Roberto Rodriguez, Ralph de la Torre, Mark Schermerhorn, Robert Hagberg, Frank Pomposelli.
Beth Israel Deaconess Medical Center, Boston, MA, USA.
OBJECTIVE:
Nitinol is a Nickel/titanium alloy that serves as the base for numerous medical devices, including the GORE TAG Thoracic Endoprothesis (TAG). . Nitinol undergoes a Martensite to Austentite transition as it is exposed to increasing temperature leading to a marked increase in strength and a return to a previously established shape. Given the increasing use of cardiopulmonary bypass with these devices we sought to understand the impact of hypothermia on this device.
METHODS:
Five 34 mm TAG devices were deployed in a temperature controlled chamber at 20, 25, 30, 35, and 37 degrees centigrade (25 total devices). An Instron was used to measure radial expansive force and standardized to the force at 37 degrees centigrade. Three 34mm TAG devices were similarly deployed in a temperature controlled water bath at each of the above temperatures. A laser micrometer was utilized to measure deployed diameter. The results were grouped by temperature and an ANOVA analysis performed for statistical significance
RESULTS:
A statistically significant decrease in expansive force at 20, 25, and 30 degrees centigrade of 65%, 46%, and 6% was noted. A statistically significant decrease in radial diameter at 20 and 25 degrees of 17% and 11% was noted. While a difference was noted at 30 degrees it was not significant.
CONCLUSIONS:
The nitinol based TAG device shows marked decreases in radial expansive force and deployed diameter at temperatures at or below 30 degrees centigrade. Until further testing is performed hypothermic CPB should be avoided in all patients with nitinol- based endografts.
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