Screening for abdominal aortic aneurysm in the population of the city of Vitória, ES, Brazil
(Portuguese
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Fanilda Souto Barros1,Sandra Maria Pontes1,Maria Alice S. A. Taylor1,Leonard Herman Roelke2,João Luiz Sandri3,Cláudio de Melo Jacques4,Eliana Zandonade5,Daniela Pontes Nefal6,Juliana A. De Vita6,Carolina A. Borges6,Giuliano de Almeida Sandri6,Isabela G. Moreira6
1.
Vascular ultrasonographer, Angiolab-Laboratório de Diagnóstico Vascular,
Vitória, ES, Brazil.
2.
Surgeon and vascular ultrasonographer. Professor, Angiology
and Vascular Surgery, Universidade Federal do Espírito Santo
(UFES), Vitória, ES, Brazil.
3.
Vascular surgeon. Professor, Angiology and Vascular Surgery,
Escola de Medicina da Santa Casa de Misericórdia (EMESCAM),
Vitória, ES, Brazil.
4.
Vascular surgeon and angiologist.
5.
Professor, Head of Department of Statistics, UFES, Vitória,
ES, Brazil.
6.
Medical undergraduate students, EMESCAM e UFES.
Correspondence:
Fanilda Souto Barros
Rua Joaquim Lírio, 340/701
CEP 29055-460 - Vitória, ES, Brazil
ABSTRACT
Objectives:
To determine the prevalence of abdominal aortic aneurysm in the
population of the city of Vitória, ES, Brazil, and associate
it to possible risk factors.
Method:
Prevalence study performed by stratified random sample according
to age group and socioeconomic class. The exams were performed at
primary health care facilities selected from IBGE (Brazilian Institute
of Geography and Statistics) census sectors. The sample was recruited
by the team of the Family Health Program, after an awareness campaign
on the importance of the disease diagnosis. The exam was performed
by vascular ultrasonographers, using the HDI 5000-ATL and the portable
Sonosite.
Results:
834 individuals were assessed from December, 2002 to June, 2003.
Of these, 21 had abdominal aortic aneurysm (prevalence of 2.5%).
Considering all cases, 15 (71.4%) were male, 14 (66.7%) were from
65 to 75 years old, 13 (61.9%) were Caucasians, 14 (66.7%) were
smokers or ex-smokers, 12 (57.1%) had arterial hypertension. Of
the aneurysms found, 20 (95.2%) were infrarenal, fusiform, and with
a mean diameter of 3.43 ± 0.57 cm. When cases were compared
to the other patients from the sample, we found a statistically
significant association to gender (?2 = 13.401; P = 0.000), age
(?2 = 11.39; P = 0.036), and smoking (?2 = 13.984; P = 0.001).
Conclusion:
The abdominal aortic aneurysm prevalence found in the population of Vitória, ES, Brazil was 2.5%. The authors encourage the screening for the abdominal aortic aneurysm in the following risk group: men over 65 years old with a smoking history.
Key-words:
diagnosis, aneurysm, abdominal aorta.
J
Vasc Br 2005;4(1):59-65
The abdominal
aortic aneurysm (AAA) is a vascular disease that deserves constant attention
for identification studies as well as for therapeutic improvement. Its
clinical importance is based on the high mortality that occurs due to
its rupture,1 contrasting with the low mortality (2.8%) described with
the elective surgical treatment at specialized services.2
The gradual
increase in the prevalence of the AAA is due to the higher life expectancy
of the elderly population and to technological advances, among which
we highlight the more accessible non-invasive diagnostic methods and
another correction option, besides the conventional surgery, which is
the endovascular treatment. The latter offered more integration between
the surgeon and the patient, since the patient's opinion is necessary
in both therapeutic modalities, a fact that was not present in former
recommendations.3
The importance
and justification for the performance and encouragement of the screening
for AAA is mainly based on three facts:
- Its evolution, which can be asymptomatic until rupture, making
the initial clinical diagnostic difficult.
- The possibility of a precise diagnosis by non-invasive and low-cost
technique represented by the vascular ultrasonography.4
- The life expectancy of treated patients to be equal of individuals
of the same age group without the disease.5
MATERIAL
AND METHODS
Prevalence study performed by random sample (proportional by age group, gender, and socioeconomic class in the population of Vitória, ES, Brazil).
The sample was defined to estimate a proportion. The size of the considered population was 26,144 individuals with more than 60 years old in Vitória, according to IBGE data. In order to reach a desired precision of 1.5% and incidence of 4% with significance level of 5%, we determined the sample size in 640 individuals.
We defined the sample plan by proportionally dividing the 640 individuals into age group, gender, and income. We set a margin of approximately 30% in the final sample (834 individuals).
The project was approved by the Ethics Committee of the Universidade Federal do Espírito Santo (UFES) and was developed along with the Department of Statistics of the same university and the Family Health Program (FHP) of Vitória (ES) City Hall.
The population was recruited by the team of the FHP, after an awareness campaign on the severity of the disease and the need of an early diagnosis.
The examinations
were performed at primary health care facilities selected from the Brazilian
Institute of Geography and Statistics (IBGE) census sectors and at Angiolab
- Vascular Laboratory. The survey for possible associated risk factors
was made through a questionnaire.
The only
exclusion criterion was being less than 60 years old.
Examination technique
The examination
was performed by three vascular ultrasonographers, who adopted equal
criteria for the AAA diagnosis. The ultrasound devices used were the
ATL-HDI 5000 and the Sonosite (portable), both with 2-4 MHz convex transducers
equally calibrated for the analysis of measurements. The examinations
lasted approximately 5 minutes. The patient's preparation prior to the
examination consisted of a light diet on the previous day without any
medication. In case of technical difficulty due to gauze interposition,
the patient was referred to a laboratory with a better resolution device,
where the examination could be performed again. The number of patients
with technical limitation was four (0.47% of the total population).
The ultrasound examination comprehended the abdominal aorta from its segment above the celiac trunk to the iliac arteries bilaterally. The diameter measurement was made below the emergency of the renal arteries and above the aortic bifurcation, taking as measurements, in a transverse cut, the anteroposterior diameter of the aortic segment with the patient in a supine position.
The AAA diagnosis was considered with an abdominal aortic diameter equal or higher than 3 cm.
If the
presence of the AAA was confirmed, patients were sent to the vascular
surgery service and to the vascular laboratory, where the study would
be complemented by a color flow duplex scanning of the carotid, iliac
and lower limb arteries, with the aim of investigating the presence
of the obstructive disease and/or associated peripheral aneurysmatic.
RESULTS
Of the 834 assessed people, from December, 2002 to June, 2003, we found 21 cases of AAA, reporting a prevalence of 2.5% in the population of Vitória, ES, Brazil.
Of the cases, 15 (71.4%) were male, 14 (66.7%) were from 65 to 75 years old, 13 (61.9%) were Caucasians, 14 (66.7%) were smokers or ex-smokers, 12 (57.1%) had arterial hypertension.
Concerning
the aneurysm characteristics, 20 (95.2%) were fusiform and infrarenal.
Mean diameter of the AAA was 3.43 cm 0.57 cm.
When cases were compared to the other patients from the sample, we found a statistically significant association to gender (?2 = 13.401; P = 0.000), age (?2 = 11.39; P = 0.036), and smoking (?2 = 13.984; P = 0.001).
Next, we
will describe the comparison between groups with and without aneurysm
and then describe the group with aneurysm.
Comparison
between groups with and without aneurysm
Table 1
presents absolute values and percentages of the sample profile variables,
according to the studied groups. Chi-square tests were also calculated
and the results are presented here.
 Table
1 - Sample profile: absolute and percentage values
 |
| |
AAA |
| Variables
|
Yes
|
No
|
|
|
| |
n |
%
|
n
|
%
|
χ2 |
P |
|
| Gender |
|
|
|
|
|
|
| Female |
6 |
28.6 |
544 |
66.9 |
13.401 |
0.000* |
| Male |
15 |
71.4 |
269 |
33.1 |
|
|
| Total
|
21
|
100.0
|
813
|
100.00
|
|
|
| Grouped
age |
|
|
|
|
|
|
| 60
|--- 65 |
|
|
159 |
20.1 |
|
|
| 65
|--- 70 |
7 |
33.3 |
214 |
27.1 |
|
|
| 70
|--- 75 |
7 |
33.3 |
197 |
24.9 |
11.89 |
0.036
† |
| 75
|--- 80 |
2 |
9.5 |
130 |
16.4 |
|
|
| 80
|--- 85 |
3 |
14.3 |
52 |
6.6 |
|
|
| over
85 |
2 |
9.5 |
39 |
4.9 |
|
|
| Total
|
21
|
100.0
|
791
|
100.0
|
|
|
| Color |
|
|
|
|
|
|
| Caucasian |
13 |
61.9 |
295 |
47.5 |
|
|
| Black |
1 |
4.8 |
110 |
17.7 |
3.565 |
0.168 |
| Mulatto |
7 |
33.3 |
216 |
34.8 |
|
|
| Total
|
21 |
100.0 |
621
|
100.0
|
|
|
|
* P ≤
0.001
† P ≤ 0.005
‡ P ≤ 0.01
A statistical significance is highlighted between groups for the gender variable (71.4% of the group with aneurysm was male) and grouped age.
Possible
risk factors
Table 2
presents absolute values and percentages of the variables of possible
risk factors, according to the studied groups. Chi-square tests were
also calculated and the results are presented here. A statistical significance
is highlighted between groups for the smoking variable.
Table
2 - Possible risk factors
|
| |
|
AAA |
|
|
| Variables
|
|
Yes
|
|
No
|
|
|
|
| |
|
n |
%
|
n
|
%
|
?2 |
P |
|
| Dyslipidemia
|
|
|
|
|
|
|
|
|
yes |
6
|
28.6
|
244
|
30.6 |
0.039
|
0.844 |
|
no |
15
|
71.4 |
554 |
69.4 |
|
|
| Total
|
|
21
|
100.0
|
798 |
100.0
|
|
|
| Diabetes
|
|
|
|
|
|
|
|
|
yes |
5
|
23.8
|
130
|
16.1
|
Fisher
|
0.366 |
|
no |
16
|
76.2
|
676
|
83.9
|
|
|
| Total
|
|
21 |
100.0
|
806
|
100.0
|
|
|
| SAH
|
|
|
|
|
|
|
|
|
yes |
12
|
57.1
|
472
|
58.3 |
0.011 |
0.918 |
|
no |
9
|
42.9 |
338
|
41.7
|
|
|
| Total
|
|
21 |
100.0 |
810
|
100.0
|
|
|
| Coronary
heart disease |
|
|
|
|
|
|
|
|
yes |
5
|
23.8 |
111
|
14.0 |
Fisher
|
0.206 |
|
no |
16
|
76.2
|
680
|
86.0 |
|
|
| Total
|
|
21
|
100.0 |
791
|
100.0
|
|
|
| Smoking
|
|
|
|
|
|
|
|
|
yes |
4
|
19.0
|
59 |
7.3
|
13.984
|
0.001* |
|
no |
7
|
33.3
|
594
|
73.1 |
|
|
|
ex-smoker |
10
|
47.6
|
160
|
19.7
|
|
|
| Total
|
|
21 |
100.0
|
813
|
100.0
|
|
|
| COPD
|
|
|
|
|
|
|
|
|
yes |
1
|
4.8
|
14
|
1.7
|
Fisher
|
0.320 |
|
no |
20
|
95.2
|
799
|
98.3 |
|
|
| Total
|
|
21 |
100.0 |
813 |
100.0
|
|
|
| Family
history of AAA |
|
|
|
|
|
|
|
|
yes |
|
|
1
|
0.1
|
Fisher
|
1.000 |
|
no |
21
|
100.0
|
801
|
99.9
|
|
|
| Total
|
|
21
|
100.0
|
802
|
100.0
|
|
|
|
P ≤
0.005; * P ≤ 0.001; † P ≤ 0.01.
SAH = systemic arterial hypertension; COPD = chronic obstructive pulmonary
disease; AAA = abdominal aortic aneurysm.
Description
of the group with aneurysm
The tables characterizing the group with aneurysm are then presented. We highlight, in some tables, the valid percentage term by which only individuals with the required information were recorded.
Of the
21 cases with AAA, 15 (71.4%) were male, 13 (61.9%) were Caucasians.
Mean age was 74.1 years old, with a standard deviation of 7.59 years.
Table 3 presents age frequencies in the patients.
Table
3 - Absolute frequency and age percentage of patients with aneurysm
|
| Age |
|
Frequency |
% |
|
| 68,00 |
3 |
14,3 |
| 73,00 |
3 |
14,3 |
| 66,00 |
2 |
9,5 |
| 70,00 |
2 |
9,5 |
| 74,00 |
2 |
9,5 |
| 83,00 |
2 |
9,5 |
| 67,00 |
1 |
4,8 |
| 71,00 |
1 |
4,8 |
| 72,00 |
1 |
4,8 |
| 76,00 |
1 |
4,8 |
| 79,00 |
1 |
4,8 |
| 86,00 |
1 |
4,8 |
| 96,00 |
1 |
4,8 |
| Total |
21 |
100,0 |
|
According
to the data in Table 4, the mean aneurysm size of 3.47 cm was calculated,
with a standard deviation of 0.61 cm.
Table
4 - Absolute frequency and percentage of aneurysm size
|
| AAA
cm |
|
Frequency |
% |
|
| 3.1 |
5 |
23.8 |
| 3.0 |
4 |
19.0 |
| 3.2 |
4 |
19.0 |
| 3.6 |
2 |
9.5 |
| 3.7 |
2 |
9.5 |
| 3.9 |
1 |
4.8 |
| 4.0 |
1 |
4.8 |
| 4.9 |
1 |
4.8 |
| 5.2 |
1 |
4.8 |
| Total |
21 |
100.0 |
|
The fusiform and infrarenal aneurysm accounted for 95.2% and in 18 cases (85.7%) the presence of a mural thrombus was detected.
Of the 21 patients with aortic aneurysm, 18 were assessed for peripheral aneurysm investigation and we found 11% of iliac and popliteal association, being both bilateral. 14 patients were studied for investigating peripheral and carotid obstructive disease, according to established criteria for stenosis graduation by Eco-Color Doppler.6-7 We found the following results:
- In the right internal carotid artery: stenosis lower than 50% in eight patients (57.1%), between 50% and 60% in two patients (14.3%), equal or higher than 70% in one patient (7.1%), and two patients (14.3%) were normal.
- In the left internal carotid artery: stenosis lower than 50% in nine patients (64.3%), between 50% and 60% in one patient (7.1%), equal or higher than 70% in two patients (14.3%), and two patients (14.3%) were normal.
Concerning lower
limb arteries, 21.4% of patients presented obstructive injuries considered
severe in the femoro-popliteal segment and/or tibiofibular bilaterally.
All patients were referred to annual control of the aneurysm measurement.
There was
one case of a 5-cm aneurysm. The patient was 72 years old, Caucasian,
female and presented stenosis higher than 70% in the left internal carotid
artery. She was submitted to carotid endarterectomy and later to a surgical
treatment of the AAA, evolving uneventfully.
DISCUSSION
The main
objective of this study was to register the prevalence of AAA in the
population of Vitória, ES, Brazil, to promote an information campaign
on the existence of the disease and awareness of the importance of an
early diagnosis.
We highlight the existing difficulties in our environment in order to perform an epidemiological study of this size:
1. The randomized study was only possible due to the support of the FHP, recruiting the population and lending the primary health care facilities for assessing the patients.
2. In
loco examinations were only feasible due to a lended Sonosite-ATL
portable device, since the public service does not have such equipment
in outpatient clinics and high costs would not allow the project development.
Forming a multidisciplinary team (physicians, students, nurses, and statistician) is still a hard task, since it is difficult to receive payment for the hours worked on the research project.
The general prevalence (male and female) found by our survey of 2.5%, compared to studies that used similar criteria, is lower than the one described by Leopold et al., which was 3.2%8 and similar to the one described by Pleumeekers et al., which was 2.1%.9
When we analyzed the sample of male alone, we found a prevalence of 5.2% (15/284), similar to the results described in the literature.1,10
In Brazil, Bonamigo & Siqueira screened 2,281 men with more than 54 years old. Of this group, 768 were under cardiologic clinical treatment, 501 had been submitted to a revascularization of the myocardium or had acute coronary lesions showed by the cardiac catheterization and 1,012 individuals were from the general population. They found a prevalence of 4.3, 6.8 and 1.7%, respectively.11
Molnar
et al. surveyed 411 elderly patients (more than 65 years old) and found
a prevalence of 2.1%, analyzing both genders. This percentage increased
to 4.1% when only male patients were considered.12
In our
study, we did not find aneurysm in individuals younger than 65 years
old, confirming the guidance of several authors for group screening
above that age group.10,11,13
Most part
of aneurysms in our sample was small (mean size of 3.47 cm), similarly
to findings from other surveys.14,15
Considering
the surgical indication for aneurysms with a diameter equal or higher
than 5 cm and knowing that it grows slowly, we question the cost benefit
ratio of screening. Some studies were performed aiming at finding answers
to such doubts.10-16
One of these studies, called MASS, showed that all men above 65 years old should be screened for AAA. The prevalence of AAA in 27,000 surveyed men was 5% and the risk of death in the screened population was significantly lower to the risk of the population that was not screened.
Since data concerning the prevalence and risk in women need more studies, we assume that screening for women also has a research value, besides the clinical value.
The association of 11% of iliac aneurysm and the popliteal artery in patients with AAA found in our study was lower than the values described in the literature.17,18
When comparing groups with and without aneurysm, statistically significant risk factors were as follows: age, gender and smoking. Arterial hypertension, although frequent in the group with aneurysm, did not present statistical significance when compared to the presence of arterial hypertension in the population.19
The association of the carotid disease in 86% of patients with aneurysm who accepted the carotid study, being 14% of them considered severe (stenosis equal or higher than 70% or occlusion), confirms the indication for AAA screening in patients with carotid disease and vice versa.20
The presence of severe peripheral artery obstruction found in 21% of patients with AAA was higher than the values described in the literature.21,22
We did not find an association of AAA to coronary heart disease or to COPD (chronic obstructive pulmonary disease), although we are aware of the importance of such association, according to Bonamigo & Siqueira and other authors.9,11 The explanation for this may be the fact that the investigation of these diseases by questionnaire, as we did in our survey, is not statistically correct.
We conclude that, although there are difficulties in performing population studies in our environment, an incentive is necessary for surveying risk groups. According to our results, similar to others, we advise the AAA screening in men over 65 years old with risk factors such as smoking.
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