Thomas Schmitz-Rode

Massive pulmonary embolism: percutaneous emergency treatment by pigtail rotation catheter.

OBJECTIVES This study was designed to assess the feasibility, efficacy and safety of mechanical fragmentation of pulmonary emboli using a new rotational pigtail catheter system. BACKGROUND Acute massive pulmonary embolism associated with right ventricular dysfunction is frequently lethal, despite high-dose thrombolytic therapy. Adjunctive catheter fragmentation may prevent a fatal outcome. METHODS In 20 patients (age 58.9+/-10.5 years) with severe hemodynamic impairment, massive pulmonary emboli were fragmented by mechanical action of the rotating pigtail. Fifteen patients received thrombolysis after embolus fragmentation or no thrombolysis at all (noninterference group). RESULTS Prefragmentation pulmonary arterial occlusion was 68.6 +/- 11.3% for both lungs. Pulmonary placement and navigation of the fragmentation catheter was easy and rapid. Fragmentation time was 17+/-8 min. The noninterference group showed a decrease pre- to postfragmentation of shock index from 1.28+/-0.53 to 0.95+/-0.38 (p = 0.011), mean pulmonary artery pressure from 31+/-5.7 to 28+/-7.5 mm Hg (p = 0.02) and a recanalization by fragmentation of 32.9+/-11.8% (mean angiographic score per treated lung from 7.4 to 5.0). Overall mortality was 20%. CONCLUSIONS Fragmentation by pigtail rotation catheter provided for a rapid and safe improvement of the hemodynamic situation and an average recanalization of about one-third of the pulmonary embolic occlusion. The method appears useful especially in high-risk patients threatened by right ventricular failure, to accelerate thrombolysis, and as a minimal-invasive alternative to surgical embolectomy.

Surface electromyography and muscle force: Limits in sEMG-force relationship and new approaches for applications

The estimation of the force generated by an activated muscle is of high relevance not only in biomechanical studies but also more and more in clinical applications in which the information about the muscle forces supports the physicians decisions on diagnosis and treatment. The surface electromyographic signal (sEMG) reflects the degree of activation of skeletal muscles and certain that the sEMG is highly correlated to the muscle force. However, the largest disadvantage in predicting the muscle force from sEMG is the fact that the force generated by a muscle cannot be directly measured non-invasively. Indirect measurement of muscle force goes along with other unpredictable factors which influence the detected force but not necessarily the sEMG data. In addition, the sEMG is often difficult to interpret correctly. The sEMG-force relationship has been investigated for a long time and numerous papers are available. This review shows the limitations in predicting the muscle force from sEMG signals and gives some perspectives on how these limitations could be overcome, especially in clinical applications, by using novel ways of interpretation.

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

AbstractPurpose: 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 minitored 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.

Fibrin-polylactide-based tissue-engineered vascular graft in the arterial circulation

There is a clear clinical requirement for the design and development of living, functional, small-calibre arterial grafts. Here, we investigate the potential use of a small diameter, tissue-engineered artery in a pre-clinical study in the carotid artery position of sheep. Small-calibre ( approximately 5 mm) vascular composite grafts were molded using a fibrin scaffold supported by a poly(L/D)lactide 96/4 (P(L/D)LA 96/4) mesh, and seeded with autologous arterial-derived cells prior to 28 days of dynamic conditioning. Conditioned grafts were subsequently implanted for up to 6 months as interposed carotid artery grafts in the same animals from which the cells were harvested. Explanted grafts (n = 6) were patent in each of the study groups (1 month, 3 months, 6 months), with a significant stenosis in one explant (3 months). There was a complete absence of thrombus formation on the luminal surface of grafts, with no evidence for aneurysm formation or calcification after 6 months in vivo. Histological analyses revealed remodeling of the fibrin scaffold with mature autologous proteins, and excellent cell distribution within the graft wall. Positive vWf and eNOS staining, in addition to scanning electron microscopy, revealed a confluent monolayer of endothelial cells lining the luminal surface of the grafts. The present study demonstrates the successful production and mid-term application of an autologous, fibrin-based small-calibre vascular graft in the arterial circulation, and highlights the potential for the creation of autologous implantable arterial grafts in a number of settings.

Tissue-Engineered Small-Caliber Vascular Graft Based on a Novel Biodegradable Composite Fibrin-Polylactide Scaffold

Small-caliber vascular grafts (< or =5 mm) constructed from synthetic materials for coronary bypass or peripheral vascular repair below the knee have poor patency rates, while autologous vessels may not be available for harvesting. The present study aimed to create a completely autologous small-caliber vascular graft by utilizing a bioabsorbable, macroporous poly(L/D)lactide 96/4 [P(L/D)LA 96/4] mesh as a support scaffold system combined with an autologous fibrin cell carrier material. A novel molding device was used to integrate a P(L/D)LA 96/4 mesh in the wall of a fibrin-based vascular graft, which was seeded with arterial smooth muscle cells (SMCs)/fibroblasts and subsequently lined with endothelial cells. The mold was connected to a bioreactor circuit for dynamic mechanical conditioning of the graft over a 21-day period. Graft cell phenotype, proliferation, extracellular matrix (ECM) content, and mechanical strength were analyzed. alpha-SMA-positive SMCs and fibroblasts deposited ECM proteins into the graft wall, with a significant increase in both cell number and collagen content over 21 days. A luminal endothelial cell lining was evidenced by vWf staining, while the grafts exhibited supraphysiological burst pressure (>460 mmHg) after dynamic cultivation. The results of our study demonstrated the successful production of an autologous, biodegradable small-caliber vascular graft in vitro, with remodeling capabilities and supraphysiological mechanical properties after 21 days in culture. The approach may be suitable for a variety of clinical applications, including coronary artery and peripheral artery bypass procedures.

Individually adapted examination protocols for reduction of radiation exposure in chest CT.

Wildberger JE, Mahnken AH, Schmitz-Rode T, et al. Individually adapted examination protocols for reduction of radiation exposure in chest CT. Invest Radiol 2001;36:604–611. rationale and objectives. To develop a simple directive for the reduction of radiation exposure without loss of diagnostic information in routine chest CT examinations. methods.Two hundred fifty adult patients (164 male, 86 female) were entered into a prospective trial. All examinations were performed with a multislice CT technique (Somatom Volume Zoom, Siemens). Four groups of 50 patients each were scanned with patient-related specific parameters: individual mA-s values were derived from the estimated body weight: kilograms + 10, ± 0, − 10, and − 20 mAs. The results were compared with those of 50 patients who were examined by a standard chest protocol by using the parameters 120 mAs and 140 kV. All other parameters including the tube voltage were kept constant. Subjective image quality was rated on a three-point scale: 1 = excellent, 2 = fair, 3 = nondiagnostic. In addition, objective criteria based on signal-to-noise measurements were assessed by using a region-of-interest methodology. results.Image quality was sufficient in all cases. Mean subjective gradings of image quality, based on soft-tissue window settings, were 1.1 for the 120-mAs protocol, 1.1 for the (body weight [kg] + 10) mAs protocol, 1.1 for the (body weight [kg] ± 0) mAs protocol, 1.3 for the (body weight [kg] − 10) mAs protocol, and 1.2 for the (body weight [kg] − 20) mAs protocol. Objective criteria based on noise measurements showed mean ± standard deviation values of 5.7 ± 0.8 Hounsfield units (HU) for the 120-mAs protocol. For the reduced-dose protocols, values were calculated as 7.6 ± 1.2 HU (group + 10), 7.9 ± 1.3 HU (group ± 0), 8.7 ± 1.2 HU (group − 10), and finally 9.1 ± 1.3 HU (group − 20). The best correlation for an entire subgroup was achieved with the − 10 protocol (body weight [kg] − 10) mAs, with nearly constant noise related to body weight in all patients. conclusions.By deriving mAs values from body weight estimation, an individually adapted protocol for chest CT can be recommended and easily employed in a clinical setting. With an adaptation of the tube current–time product based on the estimated body weight of the patient − 10 (body weight [kg] − 10 mAs), a well-balanced examination without significant loss of information, even in soft-tissue window settings, can be performed with this particular scanner. For this adapted mAs protocol, a mean reduction of radiation exposure of 45% was achievable, compared with the standard protocol. A maximum decrease per case down to 31 mAs was obtained, without relevant loss of image quality. Therefore, for other types of CT scanners, analogous protocols may be adapted.

Posterior semicircular canal dehiscence: a morphologic cause of vertigo similar to superior semicircular canal dehiscence

Abstract.The aim of this study was to assess imaging findings of posterior semicircular dehiscence on computed tomography and to evaluate incidence of posterior and superior semicircular canal dehiscence in patients presenting with vertigo, sensorineuronal hearing loss or in a control group without symptoms related to the inner ear. Computed tomography was performed in 507 patients presenting either with vertigo (n=128; 23 of these patients suffered also from sensorineuronal hearing loss), other symptoms related to the inner ear, such as hearing loss or tinnitus (n=183) or symptoms unrelated to the labyrinth (n=196). All images were reviewed for presence of dehiscence of the bone, overlying the semicircular canals. Twenty-nine patients had superior semicircular canal dehiscence. Of these patients, 83% presented with vertigo, 10% with hearing loss or tinnitus and the remaining 7% with symptoms unrelated to the inner ear. In 23 patients dehiscence of the posterior semicircular canal was encountered. Of these patients, 86% presented with vertigo, 9% with hearing loss or tinnitus and 5% with symptoms unrelated to the inner ear. Defects of the bony overly are found at the posterior semicircular canal, in addition to the recently introduced superior canal dehiscence syndrome. Significant prevalence of vertigo in these patients suggests that posterior semicircular canal dehiscence can cause vertigo, similar to superior semicircular canal dehiscence.

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.

TREATMENT OF EXPERIMENTALLY INDUCED ANEURYSMS WITH STENTS

OBJECTIVE: Although Guglielmi detachable coil systems have been widely accepted for treatment of intracranial aneurysms, primary stenting of aneurysms using porous stents, stent grafts, or implantation of coils after stent placement constitute emerging techniques in endovascular treatment. The aim of the present study was to use an animal model to investigate these different approaches to treat cerebral aneurysms with regard to the rate of closure and the histopathological changes within the aneurysm cavity and the parent vessel after stent placement. METHODS: We created aneurysms in 30 rabbits by distal ligation and intraluminal incubation of the right common carotid artery with elastase. Ten animals were treated with porous stents alone, 10 animals with stent grafts (covered stents), and 10 animals with stents and additional coiling via the interstices of the stent, which enabled dense packing of the coils. Five animals in each group were observed for 1 month and the other animals for 3 months. Histological analyses were performed, including immunohistochemical investigations for estimating the proliferation of the intima and possible inflammatory infiltration. RESULTS: Covered stents led to a complete and stable aneurysm occlusion with only minimal proliferative carrier vessel wall changes. One covered stent was completely occluded with old thrombus, and the other 9 remained patent. Porous stents occluded two of five aneurysms in the 1-month follow-up group and four of five after 3 months. However, progressive sprouting of neointima inside the carrier vessel that resulted in a stenosis of up to 40% was present. In the Stent + Coil group, one aneurysm showed recanalization after 1 month, and three of five aneurysms were recanalized after 3 months after coil compaction. Moreover, in-stent stenosis of up to 30% was present. CONCLUSION: This study demonstrates the possible shortcomings and problems of emerging stent techniques to treat intracerebral aneurysms, shows where technical advances have to be made, and describes in which cases of aneurysm morphology caution has to be exercised when considering an endovascular approach using stents.

Use of a nonmetallic guide wire for magnetic resonance-guided coronary artery catheterization.

Rationale and Objectives:Metallic guide wires can be subject to substantial heating when used in the magnetic resonance (MR) environment. Therefore, animal experiments were performed to test the feasibility of a non-metallic and MR-safe guide wire with passive markers for catheterization of coronary arteries under MR guidance. Materials and Methods:Self-made guide wires consisting of a resin-microparticle compound covered by polytetrafluoroethylene were used to catheterize both coronary arteries of swine together with a non-braided catheter. Time needed for catheterization was recorded. Results:MR-guided coronary artery catheterization with passive visualization of a self-made non-metallic guide wire is possible. In average 141 seconds (SD 68) were needed to manipulate the guide wire together with a catheter from the carotid artery into the left or right coronary artery ostium. Conclusion:Standard nitinol guide wires have to be considered unsafe for MR-guided interventions due to possible heating of electrical conducting structures in the MR environment. Passive visualization techniques allow MR-guided catheterization of small arteries like coronaries. However, there is the substantial disadvantage of obscuring the underlying anatomy of small vessels by the passive markers needed for real-time MR guidance.