In-vitro evaluation of coronary stents

In-vitro evaluation of various kinds of clinically available coronary stents has been performed in order to establish a standard test methodology. First, a silicone tube with an internal diameter of 3 mm was fabricated as a model for the coronary artery. The model provides an equivalent Young's modulus to the natural vessel. Then, changes in the ratio of the stent diameter (elastic recoil) were measured after deflation of an inserted balloon. Radial changes caused by external pressure on the tube were also measured (radial strength). As a result, elastic recoil remained within 6% at the maximum, and radial strength decreased linearly with a range of 0-200 mmHg. The maximum of radial strength was 5% at 200 mmHg. Secondly, an artificial coronary circuit was developed and installed into a pulsatile flow-type mock circulatory system, where arterial pressure and flow waveforms could be reproduced that were similar to those of the human coronary arteries. The pulsatile flow test revealed that a subsequent change in stent diameter was achieved by a change in a pulsatile coronary flow. However, the maximum change amounted to only 1.5% in the radial direction.