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Papers of the Month - May 1998
1. Lipski DA, Ernst CB. Natural history of the residual infrarenal
aorta after infrarenal abdominal aortic aneurysm repair.
J VascSurg 1998; 27: 805©12.
Brief abstract (adapted from authors)
Methods & Results: 800 translumbar aortograms were reviewed,
performed on 272 AAA patients, preoperatively and postoperatively.
The mean follow up time from the preop study to the most recent
postop study was 42 months. Magnification was adjusted by
normalizing to first lumbar vertebral body height.
The length of the native infrarenal aorta cephalad to the graft
increased a mean of 3 mm. However, in a subset of 43% of the
patients, it elongated >5 mm; and in 24% it elongated >10 mm. The
mean dilatation of this segment was 1 mm; but in 21 patients (8%)
it dilated more than 5 mm.
Conclusion: A mean period of 42 months after conventional AAA
repair, the cuff elongates and dilates. The average increases are
small, but in a subset of patients the increases are sufficiently
great to pose "potentially serious implications for endovascular
treatment of AAA.
Comment by mdt © As reviewed by the authors and mentioned in the
discussion section by Dr. Hallett (Mayo Clinic), the concern is
that after endovascular repair, the aorta may dilate sufficiently
to pull away from the graft and result in an endoleak. Dr. Hallett
cited a study from Mayo Clinic with a 6 year follow©up, which
found that 13% of the patients had dilated to 30 mm. Dr. Hallett
also raised the interesting question of whether there were any
clinical characteristics that might predict which patients belong in the
subset that will undergo significant dilatation. This is perhaps
where the laboratory might come into play, to see if homozygosity for a
genetic susceptibility allele (J Vasc Surg 1998; 27: 500) or high titer of
serum antibody against aorta©specific antigenic proteins (Surg Forum
1997; 48: 401) might have predictive power.
2. Vorp DA, Raghavan ML, Webster MW. Mechanical wall stress in AAA:
Influence of diameter and asymmetry. J Vasc Surg 1998; 278:632©9.
Purpose: To investigate the effect of maximum diameter and asymmetric
bulge on wall stress, by holding diameter constant while varying shape or
to hold assymetry constant while varying diameter.
Results: Both diameter and bulge (assymetry) influence distribution of
wall stress. The magnitude of peak stress increased nonlinearly with
increases in either variable. Interestingly, under some
combinations of diameter and bulge, the maximum stress occurred in the
midsection, and in others it occurred elsewhere.
Conclusion: The stress within the wall of a AAA (and possibly the
potential for rupture) are as dependent on shape as they are on
maximum diameter.
Comment by mdt: I am not an engineer, but I found this paper interesting.
As observed by the authors, the prediction of wall stress might become
useful in the future to help to balance the risk of rupture against the
risk of elective repair.
3. Vasseur M©A, Haulon S, Beregi JP et al. Endovascular treatment of
abdominal aneurysmal aortitis in Behcet's disease. J Vasc Surg
1998; 27: 974©6.
Case Report (abstracted): Open surgical repair of aneurysms in
Behcet's is difficult, and anastamotic false aneurysms (30©50%) are
common because of aortic wall fragility. Accordingly, the authors
performed an endovascular repair on a 37 y/o patient with the
disease. Recovery was uneventful, and at follow©up at 6 months all
was well.
Comment by mdt: Compliments to the authors. Another reason for citing
this paper this month is that it gives me a platform to continue
discussions of autoimmune mechanisms in aneurysmal diseases. One of the
proteins with an important epitope in Behcet's has been identified
as a retinal protein related to photoreceptor function.
We have been interested to note that it
may share an epitope with an aorta©specific antigenic protein that we have
implicated in AAA disease. This observation may explain why uvietis
and AAA may be paired in Behcet's.