter cone by the impeller instrument in five of six instances. Residual thrombus was removed by closing the filter in five of six sheep. In pigs, the filter captured emboli in three cases during hydrodynamic embolectomy. Pulmonary embolization did not occur with the filter in place. After filter removal, minor pulmonary clot embolization occurred in one case. CONCLUSION: The temporary tulip filter was effective in these animal models in capturing and removing thrombus material that may dislodge from iliocaval veins during mechanical thrombectomy.

Animals↗
PubMedDate not supplied

Comparative in vitro study of two percutaneous hydrodynamic thrombectomy systems.

PURPOSE: To test the efficacy of clot removal in small- and large-caliber vessels and determine the extent of procedure-related particle embolization for two rheolytic thrombectomy devices, the Hydrolyser and Angiojet. MATERIALS AND METHODS: Both systems were applied with and without guiding catheters in an arterial (7-mm tube diameter, wall-adherent thrombus [mean, 5.3 g], flow of 500 mL/min)and a venous (20-mm tube diameter, free-floating thrombus [mean, 12 g], flow of 1,500 mL/min) flow model. RESULTS: Particle embolization was significantly lower for the Angiojet device (mean, 1.8% +/- 2.9 [standard deviation] vs mean 4.8% +/- 6.1 for particles > 1,000 microns). When the devices were used without guiding catheters, mean clot removal rates were 65% +/- 12 with the Hydrolyser and 49% +/- 9.2 with the Angiojet in the arterial flow model and 88% +/- 15.5 with the Hydrolyser and 85% +/- 17.8 with the Angiojet in the venous flow model. Significant improvements in clot removal rates were achieved with use of guiding catheters: 81% +/- 5.4 with the Hydrolyser and 89% +/- 3.9 with the Angiojet in the arterial flow model and 95% +/- 1.4 with the Hydrolyser and 97% +/- 0.84 with the Angiojet in the venous flow model. CONCLUSION: Use of guiding catheters improved the performance of both systems significantly. Both rheolytic catheters remove sufficient amounts of soft thrombus from a large-caliber vessel, especially when applied with a guiding catheter. However, firmer thrombus is difficult to remove. The particle embolization rate is low for both systems.

Animals↗
PubMedDate not supplied

Circular spirit level guidance system for CT- and MR-guided punctures.

A circular spirit level guidance system was tested for control of CT- and MR-guided punctures. The device consists of a needle holder fixed to a ground plate and two protractors. This allows adjustment of the fixed needle according to the angulation of the supposed puncture path as measured on tomographic images. A circular spirit level is fixed to the needle and leveled. Now the needle can be removed from the needle holder; by leveling the circular spirit level during the puncture, the formerly adjusted angulation is achieved. The system was tested in vitro and in vivo (22 patients) under CT and MR guidance. The average needle deviation was measured to be 1.96 degrees in vitro and 2.51 degrees in vivo. This simple device allows accurate puncture under CT and MR guidance.

Humans↗
PubMedDate not supplied

Fragmentation of pulmonary emboli: in vivo experimental evaluation of two high-speed rotating catheters.

PURPOSE: To test two over-the-wire systems for fragmentation of pulmonary emboli. METHODS: In 11 dogs, 22 embolic occlusions of lobar or central pulmonary arteries were performed by injection of preformed emboli through a jugular vein sheath. A commercially available device (thrombolizer) and a modified version of the impeller catheter were introduced via the femoral vein and positioned at the embolus site. RESULTS: Catheter placement at the site of the emboli was possible. In more than half of the cases a hydrophilic or an extra-stiff guidewire was necessary. The thrombolizer did not rotate properly with its original pneumatic drive and required a major modification. When sufficient rotation was provided, both fragmentation catheters were able to clear the occluded main arteries. Side branches were partly obstructed by the resulting fragments. Recanalization led to a reduction of the emboli-induced elevation of the pulmonary arterial pressure by two-thirds. Histology of the recanalized pulmonary artery segments revealed localized (impeller catheter) and widespread (thrombolizer) periarterial hemorrhage. CONCLUSION: Embolus fragmentation led to a hemodynamic improvement. The impeller catheter was less traumatic compared with the thrombolizer, which was technically insufficient.

Animals↗