Limitations to the Therapeutic Potential of Endoluminal Stent Placement in the Thoracic Aorta
To the Editor:
In their recent study, Rousseau et al1 report the successful delayed treatment of traumatic rupture of the thoracic aorta by endoluminal stent placement. The results of this technique in the authors’ hands were excellent. The authors suggest that this alternative treatment to conventional surgery is feasible and safe but that its use may be restricted by limited durability of the stent graft material.
We wish to raise a point that may further limit the therapeutic potential of stent placement in the thoracic aorta. It is our experience from implanting >150 endoluminal stents into the abdominal aorta in order to exclude aneurysms that despite excellent immediate success rates, >10% of the stents had to be surgically removed within the first 4 years after stent implantation (References 2 and 3 and unpublished observations). Others have made similar observations.4 Surgical explantation of the stents in our patients became necessary not only because of problems with the stent durability but mainly because of dislocation of the stents and reexposure of the old aneurysms to systemic blood pressure. These dislocations were due to dilatation of the aorta at the anchoring site of the stent. Dilatation of the aorta may also occur in the thoracic aorta. Because of the elastic nature of the vessel walls, dislocation of stents may even be facilitated. Although our experience with the placement of thoracic stents is limited, we would expect a similar condition in these cases. Thus, we propose that stent graft placement into the thoracic aorta should only be considered a palliative treatment option. The possible requirement for surgical explantation of the stent at a later time point should be taken into account at the time the decision for stent placement is made.
- Copyright © 2000 by American Heart Association
Rousseau H, Soula P, Perreault P, Bui B, Janne d’Othée B, Massabuau P, Meites G, Concina P, Mazerolles M, Joffre F, Otal P. Delayed treatment of traumatic rupture of the thoracic aorta with endoluminal covered stent. Circulation. 1999;99:498–504.
Schlensak C, Blum U, Munzar T, Spillner G, Beyersdorf F. Three-year follow-up after endoluminal treatment for abdominal aortic aneurysm. Thorac Cardiovasc Surg. 1998;45(suppl I):177. Abstract.
Doenst et al, from the team who played a major role in the widespread diffusion of stent grafting for abdominal aortic aneurysms (AAA) by their major publication in the New England Journal of Medicine,R1 raise an essential point concerning long-term benefits of aortic endoprostheses.
All prospective studies and registers do indeed show that stent grafting gives good immediate results for treatment of AAA, with a 30-day morbidity and mortality rate less than that of classic surgery. On middle-term follow-up studies, the complication rate, however, is not negligible and mostly consists of secondary leaks.R2 Whereas size increase of the proximal aneurysmal neck may account for some of these endoleaks, most are related to changes in aneurysmal volume after successful exclusion, which results in device distortions, kinkings, or modular disconnections. Most of these complications can be treated via an endovascular approach. This demonstrates the importance of close follow-up to detect and treat them. Lastly, these somewhat deceiving results were observed with first-generation devices. New models, as used in our study, seem to confer substantial advantages.
In addition, thoracic aortic aneurysms differ considerably from AAAs in several ways. First, only 1 tubular device is needed for endovascular treatment in most patients, thereby eliminating the risk for leaks between adjacent stent grafts. Second, in our article, the only accepted indication concerned isthmic lesions that occurred on otherwise healthy aortas and in patients in whom surgery was contraindicated in many cases. Third, oversizing by at least 10% the diameter of the device (compared with the normal aortic diameter) reduces the risk of migration, even if aortic size increases with time.
The Stanford teamR3 has reported similar results as we did, with a mean follow-up of 15 months for traumatic thoracic aortic lesions, and they did not observe any aneurysm expansion or rupture. Their overall experience of stent grafting in a relatively large population also encompasses other aortic diseases. So far, the main concerns about thoracic stent grafting involve potential complications, such as mortality and paraplegia rates.R4 R5 But on the basis of nonrandomized studies, it appears that these complications probably occur less frequently than with surgery. To the best of our knowledge, stent-graft explantation has not yet been necessary or considered at the level of the thoracic aorta.
In conclusion, our current experience (20 patients, mean follow-up of 20 months, range 1 to 42 months) is still preliminary but has led to encouraging results. The benefits of aortic endoprostheses in terms of morbidity and mortality by far outweigh those of classic surgery by thoracotomy. In our opinion, this enforces justifications for their use, although this area is still in the prospective study stage.
Blum U, Voshage G, Lammer J, Bayersdorf F, Töllner D, Kretschmer G, Spillner G, Polterauer P, Nagel G, Hölzenbein T, Thurnher S, Langer M. Endoluminal stent grafts for infrarenal abdominal aortic aneurysms. N Engl J Med. 1997;336:13–20.
Harris PL, Buth J, Mialhe C, Myhre HO, Norgren L. The need for clinical trials of endovascular abdominal aortic aneurysm stent-graft repair: the EUROSTAR Project: EUROpean collaborators on Stent-graft Techniques for abdominal aortic Aneurysm Repair. J Endovasc Surg. 1997;4:72–77.