Are aortic aneurysms caused by atherosclerosis?

Candidate locus analysis of familial ascending aortic aneurysms and dissections confirms the linkage to the chromosome 5q13-14 in Finnish families

OBJECTIVE

The purpose of the study was to carry out a candidate gene analysis in families with familial thoracic aortic aneurysms and dissections.

METHODS

The study material consisted of 11 Finnish families (with 115 members genotyped) who underwent echocardiographic examination for measurement of the aortic root diameter. Selected candidate genes included the loci for Marfan and Ehlers-Danlos syndromes, the genes of matrix metalloproteinases 3 and 9 and tissue inhibitor of metalloproteinase 2 as well two loci on the chromosomes 5q13-14 and 11q23.2-q24, previously found to be linked to the disease.

RESULTS

The chromosomal locus 5q13-14 was linked to the disease risk (nonparametric linkage score 3.0, P =.005) confirming the previous linkage. Other candidate genes and loci were excluded as major loci in these families.

CONCLUSIONS

The identification of the gene at chromosomal location 5q13-14 causing the development of such diseases would give us important knowledge on the pathogenesis of the disease and enable the identification of subjects at risk. This in turn would lead to appropriate treatment before the occurrence of fatal complications and, likely, to the development of new treatment methods.

Mechanisms of abdominal aortic aneurysm formation

Abdominal aortic aneurysms (AAA) are permanent dilations in the infra-renal area in which the arterial tissue is characterized by inflammation and medial degeneration. AAAs are a common vascular disorder and cause significant mortality in the aged population. Despite the high prevalence of this disease, there is limited knowledge on the mechanisms responsible for the vascular pathology. Therefore, current therapeutic options are restricted to surgical intervention and are predicated on the assumed propensity for rupture as the vessel enlarges. Current research focuses on inflammatory processes and their role in proteolytic degradation of the elastin and collagen fibers of the vessel wall. Definition of specific mechanisms would identify target sites for potential pharmacologic intervention and markedly improve the medical treatment and prognosis of AAA.

Height in young adulthood and risk of death from cardiorespiratory disease: a prospective study of male former students of Glasgow University, Scotland

To investigate the association between height in young, socially homogeneous males and cause-specific mortality, the authors conducted a prospective study of 8,361 male former students who underwent medical examinations while attending Glasgow University, Scotland, from 1948 to 1968. The mean age at examination was 20.5 (range, 16.1-30.0) years. The median follow-up time was 41.3 years. There were 863 deaths. In Cox proportional hazards modeling, there was no association between height and all-cause mortality with age-adjusted hazard ratios per 10-cm increase in height (hazard ratio = 0.92, 95% confidence interval: 0.83, 1.02). Height was inversely associated with all cardiovascular disease and coronary heart disease mortality, with hazard ratios per 10-cm increase in height of 0.78 (95% confidence interval: 0.66, 0.93) and 0.76 (95% confidence interval: 0.62, 0.93), respectively. Sizeable inverse associations with stroke and respiratory disease were also found, although these did not reach conventional levels of significance. There was no association with cancer or noncardiorespiratory disease mortality. There was a positive, although nonsignificant, association between height and mortality from aortic aneurysm. Controlling for confounding variables had little effect on these results. The findings suggest that factors operating in early life, and which influence height, also influence future cardiovascular health in men.

Association of a G994 -->T missense mutation in the plasma platelet-activating factor acetylhydrolase gene with risk of abdominal aortic aneurysm in Japanese

OBJECTIVE

To investigate a possible association with plasma platelet activating factor acetylhydrolase (PAF-AH) gene mutation with the risk of abdominal aortic aneurysm (AAA).

SUMMARY BACKGROUND DATA

Plasma platelet activating factor acetylhydrolase is known to catalyze platelet activating factor (PAF), thereby inactivating its inflammatory function. Deficiency of this enzyme is caused by a missense mutation (G994 -->T) in exon 9 of the plasma PAF-AH gene.

METHODS

We did a case-control study including 131 patients (median age 73.4 [range 50-84] years) and 106 controls matched for age and sex. Genomic DNA was analyzed for the mutant allele by a specific polymerase-chain reaction. Plasma PAF-AH activity was measured in both groups.

RESULTS

The frequency of the mutant allele (T allele) in the plasma PAF-AH gene in AAA patients was significantly higher than in control subjects. The association of the missense mutation with AAA was statistically significant and independent of other risk factors. Among AAA patients with normal genomic type, plasma PAF-AH activity was strongly correlated to the plasma concentration of low density lipoprotein cholesterol (LDL-C), while the correlation was not observed among AAA patients with heterozygotes genotype. Patients having AAA with both T allele and hyperlipidemia were more likely to have other atherosclerotic diseases such as ischemic heart disease, stroke and peripheral arterial occlusive diseases than patients with the normal genomic type and normal lipid level.

CONCLUSIONS

The genetic mutation of plasma PAF-AH gene appear to be an independent risk factor for AAA. Our findings need to be confirmed in a larger, prospective study including patients from different populations.

Alpha-tocopherol (vitamin E) and beta-carotene supplementation does not affect the risk for large abdominal aortic aneurysm in a controlled trial

Antioxidants may retard atherogenesis and limit inflammatory processes involved in aneurysm formation. We evaluated effects of alpha-tocopherol and beta-carotene supplementation on incidence of large abdominal aortic aneurysm (AAA) in a randomised, double-blind, placebo-controlled trial. Subjects (n=29133) were 50-69-years-old male smokers, participants in the Finnish alpha-Tocopherol, beta-Carotene Cancer Prevention (ATBC) Study. They were randomised to receive either 50 mg/day of alpha-tocopherol, or 20 mg/day of beta-carotene, or both, or placebo in a 2x2 design. Incidence of AAA was evaluated from mortality and hospital registers. During 5.8 years of follow-up, 181 men were diagnosed with either ruptured AAA (n=77) or nonruptured large AAA treated with aneurysmectomy (n=104). Relative risk (RR) for AAA was 0.83 (95% confidence interval [CI] 0.62-1.11) among men receiving alpha-tocopherol compared with those who did not, and 0.93 (95% CI 0.69-1.24) among men receiving beta-carotene compared with those who did not. A modest though nonsignificant decrease in risk for nonruptured AAA was observed among alpha-tocopherol supplemented men (RR 0.71, 95% CI 0.48-1.04) compared with men not receiving alpha-tocopherol. For beta-carotene, RR for nonruptured AAA was 0.86 (95% CI 0.59-1.27) compared with men not receiving beta-carotene. Neither antioxidant affected risk for ruptured AAA. In conclusion, long-term supplementation with alpha-tocopherol or beta-carotene had no preventive effect on large AAA among male smokers.

Abdominal Aortic Aneurysm in Normotensive Patients: Association with Angiotensin-converting Enzyme Gene Polymorphism

OBJECTIVE AND DESIGN

to assess if deletion of the angiotensin-converting enzyme (ACE) gene is a risk factor for abdominal aortic aneurysms (AAAs) in normotensive patients.

MATERIALS AND METHODS

ACE gene polymorphism was examined by polymerase chain reaction in 124 subjects with AAA and in 112 control subjects. AAA normotensive patients (group A, n=56) were compared to normotensive control subjects (group B, n =112) and to AAA hypertensive patients (group C, n =68). All subjects enrolled in this study were Caucasian and from central and southern Italy.

RESULTS

the distribution of ACE genotypes was: normotensive patients with AAAs (group A): 3 II, 14 ID, 39 DD; normotensive control subjects (group B): 36 II, 48 ID, 28 DD; hypertensive patients with AAAs (group C): 14 II, 32 ID, 22 DD. The DD genotype was more common in group A than in control groups (A vs B p<0.001; A vs C p <0.001). The ID genotype was more common in group A as well (A vs B p <0.05; A vs C p <0.005).

CONCLUSIONS

our data suggest a role for ACE I/D gene polymorphism in the pathogenesis of AAA in normotensive patients.

Ehlers-Danlos syndrome type IV and multiple aortic aneurysms--a case report

Beside atherosclerosis, aortic aneurysms can be part of the clinical spectrum of many systemic diseases, including infectious, inflammatory, genetic and, less often, congenital disorders. A 48-year-old white man presented with multiple large aneurysms of the aorta and its main branches. Medical history was unremarkable except for the presence of a softened abdominal mass since he was 28 years old. On the physical examination, an arterial murmur was heard over the left carotid artery and a palpable mass was noted in the whole right side of the abdomen. No skin or joint abnormalities were noted. Aortography, computed tomography, and magnetic resonance angiography showed multiple large aneurysms of the descending thoracic and abdominal aorta. Aneurysms of the innominate, left subclavian, and carotid arteries were also seen. This case resembles those previously reported, in which multiple aortic aneurysms were associated with abnormalities of the type III procollagen gene (COL3A1). Although the classic stigmas of the Ehlers-Danlos syndrome type IV were lacking, this genetic disease may be the cause of the multiple aneurysms in this patient.

Epidemiology of abdominal aortic aneurysms in the Asian community

BACKGROUND

Studies relating to the ethnic origin of patients with an abdominal aortic aneurysm (AAA) are few and are mainly concerned with the differences between black and white Americans. The purpose of this study was to determine whether the incidence of AAA among the Asian population of Bradford is different from that in the Caucasian population.

METHODS

A retrospective study of patients with an AAA was carried out between 1990 and 1997 using data collected by the Patient Administrative Service, personal databases of the vascular consultants and theatre records. Information about the ethnic composition of the population of Bradford was obtained from the 1991 national census. Demographic data, including ethnic origin and clinical details, were obtained from patient notes.

RESULTS

Two hundred and thirty-three patients with an AAA were identified during the study interval. The Asian population comprised 14.0 per cent of the total population of Bradford. Twenty-eight AAAs would be expected per year. All of the aneurysms identified occurred in the Caucasian population and none in the Asian community.

CONCLUSION

These early results suggest that AAA is rare among the Asian population.

Life-style factors and risk for abdominal aortic aneurysm in a cohort of Finnish male smokers

Prospective studies evaluating risk factors for abdominal aortic aneurysm are few. We studied the association of life-style factors with risk for abdominal aortic aneurysm among 29,133 male smokers 50-69 years of age, participants in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study. During a mean follow-up of 5.8 years, 181 were diagnosed with ruptured abdominal aortic aneurysm or nonruptured abdominal aortic aneurysm plus aneurysmectomy. Risk for abdominal aortic aneurysm was positively associated with age [relative risk (RR) = 4.56, 95% confidence interval (CI) = 2.42-8.61 for > 65 vs < or = 55 years], smoking years (RR = 2.25, 95% CI = 1.33-3.81 for > 40 vs < or = 32 years), systolic blood pressure (RR = 1.92, 95% CI = 1.13-3.25 for > 160 vs < or = 130 mmHg), diastolic blood pressure (RR = 1.80, 95% CI = 1.05-3.08 for > 100 vs < or = 85 mmHg), and serum total cholesterol (RR = 1.85, 95% CI = 1.09-3.12 for > 6.5 vs < or = 5.0 mmol/liter). High-density lipoprotein cholesterol showed a strong inverse association with risk for aortic aneurysm (RR = 0.16, 95% CI = 0.08-0.32 for > 1.5 vs < or = 0.9 mmol/liter). High energy intake was associated with lower risk for aortic aneurysm (RR = 0.59, 95% CI = 0.38-0.94 for the highest quartile vs the lowest), whereas no associations with nutrients were evident. We conclude that classical risk factors for atherosclerotic diseases seem to be important in pathogenesis of large abdominal aortic aneurysms.

Abdominal aortic aneurysm and aortic occlusive disease: a comparison of risk factors and inflammatory response

OBJECTIVE

to compare patients with abdominal aortic aneurysm (AAA) and aortic occlusive disease (AOD) with regard to risk factors for atherosclerosis, co-morbid conditions and inflammatory activity.

PATIENTS AND METHODS

a total of 155 patients undergoing abdominal aortic surgery between January 1993 and October 1997: 82 (53%) had aneurysmal disease and 73 (47%) had occlusive disease. Principal risk factors were compared: age; gender; smoking; hypertension; hyperlipidaemia; diabetes mellitus; severe peripheral vascular disease (PVD) and ischaemic heart disease. Aortic wall tissue samples were obtained during surgery. A prospective blind analysis was performed for the presence of inflammatory cytokines TNF-alpha, IL-1 beta, IL-6 and TGF-beta.

RESULTS

the average age of AAA patients was 74 years (50-88), while that of AOD patients was 61 years (43-82) (p<0.0001). Diabetes mellitus was found to be much more prevalent in the AOD group (p<0.001), while hypertension and severe PVD were more prevalent in the AAA group (p<0.001). No differences were found concerning any of the risk factors. Inflammatory cytokine activity: AAA tissue samples contained significantly higher mean TNF-alpha and IL-6 levels compared to the AOD samples (5.6+/-2.7 x 10 E-4 vs. 4.4+/-2.7 x 10 E-5 atmoles/microl (p=0. 01), and 0.6+/-0.4 vs. 0.01+/-0.006 atmoles/microl (p=0.02) respectively). No differences were found related to IL-1 beta and TGF-beta.

CONCLUSIONS

(1) Patients with AAA have fewer atherosclerotic risk factors than do patients with AOD. (2) Patients with AAA and AOD have significantly different inflammatory activity. (3) The data supports the hypothesis that AAA and AOD are probably two different pathological entities.

Updated mortality among diverse operating segments of a petroleum company

OBJECTIVES

To update mortality for 34 560 employees from diverse operating segments of a Canadian petroleum company; and to investigate potential relations with occupational factors.

METHODS

Employees from 1964-83 were linked to the Canadian mortality data base to provide 11 years additional follow up. There were 6760 deaths and 750 683 person-years of follow up compared with 3909 and 428 190, respectively, in the earlier study. Analyses used standardised mortality ratios (SMRs) to compare worker cause specific mortality with the Canadian general population. Duration of employment and latency analyses were performed for causes previously found to be increased in this and other petroleum cohorts, as well as any findings of interest.

RESULTS

For the period 1964-94, employees experienced significantly low overall mortality (SMR=0.86 men, SMR=0.80 women). Kidney cancer, which has been increased in some studies of petroleum workers, was not increased. Acute non-lymphocytic leukaemia in exposed operating segments was consistent with the expected or only slightly, non-significantly increased. The most notable finding was increased deaths from mesothelioma among refinery and petrochemical workers (SMR 8.68; 95% confidence interval (95% CI) 5.51 to 13.03), most of whom were long term employees in jobs with presumed exposure to asbestos (mechanical and pipefitters). Deaths from multiple myeloma among marketing and distribution workers, which were previously increased, remained increased (SMR 2.08; 95% CI 0.95 to 3.95) in the update period 1984-94; however, there was no clear pattern by duration of employment or latency. Aortic aneurysms, which also were previously significantly increased among marketing and distribution workers approached the expected in the update period (SMR 1.18; 95% CI 0. 65-1.98). Analyses by duration of employment showed suggestive trends for aortic aneurysms, but earlier studies of this cohort have not found a relation between aortic aneurysms and exposure to hydrocarbons.

CONCLUSION

The additional 2851 deaths and 322 493 person-years of follow up strengthened the assessment of mortality patterns relative to occupational factors. With the exception of mesothelioma, no clear work related increases in disease were identified.

Increased matrix metalloproteinase 2 expression in vascular smooth muscle cells cultured from abdominal aortic aneurysms

OBJECTIVES

Recent evidence has implicated matrix metalloproteinase 2 (MMP-2) in the pathogenesis of aneurysms. The aim of this study was to examine MMP-2 production and expression by aortic smooth muscle cells (SMCs) and dermal fibroblasts derived from patients with abdominal aortic aneurysms (AAAs).

METHODS

Aortic SMCs and dermal fibroblasts were cultured from patients with AAAs or from age-matched controls with atherosclerosis. The production of MMP and tissue inhibitor of metalloproteinase into culture media was analyzed with the use of gelatin zymography, Western blotting, and enzyme-linked immunosorbent assay. Gene expression was analyzed with Northern blotting.

RESULTS

All cells studied constitutively produced MMP-2. Aortic SMCs cultured from aneurysmal tissue expressed MMP-2 protein and messenger RNA at a significantly higher level than SMCs from controls (P =.008). Dermal fibroblasts from patients with AAAs expressed MMP-2 at a similar level to controls. In both cell types, tissue inhibitor of metalloproteinase 2 and membrane type 1-MMP were expressed at similar levels.

CONCLUSIONS

These data suggested that the regulation of MMP-2 gene expression was altered in the aortic SMCs of patients with aneurysms, but this finding was not repeated in other mesenchymal tissue.

Dilation and reduced distensibility of carotid artery in patients with abdominal aortic aneurysms

BACKGROUND

Although patients with abdominal aortic aneurysms (AAA) frequently have coexisting systemic atherosclerosis, the dilatative manifestation of AAA is the opposite of the occlusion characteristic of atherosclerotic disease. It has been suggested that this dilatative disease is caused by an alteration in connective tissue metabolism in systemic arterial wall. Such a condition might alter systemic arterial diameter and wall behavior. We investigated arterial characteristics in AAA patients, including morphologic changes and wall mechanics in the carotid artery.

METHODS AND RESULTS

Atherosclerotic intimal changes such as intima-media thickness (IMT), plaque formation, diameter, and wall elasticity of the carotid artery were determined ultrasonographically in patients with AAA (n = 102) and compared with age-matched patients with the atherosclerotic diseases arteriosclerosis obliterans (ASO, n = 115) and coronary artery disease (CAD, n = 123) and with age-matched healthy control patients (CTL, n = 45). Intimal disease in AAA was significantly milder than in ASO, at the same level as CAD, and more severe than in CTL. Although end-diastolic luminal diameters (mm) in AAA (7.05 +/- 1.08), ASO (6.74 +/- 0.18), and CAD (6.66 +/- 0.83) were significantly higher than in CTL (5.97 +/- 0.93), they were also excessively increased compared with the equivalent diameters seen in ASO (P <.01) and CAD (P <.01). Luminal distensibility (x 10(-6) cm(2). dyne(-1)) in AAA (0.83 +/- 0.48) was excessively decreased compared not only with CTL (1.70 +/- 1.11, P <.01) but also with ASO (1.12 +/- 0.47, P <.01) and CAD (1.18 +/- 0.59, P <. 01). These relations remained true when adjusted for blood pressure and luminal diameter. Intra-AAA group analysis showed that distensibility in ruptured cases (n = 14) was significantly lower than in nonruptured cases (n = 88) (0.58 +/- 0.24 vs 0.88 +/- 0.50, P <.05).

CONCLUSIONS

Excessive arterial dilation and reduced distensibility without severe intimal disease were found in the carotid arteries of patients with AAA. This suggests that these patients may be subject to systemic arterial alterations, including structural and functional abnormalities.

Smoking, lung function and the prognosis of abdominal aortic aneurysm. The UK Small Aneurysm Trial Participants

BACKGROUND

the UK Small Aneurysm Trial was established to test the benefit of prophylactic elective surgery for small abdominal aortic aneurysms (4.0-5.5 cm in diameter) and identify prognostic risk factors, including smoking. PATIENTS, METHODS AND OUTCOMES: one thousand and ninety patients (902 men and 188 women, mean age 69.3 years) were randomised to either early elective surgery or ultrasonography surveillance until the aneurysm diameter exceeded 5. 5 cm, mean follow-up was 4.6 years. Baseline assessments included lung function tests and cotinine (a smoking marker). The principal outcome measures were all-cause mortality and aneurysm rupture.

RESULTS

during the course of the trial, aneurysm rupture was diagnosed in 25 patients and 309 patients died. Whereas self-reported smoking status was not significantly associated with survival, patients without any trace of plasma cotinine had a significantly improved long-term (6-year) survival, p=0.02. Current smokers had a lower FEV(1)than past- and never-smokers. FEV(1)was the most powerful predictor of long-term (6-year) survival, the crude death rates per 100 person-years were 9.1, 6.9 and 4.6 for those with FEV(1)<1.9 l, 1.9-2.5 l and >2.5 l respectively, p=0.001. Moreover, the rupture rate was 1.9% per year for patients positive for plasma cotinine compared with 0.5% in those without trace of plasma cotinine, p=0.004.

CONCLUSIONS

self-reported smoking status underestimates the effect of continued smoking on the prognosis of patients with small abdominal aortic aneurysm. Patients with high plasma cotinine concentrations (smokers) have an increased risk of aneurysm rupture and poorer long-term survival.

Natural history, pathogenesis, and etiology of thoracic aortic aneurysms and dissections

The natural history of thoracic aortic aneurysms and dissections is diverse, reflecting a broad spectrum of etiologies which include increasing aortic size, hypertension, and genetic factors. The pathogenesis is related to defects or degeneration in structural integrity of the adventitia, not the media, which is required for aneurysm formation. The ascending and descending aorta appear to have separate underlying disease processor that lead to a weakened vessel wall and an increased susceptibility for dissection. Etiologic factors for aortic aneurysms and dissections are multifactorial, reflecting genetic, environmental, and physiologic influences.

Evaluation of aneurysm models, particularly of the aorta and cerebral arteries

Irrespective of their intended use, the best models of spontaneous aneurysms in humans are produced under conditions analogous to those occurring in humans and specific for the site. Even if appropriate for other purposes, models dependent on artificial conditions (physical and thermal trauma, chemical and enzymatic degradative processes), not in compliance with the above, bear no relationship to the etiology or pathology of the lesion or disease under investigation. Surgical models of poststenotic dilatation and aneurysm, arteriovenous shunts, and venous graft aneurysms are suitable for study of the prevailing hemodynamics and pathological effects of the associated stresses on the vessel wall which have bearing on degenerative aneurysms at other sites. The protracted course of atherosclerosis and constraints of time and research funds when reproducing the pathology and conditions prevailing in the human situation legitimize the use of models which accelerate development and complications. The limitations of any model are of paramount consideration. The value of some current models of aortic and cerebral aneurysms is discussed.

Improved graft patency and altered remodeling in infrainguinal vein graft reconstruction for aneurysmal versus occlusive disease

PURPOSE

This study attempted to determine whether autogenous vein used for infrainguinal reconstruction in patients with aneurysmal disease might demonstrate an altered adaptive response compared with those patients who underwent reconstructive surgery for occlusive disease, potentially altering graft patency.

METHODS

From 1974 to 1997, 43 patients underwent vein grafting for 60 popliteal artery aneurysms (PAA).

RESULTS

In an attempt to monitor early vein graft adaptation, serial graft surveillance by Duplex ultrasound scan was performed in a statistically valid subset of age-, sex-, and distal anastomotic site-matched patients with PAA and patients with occlusive disease (OD; n = 8 PAA; n = 8 OD). Compared with an age-matched and sex-matched cohort of patients (n = 60 grafts in each group) with occlusive disease and who had femoral below-knee bypass grafts (FBP) only, patients undergoing infrainguinal reconstruction for PAA had a higher 5-year primary graft patency (92% +/- 4% for PAA vs 66% +/- 7% for FBP; P <.01). Duplex surveillance demonstrated a progressive increase in arterialized vein graft diameter in the PAA group versus the OD group. In univariant analysis, aneurysmal disease was a significant predictor of final follow-up diameter (P =.002). In a linear regression model, controlling for diameter at first follow-up after bypass grafting, first follow-up diameter was also predictive of final follow-up diameter.

CONCLUSION

These data suggested altered remodeling of vein grafts in patients with popliteal artery aneurysm, which may have a beneficial effect on patency.

Amlodipine potentiates metalloproteinase activity and accelerates elastin degradation in a model of aneurysmal disease

AIMS

Abdominal aortic aneurysms are characterised by changes in the extracellular matrix of the arterial media, in particular a reduction in elastin concentration. These changes are mediated by increased levels of endogenous matrix metalloproteinases (MMPs). Recently, calcium channel blockers have been shown to increase the proteolytic activity of MMP-2 secreted by vascular smooth muscle cells. It may therefore by hypothesised that calcium antagonists may potentiate the activity of MMPs in aneurysmal disease and thus accelerate AAA expansion. In this study, the ability of amlodipine--a calcium antagonist--to influence elastin degradation, was assessed in a previously described model of aneurysmal disease.

METHODS

Porcine aortic segments (n = 8) were pre-incubated in exogenous pancreatic elastase for 24 h prior to culture in standard conditions for 6 days with 10 and 100 micrograms/l amlodipine. Control segments were cultured both with and without amlodipine and without elastase. At the termination of culture MMPs were extracted from the tissue and quantified by a combination of substrate gel enzymography and immunoblotting. The volume fractions of elastin and collagen were determined by stereological analysis of EVG stained sections.

RESULTS

Gel enzymography demonstrated significantly increased MMP-9 activity in the amlodipine treated segments, median 4.218 vs. 2.809 arbitrary units (p < 0.01) and this elevated activity was reflected in a significant destruction of medial elastin 27.0 vs. 40.5% (p < 0.05).

CONCLUSION

Therapeutic ranges of amlodipine significantly enhanced elastin degradation and potentiated MMP-9 activity within the aortic organ cultures.

Population-based record linkage study of the incidence of abdominal aortic aneurysm in Western Australia in 1985-1994

BACKGROUND

The incidence of abdominal aortic aneurysm (AAA) has increased steadily during the past 30 years.

METHODS

Trends in the incidence and surgical intervention for AAA in Western Australia were reviewed for the interval 1985-1994. A population-based health database was used to link morbidity and mortality records of all patients aged 55 years or more who died from rupture or were admitted and treated surgically for AAA. Three groups were separated for analysis: patients with a ruptured AAA, those admitted for elective repair and those admitted as an emergency with an acute (non-ruptured) aneurysm.

RESULTS

There was a decline in the incidence of both emergency and elective procedures for AAA after 1992. While the mortality rate from ruptured AAA has also fallen since 1991, the overall case fatality rate for ruptured AAA has fallen by only 1.3 per cent (from 80.7 to 79.3 per cent).

CONCLUSION

The decline in mortality rate and emergency procedures may result from a fall in the incidence of ruptured AAA, due to an increasing rate of elective surgery before 1992. The decline in elective procedures from 1992 may be due to a fall in the prevalence of AAA owing to high rates of elective surgery, or to a fall in the incidence of the disease itself.

Epidemiology and potential for prevention of abdominal aortic aneurysm

BACKGROUND

Ruptured abdominal aortic aneurysm (AAA) is a common cause of death which is preventable by elective repair of an asymptomatic AAA.

METHODS

The literature was reviewed with emphasis on epidemiological studies and population-based screening surveys.

RESULTS AND CONCLUSION

The prevalence of small AAA ranges between 3 and 8 per cent. The incidence of asymptomatic AAA seems to be increasing, although exact incidence estimates vary. The most important risk factors for AAA are male sex, age, family history and smoking. Hypertension is associated with a mildly increased risk, but diabetes is not associated with any increase. Primary prevention of AAA is not a realistic option. There is no evidence of an effective medical treatment to prevent growth of small AAAs, although trials with propranolol are under way. The only intervention to prevent death from aneurysm is elective repair of the asymptomatic lesion. Screening for asymptomatic AAA can reduce the incidence of rupture. However, further studies are needed to determine the cost effectiveness of screening compared with that of other health programmes.

Unrestricted usage of immunoglobulin heavy chain genes in B cells infiltrating the wall of atherosclerotic abdominal aortic aneurysms

The aim of this study was to provide evidence for the hypothesis that the B cell rich infiltrate concentrated in the adventitia of atherosclerotic abdominal aortic aneurysms is an autoimmune response to specific tissue antigens. Detailed histological examination of biopsies from 26 atherosclerotic abdominal aortic aneurysms showed in the adventitia, the presence of lymphoid follicles in 7/26 (27%) and of plasma cells in all cases. DNA prepared from the outer aneurysm wall (n = 25) was amplified using the polymerase chain reaction to investigate the repertoire of the immunoglobulin heavy chain (VH) genes used. Amplification of the VDJ region of VH, using both framework 2 and 3 primers, revealed unrestricted usage of the VH gene in 24/25 cases. The only case where restricted usage of the VH genes was observed, might have been attributable to severe virally-induced tissue inflammation. These results indicate that, in the vast majority of atherosclerotic abdominal aortic aneurysms, the B cell rich adventitial infiltrates are not an autoimmune response to a limited repertoire of tissue antigens.

Relationship of cardiovascular risk factors to racial differences in femoral bypass surgery and abdominal aortic aneurysmectomy in Massachusetts

Atherosclerosis is more severe in blacks than in whites, but abdominal aortic aneurysms, which have traditionally been thought to have an atherosclerotic etiology, appear to be less common in blacks. Because of this incongruity, we compared risk factor profiles in patients undergoing abdominal aortic aneurysm repair and patients undergoing femoral bypass for atherosclerotic occlusive disease. A dual case-control study was conducted, first, comparing patients who had undergone aneurysmectomy to a control group of patients who had undergone appendectomy; and then comparing patients who had undergone femoral bypass surgery to the same appendectomy controls. We initially used hospital discharge data for the entire state of Massachusetts and, in a second phase, data obtained from a review of medical records from Boston University Medical Center Hospital and Boston City Hospital. The statewide database indicated that rates of femoral bypass surgery were higher in blacks than in whites, but after adjusting for differences in hypertension, diabetes, and low socioeconomic status, the black/white odds ratio for femoral bypass fell to 1.44 (95% confidence interval: 1.08, 1.92). A similar analysis based on the hospital chart review, provided better control of confounding and indicated that there was no racial difference in rates of femoral bypass after correcting for other risk factors (odds ratio = 0.94; 95% confidence interval: 0.40, 2.22; p = 0.90). In contrast, the statewide database found higher rates of abdominal aortic aneurysm surgery in whites, and particularly in white males. Smoking and hypertension were strong risk factors for aneurysmectomy, but diabetes mellitus and socioeconomic status were not. After adjusting for other variables, the black/white odds ratio for aneurysmectomy was 0.29 (95% confidence interval: 0.07, 1.23; p = 0.09).

CONCLUSIONS

Substantial differences are found in the risk factor profiles for aneurysmal disease and femoral atherosclerotic occlusive disease. Diabetes is a particularly strong risk factor for femoral disease, but not for aneurysmal disease. In addition, blacks had higher rates of femoral bypass surgery in Massachusetts, but the apparent racial difference appeared to be due to a greater prevalence of hypertension, smoking, and diabetes in blacks. In contrast, abdominal aortic aneurysms occurred predominantly in white males, and adjustment for other risk factors further accentuated the greater risk in whites.

Interaction between fibrillin genotype and blood pressure and the development of aneurysmal disease

Debate as to whether abdominal aortic aneurysms (AAA) are caused by atherosclerosis or whether they have a strong genetic etiology continues. We have investigated the hypothesis that risk factors are likely to be strongest in patients with generalized aneurysmal disease. We screened 232 consecutive AAA patients for popliteal aneurysm and investigated cardiovascular and genetic risk factors in these patients. Ultrasonography demonstrated the presence of a popliteal aneurysm in 24 of 232 (10%) patients. Multivariate analysis identified four independent factors associated with popliteal aneurysm: age (p = 0.013), height (p = 0.017), triglyceride concentration (p = 0.009), and systolic blood pressure (p = 0.037). In the AAA patients a significant association of fibrillin-1 genotype was present, determined by a tandem repeat polymorphism, with both systolic and pulse pressure. The genotypes associated with the highest pressures were significantly more common among the patients with popliteal aneurysm, p = 0.03. Following these findings we investigated whether there was an association between fibrillin-1 genotype and blood pressure in a healthy population, 245 men aged 50-61 years. Again we found a significant association between fibrillin genotype and pulse pressure, p = 0.003. We suggest that a strong interaction occurs between fibrillin genotype and blood pressure which contributes to the development of aneurysmal disease.

Increasing incidence of aneurysms of the abdominal aorta in The Netherlands

OBJECTIVES

To study the trend in incidence of aneurysms of the abdominal aorta in The Netherlands during the past two decades.

SETTING

The Dutch population from 1972 to 1992.

DESIGN

Analysis of all hospital admissions and deaths due to aneurysms of the abdominal aorta.

OUTCOME MEASURES

Age adjusted and age specific mortality and discharge rates. In-hospital mortality after surgery upon aneurysms of the abdominal aorta.

RESULTS

From 1972 to 1992 age adjusted mortality from aneurysms of the abdominal aorta rose from 3.1 to 8.1 per 100,000 in men, and from 1.4 to 2.2 in women. Age adjusted discharge rates (alive and dead) for non-ruptured abdominal aortic aneurysms increased from 3.7 to 37.6 per 100,000 in men and from 1.2 to 5.5 in women. For ruptured aneurysms, the age adjusted discharge rates increased from 2.4 to 10.3 per 100,000 in men and from 0.7 to 1.7 in women. Age adjusted in-hospital mortality after surgery upon non-ruptured aneurysms was halved from 13% in 1972 to 7% in 1992, mortality after acute repair upon ruptured aneurysms also decreased from 52% in 1972 to 36% in 1992.

CONCLUSIONS

There was an impressive increase in the hospital based incidence for aneurysms of the abdominal aorta during the past two decades in The Netherlands. An improved detection rate through ultrasound is probably a major contributor to this increase, but gender differences and the rise in the number of ruptured aneurysms suggest that a real increase in incidence may exist, especially in men. Surgical outcome for both ruptured and non-ruptured aneurysms of the abdominal aorta improved.

Unravelling the familial tendency to aneurysmal disease: popliteal aneurysm, hypertension and fibrillin genotype

PURPOSE

To screen patients with abdominal aortic aneurysm for popliteal aneurysm and investigate cardiovascular and genetic risk factors associated with aneurysmal disease at more than one site (generalised aneurysmal disease). SUBJECTS, DESIGN AND SETTING: All patients referred to the Regional Vascular Surgical Service at Charing Cross Hospital with unruptured abdominal aortic aneurysm between 1989 and 1993 were screened for popliteal aneurysms, using ultrasonography.

MAIN OUTCOME MEASURES

Palpation of a popliteal aneurysm or ultrasonographic detection of popliteal dilatation, where the ratio maximum popliteal fossa diameter/suprageniculate popliteal diameter was > or = 1.5, in relation to cardiovascular and genetic risk factors.

RESULTS

Clinical examination detected popliteal aneurysms in only 11/232 patients (5%), but ultrasonography demonstrated the presence of popliteal aneurysm in a further 13 patients, 24/232 in total (10%). Multivariate regression identified four independent factors associated with popliteal dilatation disease: age (p = 0.046), height (p = 0.006), systolic hypertension (p = 0.037) and triglyceride concentration (p = 0.009). Generalised aneurysmal disease and systolic blood pressure were associated with polymorphic variation in the fibrillin-1 gene, but not with variations in the apolipoprotein B and type III collagen genes.

CONCLUSIONS

Few patients with abdominal aortic aneurysm (10%) also have popliteal aneurysms: the risk of popliteal dilatation increases with age, height, systolic blood pressure, triglyceride concentration and fibrillin genotype. The strong interaction between fibrillin genotype and blood pressure may contribute to the familial tendency to aortic aneurysm.

The aorta. Aortic aneurysm, trauma, and dissection

Because of the close relationship between the esophagus and the aorta, multiplane transesophageal echocardiography provides an excellent way to view the thoracic aorta. In this article, clinical features of aortic aneurysm, trauma, and aortic dissection are described, as is the potential use of transesophageal echocardiography in the assessment of these entities.

Risk factors for abdominal aortic aneurysms in smokers

OBJECTIVE

To investigate features of the smoking habit and other cardiovascular risk factors associated with the development of abdominal aortic aneurysm in smokers.

DESIGN AND SETTING

Case control study of smokers recruited, between 1989 and 1992, in a London teaching hospital.

SUBJECTS

Consecutive smokers referred with abdominal aortic aneurysm (cases n=44) and 244 age and sex-matched smokers attending Dermatology, Orthopaedic and Urology clinics (controls).

MAIN RESULTS

Hypertension was more common amongst the patients with aneurysm (30%) than the controls (19%). Measured systolic and diastolic blood pressures were significantly higher in the aneurysm patients. The relative risk of having an abdominal aortic aneurysm increased 3.4-fold (95% CI 1.06-10.89) for those with a diastolic blood pressure of >90mmHg, p=0.035 and 4.1-fold (95% CI 1.27-13.16) for those with a mean arterial pressure > or = 100mmHg, p=0.009. Plasma lipids, fibrinogen and cotinine were similar amongst patients with aneurysm and controls. The cumulative smoking exposure was similar in the patients with aneurysm and controls, median 49 and 44 pack-years respectively. The relative risk of developing an aneurysm increased with the number of cigarettes currently smoked, p=0.008, and with increasing depth of inhalation, p=0.025, but was not associated with the tar or nicotine yield of current cigarettes.

CONCLUSIONS

In smokers, the risk of developing an abdominal aortic aneurysm increases with increasing mean arterial and diastolic blood pressure and two aspects of current smoking habit: the number of cigarettes currently smoked and the depth of inhalation.

A mural thrombus of an infrarenal aortic aneurysm demonstrated as photon deficiency in a radionuclide study

Radionuclide angiogram (RNA) and aortogram may underestimate external aneurysmal diameter. Photon deficient areas are not uncommon along the abdominal aortic aneurysm (AAA) on RNA. To determine whether or not photon deficient areas along the aneurysm could represent a large thrombus, we studied radionuclide aortic angiography in thirty-eight patients during a preoperative cardiac gated study. All the patients (men, ages from 60 to 78) had CT, US, and/or aortogram for comparison. The presence of a thrombus was determined by CT, US, and/or surgical findings. Twelve of 38 (32%) patients' RNA and blood pool images showed photon deficient areas along the aneurysmal walls having a large concentric or eccentric thrombus of the AAA. A large photon deficient area could be detected along the narrowing calibre of the aorta lumen. This finding results from a large mural thrombus being interposed between the left or right bowel/mesentery activity and the activity of the aneurysms functioning patent lumen. We concluded that a photon deficient area along an inferorenal aortic aneurysm may indicate a large thrombus of either eccentric or concentric type within an AAA.

Predictors of myocardial lesions in men with minimal coronary atherosclerosis at autopsy. The Honolulu heart program

Some cardiovascular risk factors are associated with clinical coronary heart disease but not with autopsy evidence of coronary atherosclerosis. To determine whether these risk factors might operate through mechanisms other than atherosclerosis, we examined associations between cardiovascular risk factors and subsequent intramural myocardial lesions assessed by protocol autopsy between 1965 and 1984 in 120 Japanese-American men from the Honolulu Heart Program who had minimal coronary atherosclerosis (American Heart Association (AHA) panel score < 3 on scale of 1 to 7). Age-adjusted prevalence of myocardial lesions was related to smoking status (P < 0.01), as well as amount, duration, and pack-years of smoking (P < 0.03). In a multiple logistic model, smoking (20 pack-years) was directly associated and fish intake (> or = 2 times/wk) was inversely associated with myocardial lesions independently of age, cholesterol, systolic blood pressure, body mass index, alcohol, diabetes, total calories, and animal protein intake (odds ratio (OR) = 1.5, 95% confidence intervals (CI) = 1.1 to 2.0 and OR = 0.35, 95% CI = 0.2 to 0.9, respectively). The protective effect of fish intake was most evident among men who did not have hypertension at baseline. Indices of obesity, body fat distribution, and physical activity and levels of triglyceride and alcohol intake were not associated with myocardial lesions. Thus, the adverse effects of smoking and the protective effects of fish consumption may extend to individuals relatively free of coronary atherosclerosis, possibly through hemostatic mechanisms or effects on small intramural arteries.

Epidemiology of aortic aneurysm in the United States

Recent apparent increases in occurrence of aortic aneurysm were reported for abdominal aortic aneurysm from several countries. In order to assess U.S. trends, an analysis of mortality and hospitalization data from the National Center for Health Statistics for aortic aneurysm in the United States in 1979-1992 was performed. In 1991, 16,696 deaths were attributed to aortic aneurysm, abdominal aneurysm accounting for 52%. Between 1979 and 1990, dissecting aneurysm death rates showed inconsistent changes in males and slight increases in females. Age-adjusted rates were higher in blacks than whites, and in males than females. Death rates for abdominal aneurysms showed slight decreases in white males and slight increases in black males and white females. Rates were higher in whites than blacks, and in males than females. The number of hospital discharges with a first-listed diagnosis of aortic aneurysm increased from 39,000 in 1979 to 67,000 in 1992. The rate of diagnoses increased from 1979 to 1984 with no consistent change thereafter for total and abdominal aneurysms, which comprised over 75% of total diagnoses. The number of all-listed aortic aneurysm resections with graft replacement increased from 10,000 in 1979 to 40,000 in 1988 with no consistent change thereafter. Increased utilization of diagnostic ultrasound of the abdomen and retroperitoneum leading to improved case finding for abdominal aneurysms may have been one cause of increasing hospital discharge rates prior to 1985. Continued monitoring of national data on mortality and morbidity from aortic aneurysms is desirable to assess effects of diagnostic, therapeutic, and preventive interventions.

The role of vitamin D3 in the aetiology of abdominal aortic aneurysms

Abdominal aortic aneurysms (AAAs) have traditionally been attributed to atherosclerosis, although there is increasing epidemiological, biochemical and genetic evidence that aneurysmal arterial disease is different from occlusive atherosclerosis. One of the most consistent biochemical findings in the aneurysmal aorta is a significant reduction in elastin protein; the cause, for this remains unclear. There is in vitro evidence that vitamin D3 (1,25 dihydrocholecalciferol) inhibits the production of elastin by smooth muscle cells. On the basis of this observation and the possibility that some subjects may be exposed to excess vitamin D3, the hypothesis that vitamin D3 may be a previously unrecognized aetiological factor in the pathogenesis of AAA is developed.

Production and localization of 92-kilodalton gelatinase in abdominal aortic aneurysms. An elastolytic metalloproteinase expressed by aneurysm-infiltrating macrophages

Abdominal aortic aneurysms (AAA) are characterized by disruption and degradation of the elastic media, yet the elastolytic proteinases involved and their cellular sources are undefined. We examined if 92-kD gelatinase, an elastolytic matrix metalloproteinase, participates in the pathobiology of AAA. Gelatin zymography of conditioned medium from normal, atheroocclusive disease (AOD), or AAA tissues in organ culture showed that all tissues produced 72-kD gelatinase. AOD and AAA cultures also secreted 92-kD gelatinase, but significantly more enzyme was released from AAA tissues. ELISA confirmed that AAA tissues released approximately 2-fold more 92-kD gelatinase than AOD tissue and approximately 10-fold more than normal aorta. Phorbol ester induced a 5.3-fold increase in 92-kD gelatinase secretion by normal aorta and AOD and an 11.5-fold increase by AAA. By immunohistochemistry, 92-kD gelatinase was not detected in normal aorta and was only occasionally seen within the neointimal lesions of AOD tissue. In all AAA specimens, however, 92-kD gelatinase was readily localized to numerous macrophages in the media and at the adventitial-medial junction. The expression of 92-kD gelatinase mRNA by aneurysm-infiltrating macrophages was confirmed by in situ hybridization. These results demonstrate that diseased aortic tissues secrete greater amounts of gelatinolytic activity than normal aorta primarily due to increased production of 92-kD gelatinase. In addition, the localization of 92-kD gelatinase to macrophages in the damaged wall of aneurysmal aortas suggests that chronic release of this elastolytic metalloproteinase contributes to extracellular matrix degradation in AAA.

Atherosclerotic aneurysm formation in an in situ saphenous vein graft

Nonanastomotic aneurysm formation in autogenous vein grafts, although rarely described, has been uniformly associated with advanced atherosclerotic change of the vein wall. In the case reported, histologic examination of an in situ vein graft aneurysm demonstrates obliteration of normal vessel wall architecture by penetrating atherosclerotic plaque. Although these findings do not prove a causal relationship, they do provide additional support for atherosclerosis as an etiologic factor in aneurysm disease.

Evaluation of thoracic aortic atherosclerosis by transesophageal echocardiography

Transesophageal echocardiography (TEE) provides excellent images of the thoracic aorta, which cannot be visualized by transthoracic echocardiography. The purpose of this study was to assess atherosis and sclerosis of the thoracic aorta by TEE, to evaluate the risk factors for atherosis and sclerosis, and to assess the relationship between the two components of atherosclerosis. The mean value of the maximum thickness of the intima-media complex in the six segments of the thoracic aorta (MIMC) was used as an index of atherosis, and the stiffness parameter beta was used as an index of sclerosis. The study population consisted of 88 Japanese patients. Multivariate analysis showed that age, low-density lipoprotein cholesterol (or apolipoprotein B), and diabetes mellitus were significantly and independently related to MIMC, whereas age and hypertension were related to the stiffness parameter beta. Both components of atherosclerosis demonstrated a significant although weak relationship. The risk factors for atherosis appear to differ from those for sclerosis in the thoracic aorta, so we should evaluate these two components of atherosclerosis separately. TEE is a useful method of assessing thoracic aortic atherosclerosis because both atherosis and sclerosis can be examined simultaneously.

Extracellular matrix degrading metalloproteinases in the pathogenesis of arteriosclerosis

We review the importance of extracellular matrix remodelling to the processes of vascular smooth muscle cell migration and proliferation that contribute to morphogenesis of the atherosclerotic plaque. In particular, the role of the matrix degrading metalloproteinase (MMP) family is discussed. This family of neutral, ZN(2+)-requiring enzymes are capable, in principle, of degrading all matrix proteins. Their activity is tightly controlled, however, at the level of synthesis of the inactive zymogens, activation by limited proteolysis and binding to endogenous inhibitor proteins (TIMPs). Direct evidence is presented for the involvement of MMPs in proliferation and outgrowth of vascular smooth muscle cells from explants of rabbit aorta in vitro. This was obtained using two structurally-unrelated inhibitors of MMPs, Ro 31-4724 and Ro 31-7467, both of which inhibited proliferation of cells in a concentration-dependent manner, Ro 31-4724 also inhibited outgrowth. Rabbit aortic smooth muscle cells were further shown to release MMPs, namely a 95 and a 72 kDa gelatinases that were inhibited by Ro 31-4724 and Ro 31-7467. The evidence suggests that degradation of basement membrane by gelatinase is required for proliferation and outgrowth of these cells. The implications of these findings for the pathogenesis and treatment of atherosclerosis are also discussed.