Invited commentary
Article Outline
This report, coming as it does from a highly regarded center of vascular surgery excellence, deserves our attention. The authors point out that there are presently two general types of endograft devices, self-expanding and balloon-expanded. There are many differences between the two in design, functional characteristics, and clinical results. All commercially available bifurcation aortic endografts are self-expanding, so long-term data on a balloon-expanded device, even one withdrawn from clinical use, are of interest.
The LifePath Inc endograft employed individual, separated, ductile Elgiloy wires arranged along the trunk portion at intervals proximally. These individual wireforms are vulnerable to stress fractures, as shown by the material fatigue problem, even after an attempted remedy in a second iteration of the LifePath endograft. Also, the LifePath design augmented fixation with barbs in the proximal trunk, as have several current self-expanding endografts, rather than depending on the radial force of the wireforms alone.
Other types of balloon-expanded endografts that use a Palmaz balloon-expanded stent (Cordis, Warren, NJ) have achieved very different results. One reference cited by the authors of an FDA-sanctioned Investigational Device Exemption (IDE) study1 reported 77 patients who received aortic endografts with proximal balloon-expanded Palmaz stents that were fracture free and showed no migration. A single type I endoleak was corrected with an additional Palmaz stent. There have been other reports of successful outcomes in aortic endografts with proximal balloon-expanded stents,2, 3, 4, 5, 6 and none has reported a clinical adverse event due to stent fracture.
The difference in clinical outcome appears related to differences between balloon-expanded wireforms and a stent. A stent, as the term is generally understood, means a device with significant lengthwise dimension that applies force to the vessel wall over its length. This is importantly different from a wireform in that the resistive radial force can be more robust over the integral length of the stent than individual wireforms. Also, the stent's rigid structure resists flexing imposed by kinetic forces that caused problems for LifePath's wireforms.
Thus, it is important to recognize that the authors' conclusions apply specifically to their observations of the LifePath graft and not to balloon-expanded endografts of a different design that employ true stents.
References
- Absence of proximal neck dilatation and graft migration after endovascular aneurysm repair with balloon-expandable stent-based endografts. J Vasc Surg. 2005;42:639–644
- . Endovascular stent grafting in the presence of aortic neck filling defects: early clinical experience. J Vasc Surg. 2001;33:340–344
- . Endovascular repair of abdominal aortic aneurysms: stent-graft fixation across the visceral arteries. J Vasc Surg. 2002;35:109–113
- . Ten-year experience with endovascular therapy in aortic aneurysms. J Am Coll Surg. 2002;194(1 Suppl):S58–S65
- . Endovascular grafts and other image-guided catheter-based adjuncts to improve the treatment of ruptured aortoiliac aneurysms. Ann Surg. 2000;232:466–479
- Endovascular treatment of failed prior abdominal aortic aneurysm repair. Ann Vasc Surg. 2003;17:43–48
PII: S0741-5214(09)00896-9
doi:10.1016/j.jvs.2009.04.045
© 2009 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.
Refers to article:
- Long-term results of balloon-expandable LifePath endografts in abdominal aortic aneurysm: A single-center experience , 29 June 2009
