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Biomedical subjects

T Schmitz-Rode

Publications and source records attributed to T Schmitz-Rode.

At least 55 records · Page 3Linked to original sources
PubMed1999

[Diagnosis and visualization of renal artery stenosis by color-coded Doppler ultrasonography. Comparison of central and peripheral flow patterns].

PURPOSE: Comparison between central and peripheral flow patterns with color-coded duplex sonography in the diagnosis of renal artery stenosis. MATERIALS AND METHODS: In a prospective study with sixty-six patients systolic velocity (central examination) and acceleration index (peripheral examination) were determined using color-coded duplex sonography examination in order to detect and visualize renal artery stenosis. If the central and peripheral measurements were negative, no angiography was performed. In contrast, if one of the methods yielded a pathological finding, catheter angiography was performed to verify the results (21 patients), as well as in two other unclear cases. RESULTS: An agreement between central and peripheral measuring was seen in 49 of 66 patients. In ten patients central and peripheral measurements showed different results. In seven cases the peripheral measurements were not clear. Compared to angiography, peripheral measurement showed a sensitivity of 60%, a specificity of 75% and a positive predictive value of 81.8%. In contrast, central examination had a sensitivity of 100%, a specificity of 75% and a positive predictive value of 88.2%. CONCLUSIONS: Based on our preliminary results, the measurement of the systolic velocity peak seems to be an effective method to detect renal artery stenosis.

Adult↗
PubMed1999

Embolotherapy of aneurysms under temporary balloon occlusion of the neck. In vitro study of a newly designed eccentric balloon catheter.

RATIONALE AND OBJECTIVES: To test embolotherapy of aneurysms in an in vitro model using standard and specially designed eccentric occlusion balloon catheters for simultaneous delivery of the embolization agent and occlusion of the neck of the aneurysm. METHODS: Two different in vitro set-ups were used: a bifurcational aneurysm and an aneurysm with a straight parent vessel segment, both made from elastic silicone and glass. Each model was exposed to a pulsating perfusion. The effluent was collected and filtered. For the bifurcational aneurysms, commercially available occlusion balloon catheters with a working channel exiting at the tip were used. For the aneurysms with straight parent vessel, the catheters were modified so that the balloon opened eccentrically. The working channel of the catheter led to a side hole, which was located where the balloon membrane was fixed to the catheter shaft. The aneurysms were filled with coils, ethibloc, or hydrogel, and with coils combined with ethibloc or hydrogel, while the expanded balloon occluded the neck. RESULTS: Embolization of aneurysms under balloon occlusion of the neck was technically feasible with the catheter devices. Dense packing with coils was possible in all cases without coil dislocation, but unfilled interspaces remained between the coil wires. Best filling was achieved with ethibloc or hydrogel alone or in combination with coils. During the filling procedure, there was no distal embolization of the liquid agents. However, after balloon deflation, considerable amounts of hydrogel or ethibloc were washed out from the aneurysm. CONCLUSIONS: The results suggest that balloon occlusion of the neck allows compact filling and minimizes the risk of dislocation in coil embolotherapy of aneurysms. In nonbifurcational aneurysms, the eccentric balloon catheter seems to be suitable for this treatment concept. Although liquid agents may be safely delivered into the aneurysm under balloon protection, their considerable washout rate after balloon removal requires further refinements of the technique before clinical application is advisable.

Catheterization↗
PubMed1999

Mechanical thrombectomy in hemodialysis access shunts using a 5F pigtail rotation catheter. In vitro and in vivo investigations.

RATIONALE AND OBJECTIVES: To evaluate the feasibility of mechanical thrombectomy in occluded hemodialysis access shunts by using a newly developed 5F pigtail rotation catheter. METHODS: Thrombosed hemodialysis access shunts were simulated by clotted bovine blood in silicone tubing (diameter 6 mm). After retrograde and antegrade sheath placement (6F), mechanical fragmentation was performed using a 5F rotatable pigtail device. Average tube length was 27 to 47 cm; average thrombus weight was 5 to 11.9 g (8.2 +/- 1.59). Clinical application involved six patients with fresh shunt occlusions (three Brescia-Cimino shunts, three Gore-Tex shunts). RESULTS: Using the in vitro setup, the device was able to restore a continuous lumen within 10 minutes with no remaining wall-adherent thrombi. The average amount of particles in the effluent was 3.0 g (2.0 to 3.9) for particles < or = 1.0 mm and 0.67 g (0.44 to 0.96) for particles > or = 0.2 mm wet weight; (compared with initial thrombus weight, 30.7% and 1.1%, respectively). Clinically, all six hemodialysis access shunts were successfully recanalized. Technical problems did not occur. There were no clinical symptoms indicating pulmonary embolism in any of the treated patients. CONCLUSIONS: In our experimental setup as well as under clinical conditions, effective treatment of occluded hemodialysis access sites was achieved. The pigtail rotation device is an easy-to-handle, inexpensive alternative to mechanical thrombus fragmentation in occluded hemodialysis access shunts. The rate of emboli in the effluent vein of approximately one third of the initial thrombus weight must be taken into consideration in frequent intraindividual use of this technique.

Adult↗
PubMed1999

[Repositioning of a central venous catheter with a guide wire with movable core].

PURPOSE: A simple method to redirect malpositioned central venous catheters using a guide wire with movable core is described. METHODS: A 0.89 mm guide wire with movable core is inserted into the catheter. The core is withdrawn for a few centimeters producing a floppy wire tip segment, which follows the malpositioned course of the catheter. The core is then advanced in small steps, until the catheter tip flips into the correct vein. RESULTS: In 8 cases rapid repositioning of malpositioned catheters was accomplished with this technique, without moving the catheters at the entry site. CONCLUSIONS: The repositioning technique described is simple, fast, and inexpensive. Movement of the catheter at the entrance site is not necessary, thus not jeopardizing sterility, and without the need to solve the suture fixation.

Catheterization, Central Venous↗
PubMed1998

[A new MR-(and CT-) compatible bone biopsy system: first clinical results].

PURPOSE: To describe the development and clinical evaluation of a new, hand-powered or alternatively motor-driven, MRI and CT compatible percutaneous bone biopsy system. MATERIALS AND METHODS: A new coaxial drill system (Cook Europe A/S) was designed for percutaneous, MR-guided bone biopsies and powered either by hand or an optional motor (10-250 rotations/minute using 6 bar [88.2 PSI] compressed air). The system has been used in 23 patients. Fourteen procedures were performed in a 1.5 T MR scanner (Philips-Gyroscan ACS-NT) which has an attached C-arm (Philips-BV 212-Angio) in case fluoroscopy is required, and 9 procedures in a CT scanner (Siemens-Somatom Plus). RESULTS: Driven by hand or by the pneumatic motor unit, the system achieved safe and accurate MR-guided access to all of the lesions and was even able to penetrate osteosclerotic lesions. MR- or CT-guided percutaneous biopsy yielded a correct diagnosis in all but 5 cases. No procedural complications occurred. CONCLUSION: MR-guided percutaneous bone biopsy performed with the new coaxial drill system was found to be safe and reliable, and suitable for obtaining histological specimens from skeletal lesions even when covered with thick cortical or sclerotic bone.

Biopsy↗
PubMed1998

Thrombolysis of mural thrombus by ultrasound: an experimental in vitro study.

RATIONALE AND OBJECTIVES: The authors perform an in vitro evaluation of the thrombus fragmentation to determine the efficacy and degree of downstream clot fragment embolization that occurs during transcatheter ultrasound treatment of fibrin-rich mural thrombus in a peripheral venous flow model with variable diameter tubing. METHODS: The authors used a 22.5-kHz prototype intravascular ultrasound device with a flexible 0.8-mm (.032-inch) titanium wire probe encased in a 7-French teflon guide catheter, at the tip of which is a 2-mm ball. In 50 silicone tube segments (inner diameter 3, 5, 7, 9, and 11 mm; n = 10 each), firmly adherent mural thrombus was produced using bovine blood in a modification of the Chandler's loop technique. Ultrasound energy (30-36 watts/cm), maximal longitudinal catheter tip amplitude 70 m) was applied to the thrombus while a continuous flow of water was maintained in the closed loop system. Clot fragment emboli were trapped in "downstream" polyethylene filters. RESULTS: The mean rate of thrombus removal ranged from 99% +/- 0.3% in the 3-mm segments to 76% +/- 6% in the 11-mm segments. The average weight of the fragments that embolized "downstream" and were trapped in the filters, expressed as a percentage of the initial clot weight, was 11% in the 3-mm segment, 14% in the 5-mm segment, 30% in the 7-mm segment, 29% in the 9-mm segment, and 28% in the 11-mm segments. The majority of the embolized fragments appear to be larger than 1 mm. CONCLUSIONS: In this in vitro venous flow model a lack of catheter steerability was the major obstacle to complete thrombus fragmentation in vessel calibers larger than two times the tip diameter. The rate of embolism and the amount of remaining thrombus that could not be removed from the vessel were higher in the larger vessels.

Animals↗
PubMed1998

Declotting of embolized temporary vena cava filter by ultrasound and the Angiojet: comparative experimental in vitro studies.

RATIONALE AND OBJECTIVES: The authors perform an in vitro evaluation of the thrombolytic efficacy and the amount of "downstream" embolization induced by two new mechanical thrombectomy devices when applied to clots trapped in a temporary vena cava filter. METHODS: The first device used was a 22.5-kHz prototype intravascular ultrasound device with a flexible 0.8-mm (.032-inch) titanium 2-mm ball-tipped wire probe ensheathed in a 7-French teflon guide catheter. The device was inserted through a 10-French steering catheter. Under fluoroscopic control, ultrasound energy (26 +/- 4 watts/cm2, maximal longitudinal catheter tip amplitude 54 microm) was applied to 10 Ultravist-filled porcine thrombi (mean, 3500 mg). The second device, the Angiojet catheter, was applied to five Ultravist-filled porcine thrombi (mean, 3640 mg). The thrombi were treated while trapped in a temporary Günther vena cava filter (Cook Europe, Bjaverskov, Denmark) mounted in a vena cava flow model. The resultant "downstream" emboli were trapped in two tandem filters of decreasing pore size and weighed. RESULTS: Mean thrombus dissolution rate was 53% +/- 22% standard deviation (SD) for the ultrasound device (n = 10) and 63 % +/- 8% SD for the Angiojet (n = 5) (difference statistically significant at P = 0.03). For the ultrasound device, the mean embolic particle weight caught by the filters with mesh widths of 1 mm and 0.1 mm was 42% +/- 14% SD and 4% +/- 2% SD, respectively, of the initial thrombus weight. For the Angiojet, the respective numbers were 35% +/- 16% SD and 3% +/- 1% SD. Mean treatment time was 216 +/- 45 seconds SD for the ultrasound device and 153 +/- 21 seconds SD for the Angiojet. CONCLUSIONS: The thrombolytic efficacy of the Angiojet was significantly greater and the treatment time was significantly shorter than that of the ultrasound device. Both systems had a high embolization rate.

Animals↗
PubMed1998

Fragmentation of massive pulmonary embolism using a pigtail rotation catheter.

STUDY OBJECTIVES: The purpose of this study was the evaluation of the efficacy and safety of mechanical fragmentation of acute massive pulmonary emboli with a rotatable pigtail catheter. MATERIAL AND METHODS: Ten patients (4 female, 6 male, age 53.8+/-9.5 years) with acute massive pulmonary embolism with hemodynamic impairment were included in the study. The fragmentation catheter device (William Cook Europe A/S; Bjaerverskov, Denmark) consisted of a 5F catheter embedded in a flexible 5.5F sheath. Pulmonary emboli were fragmented by mechanical action of the recoiled rotating pigtail, while the guide wire was exiting an oval side hole proximal to the pigtail tip. In eight cases, an additional thrombolysis was performed. RESULTS: Fragmentation was successful in 7 of 10 patients. Average percentage of recanalization by fragmentation was 29.2+/-14.0%, and 36.0+/-10.0% exclusively of the seven successful cases. Average shock index decreased significantly prefragmentation to postfragmentation from 1.52 to 1.22 (p = 0.03) and to 0.81 48 h later (p < 0.001). Decrease of the average mean arterial pulmonary pressure prefragmentation to postfragmentation was insignificant (from 33 to 31 mm Hg, p = 0.14); further decrease within the 48 h follow-up was highly significant (from 31 to 21 mm Hg, p < 0.001) due to a synergy of fragmentation and thrombolysis (average dose 63+/-25 mg plasminogen activator). There were no procedure-related complications. Overall mortality rate was 20%. CONCLUSION: Fragmentation of massive pulmonary emboli with the pigtail rotation catheter achieved rapid partial recanalization in most cases, with ease of instrumentation, and without complications. Hemodynamic stabilization was completed in synergy with thrombolysis.

Acute Disease↗
PubMed1997

[Digital subtraction angiography with carbon dioxide using a new gas dosage system].

PURPOSE: The clinical evaluation of digital subtraction angiography with carbon dioxide using a newly developed low-tech CO2 dosage and injection system. METHOD AND PATIENTS: The hand-held system (CO2 angio set) consists of a dosage chamber in connection with a special stopcock to apportion the gas. By optimising injection volume and pressure steady gas flow characteristics are approximated. A safety design prevents unintentional gas injection. CO2 arteriographies were performed on 185 patients. Main indications were renal insufficiency and a history of adverse reactions to iodinated contrast media. In patients with femoral cannula access, catheterless reflux angiography was performed. RESULTS: The injection system provided complete and coherent visualisation of the abdominal aorta, visceral, pelvic, and lower limb arteries via catheter (71 cases) or via femoral cannula using reflux technique (114 cases). Stenoses, occlusions, and collaterals were assessable. Employing the gas reflux over the aortic bifurcation bilateral run-off studies up to the calf trifurcation were performed via unilateral femoral cannula. Use of a dedicated stacking software improved image quality of distal femoral, popliteal and calf arteries. CONCLUSION: The CO2 management system allows adequate imaging of the arteries below the diaphragm. Ease and safety of use and low costs are advantageous.

Angiography, Digital Subtraction↗
PubMed1996

[Extensive acute pulmonary embolism: fragmentation treatment with a rotatable pigtail catheter].

A 58-year-old patient with extensive pulmonary embolism complicated by cardiogenic shock and contraindications to thrombolysis was treated by mechanical embolus fragmentation using a rotatable pigtail catheter system. Considerable recanalization of the left pulmonary arteries was rapidly achieved with relative ease of instrumentation. Subsequently, the hemodynamic condition stabilized.

Acute Disease↗
PubMed1995

[The rheolytic thrombectomy of an iliac vein].

As an alternative to thrombolysis, a patient with recent rethrombosis of the right iliac vein was successfully recanalized by using a 5 F rheolytic catheter system. The patient had undergone bilateral stent recanalisation of the pelvic veins after iliocaval thrombosis due to retroperitoneal fibrosis three months earlier.

Aged↗
PubMed1995

[The diagnosis of acute pulmonary embolism: a comparison between spiral CT and DSA in an animal experiment].

PURPOSE: The value of helical computed tomography (CT) for diagnosis of acute pulmonary embolism was assessed and compared with digital subtraction angiography (DSA) as a reference method. MATERIAL AND METHODS: In 11 dogs, lobar, segmental, and subsegmental occlusions of the pulmonary arteries were produced. Subsequent to selective pulmonary angiography, the animals were examined with contrast-enhanced helical CT. RESULTS: In the main and lobar pulmonary arteries there was a complete correlation between CT and DSA in documentation of total and partial embolic occlusions. Identification of segmental and subsegmental pulmonary emboli by CT required a second run with optimized parameters in 7 of 11 cases. Nevertheless, 18% of the peripheral arteries could not be classified. CONCLUSION: Helical CT as less invasive modality is competitive with DSA in demonstration of central pulmonary emboli. However, CT imaging of peripheral pulmonary emboli requires optimal bolus timing.

Acute Disease↗
PubMed1995

Percutaneous balloon embolectomy with a self-expanding tulip sheath: in vivo experiments.

PURPOSE: To test a self-expanding tulip-shaped sheath designed for percutaneous embolectomy in an in vivo animal experiment. MATERIALS AND METHODS: In nine sheep, a total of 23 percutaneous balloon embolectomies were performed with use of a self-expanding tulip sheath device with an outer diameter of 9- or 10-F when collapsed. A 10-F instrument was used in 11 cases, and a 9-F instrument was used in 12. Radiopaque emboli were pushed into the aorta via the left carotid or contralateral femoral artery with a 16-F introducer sheath. RESULTS: The embolus was captured in the tulip cage in all 23 cases. Retrieval of the embolus into the sheath was complete in 21 of 23 cases. In two cases, minor parts of the embolus dislodged from the sheath. Major embolism did not occur. In nine cases, the outer sheath had to be cleared of remaining clot particles with aspiration. CONCLUSION: The noncovered self-expanding tulip sheath is an effective and safe instrument for percutaneous embolectomy under in vivo conditions.

Animals↗
PubMed1995

Acute massive pulmonary embolism: use of a rotatable pigtail catheter for diagnosis and fragmentation therapy.

PURPOSE: A modified pigtail catheter for angiographic documentation and mechanical fragmentation of pulmonary embolism was evaluated for its efficacy and safety. MATERIALS AND METHODS: Rotation of the 5-F pigtail catheter was performed with an electric drive or a handle. The wire left an oval side hole at the outer curvature and served as an axis of rotation. Fragmentation properties were assessed in vitro. Pulmonary positioning, steerability, rotation behavior, and safety were tested in six pigs. Pulmonary embolic occlusions were recanalized in eight dogs. RESULTS: The catheter system was promptly positioned and easily steered in the pulmonary arteries. On average, 53% of the occluded pulmonary arteries were recanalized. Recanalization reduced the emboli-induced elevation of the pulmonary artery mean pressure by 73%. Slight perivascular hemorrhage occurred in three dogs. CONCLUSION: Rapid partial recanalization was achieved with relative ease of instrumentation. The technique is an extension of the commonly performed pigtail catheterization of the pulmonary arteries, which may increase its clinical acceptance.

Animals↗
PubMed1995

[The diagnosis and fragmentation therapy of acute massive pulmonary embolism with a rotatable pigtail catheter: experimental studies].

PURPOSE: A dedicated pigtail catheter system which allows angiographic documentation and adjunctive mechanical fragmentation of pulmonary emboli was evaluated in an animal experiment. MATERIAL AND METHOD: The 5-F catheter provided with an oval side hole proximal to the pigtail tip was rotated manually or with an electric drive, and with the wire as a rotation axis. Pulmonary embolic occlusions were recanalized in ten dogs. Catheter positioning, monitoring, rotation behaviour, safety and fragmentation properties were assessed. RESULTS: The catheter system was rapidly positioned and easily monitored in the pulmonary arteries. On average, 55% (+/- 20%) of the embolic occlusions were recanalized. Embolus fragmentation reduced the emboli-induced increase of the pulmonary arterial mean pressure by 72%. In three dogs, histology revealed slight perivascular haemorrhage. CONCLUSION: Partial recanalisation of the pulmonary arteries was achieved rapidly with relative ease of instrumentation. Since fragmentation technique is an adjunct to the commonly performed pigtail catheterization of the pulmonary arteries, no special training is required.

Acute Disease↗
PubMed1993

[The recanalization of thrombosed hemodialysis shunts by oscillating-probe aspiration and with a mesh basket].

Three thrombosed hemodialysis shunts (two polytetrafluorethylene [Goretex] forearm shunts and one Brescia-Cimino shunt) were recanalized by an 8-F oscillational aspiration thrombectomy catheter. The total aspirated blood volume was less than 200 ml in each case. Subsequently, residual wall adherent thrombi were removed by means of a 6-F mesh basket catheter. The mesh basket showed optimal adaptation even to bent vessel or graft segments. The first experience with oscillational aspiration thrombectomy and mesh basket treatment in thrombosed hemodialysis shunts indicate that this technique may serve as a promising alternative to fibrinolysis or surgical shunt declotting.

Arteriovenous Shunt, Surgical↗