Comparison of Carotid Stents: An In-Vitro Experiment Focusing on Stent Design

Department of Diagnostic and Interventional Radiology / Neuroradiology, Academic Hospitals Flensburg, Germany.
Journal of Endovascular Therapy (Impact Factor: 3.59). 05/2009; 16(2):168-77. DOI: 10.1583/08-2539.1
Source: PubMed

ABSTRACT To examine and compare different carotid stent designs with regard to flexibility, adaptability (adjustability), conformability (compliance) to the vessel, and scaffolding to reduce plaque prolapse and embolization.
Six stents of different design were compared (Precise, Acculink, Protégé, Xact, Wallstent, and Cristallo Ideale). Optical microscopy was used to determine exact dimensions and scaffolding of each stent. Radial force was tested using a parallel plate setup, and flexibility (torsion and bending) was measured in water at body temperature. Particle penetration simulation was performed using plastic spheres from 1.5- to 6.0-mm outer diameter.
Stent dimensions met the manufacturers' data; none of the products showed any failure during the test program. Cell sizes in the middle part of the stents ranged from 1.36 mm(2) (Wallstent) to 15.10 mm(2) (Acculink). Bending forces at 20 degrees /30 degrees ranged from 0.063 N / 0.074 N (Cristallo Ideale) to 0.890 N / 0.616 N (Xact); forces to achieve torsion at 10 degrees /15 degrees ranged from 0.032 N / 0.043 N (Acculink) to 0.905 N / 1.071 N (Xact). According to the parallel plate method, mean lowest force was measured for Xact (0.765 N), while the Wallstent had the highest force (2.136 N). Mean radial force measurements were lowest for Cristallo Ideale (9.06 N at mid part) and highest for Protégé (24.09 N). The Cristallo Ideale stent at mid part resisted penetration by all but the smallest plastic spheres (1.5-mm spheres penetrated only at 0.65 N); the Precise and Protégé stent had the highest variation in sphere penetration (1.5- to 4.0-mm spheres). Only the Acculink let 6-mm spheres penetrate.
Despite comparable stent sizes, these carotid stents showed differences in behavior due to stent design. The open-cell design displayed the greatest flexibility and adaptability to the vessel but easily allowed particle penetration due to the open structure. Closed-cell designs had low flexibility and thus low adaptability to the vessel but high resistance to particle penetration due to the closed-cell design and high scaffolding. The hybrid stent design (Cristallo Ideale) was able to combine both the flexibility of an open-cell structure and the resistance to particle penetration of closed-cell structures.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To be functional in a practical sense for real-time control of assistive devices, a myoprocessor must successfully integrate both detection and estimation systems. This paper describes an approach for classifying electromyographic (EMG) signals using a multilayer perceptrons (MLPs) and hidden Markov models (HMMs) hybrid classifier and force estimation. Instead of using MLPs as probability generators for HMMs the authors propose to use MLPs as the second classifiers to increase discrimination rates of myoelectric patterns. This strategy is proposed to overcome weak discrimination and to consider dynamic properties of EMG signals. Two discrimination strategies (HMM, and HMM with three subnet MLPs) for discriminating signals representative of 6 primitive class of motions are described and compared. The proposed strategy increase the discrimination results considerably. Results are presented to support this approach
    Circuits and Systems, 1996., IEEE Asia Pacific Conference on; 12/1996
  • Fertility and Sterility 02/2002; 77. DOI:10.1016/S0015-0282(01)03126-0 · 4.30 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Mechanical properties of carotid stents are important for the selection of the implantable device. The efficacy of cell design is usually investigated on the basis of clinical follow-ups; however, for the specific carotid application the relative importance of the cell design on the stenting outcome is debated. Ideally, a carotid stent should have at the same time low bending stiffness (i.e., high flexibility) to correctly conform to the vessel curvatures in the stenotic region and high stiffness to sustain the vessel wall in the radial direction. In this study, experimental tests on six carotid open-cell design self-expandable stents were carried out to assess bending and radial stiffness. A four-point bending test was adopted to measure the bending stiffness. Radial stiffness was obtained by measuring the stent resistance to local compression in a V-shaped support. Geometrical features, such as the link positioning and their length, were examined as a possible determinant of the mechanical properties of the tested stents. The tested stents showed very different geometrical features and mechanical properties despite similar material and a common open-cell structure consisting in rings connected by roughly straight links. In particular, different strategies are evident regarding the link position. Three distinct behaviors were observed: stents with both low radial and bending stiffness, moderate bending and high radial stiffness, and high bending and moderate radial stiffness. In general, a large link length allows the stent to be more flexible under bending condition, whereas the mutual links positioning plays a key role in the radial stiffness of these devices. Furthermore, for a fixed strut layout, a correlation was found between the strut cross area, as well as metal-to-artery ratio and the resultant radial and bending stiffness.
    Artificial Organs 05/2010; 35(1):74-80. DOI:10.1111/j.1525-1594.2010.01018.x · 1.87 Impact Factor