Testing Method of Stent’s Radial Force

In case of coronary arteriosclerosis and heart attack balloon-expandable stents are used. These balloon crimped implants are placed to the occluded vessel part and the balloons are pumped with big pressure (4-20 bar). The opened stents ensure the continuously flow of the blood in the opened lumen. The implants have to sustain the outer load from the vessel wall and have to keep the lumen open. In this study a method was worked out which valuating the radial force of the balloon expandable coronary stents. In an experimental program many types of methods were tested to find the best one

Mechanical Properties of Coronary Veins

There are several publications available and experiments were done regarding to the vessel biomechanical properties. In the range we could find in vitro and in vivo assessments data for elasticity properties. Even though we have many results in this topic we still don’t have enough data for special veins. Three coronary veins were investigated from pig’s heart. The aim of these experiments was to define and measure the longitudinal tensile stress and tensile strength of coronary veins. The tensile tests were done successfully and the tensile stress was defined in the range of 1.66-2.57 MPa

Examination of the coatings of coronary stents

In our study the main properties of coated coronary stents are shown, such as foreshortening, recoil, surface features and failures and the expansion properties. The types and the effects of active and passive coatings are introduced. The results of our examinations with different coated coronary stents are shown as well

Drug Distribution and Stent Retention of Drug Eluting Stents

In this paper the examinations of drug eluting coronary stents are shown, such as the morphology of the coatings before expansion, drug distribution, the methodology and the value of stent retention. Surface qualities of drug coatings were examined with stereo-microscope, metallographic microscope and scanning electron microscope. Examinations with confocal microscope show drug distribution in the coatings. Stent retention is a very important property of the stent system. Stent retention is a force, needed to the stent slip down from the balloon. Three drug eluting coronary stents were tested with our method

Visibility of Balloon Dilatation Catheters

In this study, an easy to use measurement method was developed to quantify the balloon dilatation catheters visibility, thus making them comparable. The visibility of the distal and proximal markers and the balloon (average values of the markers) was determined for fourteen balloons of the same type and material, but different lengths and diameters. Repeatability of these values was tested by one volunteer and reproducibility by two volunteers three times each for all the balloons used for the study. It was found that the average visibility for balloons was 12±2%, 13±2% for distal markers, and 13±2% for proximal markers. Values of distal and proximal markers did not represent significant difference (p=0.20). There was no significant difference determined for repeatability and reproducibility either (p values were between 0.71-0.93). Hence, the developed measurement method was repeatable and reproducible making it suitable for comparison of the balloon dilatation catheters based on visibility

Different properties of coronary stents

Stents are mesh structured implants which are used to support the vessel wall in the balloon expanded vessel part. Several methods were developed and applied for the determination of mechanical properties of coronary stents, as a part of a complex pre-clinical in vitro diagnostic system: radiopacity, flaring, metallic surface area and fatigue tests. Three pieces of equipment were assembled for the examination of fatigue properties. The first method simulates the bending stress in the coronary arteries; the second method simulates the effect of the cylindrical mechanical strain which is equivalent to the systolic and diastolic pulse in the coronary arteries; and the third method is using the energy of the ultrasound concentrating to the stent. After fatigue tests stereomicroscopy, optical microscopy, scanning electron microscopy were used for the determination of surface quality and condition. The most frequent failures were scratches, pits and small shrinkage of materials originated from the manufacturing and finishing processes. Because of fatigue tests slip lines occurred in the critical curves, grain boundaries were outlined, the surface of the struts become rough, but these mutations do not affect the functionality of the stents