Effect of Heat-Treatment Temperature on Radial Force of Atrial Depressurized Device Made from Shape Memory Alloys for Heart Failure Treatment

Abstract

Nowadays, NiTi shape memory alloys have been extensively used for medical applications especially as transcatheter [6]. This research aims to investigate the effect of heat-treatment temperature on radial force of NiTi self-expanding atrial depressurized device. The function of this ADD is to expand and sustain the hole in the atrial septal and release the pressure in the heart chamber to an acceptable level, and subsequently, prevent it from closing again, without a repeating surgery. The device was made by braiding 72 NiTi wires with diameter 0.1 mm and formed to double-disc shape with 8 mm fenestration size. Heat-treatments were carried out at 560°C, 580°C, and 600°C for 10 min, respectively to obtain suitable mechanical properties and shape setting. In order to evaluate the basic performance of the device, phase transformation temperatures and radial force were investigated. The results show that ADD device can be formed perfectly and excellent superelasticity can be confirmed in all specimens at room temperature, irrespective of heat-treatment temperature. It is confirmed that both radial resistive force and chronic outward force greatly increase while the fenestration size decreases with increasing of compression load. This ensures that the device is able to resist compression of the heart wall. It can be concluded that the optimum heat-treatment temperature is 560°C since the low heat-treatment temperature produces less oxidation and the greatest recovery force.