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Papers of the Month - January 1997
1. Blum U, et al. Endoluminal stent-grafts for
infrarenal abdominal aortic aneurysms. NEJM 1997;
336:13-20.
Abstract: A prospective study of a prosthesis made of
nitinol and covered with polyester fabric... 154
patients: 21 straight grafts and 133 bifurcated grafts.
CAT & intraarterial angiography performed at an average
follow-up of 12.5 months. Results: Complete exclusion of
the AAA was achieved in 86% of the straight graft group
and 87% of the bifurcated graft group. The procedure was
converted to open repair in 3 patients. Minor (n=13) or
major (n = 3) complications (including one death)
occurred in 10%. All patients had a postimplantation
syndrome, with leukocytosis and elevated CRP.
2. Yusuf et al. Early results of endovascular aortic
aneurysm surgery with aortouniiliac graft, contralateral
iliac occlusion, and femorofemoral bypass. J Vasc Surg
1997; 25: 165-172.
Abstract: 30 patients: mean age 72, mean AAA diam 6 cm
(range, 4-9), 28 elective procedures and 2 urgent for
leak. A modified Gianturco stent, Dacron graft, and
Wallstent were used for the procedures. Results:
Endovascular repair was successful in 25/30 patients
(83%). These 25 patients were mobile and on normal diet
within 48 hours. There were two deaths; one in elective
group (3.3%) and one in ER group (50%). Overall
morbidity occurred in 4 patients (13.3%). At a median
follow-up of 4 months, 27 out of 30 patients were alive
and well.
3. Matsumura JS, Pearce WH, McCarthy WJ, and Yao JST for
the EVT Investigators. Reduction in aortic aneurysm
size: Early results after endovascular graft placement.
J Vasc Surg 1997; 25: 113-23
Abstract: CT scans were done in 34 patients at an
interval of 1 yr following stent grafting. 20 patients
had no perigraft leaks. 7 patients had an early leak
that sealed, and 7 patients had persistent perigraft
leaks. The proximal neck remained stable, but the distal
neck enlarged by .12 cm +/- .27 cm. AAA diameter
decreased in those with no leak or sealed leak. Sac
diameter increased in the seven with perigraft leaks.
Comment by mdt -
Perhaps even more informative than the papers themselves
are the companion pieces; specifically, the Editorial by
Cal Ernst in NEJM and the complete transcript of the
discussion from the floor at the SVS meeting where the
Matsumura paper was presented. Ernst puts it very
succinctly: "Attractive as endovascular treatment of AAA
may seem, its feasibility, safety, effectiveness, and
durability are as yet unproved." Ernst notes that to
date there has still been no prospective randomized trial
to compare endovascular with conventional techniques.
Many of the pioneers of endovascular repair were present
at the SVS meeting. Tom Fogarty mentioned "another
alarming potential situation... in which a leak is not
identified and yet the aneurysm continues to enlarge", a
situation that has been observed in the thoracic
experience at Stanford. Jeb Hallett observed that
bifurcated grafts may not solve the problem of an
enlarging distal neck, unless brought down to the
external iliacs, which in turn would risk mesenteric
ischemia. Juan Parodi, the first person to do an
endovascular graft in 1991 and accordingly the surgeon
with the longest experience, stated that he had seen
distal dilatation and leaks even after 3 years. IMHO,
the endovascular approach may now be recommended for
elderly patients who pose high or prohibitive surgical
risk. However, younger patients who are fit for surgery
are usually cured by the conventional surgical approach.
The same cannot be presently said for endovascular
repair.
I can't resist speculating about why the sac gradually
shrinks long term in most patients with successful seals.
Preliminary experiments in our lab suggest that there may
be several autoantigens involved in the inflammatory
changes that occur in non-specific AAA's. One or more of
these may be an aorta-specific matrix cell adhesion
molecule. If it is produced by cells in response to
cyclic deformation, the signal for its production would
be abrogated by a successful seal. Then, the autoimmne
response would down-regulate and the wall should shrink.