Discussion

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Dr W. Charles Sternbergh III (New Orleans, La). Dr Arko and his coauthors have examined an area that, as eloquently demonstrated in their manuscript, has been previously well described in the literature: the dynamic changes of the aortic neck diameter with the cardiac cycle and the potential variability in its measurement with different imaging modalities.

The authors studied 25 patients undergoing EVAR and measured aortic neck diameters with CTA and IVUS. The “take-home” results were as follows:

So to borrow a piece of the authors' title for this manuscript, what are the implications of these data for endovascular repair? For current devices, these data will not likely alter the use or sizing of endografts for EVAR. It does reconfirm that precise sizing of endografts is critical to long-term success. Our group has demonstrated that excessive endograft oversizing is associated with an increased rate of deleterious effects. The current study serves to underscore that relative undersizing is also dangerous: even a 10% oversize is probably inadequate. Thus, optimal oversizing is likely at 15% to 20%, which is already the current norm in most practices. I have the following questions for the authors:

I would like to thank Dr Arko for the timely delivery of this well-written manuscript for my review and the program committee for the opportunity to discuss this article.

Dr Arko. With regard to interobserver and intraobserver variability with this method, we did study that in regard to looking at diameter, area, and wall thickness and found that there were no statistically significant differences within or between observers. With regard to comparing a balloon-expandable vs self-expanding stent graft for EVAR, I would think that a self-expanding stent would probably do better from a fatigue standpoint long-term than a balloon-expandable stent as a result of the motion of the aortic wall and the ability of the self-expanding stent to conform to these changes. However, as you have stated, the use of a Palmaz stent in that area has done quite well. I have personal experience of having balloon-expandable stents in the aortic neck following endograft placement that fail to expand when the aortic neck dilates as well as the stent graft. The balloon-expandable stent stays the same size as when you first deploy it, so you almost get a bit of a bull's-eye effect up in the neck in which the balloon-expandable stent appears underdeployed. Thus, while it is speculation, I believe that in the long-term the self-expanding stent will do better and will conform better with the proximal neck. Others have used MRA as well as CTA to look at the dynamic changes of the proximal aortic neck. They also demonstrated that there was roughly a 10% to 11% diameter change throughout the cardiac cycle, so I was happy to see that our results were similar. The one thing that they were not able to do in those studies—but probably could if they wished to—would be to look at the thickness of the aortic wall. With regard to future implications for devices, I do believe that if you are going to use endostapling devices, this information could be valuable in the design of the stable. It certainly appears from the data that the thickness of the aorta varies around its circumference, and thus a one-size-fits-all staple may not be appropriate. As the anterior wall is thicker by nearly 47%, two lengths of staple may be required to control the length and penetration of the staple.