Aneurysm Papers of the Month - March 1995

1. Racial differences in the incidence of femoral bypass
and abdominal aortic aneurysmectomy in Massachusetts:
Relationship to cardiovascular risk factors.

LaMorte WW, Scott TE, Menzoian JO.  J Vasc Surg 1995;
21:422-31.

Abstract (condensed from authors): 

     Purpose:  Our goals were to compare and contrast
factors associated with the development of AAA's and
clinically significant atherosclerotic occlusive disease
(AOD) 1) to determine whether these diseases share a
common cause, and 2) to explore their association with
race.
     Methods:  Dual case-control studies with
multivariate analysis to compare cases with a comparison
group consisting of patients who had undergone
appendectomy....
     Results:  Black patients had higher rates of femoral
bypass than white patients after adjustment for age and
sex (p<.0001). However, femoral bypass was also
associated with hypertension, diabetes, and low household
income.  After adjusting for these additional factors in
the statewide data set, the black/white odds ratio for
femoral bypass was only 1.44.  In contrast, AAA occurred
predominantly in white men.  AAA was also associated with
smoking and hypertension, but not significantly
associated with diabetes or family income.  The
black/white odds ratio for aneurysm was 0.29; p=.09 after
adjustment for other variables.
     Conclusions: Hypertension, smoking, and male sex are
risk factors for the development of femoral
atherosclerosis and AAA formation.  However, AAA occurs
predominantly in white men and does not appear to be
associated with diabetes mellitus or income.

Comment by mdt:  Very interesting paper (!), quantifying
what is commonly known among vascular surgeons, namely
that AAA's are relatively uncommon in African Americans. 
We see this at my hospitals in New York, where
complications of peripheral AOD are common and AAA's are
rare at the St. Luke's site, while AAA's are common at
the Roosevelt site (reflecting the patient mixes at the
different institutions).  I continue to believe that the
two diseases have risk factors in common because of
"joint observable effects", which has led in the past to
a fallacy of spurious causation.  For more info on this
subject, please see the file on this Home Page named
Aneurysm Lecture.

2.  Incidence of rupture of aortic aneurysms after
conincidental operation.  

Lalak, N, Englund R, Hanel KC.  Cardiovasc Surg
1995;3:30-4.

Abstract (condensed from authors): The clinical course of
76 patients with AAA undergoing 107 coincidental surgical
procedures was analysed in order to examine the
relationship between aortic aneurysmal rupture and
coincidental treatment.  In addition, the incidence of
rupture was assessed following 82 endoxcopic procedures
in 42 patients with AAA's.  Two patients ruptured an AAA
after a procedure: one after colonoscopy and one after
CABG.  

Comment (by mdt).  Thus, the rate of rupture following
colonoscopy (1/82) is slightly less that the rate of
rupture following a coincidental surgical procedure
(1/107).  This result casts a shadow of doubt over the
hypothesis that activation of systemic collagenolytic
activity is a critical factor in rupture following a
procedure, since systemic activation after colonoscopy
would be expected to be trivial.  It should be noted,
however, that the incidence reported here is slightly
lower than the 3% incidence that has been reported by
others in the past.