Key result
Spiral articulated Palmaz-Schatz stents demonstrate ~2-fold higher compressive strength than PS-153 stents.
Why the study?
The mechanical properties of metal stents are important for stent design to resist arterial recoil and vascular spasm, but standardized quantitative evaluation methods were lacking.
Different coronary stent designs exhibit distinct compressive mechanical properties, such as ultimate strength and radial stiffness, which may have important clinical implications for resisting arterial recoil and spasm.
Stent compressive strength varies by design; leaves open whether differences affect recoil or outcomes in patients.
The mechanical properties of metal stents are important parameters in the consideration of stent design, matched to resist arterial recoil and vascular spasm. The purpose of this study was to develop a system for a standardized quantitative evaluation of the mechanical characteristics of various coronary stents. Several types of stents were compressed by external hydrostatic pressure. The stent diameter was assessed by placing a pair of small ultrasonic sono-crystals on the stent. From pressure-strain diagrams the ultimate strength and radial stiffness for each stent were determined. For all stents, except the MICRO-II and the Wiktor stent, the diameter decreased homogeneously until an ultimate compressive strength was exceeded, causing an abrupt collapse. Expanded to 3 mm, the mechanical behavior of the beStent, the Crown and the Palmaz-Schatz stent (PS153-series) were comparable. The spiral articulated Palmaz-Schatz stent showed twice the strength (1.26 atm) of the PS-153 (0.65 atm). The NIR stent yielded a maximum strength of 1.05 atm. The MICRO-II and the Wiktor stent did not collapse abruptly but rather showed a continuous decline of diameter with increasing external pressure. The Cardiocoil stent behaved in a fully elastic manner and showed the largest radial stiffness. Difference in mechanical properties between stents were documented using a new device specifically developed for that purpose. These mechanical stent parameters may have important clinical implications.
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Schrader et al. (1998) studied this question. Various coronary stents was evaluated on Ultimate strength and radial stiffness. Different coronary stents exhibited varying compressive mechanical properties under external hydrostatic pressure, with the spiral articulated Palmaz-Schatz stent showing twice the strength of the PS-153.
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