Nikolas Charalambous
University of Kiel
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by Nikolas Charalambous.
Journal of Endovascular Therapy | 2010
Stefan Müller-Hülsbeck; Philipp J. Schäfer; Nikolas Charalambous; Hiroshi Yagi; Martin Heller; Thomas Jahnke
Purpose: To examine and compare in an ex vivo study different nitinol stent designs intended for the superficial femoral artery (SFA) with regard to the appearance of fracture. Methods: Seven different 8-x40-mm nitinol stents were evaluated (Misago, Absolute, Smart, Luminexx, Sentinol, Lifestent NT, and Sinus-Superflex). Finite element analysis (FEA) was used for digitalized stent design comparison; the strain during stent movement was calculated for bending, compression, and torsion. Additional mechanical fatigue tests for bending (70°), compression (40%), and torsion (twisted counterclockwise by 180°) were performed up to 650,000 cycles or until a fracture was observed. Results: The FEA bending test showed that only the Misago, LifeStent, and Absolute stents presented no zones of high strain; in the torsion test, the Smart stent also had no zones of high strain. Macroscopic evaluation after mechanical bending indicated that the LifeStent performed the best (no stent fracture after 650,000 cycles). Misago and Absolute stents showed fractures at 536,000 cycles and 456,667 cycles, respectively (range 320,000–650,000 cycles). After compression and torsion testing, Misago showed no stent fracture after 650,000 cycles. The worst performing stent was Luminexx during all test cycles. Conclusion: The 7 SFA stents showed differences in the incidence of high strain zones, which indicates a potential for stent fracture, as demonstrated by the mechanical fatigue tests. Differences in stent design might play a major role in the appearance of stent strut fracture related to restenosis and reocclusion.
Journal of Vascular and Interventional Radiology | 2009
Thomas Jahnke; Jost Philipp Schäfer; Nikolas Charalambous; Jens Trentmann; Markus Siggelkow; Tim-Hendrik Hümme; H. Bolte; Erkan Demirbas; Martin Heller; Stefan Müller-Hülsbeck
PURPOSE To determine the safety and efficacy of total percutaneous access closure for endovascular aortic aneurysm repair with a suture-mediated preclosing technique. MATERIALS AND METHODS One hundred thirty-two femoral access sites in 70 patients who underwent endovascular aortic aneurysm repair were closed percutaneously with off-label use of two F-6 Perclose AT devices preapplied at a 90 degrees angle. Femoral access sizes ranged from 12 to 24 F. Technical success, complications, and procedure and access closure times were evaluated. Follow-up with computed tomography and/or magnetic resonance imaging was scheduled at 1-4 days and 3, 6, and 12 months and used to obtain groin hematoma and scar severity scores (grades 1-3). Data were compared with those from a cohort of 67 patients who underwent endovascular aortic aneurysm repair with surgical femoral cutdown. RESULTS Technical success was achieved with the preclosing technique in 127 of the 132 arteries (96.2%). Two to four closure devices were used per groin. Five technical failures were managed intraoperatively with surgical suture. There was no access-related mortality and no late groin complications. The mean procedure duration was 91 minutes +/- 32, and the mean access closure time was 12 minutes +/- 9. For surgical management, the mean procedure time was 153 minutes +/- 112 (P < .05), and the mean closure time was 12 minutes +/- 13 (not statistically significant). Hematoma severity score at 1-4 days was 1.8 for total percutaneous endovascular aneurysm repair and 2.1 for surgical closure. Scar severity scores at 3, 6, and 12 months were 1.1, 1.0, and 1.0 for total percutaneous endovascular aneurysm repair and 2.4, 2.4, and 2.3 for surgical management, respectively. CONCLUSIONS Total percutaneous endovascular aneurysm repair with a dual 6-F-Perclose preclosing technique is safe and effective. Compared with femoral cutdown, there are fewer late groin complications and scar tissue formation is less severe.
Journal of Endovascular Therapy | 2006
J. Biederer; Nikolas Charalambous; Friedrich Paulsen; Martin Heller; Stefan Müller-Hülsbeck
Purpose: To report an ex vivo study on the local effects of hydrodynamic thrombectomy for the treatment of acute pulmonary embolism (off-label use). Methods: Three devices (6-F AngioJet Xpeedior and 6-F and 8-F Oasis) were used for hydrodynamic thrombectomy inside the arteries of 24 inflated and perfused porcine lung explants. Each system was used at multiple positions inside 4 intact and 4 embolized lungs in vessels measuring 2 to 4 mm, 4 to 6 mm, 6 to 8 mm, and 8 to 10 mm. Angiograms prior to, during, and after catheter positioning and system operation were used to detect arterial wall trauma and to measure local clot removal per 30-second cycle. A total of 21 vessel wall samples were subjected to scanning electron microscopy (SEM) to evaluate non-perforating lesions. Results: All systems were able to remove clot material. The average recanalized vessel length normalized to 30 seconds for vessel diameters of 2 to 4 and 8 to 10 mm, respectively, was 1.17 and 1.75 cm (AngioJet), 0.97 and 0.25 cm (6-F Oasis), and 2.2 and 1.05 cm (8-F Oasis). Perforations occurred during positioning of the 6-F Oasis (4/78 maneuvers) and 8-F Oasis (13/60), but not the AngioJet (0/89); perforations were also seen during system operation (AngioJet: 21/89 activations, 6-F Oasis: 4/78, and 8-F Oasis: 9/60; all lesions inside vessels <6 mm in diameter). SEM showed 35 lesions, 14 with perforation (contrast extravasation) and 21 without perforation (induced by the tip of the guidewire). Conclusion: The AngioJet was most efficient in clot removal, followed by the 8-F Oasis. The 6-F Oasis was least efficient, but had fewest complications. According to these experiments, the tested hydrodynamic thrombectomy devices may cause perforations in vessels <6 mm in diameter. Changes in catheter design to reduce system-specific complication rates or to improve the efficacy of clot removal are warranted.
Journal of Endovascular Therapy | 2009
Stefan Müller-Hülsbeck; Philipp J. Schäfer; Tim H. Hümme; Nikolas Charalambous; Henning Elhöft; Martin Heller; Thomas Jahnke
Distal embolization following percutaneous intervention is a universal phenomenon that has been reported in various vascular beds. Distal emboli are also very common during lower extremity percutaneous peripheral interventions. Some data from case reports and registries are currently available. Clinical data have shown that the application of an embolic protection device in the lower limb arteries is safe. Prospective and, ideally, randomized trial data are warranted to justify the increased use of filters in lower extremity interventions, despite the obvious benefits that these devices provide. However, the clinical relevance of distal embolization in the lower extremity remains unquantified.
Eurointervention | 2010
Karl-Ludwig Schulte; Stefan Müller-Hülsbeck; Piergiorgio Cao; Jean-Pierre Becquemin; Ralf Langhoff; Nikolas Charalambous; Pascal Desgranges; Hicham Kobeiter; Marco Midulla; Vladimir Borovicanin; Dragica Paunovic; Jean-Paul Beregi
AIMS To evaluate a newly developed self-expanding Misago (Terumo Corp., Tokyo, Japan) nitinol stent with rapid exchange delivery catheter for the treatment of stenotic or occluded superficial femoral (SF) or popliteal arteries. METHODS AND RESULTS MISAGO 1 clinical trial enrolled 55 patients undergoing percutaneous intervention of totally occluded or stenotic lesions in SF or popliteal arteries treated with the implantation of 81 stents in five centres across Europe. Primary endpoint was restenosis rate at six months assessed by duplex sonography. Patients (67% male) were 68+/-9 years old, 60% were smokers and 31% had diabetes. Clinical symptoms of ischaemia were present in all patients. Average lesion length was 85+/-50 mm, 64% were totally occluded and 38% classified as TASC C or D. The technical success rate was 100% while the procedural success rate was 98.2% without death, MI, stroke, or major bleeding. At six months follow-up the restenosis rate was 8.5%. One patient (1.8%) died of bronchial carcinoma and two (3.6%) underwent target vessel revascularisation. Mean ankle brachial index improved from 0.70 at baseline to 0.95 at six months while walking capacity on treadmill test improved with an average of 147 m. Rutherford index at six months demonstrated improvement of 72%, without any patients having symptom deterioration. One case of stent fracture was observed. CONCLUSIONS The results from this first-in-man study indicate good safety and short to medium term efficacy profile of the Misago nitinol stent.
Journal of Magnetic Resonance Imaging | 2004
J. Biederer; Carsten Liess; Nikolas Charalambous; Martin Heller
To implement a three‐dimensional gradient‐recalled echo (GRE) volumetric interpolated breath‐hold examination (VIBE) sequence for pulmonary contrast‐enhanced MRA (CE‐MRA) in an experimental setup.
Journal of Endovascular Therapy | 2009
Nikolas Charalambous; Thomas Jahnke; H. Bolte; Martin Heller; Philipp J. Schäfer; Stefan Müller-Hülsbeck
Purpose: To evaluate the efficiency of 2 distal filtration devices designed for cerebral protection during carotid angioplasty in an in-vitro bench-top model. Methods: After positioning the respective protection devices (RX Accunet and DynaCap) 5 cm distal to the bifurcation, embolization from carotid angioplasty was simulated by injecting polyvinyl alcohol particles in groups of small (150 to 250-μm diameter, ~500 particles), medium (250 to 355-μm diameter, ~200 particles), and large (700 to 1000-μm diameter, ~80 particles). Five milligrams of each group were injected separately into the internal carotid artery (ICA) model proximal to the protection filters. Particles passing the protection devices were caught in 100-μm filters and weighed. Results: For small particles, the amount in the effluent of the ICA was 0.34±0.12 mg (6.8%) for the RX Accunet and 0.51±0.16 mg (11.2%) for the Occam DynaCap (p<0.05). For the other particle sizes, there was no statistical difference between the filters (p>0.05). Conclusion: In all test runs, neither of the tested devices prevented embolization completely, with ~3% to 6% of particles penetrating. For small particles, the lowest amount of particles passing the protection device was achieved using the RX Accunet system.
CardioVascular and Interventional Radiology | 2010
Philipp J. Schaefer; Nikolas Charalambous; Jens Trentmann; Fritz K. W. Schaefer; Justus Gross; Markus Siggelkow; Martin Heller; Thomas Jahnke
We present a safe and quick technique for crossover embolization procedures of the internal iliac artery with high-profile guiding catheter systems, after a pull-through maneuver with establishment of a crossover catheter-snare system. The attached snare is used to stabilize and direct the guiding catheter.
Journal of Endovascular Therapy | 2009
Stefan Müller-Hülsbeck; Philipp J. Schäfer; Nikolas Charalambous; Silvio R. Schaffner; Martin Heller; Thomas Jahnke
CardioVascular and Interventional Radiology | 2010
Nikolas Charalambous; Philipp J. Schäfer; Jens Trentmann; Tim H. Hümme; Christine Stöhring; Stefan Müller-Hülsbeck; Martin Heller; Thomas Jahnke