title: Hypothermia severely effects performance of nitinol-based endovascular grafts in vitro.
abstract: BACKGROUND
  Nitinol is an alloy that serves as the base for numerous medical devices, including the GORE TAG Thoracic Endoprosthesis (W.L. Gore & Associates, Flagstaff, AZ) thoracic aortic graft device. Given the increasing use of therapeutic hypothermia used during the placement these devices and in post-cardiac arrest situations, 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°C, 25°C, 30°C, 35°, and 37°C (25 total devices). A halographic measurement device was used to measure radial expansive force and normalized to the force at 37°C. Three 34-mm 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.
  
  
  RESULTS
  A statistically significant decrease in expansive force at 20°C, 25°C, and 30°C of 65%, 46%, and 6%, respectively, was noted. A statistically significant decrease in radial diameter at 20°C and 25°C of 17% and 11%, respectively, was noted. Although a 9% difference was noted at 30°C, 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°C. Surgeons should be aware of the potential implications of placing nitinol-based endoprostheses in hypothermic conditions. In addition, all health care providers should be aware of the changes that occur in nitinol-based endoprostheses during therapeutic hypothermia.
authors.affiliation: Department of Surgery, Division of Cardiac Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Robich
authors.forename: Robert
authors.initials: R
authors.lastname: Hagberg
authors.forename: Marc L
authors.initials: ML
authors.lastname: Schermerhorn
authors.forename: Frank B
authors.initials: FB
authors.lastname: Pomposelli
authors.forename: Michael C
authors.initials: MC
authors.lastname: Nilson
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Gendron
authors.forename: Frank W
authors.initials: FW
authors.lastname: Sellke
authors.forename: Roberto
authors.initials: R
authors.lastname: Rodriguez
mesh_terms: D000497:Alloys; D001672:Biocompatible Materials; D001807:Blood Vessel Prosthesis; D003080:Cold Temperature / Q000009:adverse effects*; D019563:Mechanics; D011474:Prosthesis Design; D011475:Prosthesis Failure / Q000209:etiology*; D015607:Stents
chemical_list: D000497:Alloys; D001672:Biocompatible Materials; C013616:nitinol