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Ann Thorac Surg 1998;66:24-25
© 1998 The Society of Thoracic Surgeons
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Discussion |
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 Top Discussion |
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Because outside of our center and Japan almost nobody else has explored endovascular stent grafting for descending thoracic aneurysms, it is refreshing to hear the Austrian experience using a Talent device. This is the only way we will ever figure out whether this approach has merit, and, if so, in which patients. The Vienna experience is small but does confirm our findings in 122 patients treated similarly with a stent graft between 1992 and 1997.
Stent grafting of the descending thoracic aorta is feasible and safe. Because of anatomic features, however, it is not advisable for all patients, which leads me to my first question. How could all 58 earlier patients in your series going back to 1989 treated with open surgical techniques have been "suitable candidates for a stent graft" on anatomic grounds?
Second, and in a similar vein, in the 8 months since you have been doing stent grafts, how many other patients required open surgical repair? This is not for everybody, as I am sure some of the audience knows.
Third, the Vienna group early in their experience was quite aggressive in creating a proximal neck or a "stent graft landing zone" by transposing the left subclavian artery in 50% of patients. In our experience we have resorted to this option in only about 12% of patients where there just is not enough neck beyond the left subclavian artery for a safe landing zone. Nevertheless, this indicates to me that most of your aneurysms involved the very proximal descending thoracic aorta, such that spinal cord injury would be expected to be very rare. Therefore, observing no cases of paraplegia in your initial 10 patients is not surprising. On the other hand, in our experience where occasionally the entire descending thoracic aorta has been covered, the paraparesis/paraplegia rate is 3%. Interestingly, all 4 of these unfortunate patients underwent simultaneous or previous abdominal aortic aneurysm repair. The audience should note that stent grafting does not confer any lower risk of spinal cord injury than does open surgical graft replacement, as Dr Ehrlich’s comparisons might be interpreted.
Fourth, your primary success and secondary success rates were 80% and 90%, with 2 patients requiring additional stent grafts for early endoleaks. These figures parallel our numbers of 83% when leaving the operating room and 96% at hospital discharge. Ten of our patients required coil embolization for small endoleaks, and 6, another stent graft. But this leads me to an important point. In the article you state, "It is uncertain if residual leakage into the aneurysm sac may lead to late aortic rupture." I am afraid we learned the hard way that it is absolutely imperative to eliminate all blood flow into the aneurysm sac and seal all endoleaks before the patient leaves the hospital. If this goal is not achieved, we consider it "treatment failure"; quite honestly, we have not done these patients a favor. Do you really believe it is safe to ignore a benign-appearing puff or endoleak?
Finally, I am disturbed that your one death resulted from erosion of the stent graft through the aortic wall. Our overall 30-day death rate is 11%, but no death has been directly attributable to our very primitive, home-brew stent graft device. Does the Talent endoluminal spring-graft system have features that might predispose to aortic perforation? Are all nitinol wire components covered by the Dacron graft material?
Newer commercial stent graft device systems for descending thoracic aortic aneurysms from Prograft/W.L. Gore, and Meadox/Boston Scientific Corp, which are smaller and promise more precise and controllable stent graft deployment, are now being tested in the United States or close to Food and Drug Administration approval for phase I trials. I believe this endovascular stent graft approach does have a role to play in the future, which incidently carries enormous potential cost savings. The magnitude of this role, however, remains to be defined.
I hope you, Dr Havel, and Dr Wolner continue to explore the benefits as well as the limitations of stent/grafting of the thoracic aorta in Vienna.
DR EHRLICH: Thank you, Dr Miller, for your interesting and intriguing questions. I will try to answer them in order and as concisely as possible. Furthermore, I would like to congratulate you and your Stanford group for your pioneer work in this field and your excellent results achieved so far.
In regard to the 59 patients, they were selected out of 96 patients who were treated conventionally in this first period, which would bring us to about 60% of suitable candidates. In the second period, where we performed the first 10 endovascular stent graft procedures, 17 patients had been treated in the same time frame conventionally, which would bring us to about 40% of suitable candidates for this technique. This latter percentage is similar to the results published by Dr Mitchell from Stanford.
In terms of transposition of the subclavian artery, yes, we are quite aggressive in this matter; however, we do believe that it is important to create a sufficient proximal neck for the landing zone of the stent graft, especially because most of our aneurysms involved the very proximal part of the descending aorta. You are on the safe side after performing the transposition and do not have to fear occluding the ostium of the subclavian artery.
In regard to leakage after stent graft placement, we observed this complication in 2 of our patients, and those 2 patients had been successfully restented with total occlusion of the aneurysmal sac after the second intervention. You are absolutely right, it is imperative to eliminate all blood flow into the aneurysmal sac before the patient leaves the hospital and prevent late aortic rupture.
In regard to the 1 patient who died after stent graft placement on the ward, the proximal flange perforated the aortic wall, which caused aortic rupture and led to the death of this patient. This technical feature has to be taken into consideration for further stent graft developments. Both flanges, especially the proximal one, have to be designed to be less sharp to therefore, prevent erosion of the graft through the aortic wall.
Once again, I thank you for your kind remarks.
This article has been cited by other articles:
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  T. G. Gleason and L. C. Benjamin Conventional Open Repair of Descending Thoracic Aortic Aneurysms Perspectives in Vascular Surgery and Endovascular Therapy, June 1, 2007; 19(2): 110 - 121. [Abstract] [PDF]
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