ABSTRACT
PURPOSE: We aim to quantify multiaxial cardiac pulsatility-induced deformation of the thoracic aorta after ascending thoracic endovascular aortic repair (TEVAR) as a part of the GORE ARISE Early Feasibility Study. MATERIALS AND METHODS: Fifteen patients (7 females and 8 males, age 73±9 years) with ascending TEVAR underwent computed tomography angiography with retrospective cardiac gating. Geometric modeling of the thoracic aorta was performed; geometric features including axial length, effective diameter, and centerline, inner surface, and outer surface curvatures were quantified for systole and diastole; and pulsatile deformations were calculated for the ascending aorta, arch, and descending aorta. RESULTS: From diastole to systole, the ascending endograft exhibited straightening of the centerline (0.224±0.039 to 0.217±0.039 cm-1, p<0.05) and outer surface (0.181±0.028 to 0.177±0.029 cm-1, p<0.05) curvatures. No significant changes were observed for inner surface curvature, diameter, or axial length in the ascending endograft. The aortic arch did not exhibit any significant deformation in axial length, diameter, or curvature. The descending aorta exhibited small but significant expansion of effective diameter from 2.59±0.46 to 2.63±0.44 cm (p<0.05). CONCLUSION: Compared with the native ascending aorta (from prior literature), ascending TEVAR damps axial and bending pulsatile deformations of the ascending aorta similar to how descending TEVAR damps descending aortic deformations, while diametric deformations are damped to a greater extent. Downstream diametric and bending pulsatility of the native descending aorta was muted compared with that in patients without ascending TEVAR (from prior literature). Deformation data from this study can be used to evaluate the mechanical durability of ascending aortic devices and inform physicians about the downstream effects of ascending TEVAR to help predict remodeling and guide future interventional strategies. CLINICAL IMPACT: This study quantified local deformations of both stented ascending and native descending aortas to reveal the biomechanical impact of ascending TEVAR on the entire thoracic aorta, and reported that the ascending TEVAR muted cardiac-induced deformation of the stented ascending aorta and native descending aorta. Understanding of in vivo deformations of the stented ascending aorta, aortic arch and descending aorta can inform physicians about the downstream effects of ascending TEVAR. Notable reduction of compliance may lead to cardiac remodeling and long-term systemic complications. This is the first report which included dedicated deformation data regarding ascending aortic endograft from clinical trial.
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.
