Screening for abdominal aortic aneurysm in the population of the city of Vitória, ES, Brazil
(Portuguese PDF version)

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.

click hereTable 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.

click hereTable 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.

click hereTable 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.

click hereTable 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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