Prevalence of abdominal aortic dilatation in patients aged 60 years or older with coronary disease

Abstracts

CONTEXTO: A realização de programas de triagem para o aneurisma da aorta abdominal de forma indiscriminada auxiliará uma pequena porcentagem de indivíduos, mas ao considerarmos grupos com fatores de risco relacionados à dilatação da aorta, aumentando a probabilidade da doença, este permitirá um direcionamento adequado dos recursos e um benefício maior à população. Programas direcionados pelas sociedades médicas, permitindo um diagnóstico precoce das doenças vasculares e conseqüentemente um melhor preparo do doente, promoveriam melhores taxas de sobrevida com menor morbidade. OBJETIVO: Avaliar a prevalência da dilatação da aorta abdominal em uma amostra de pacientes idosos com mais de 60 anos de idade, portadores de coronariopatia aterosclerótica diagnosticada por cineangiocoronariografia. MÉTODOS: Para a seleção dessa amostra, levou-se em consideração o fato de que a avaliação pré-operatória de cirurgia vascular não tenhasido a indicação do cateterismo. Procedeu-se então a avaliação, baseada na anamnese, exame físico e Doppler ultra-som da aorta abdominal. A análise estatística iniciou-se com o teste qui-quadrado, com a posterior análise de regressão logística multivariada e regressão logística univariada, considerando significativo um p < 0,05. RESULTADOS: Dos 180 pacientes, 57 (31,7%) dos casos pertencem ao sexo feminino, e 123 (68,3%) ao masculino. A faixa etária variou entre 60 e 80 anos, com idade média de 66,7 anos. Dos 16 indivíduos portadores de dilatação da aorta abdominal (10 aneurismas e 6 ectasias), apenas um era do sexo feminino. O risco para um indivíduo com 1 lesão aterosclerótica coronariana de apresentar dilatação da aorta abdominal foi de 0,4% no grupo avaliado. Da mesma forma, nos portadores de 2 ou 3 lesões, o risco foi de 1,7%, e naqueles com mais de 3 lesões, de 4,5%. Quando associados ao tabagismo, estes valores alteraram-se respectivamente para 6,9, 11,8 e 27,1%. CONCLUSÃO: O presente estudo permite concluir que a prevalência de dilatação da aorta abdominal foi de 8,9% (16 de 180 pacientes) nesta amostra específica. Apresentou-se de forma mais freqüente nos indivíduos do sexo masculino, tabagistas e em presença de lesões ateroscleróticas difusas das artérias coronárias.

Aorta abdominal; aneurisma da aorta; coronariopatia; idosos

ORIGINAL ARTICLE

Prevalence of abdominal aortic dilatation in patients aged 60 years or older with coronary disease

Guilherme Vieira Meirelles^I; Mario Mantovani^II; Domingo Marcolino Braile^III; José Dalmo Araújo Filho^IV; José Dalmo Araújo^V

^IAssistant physician, Trauma Surgery, Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brazil. Assistant physician, Vascular Surgery, Pontifícia Universidade Católica de Campinas (PUC-Campinas), Campinas, SP, Brazil. MSc., Department of Surgery, UNICAMP, Campinas, SP, Brazil. Member, SBACV

^IIProfessor, Trauma Surgery, UNICAMP, Campinas, SP, Brazil

^IIIProfessor, Cardiac Surgery, UNICAMP, Campinas, SP, Brazil

^IVMember, SBACV

^VMember, SBACV. Head, Vascular Surgery Service, Instituto de Moléstias Vasculares (IMC), São José do Rio Preto, SP, Brazil

^{Correspondence}

ABSTRACT

BACKGROUND: Indiscriminate screening programs for abdominal aortic aneurysm will help a small percentage of individuals. However, when considering groups with risk factors associated with aortic dilatation, which increases the probability of the disease, such programs will provide an adequate allocation of resources and a greater benefit to the population. Programs guided by medical societies, providing an early diagnosis of vascular diseases and consequently a better preparation of patients, would result in better survival rates with lower morbidity.

OBJECTIVE: To evaluate the prevalence of abdominal aortic dilatation in patients aged 60 years or older with atherosclerotic coronary disease diagnosed by coronary angiography.

METHODS: The sample selected for this study considered the fact that preoperative assessment of vascular surgery had not been indication for catheterization. Evaluation was then performed, based on anamnesis, physical examination and ultrasound Doppler of the abdominal aorta. Statistical analysis started with chi-square test, with further multivariate logistic regression analysis and univariate logistic regression, with p < 0.05 considered significant.

RESULTS: Of 180 patients, 57 (31.7%) were female and 123 (68.3%) were male. Age varied from 60 to 80 years, with mean of 66.7 years. Among the 16 individuals with abdominal aortic dilatation (10 aneurysms and six dilatations), only one was female. The risk of an individual with one atherosclerotic coronary lesion presenting abdominal aortic dilatation was 0.4%. Similarly, in those with two or three lesions the risk was 1.7, and 4.5% in those with more than three lesions. When associated with smoking, these values were 6.9, 11.8 and 27.1%, respectively.

CONCLUSION: The present study leads to the conclusion that prevalence of abdominal aortic dilatation was 8.9% (16 out of 180 patients) in this specific sample. It was more prevalent in males, smokers and associated with presence of diffuse atherosclerotic lesions of the coronary arteries.

Keywords: Abdominal aorta, aortic aneurysm, coronary disease, elderly.

Introduction

Aneurysmal disease has been presenting therapeutic proposals that progressed in association with scientific development. It was initially treated by abdominal aortic ligation, then gradual occlusion by wiring technique, cellophane wrapping of the aneurysm to cause fibrosis and reduce risk of rupture, and nowadays endoaneurysmorraphy using synthetic grafts.^1-4 The most recent innovation is circulatory exclusion of the aneurysm by implanting a stent graft, which allows approach of high surgical risk patients.⁵

Early diagnosis of abdominal aortic aneurysms (AAA) significantly contributes to elective indication for patients' treatment and prognosis, with operative mortality lower than 5%, decreasing with the use of stent grafts.^6,7

On the other hand, AAA rupture was responsible for 14,982 deaths in individuals aged 55 years or older in the USA in 1988 (National Center for Health Statistics). In that same year, 40,000 aneurysmectomies of the abdominal aorta were performed.⁸

In a study of AAA rupture, Johansson & Swedenborg⁹ concluded that 27-50% of patients die before being admitted to a hospital, 24-58% before surgical intervention and 42-80% in the perioperative period, which represents a mortality rate of 78-94%.

AAA diagnosis is still a challenge, and clinical examination has sensitivity lower than 50%,¹⁰ requiring complementary imaging examinations¹¹ and sometimes having rupture as its first manifestation.¹²

Ultrasonography is the most widely used method nowadays. Computed tomography, along with magnetic nuclear resonance, are currently considered diagnostic methods of choice to evaluate aortic aneurysms, with measurement errors between 5 mm in diameter in 12-17% of cases, when evaluated by different examiners.¹³ Some situations, such as excessive tortuosity, can result in false diameters.^14-16

As to etiopathology, degenerative aneurysms result from a multifactorial process leading to degradation of the protein matrix. Evidence suggests that structural proteins (collagen and elastin) suffer the action of metalloproteinase (gelatinase, matrilysin and macrophage elastase) and are associated with AAA occurrence. Atherosclerosis is still being studied as participative factor. Atherogenic diets produce narrowing of the medial layer in primates. Cathepsins S and K act as potent elastase, and the genes of this enzyme are expressed in the atheromatous plaque. Cysteine C levels (cathepsin inhibitor) are reduced in the atheromatous plaque. Patients with AAA have reduced serum levels of cathepsins. Mechanical factors, such as blood flow direction (shearing stress) and nutrition of the aortic wall, are also studied as factors associated with atherosclerosis.¹⁷

Patients with AAA, when submitted to successful surgery, die due to myocardial infarction in 22.2% of cases over a 2-year period of follow-up, which shows a great prevalence of coronary artery disease in this group of patients.¹⁸

In a series of 1,000 patients with vascular disease, Hertzer¹⁹ showed that 60% presented advanced coronary lesions. This confirms a correlation between presence of aneurysm and coronary atherosclerotic lesion, as well as the importance of an early diagnosis for possible elective repair of AAA.

Considering that presence of coronary atherosclerotic obstructive disease correlates with AAA, screening of this population was performed to search for an early diagnosis and with the aim of providing an adequate treatment.

Methods

A total of 180 patients with coronary artery disease were selected, recruited from a list of cardiac catheterization at Instituto de Moléstias Cardiovasculares (IMC) de São José do Rio Preto, from July 1994 to March 1995, in accordance with the ethical norms recommended by the Research Ethics Committee.

Inclusion and exclusion criteria

Inclusion criteria were patients aged 60 years or older, with atherosclerotic obstructive coronary lesion diagnosed by coronary angiography.

Exclusion criteria were patients aged less than 60 years or submitted to coronary angiography as preoperative assessment of aortic aneurysm or another peripheral vascular disease.

Clinical evaluation

Vascular evaluation consisted of anamnesis, history and complementary questionnaire, followed by general and special physical examination. Any information about symptoms of chronic arteriopathy was emphasized by asking questions and encouraging the patient's answer. Physical examination aimed at identifying aortic dilatation and peripheral vascular disease.

The patients were submitted to color-flow Doppler ultrasonography of common, internal and external aortic and iliac arteries. Evaluation parameters were comparison between image of cross-sectional view by B mode (lumen diameter) at the evaluation site in relation to the artery diameter in its proximal portion, associated with changes in systolic and diastolic velocities for evaluation of stenoses.

Diagnostic criteria of abdominal aortic dilatation

Diameter of the dilated portion of this artery 1.5 larger than the diameter in its proximal arterial segment, evaluated by Doppler ultrasound, was considered diagnostic criterion for AAA.^20,21

Diagnostic criterion for abdominal aortic dilatation was presence of dilatation larger than 20% and smaller than 1.5 the aortic diameter in its proximal arterial segment, evaluated by Doppler ultrasound.^20,21

For statistical evaluation, we chose to evaluate abdominal aortic aneurysms and dilatations together in a group called abdominal aortic dilatation.

Criterion for classification of coronary lesions

Trunk lesions of the left coronary artery were considered significant when ≥ 50% or lesion ≥ 75% in another coronary segment. Degrees of coronary impairment were also assessed, considering number of coronary lesions, independent of degree of stenosis. Coronary lesions were divided into three groups as to number of lesions: in the first group (N1), the patients had only one lesion; in the second (N2), the patients had two or three lesions; and in the third group (N3), the patients had four or more coronary lesions.

Statistical evaluation

Chi-square test was used to verify existence of association between variables.²²

To study the influence of coronary disease in aortic dilatation, uni- and multivariate logistic regression was used, p < 0.05²² being considered significant.

Results

A total of 180 patients were assessed, 57 (31.7%) female and 123 (68.3%) male, with 16 dilatations (8.9%), 15 of them in male patients (93.75%).

Ages varied between 60 and 80 years (mean of 66.7 years). Of the patients included in the study, 79.4% were 70 years or younger, with prevalence of aortic dilatation in 7.7%. In those aged 70 years or older (20.6%), prevalence of dilatation was 13.5%.

Coronary lesions

Evaluation of coronary disease divided as to number of lesions showed the following result: in the first group (N1), the patients had only one lesion (47 cases, 26.1%). In the second group (N2), the patients had two or three lesions (81 cases, 45.0%) and in the third group (N3) the patients had four or more coronary lesions (52 cases, 28.9%).

When comparing the relationship between number of coronary lesions and aortic dilatation, there were two dilatations in N1 (4.5%); six in N2 (7.4%); and eight in N3 (15.4%) (Table 1, Figure 1).

Degree of coronary lesion

Comparative evaluation of coronary lesions, determined by presence and quantity of significant coronary stenoses, presented the following results. In 25 cases (13.9%), the patients did not have significant lesions. One group of 65 cases (36.1%) had significant lesion, and the other 93 cases (50.0%) had two or more significant lesions.

Prevalence of abdominal aortic dilatation as to degree of significant coronary lesion was two (8.0%) in patients without lesions, six (9.2%) in those with one lesion and eight (8.9%) in those with two or more coronary lesions.

Degree of aortic dilatation

By distinguishing AAA dilatation and comparing these cases with those of individuals without aortic disease, there were 164 cases without dilatation (91.1%), six cases (3.4%) of patients with ectasia, and aortic aneurysm was present in 10 cases (5.5%).

Multivariate logistic regression

Multiple logistic regression was also analyzed, considering the variables smoking and number of coronary lesions in the prevalence of abdominal aortic dilatation in the model (variable criterion p < 0.20) (Table 2, Figure 2).

Table 3 presents the combination of factors concerning determination of the risk of presenting abdominal aortic dilatation.

Discussion

Use of Doppler ultrasound for an early diagnosis of abdominal aortic dilatations reduced mortality due to rupture^23,24 and a single measurement in elderly individuals is sufficient to determine presence of AAA.²⁵

Operative mortality of AAA varies among published studies: in the UK trial, it was 5.8%; in the Canadian Aneurysm Study, 4.7%; in Michigan's, 5.6% and in Ontario's, 3.8% (< 70 years of 3%; ≥70 years of 4%),^26-29 and all of them were better than when operated in the emergency room due to AAA rupture, with mortality between 78 and 94%.⁹

Necropsy examinations in the general population show high percentage of ruptured aneurysms as cause of death. (Table 4). Populations such as those presented by Darling et al.,³⁰ showing incidences of similar ruptures in patients with AAA of 4.1-5.0 cm and 5.1-7.0 cm, in autopsy studies, have had a great influence in valuing the risk offered even by small aneurysms.

Cronenwett et al.³⁴ described growths of 0.4-0.5 cm/year, with mean follow-up of 37 months. Out of 73 patients (mean age of 70 years) with aneurysms smaller than 6 cm (mean diameter of 4.3 cm), three (4%) required emergency surgery due to rupture (one death), and 26 (36%) progressed to elective surgical treatment due to increase. In total, 29 (40%) of the patients progressed for surgical treatment over that period, presenting factors associated with higher chance of events.

Kingston carried out a follow-up study of 268 patients with aneurysms smaller than 5 cm in diameter (smaller than 4 cm in 129 of them), stressing the importance of evaluating those individuals sequentially. That study reports that over a mean period of 42 months, there was the need of surgical intervention in 31 individuals (24%) in the latter group (< 4 cm), due to situations such as diameter increase of more than 0.5 cm in 6 months, pain, occlusive disease, peripheral embolism or coexistence of iliac and femoral aneurysms. In the group with aorta between 4 and 5 cm in diameter, 83 out of 139 patients (60%) progressed to surgery over the same period of time.²⁶

Evaluation programs, such as in Kingston study , and subsequent publication by the same author (42 months of follow-up) showed annual growth rates of small aneurysms (4.5-4.9 cm in diameter) of 0.7 cm/year, and conditioned the possibility of reaching proportions of higher risk of rupture to a matter of time. According to the authors, the possibility of elective surgery should be considered, analyzing the situation of each case.^26,35

In the United Kingdom small aneurysm trial, over a 6-year period, out of 1,090 patients (aged between 60-76 years) with AAA (diameter ranging between 4-5.5 cm; mean of 4.6 cm), 61% progressed to surgery due to symptoms or expansion higher than 5.5 cm in diameter. Risk of rupture remained low (1%/year), and expansion rate was 3.3 mm/year.²⁹

A recent survey published by Irvine et al.³⁶ shows a lower mortality rate among patients who underwent abdominal aortic aneurysmectomy when diagnosed by a screening program (mortality 3%) compared with other methods (mortality 9%) (p = 0.05). The first group had lower mean age and better health status.

In a survey carried out by Hallin et al.³⁷, out of 132 publications including 54,048 patients, there was growth rate of 0.2-0.4 cm per year for aneurysms with diameter smaller than 4 cm; from 0.2-0.5 cm to 4.5-5 cm; and for those larger than 5.0 cm, growth was 0.3-0.7 per year. In those same groups, risk of rupture in 4 years was 2, 10 and 22% respectively.

Findings in the literature determine different values to identify aneurysms in screening programs (Table 5).

The findings in the present study do not differ from those in the literature. Considering dilatations larger than 2.5 cm, there were 10.6% (19 out of 180) of cases, comparable to the results obtained by Heather et al.,²⁴ who found 7.8% of patients with aortic diameter larger than 2.5 cm. However, considering proximal diameter of the abdominal aorta, there were dilatations located in 8.9% (16 out of 180) of cases. In 5.0% (nine out of 180) of cases, abdominal aortic diameter was ≥ 3 cm, which does not significantly differ from the previously described findings in the literature.

As to gender, results from the literature, such as those presented by Vardulaki et al.,⁴⁵ in which 2,832 women and 2,203 men were evaluated, there was prevalence of 1.1 and 6.8% respectively, with statistical significance. Similarly, Scott et al.⁴⁰ observed prevalence of dilatation in the male group (7.8%) and in the female group (1.4%). Among our patients, there was high prevalence of male patients (123 out of 180; 68.3%) with mean age of 66.7 years. Fifteen out of 16 dilatations occurred in male patients, with prevalence of 13% (16/123) in this group, and 1.7% (1/57) in the female group (p 0.004 — chi-square).

Since it is more frequent in the elderly, we chose to study it in this group, evaluating its relationship with presence, extension and severity of atherosclerotic coronary disease.

The World Health Organization (WHO) suggests that individuals at 60 years are reported as elderly.⁴⁶ Age is a factor associated with higher frequency of AAA. In the male gender, the highest rate for aneurysm rupture occurs between 65-85 years; for women it increases with age.⁴⁷ Many authors report increase ranging between decades.

Vardulaki et al.⁴⁵ published an article associating AAA with age, with the following intervals: 65-69 years with 2.7% of AAA, 70-74 with 3.9% and 75-79 with prevalence of 4.4%. In this study, mean age was 66.7 years (79.4% with age lower than 70 years); therefore, a lower age group than that discussed in other studies, considering relative risk. However, when dividing patients into groups aged more or less than 70 years, there was no statistical difference as to chance of having aortic dilatation.⁴⁸

A prospective study by the American Cancer Society, including 1 million individuals, verified that users of one to 19 cigarettes/day have incidence 90-155% higher of cardiovascular disease than non-smokers.⁴⁹ Being smoker is a factor related to prevalence of dilatation in all surveyed literature.^10,45

In this study, the chance of smoking patients having aortic dilatation was 6.83 times higher when compared with groups of non-smokers. Considering risk of occurrence of this event, such factor significantly influenced the model of coronary distribution, increasing risk of dilatation.

In coronary disease, which was the objective of this study, when evaluating several classification models of atherosclerotic disease, the number of coronary lesions was correlated with prevalence of abdominal aortic dilatation, indicating that individuals who have a more diffuse atherosclerotic disease, independent of percentage of artery obstruction, present higher probability of abdominal aortic dilatation.

By dividing groups, the individuals with one single lesion had a risk of aortic dilatation of 0.9%, increasing to 1.7% in those with two or three lesions and reaching 4% when there are more than three lesions in the arteries. Similarly, the chance of having aortic dilatation is 1.8 times higher in patients with two or three obstructive atherosclerotic lesions of the coronary artery, when compared with the group of one lesion, and reaches 4.1 times in the group with more than three lesions.

When associated with smoking, the risk significantly increases in all three groups to 6.9, 11.8 and 27.1%, respectively. Therefore, there was a significant difference between groups divided by number of coronary lesions.

Screening programs of AAA are justified to evaluate specific populations with risk factor directly associated with aortic dilatation.^10,45

Conclusion

It can be concluded that prevalence of abdominal aortic dilatation was 8.9% (16 out of 180) in elderly patients with coronary diseases. It was more frequent in male individuals, with diffuse atherosclerotic lesions of the coronary arteries, being more intense in smokers.

References

Manuscript received September 29, 2006, accepted March 7, 2007.

It was presented as free paper at Congresso Brasileiro de Angiologia e Cirurgia Vascular, held in Porto Alegre (Brazil), in 2005.

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Publication Dates

• Publication in this collection
  20 Sept 2007
• Date of issue
  June 2007

History

• Accepted
  07 Mar 2007
• Received
  06 Sept 2006