The UK Endovascular Aneurysm Repair (EVAR) Trials: Design, Methodology and Progress

OBJECTIVES

The endovascular aneurysm repair (EVAR) trials aim to assess the efficacy of EVAR in the treatment of AAA in terms of mortality, quality of life, durability and cost-effectiveness.

DESIGN

Male and female patients aged at least 60 years with an AAA diameter measuring at least 5.5 cm on a computed tomography (CT) scan are assessed for anatomical suitability for EVAR. Suitable patients are offered entry either into EVAR Trial 1 if they are considered fit for conventional open repair or EVAR Trial 2 if they are considered unfit. EVAR 1 randomly allocates patients to EVAR or open repair and EVAR 2 randomly allocates patients to EVAR with best medical treatment or best medical treatment alone. Target recruitment for EVAR Trials 1 and 2 is 900 and 280 patients, respectively.

PROGRESS

Recruitment began in September 1999 and there are currently 40 UK centres participating in the trials. Monthly targets are being exceeded in EVAR Trial 1 with 1037 patients randomised by October 2003. EVAR Trial 2 is also meeting monthly targets with a total of 319 patients randomised. When recruitment closes in December 2003 patients will need to be followed for at least 1 year from their operation. Publication of full results for both trials is expected in mid 2005.

Familial clustering of abdominal aortic aneurysm--smoke signals, but no culprit genes

Even after 20 years of work

Genetic approach to the role of cysteine proteases in the expansion of abdominal aortic aneurysms

Background

The elastinolytic cysteine proteases, including cathepsins S and K, are overexpressed at sites of arterial elastin damage. Cystatin C, an inhibitor of these enzymes, is expressed in arterial smooth muscle cells; an imbalance in cystatin C has been implicated in the aortic wall degeneration observed in abdominal aortic aneurysms (AAAs). The aim of the study was to investigate the impact of a polymorphism in the signal peptide of the cystatin C gene on the growth of small AAAs.

Methods

Some 424 patients with a small AAA (4·0–5·5 cm) were monitored for AAA growth by ultrasonography and provided a DNA sample for analysis of the + 148 G > A polymorphism in the cystatin C signal peptide and the—82 G > C polymorphism in the gene promoter. The median length of follow-up was 2·8 years and AAA growth rates were calculated by linear regression analysis.

Results

For patients of + 148 GG (n = 263), GA (n = 147) and AA (n = 20) genotypes, the mean(s.d.) AAA growth rates were 0·37(0·29), 0·37(0·23) and 0·30(0·26) cm, and initial diameters were 4·58(0·35), 4·58(0·35) and 4·62(0·36) cm, respectively. Patients of + 148 AA genotype had a slower aneurysm growth rate (unadjusted P = 0·058; after adjustment for age, sex, initial AAA diameter and smoking, P = 0·027). There also was a trend for the rare homozygotes of the—82 C allele to have slower AAA growth (adjusted P = 0·055). Smoking history had a stronger association with aneurysm growth (P = 0·003).

Conclusion

There was a weak association between variation in the cystatin C gene and AAA growth. Medical strategies to limit AAA growth might include the inhibition of cysteine proteases.

Prostaglandin E2 receptors in abdominal aortic aneurysm and human aortic smooth muscle cells

BACKGROUND

Prostaglandin (PG) E(2) (PGE(2)) appears to have a role in stimulating production of interleukin-6 (IL-6) and apoptosis of smooth muscle cells in diseased aortic tissue. These actions are mediated by cellular receptors for PGE(2) EP receptors.

OBJECTIVE

This study was undertaken to identify EP receptors associated with production of IL-6 by aortic explants.

METHODS

Biopsy specimens of abdominal aortic aneurysm were used for explant culture and preparation of messenger RNA. The presence of EP1, EP2, EP3, and EP4 receptors in tissue and cells was investigated with reverse-transcriptase polymerase chain reaction. IL-6 and cyclic adenosine monophosphate were measured with an enzyme-linked immunosorbent assay.

RESULTS

PGE(2) or 11-deoxy-PGE(1) (EP 2/3/4 agonist) reversed partially the indomethacin suppression of IL-6 secretion from explant cultures, whereas butaprost (EP2 receptor agonist) and sulprostone (EP 1/3 receptor agonist) had no effect. Aortic biopsy specimens expressed EP2, EP3-III, and EP4 receptors. Aortic smooth muscle cells expressed EP2 receptor and four variants of EP3 receptor, ie, EP3-Ib, EP3-II, EP3-III, and EP3-IV, but PGE(2) did not stimulate secretion of IL-6. In contrast, PGE(2) or 11-deoxy-PGE(1) stimulated secretion of IL-6 from aortic macrophages.

CONCLUSIONS

In aortic explants, PGE(2) stimulates IL-6 secretion by activation of EP4 receptors, present in macrophages.

Risk factors for postoperative death following elective surgical repair of abdominal aortic aneurysm

Background

In regional and national studies death within 30 days of elective open surgical repair of an abdominal aortic aneurysm has been reported to be 7–8 per cent or even higher. Identification of preoperative factors associated with this mortality risk is important for informing surgical policy and may suggest suitable preoperative interventions.

Methods

During the course of the UK Small Aneurysm trial, 820 patients aged 60–80 years underwent elective open surgical repair of an abdominal aortic aneurysm. The relationship between 30-day mortality rate and 13 prespecified potential prognostic factors (including age, sex, aneurysm diameter, electrocardiographic evidence of myocardial ischaemia, lung function, creatinine level, hospital centre and tube or bifurcated graft) was studied.

Results

The postoperative mortality rate was 5·6 per cent overall (46 deaths in 820 patients). In univariate analyses postoperative mortality risk was associated significantly with higher serum creatinine (P = 0·002), poor lung function with low forced expiratory volume in 1 s (FEV1) (P = 0·003) and older age (P = 0·03). Evidence of the relationship between age and postoperative death was weaker (P = 0·08) after adjustment for creatinine and FEV1. The predicted postoperative mortality risk ranged from 2·7 per cent in younger patients with a low creatinine level and high FEV1 to 7·8 per cent in older patients with above average creatinine levels and below average FEV1. There was no evidence of between-hospital or between-surgeon variability in postoperative risk.

Conclusion

Poor preoperative lung and renal function were associated strongly with postoperative death. Age was less important once these two prognostic indicators were taken into account. The potential for preoperative improvement in lung and renal function to reduce the postoperative mortality rate should be addressed in future studies.

Smoking, cadmium accumulation and aortic aneurysm

Background

Smoking is an important risk factor for abdominal aortic aneurysm (AAA), a disorder associated with loss of medial smooth muscle cells. Cadmium, one of the toxic components inhaled in cigarette smoke, is known to alter the metabolism of aortic smooth muscle cells. This was an investigation of the hypothesis that excess cadmium accumulation in the abdominal aorta is associated with the development of aneurysms.

Methods

Samples of abdominal aorta were obtained at the time of surgery from 12 patients with AAA (seven men and five women, mean age 72 years) and at autopsy from 17 patients (ten men and seven women, mean age 76 years) with an undilated aorta (diameter 1·6–2·2 cm). The smoking history of all patients was noted. The aorta was dissected into three layers, intima, media and adventitia; each was dried to a constant weight, hydrolysed and cadmium was measured by atomic absorption spectrometry. In separate experiments 5-bromo-2′-deoxyuridine uptake and picogreen assay of DNA were used to investigate the effect of cadmium on the proliferation of cultured aortic smooth muscle cells.

Results

The mean(s.e.) cadmium content of the intima, media and adventitia was 1·14(0·24), 3·25(0·53) and 1·87(0·38) ng per mg dry weight respectively; the medial concentration was significantly higher than the concentration in the other two layers (P < 0·005). The medial cadmium content was similar in AAA and normal diameter aortas: 3·65(1·00) and 2·97(0·59) ng per mg dry weight respectively. Only trace amounts of cadmium were present in the aorta of those who had never smoked and there was a strong positive association between medial cadmium content and pack-year history of smoking (rs = 0·87, P < 0·001). Cadmium inhibited the proliferation of smooth muscle cells cultured on polymeric collagen, 5-bromo-2′-deoxyuridine uptake (IC50 1·4 nmol l−1) and DNA content (IC50 6·3 nmol l−1). Cadmium was less toxic, by more than tenfold, to smooth muscle cells cultured on fibronectin, monomeric collagen or plastic.

Conclusion

Cadmium accumulates selectively in the medial layer of the abdominal aorta of smokers, where it may inhibit DNA synthesis and proliferation of smooth muscle cells. The toxic effects of cadmium on cultured smooth muscle cells depend on their underlying matrix and this may explain why the accumulation of cadmium in aortic media was not associated with the development of aneurysms.

Interleukin 6 and the prognosis of abdominal aortic aneurysms

Background

Abdominal aortic aneurysm (AAA) is a familial disorder, inflammation being an important pathophysiological feature. Increased plasma concentrations of the inflammatory cytokine interleukin (IL) 6 have been associated with AAA and early aortic dilatation. This study was designed to test the hypothesis that high concentrations of plasma IL-6 and/or IL-6 genotype predict rapid AAA growth.

Methods

Genomic DNA from 466 patients, kept under ultrasonographic surveillance for small AAAs, was analysed for a G to C polymorphism at position −174 of the IL-6 promoter. Baseline plasma IL-6 concentration was measured by enzyme-linked immunosorbent assay and AAA growth rates were calculated by linear regression.

Results

The median concentration of plasma IL-6 was 4·9 (range 0–604) pg ml−1. IL-6 concentration was not associated with aneurysm growth rate. The frequency of the C allele was 0·40, similar to that in the healthy population. Patients of GG genotype had a lower plasma concentration of IL-6 than patients of either GC or CC genotype (median 1·9, 4·8 and 15·6 pg ml−1 respectively; P = 0·047, Kruskal–Wallis test). The AAA growth rate for patients of GG, GC and CC genotypes was 0·38, 0·36 and 0·36 cm per year respectively (P = 0·37). Mortality was lower for patients of GG genotype than for those with GC or CC genotype: hazard ratio 0·51 (95 per cent confidence interval (c.i.) 0·25–1·00), P = 0·05; and 0·32 (95 per cent c.i. 0·12–0·93), P = 0·036, for all-cause and cardiovascular mortality respectively.

Conclusion

Genetic polymorphism is associated with clinical events in patients with an AAA. The G to C IL-6 polymorphism at position −174 predicts future cardiovascular mortality. Neither plasma IL-6 concentration nor IL-6 genotype predicts AAA growth.

Role of Chlamydia pneumoniae in an experimental animal model of aneurysm formation

Background

Chlamydia pneumoniae has been implicated in the pathogenesis of vascular disease. C. pneumoniae DNA is present in 40–50 per cent of abdominal aortic aneurysm biopsies. This study investigated whether C. pneumoniae has a causal role in experimental aortic dilatation.

Methods

Experimental aneurysms were established in cholesterol-fed rabbits by periaortic application of calcium chloride solution and a combination of thioglycollate (a non-specific macrophage activator) or C. pneumoniae (live, formalin fixed or heat inactivated at 108 organisms per ml). After 3 weeks, aortic diameter was measured and aortas were harvested for analysis of macrophage counts. C. pneumoniae DNA was measured by polymerase chain reaction and C. pneumoniae antigens (both membrane and heat shock protein 60) were determined by immunostaining.

Results

Live or formalin-fixed C. pneumoniae at concentrations of 108 organisms per ml mimicked the effects of thioglycollate to produce aortic dilatation associated with macrophage influx. Lower concentrations of C. pneumoniae had a minimal effect.

Conclusion

In this experimental study, high doses of C. pneumoniae membrane antigens stimulated macrophage influx and aortic dilatation. Lipopolysaccharide had a lesser effect. C. pneumoniae antigens could contribute to an in vivo aggregate pathogen burden by provoking an inflammatory response.

Risk factors for aneurysm rupture: results from the UK small aneurysm study and trial

Background

The UK Small Aneurysm Trial has shown that ultrasonographic surveillance is a safe management option for patients with small abdominal aortic aneurysms (4·0–5·5 cm in diameter), with an annual rupture rate of 1 per cent. In this study risk factors associated with aneurysm rupture have been investigated using both patients randomized into the UK Small Aneurysm Trial and those monitored for aneurysm growth in the associated study.

Methods

The cohort of patients included 1090 from the trial and 1167 from the associated study. In this cohort of 2257 patients (79 per cent men), aged 59–77 years, 103 instances of abdominal aortic aneurysm rupture were identified during the 7-year follow-up (1991–1998). The relationship between rupture and ten prespecified risk factors (including age, sex, aneurysm diameter, smoking status, plasma cholesterol, lung function and ankle: brachial pressure index) was investigated using Kaplan–Meier survival and Cox regression analysis.

Results

Almost all patients (98 per cent) had initial aneurysm diameters in the range 3–6 cm and the majority of ruptures (76 per cent) occurred in patients with aneurysms known to be larger than 5 cm in diameter. Kaplan–Meier survival and Cox regression analysis were used to identify baseline risk factors associated with aneurysm rupture. After 3 years, the annual rate of aneurysm rupture was 2·2 (95 per cent confidence interval 1·7–2·8) per cent. The risk of rupture was independently and significantly associated with female sex (P < 0·001), larger initial aneurysm diameter (P < 0·001), lower FEV1 (P = 0·004), current smoking (P = 0·01) and higher mean blood pressure (P = 0·01). Age, body mass index, serum cholesterol concentration and ankle: brachial pressure index were not associated with an increased risk of aneurysm rupture.

Conclusion

Within this cohort of patients women had a threefold higher risk of aneurysm rupture than men. Effective control of blood pressure and cessation of smoking are likely to diminish the risk of rupture.

Long-term outcomes of immediate repair compared with surveillance of small abdominal aortic aneurysms

BACKGROUND

Two clinical trials, one British and one American, have shown that early, prophylactic elective surgery does not improve five-year survival among patients with small abdominal aortic aneurysms. We report long-term outcomes in the United Kingdom Small Aneurysm Trial.

METHODS

We randomly assigned 1090 patients, 60 to 76 years of age, with small abdominal aortic aneurysms (diameter, 4.0 to 5.5 cm) to one of two groups: 563 were assigned to undergo early elective surgery, and 527 were assigned to undergo surveillance by ultrasonography. Patients were followed in the trial until June 1998 and thereafter until August 2001; the mean duration of follow-up was 8 years (range, 6 to 10).

RESULTS

The mean duration of survival was 6.5 years among patients in the surveillance group, as compared with 6.7 years among patients in the early-surgery group (P=0.29). The adjusted hazard ratio for death from any cause in the early-surgery group as compared with the surveillance group was 0.83 (95 percent confidence interval, 0.69 to 1.00; P=0.05). The 30-day operative mortality in the early-surgery group (5.5 percent) led to an early disadvantage in terms of survival. The survival curves crossed at three years, and at eight years, mortality in the early-surgery group was 7.2 percentage points lower than that in the surveillance group (P=0.03). There was no evidence that age, sex, or the initial size of the aneurysm modified the hazard ratio or that delayed surgery in the surveillance group increased 30-day postoperative mortality. Death was attributable to a ruptured aneurysm in 19 of the 411 men who died (5 percent) and in 12 of the 85 women who died (14 percent) (P=0.001). The rate of early cessation of smoking was higher in the early-surgery group than in the surveillance group.

CONCLUSIONS

Among patients with a small abdominal aortic aneurysm, we found no long-term difference in mean survival between the early-surgery and surveillance groups, although after eight years, total mortality was lower in the early-surgery group. This difference may be attributed in part to beneficial changes in lifestyle adopted by members of the early-surgery group.

Cadmium accumulation in aortas of smokers

Abdominal aortic aneurysm is a smoking-related disorder. Cadmium, inhaled from cigarettes, may accumulate in the aorta and facilitate weakening of the aorta through adverse effects on smooth muscle cell metabolism. Cadmium was measured by atomic absorption spectrometry in infrarenal aortas from 13 patients with abdominal aortic aneurysm and from 17 age- and sex-matched patients with normal-diameter abdominal aorta. Total cadmium content was associated with smoking, assessed as pack-years (r=0.54, P=0.004), but was similar in aneurysmal and undilated aortas. The cadmium content (mean+/-SE) was higher in the media (3.25+/-0.53 ng/mg dry wt, 7+/-1.2 micromol/L) than in the intima or adventitia (1.14+/-0.24 and 1.87+/-0.38 ng/mg dry wt, respectively; ANOVA, P<0.005). There was a strong correlation between medial cadmium content and pack-years of smoking (r=0.87, P<0.001). In aortic smooth muscle cells cultured on fibrillar collagen, cadmium inhibited DNA synthesis and collagen synthesis and diminished cell numbers (IC(50) 2 micromol/L, 6 micromol/L, and 6 micromol/L, respectively), but higher concentrations of cadmium were required for upregulation of metallothionein (EC(50) 23 micromol/L). The cadmium content of the aorta increases in direct proportion to the pack-years of cigarettes smoked, with selective accumulation in the medial layer. However, the cadmium content of aneurysmal aortas was not higher than that of nondilated aortas for patients with matched smoking history. In smokers, the level of cadmium accumulation is probably sufficient to impair the viability of cultured smooth muscle cells. Similar mechanisms could underlie the development of degenerative aortic disease in smokers.

Provocation of experimental aortic inflammation and dilatation by inflammatory mediators and Chlamydia pneumoniae

BACKGROUND

The macrophage appears to have a key role in the inflammation and proteolysis associated with the growth and development of abdominal aortic aneurysms. The role of inflammatory mediators and Chlamydia pneumoniae in stimulating the influx of macrophages and dilatation of the abdominal aorta was investigated in an experimental model.

METHODS

Periaortic application of calcium chloride solution (and monocyte chemoattractant protein (MCP) 1, a cocktail of cytokines or C. pneumoniae) to the abdominal aorta of New Zealand White rabbits was performed at laparotomy. Some animals were fed a cholesterol-rich diet. The diameter of the aorta was measured by ultrasonography and after perfusion fixation, 3 weeks after laparotomy. Aortic sections were stained with RAM-11 to identify macrophages for counting. The presence of C. pneumoniae DNA was confirmed using the polymerase chain reaction.

RESULTS

Aortic macrophage influx in response to MCP-1, thioglycollate or C. pneumoniae was more than doubled in the cholesterol-fed animals. In response to human recombinant MCP-1 (1 microg) the mean(s.d.) macrophage count increased from 79(19) to 340(215) per unit area (P < 0.02). Even in cholesterol-fed animals, application of MCP-1 (recombinant human or rabbit form) was not associated with aortic dilatation. Application of thioglycollate 0.1 mol/l, or live or formalin-inactivated C. pneumoniae (0.5 x 108 organisms), was associated with a similar increase in macrophages to that caused by MCP-1 and a significant (approximately twofold) increase in aortic diameter after 3 weeks.

CONCLUSION

Macrophage influx into rabbit abdominal aorta, without macrophage activation, is insufficient to cause experimental aortic dilatation. C. pneumoniae antigens appeared to stimulate aortic dilatation, probably by specific activation of macrophages.

Aortic aneurysm diameter and risk of cardiovascular mortality

After successful surgical repair of an abdominal aortic aneurysm, patients have for many years an increased risk of death from cardiovascular causes. We have tested the hypothesis that for patients with abdominal aortic aneurysms, the risk of nonaneurysm cardiovascular mortality before and after surgery increased with aneurysm diameter. Records of aneurysm repair or rupture and mortality were available from 2305 patients entered into the UK Small Aneurysm Trial and Study. Two hundred fifty-nine deaths occurred before aneurysm repair or rupture (mean follow-up 1.7 years), and 325 occurred after surgical repair (mean follow-up 3.6 years). The risk of nonaneurysm-related mortality and cardiovascular death before and after surgery increased with aneurysm diameter at baseline, even after adjustment for other known risk factors. The adjusted hazard ratios for cardiovascular mortality, per standard deviation (0.8-cm) increase in aneurysm diameter, were 1.34 (95% CI 1.01 to 1.79) and 1.31 (95% CI 1.06 to 1.63) in the periods before aneurysm repair or rupture and after aneurysm repair, respectively. The significant association between aortic diameter and cardiovascular mortality, excluding aneurysm-related deaths, suggests that aneurysm diameter is an independent marker of cardiovascular disease risk.

Interleukin-6 (IL-6) and the prognosis of abdominal aortic aneurysms

BACKGROUND

Abdominal aortic aneurysm is a multifactorial disorder in which inflammation is an important pathophysiological feature. In explant culture, aneurysm biopsies secrete large amounts of interleukin-6 (IL-6), and among aneurysm patients, the circulating concentration of IL-6 appears to be increased.

METHODS AND RESULTS

We investigated, in 19 patients, whether aneurysm wall was an important source of circulating IL-6. We also tested the hypotheses, in 466 patients with a small aneurysm, that (1) high concentrations of circulating IL-6 signaled rapid aneurysm growth and (2) the -174 G-->C polymorphism in the IL-6 promoter predicted survival. For 19 patients with large or inflammatory aneurysms, the concentration of IL-6 was higher in the iliac arteries than the brachial arteries (median difference 26.5 pg/mL, this difference increasing with aneurysm diameter, P=0.01). In 466 patients with small aneurysms, the frequency of the -174 C allele (0.40) was similar to that in a normal healthy population. Patients of GG genotype had lower plasma concentrations of IL-6 than patients of GC and CC genotypes (medians 1.9, 4.8, and 15.6 pg/mL, respectively, Kruskal-Wallis P=0.047). Cardiovascular and all-cause mortalities were lower for patients of GG genotype than for patients of GC and CC genotype: hazard ratios 0.32 (95% CI 0.12 to 0.93), P=0.036, and 0.51 (95% CI 0.25 to 1.00), P=0.05, respectively. There was no association between plasma IL-6 or IL-6 genotype and aneurysm growth.

CONCLUSIONS

Aortic aneurysms appear to be an important source of circulating IL-6, the concentration being influenced by genotype. For patients with small aneurysms, the -174 G-->C IL-6 genotype predicts future cardiovascular mortality.

Fibrin monomer and fibrinopeptide B act additively to increase DNA synthesis in smooth muscle cells cultured from human saphenous vein

PURPOSE

We investigated the hypothesis that fibrinogen increased DNA synthesis (and cell proliferation) of smooth muscle cells (SMCs) cultured from human saphenous vein and that the increased DNA synthesis was attenuated when cells were cultured on polymeric collagen.

METHODS

SMCs were cultured from human saphenous vein on plastic, fibronectin, monomeric, and polymeric collagen. Fibrinogen products were prepared by proteolytic digestion. DNA synthesis was measured by bromodeoxyuridine incorporation into DNA, cell proliferation by cell counting, cyclic adenosine monophosphate by enzyme-linked immunosorbent assay, and fibrinopeptide B labeled with iodine 125 used for binding studies.

RESULTS

Fibrin monomer (0.003-0.1 micromol/L) stimulated a concentration-dependent increase in DNA synthesis of up to 10-fold, which could be inhibited by the peptide Bbeta15-42. The stimulation of DNA synthesis was highest for cells cultured on plastic and lowest for cells cultured on type I collagen polymer. Much higher concentrations of fibrinogen (0.3-1 micromol/L) were required to effect similar increases in DNA synthesis. Fibrinogen had a particular effect to augment DNA synthesis, up to 14-fold, when cells were cultured on monomeric type I collagen. This augmented DNA synthesis was inhibited by a neutralizing antibody to urokinase-type plasminogen activator. Incubation of cells cultured on collagen monomer with fibrinogen resulted in production of fibrinopeptide B. Fibrinopeptide B (5 micromol/L) increased DNA synthesis by fourfold and had additive effects with fibrin monomer to increase DNA synthesis. Iodinated tyrosine fibrinopeptide B bound to SMCs (dissociation constant 0.6 micromol/L).

CONCLUSION

Cultured human saphenous vein SMCs appear to have high-affinity receptors for fibrin monomer and fibrinopeptide B, the engagement of which stimulates DNA synthesis. These mechanisms may be pertinent to the association between fibrinogen and vein graft stenosis in vivo.

Are we ignoring the importance of ankle pressures in patients with abdominal aortic aneurysm?

BACKGROUND AND PURPOSE

the ankle/brachial pressure index (ABPI) has been shown to be a reliable marker of cardiovascular risk in population studies. We investigated whether the ABPI was a useful prognostic index for patients with abdominal aortic aneurysm.

METHODS

patients entered into the U.K. Small Aneurysm Trial and Study had their ABPI measured in both legs at baseline (mean ABPI reported) and were followed up until 30 June 1998, with information about cause of death being obtained from the Office of National Statistics. This study focussed on cardiovascular and all-cause mortality.

RESULTS

a total of 1827 men and 478 women, mean age 69 years, median aneurysm diameter 4.4 cm, were followed up for a median of 5.7 years. A total of 829 deaths were reported (rate 8.1 per 100 person-years), 546 (66%) from cardiovascular causes. The all-cause mortality risk increased as the ABPI decreased, hazard ratio 1.25 per 0.2 unit decrease in ABPI (95% CI 1.17 to 1.34, p<0.001). For patients in the lowest tertile group (ABPI <0.87) there were 11.6 deaths per 100 person-years. This increased risk persisted after adjustment for age, sex, evidence of ischaemia on resting ECG and initial aneurysm diameter, adjusted hazard ratio 1.17 per 0.2 unit decrease in ABPI (95% CI 1.07 to 1.28, p<0.001).

CONCLUSION

the ankle/brachial pressure index is an important prognostic indicator for patients with abdominal aortic aneurysm. Patients with an ABPI below 0.87 (limit of lowest tertile) have the highest mortality risk and best clinical practice demands that attention is focussed on active treatment to minimise their cardiovascular risk factors.

The natural history of abdominal aortic aneurysms and their risk of rupture

The UK Small Aneurysm Trial has shown that ultrasound surveillance is a safe management option for patients with small abdominal aortic aneurysms (4.0 to 5.5 cm in diameter), with an annual rupture rate of only 1%. We investigated baseline risk factors associated with aneurysm rupture in the 1090 trial patients and an additional 1167 patients enrolled in the UK Small Aneurysm Study. In this cohort of 2257 patients there were 103 cases of aneurysm rupture. After 3 years the annual rate of rupture was 2.2% (95% CI 1.7 to 2.8). The risk of rupture was independently and significantly associated with female sex (p < 0.001), larger initial aneurysm diameter (p < 0.001), current smoking (p = 0.01) and higher mean blood pressure (p = 0.01). Age, body mass index, serum cholesterol concentration and ankle/brachial pressure index were not associated with an increased risk of aneurysm rupture. The most surprising finding was that women had a 3-fold higher risk of aneurysm rupture than men. Effective control of blood pressure and cessation of smoking are two simple measures that are likely to diminish the risk of aneurysm rupture and improve the cardiovascular health of patients with abdominal aortic aneurysm.

Interaction of fibrinogen with saphenous vein endothelial cells stimulates tyrosine phosphorylation of cortactin

Fibrinogen can engage diverse receptors on vascular cells, including ICAM-1. We have investigated the effect of fibrinogen on the tyrosine phosphorylation of cortactin, a cytoskeletal protein in human saphenous vein endothelial cells (HSVECs). Incubation of HSVECs with fibrinogen (0-4 microM) caused a concentration-dependent increase in the tyrosine phosphorylation of cortactin. Fibrinogen (4 microM) and fibrinogen fragment D (4 microM) caused 250% and >450% increase in tyrosine phosphorylation of cortactin respectively, but fibrinogen fragment E (50 kDa form) was ineffective. Preincubation of HSVECs with soluble ICAM-1 attenuated the response to fibrinogen. At physiological concentrations fibrinogen binds to receptors (probably including ICAM-1) on HSVECs, to increase tyrosine phosphorylation of cortactin.

Risk factors for postoperative death following elective surgical repair of abdominal aortic aneurysm: results from the UK Small Aneurysm Trial. On behalf of the UK Small Aneurysm Trial participants

BACKGROUND

In regional and population studies, the mortality rate within 30 days of elective surgical repair of abdominal aortic aneurysm is approximately 8 per cent. Identification of preoperative factors associated with this mortality risk is important for informing surgical policy and may suggest suitable preoperative interventions.

METHODS

In the UK Small Aneurysm Trial, 820 patients aged 60-80 years underwent elective open surgical repair of an abdominal aortic aneurysm. The relationship between 30-day mortality rate and 13 prespecified potential prognostic factors was investigated. The value of a published clinical prediction rule was also evaluated.

RESULTS

The postoperative mortality rate was 5.6 per cent overall (46 deaths in 820 patients). Postoperative mortality risk was significantly associated with older age (P = 0. 03), higher serum creatinine level (P = 0.002) and lower forced expiratory volume in 1 s (FEV1) (P = 0.003) in univariate analyses. Evidence of a relationship between age and postoperative death was weakened (P = 0.08) after adjustment for creatinine level and FEV1. The predicted postoperative mortality risk ranged from 2.7 per cent in younger patients with below average creatinine levels and above average FEV1, to 7.8 per cent in older patients with above average creatinine levels and below average FEV1. The published clinical prediction rule did not validate well on these data; observed risk did not correlate with predicted risk except for a small group of high-risk patients.

CONCLUSION

Poor preoperative lung and renal function was strongly associated with postoperative death. Age was less important once these two important prognostic factors had been taken into account. The potential for preoperative improvement in lung and renal function to reduce postoperative mortality rates should be addressed in future studies.

Arterial flow induces changes in saphenous vein endothelium proteins transduced by cation channels

OBJECTIVES

expression of leukocyte adhesins and proteins controlling thrombosis is likely to be an important determinant of graft patency early following vein bypass. We have previously demonstrated rapid increase in endothelial ICAM-1 and nitric oxide synthase (eNOS) concentrations in human saphenous vein exposed to arterial flow. The aim of this study was to investigate whether ion-channel-blocking drugs could alter these flow-induced changes.

METHODS

human saphenous vein segments, freshly excised from patients, were placed in a validated in vitro circuit using flow conditions shown to simulate arterial or venous circulations for 90 min, in the presence or absence of ion-channel blockers. The concentrations of ICAM-1, VCAM-1, eNOS and tissue factor (TF) were assessed by quantitative immunohistochemistry in vein exposed to flow and compared with that in freshly excised vein from the same patient. The endothelial protein concentration was calculated as the mean area of staining as percentage of that for the control protein CD31, using computer-aided image analysis.

RESULTS

after arterial flow conditions the area ratio of ICAM-1 increased from 21.4+/-1.4 to 44.6+/-2.0%, of eNOS increased from 50.0+/-5.6 to 70.1+/-5.0%, of VCAM-1 decreased from 16.6+/-3.4 to 3.6+/-1.0%, whereas TF staining area ratio was unchanged. Inclusion of the non-selective K(+)channel blocker, tetraethylammonium, in the arterial perfusion solution abolished all these arterial flow-induced changes. Inclusion of the K(+)ATP channel blocker, glibenclamide, selectively abolished the arterial flow-induced changes in ICAM-1 and VCAM-1. Inclusion of the calcium channel blocker, nifedipine, abolished the arterial flow-induced changes in eNOS and VCAM-1 but increased the TF staining area ratio from 3.0+/-0.4 to 8.5+/-0.7%, p=0.01. Inclusion of the stretch-activated cation-channel blocker, gadolinium, enhanced the arterial flow-induced increase in eNOS, but prevented the arterial flow-induced increase in ICAM-1.

CONCLUSIONS

perfusion of veins under arterial flow conditions with gadolinium was associated with low endothelial concentrations of ICAM-1, VCAM-1 and TF, but high levels of eNOS. Such a concentration of endothelial proteins may be advantageous in newly implanted vein grafts. In contrast, nifedipine could have adverse effects by promoting increase in TF concentration.

Regulation by fibrinogen and its products of intercellular adhesion molecule-1 expression in human saphenous vein endothelial cells

It has been reported that fibrinogen may act as a bridging ligand, binding to intercellular adhesion molecule-1 (ICAM-1) on human umbilical vein endothelial cells and to Mac-1 on THP-1 cells (a monocytic cell line) to increase adhesion. In this study, we investigated whether fibrinogen altered the expression of ICAM-1 and, thus, increased the adhesion of THP-1 cells to cultured human saphenous vein endothelial cells (HSVECs). Incubation of HSVECs with 0.3 to 4 micromol/L fibrinogen caused a time- and concentration-dependent increase in ICAM-1, as determined by ELISA. The 4- to 5-fold increase in ICAM-1 protein concentration in HSVECs stimulated by 4 micromol/L fibrinogen for 6 hours was concomitant with a 4- to 5-fold increase in ICAM-1 mRNA. This fibrinogen-stimulated ICAM-1 upregulation was associated with a 2-fold increase in THP-1 cell adhesion to HSVECs. The fibrinogen-derived peptide Bbeta15-42 bound to HSVECs (K(d) 0.18 micromol/L). Preincubation of HSVECs with Bbeta15-42, a neutralizing antibody to urokinase plasminogen activator (uPA), or the F(ab)(1) fragment of a monoclonal antibody to vascular endothelial cadherin significantly attenuated the increase in ICAM-1 stimulated by fibrinogen. Capillary electrophoretic analysis indicated that anti-uPA prevented the release of any fibrinopeptide B (Bbeta1-14) in cultures of HSVECs incubated with 4 micromol/L fibrinogen for 6 hours. Moreover, incubation of HSVECs with either fibrin monomer (1 micromol/L) or monoclonal antibodies to vascular endothelial cadherin (25 microg/mL) increased ICAM-1 protein concentration 3- to 4-fold. These findings indicate that cleavage of fibrinopeptide B from fibrinogen by endothelial uPA permits the exposed Bbeta15-42 sequence of fibrinogen to bind to vascular endothelial cadherin on HSVECs and to upregulate the expression of ICAM-1.

Surgery for small asymptomatic abdominal aortic aneurysms

BACKGROUND

An aneurysm is an abnormal ballooning of an artery. One site in which this occurs is in the abdominal aorta, which is the major artery running through the abdomen. Some abdominal aortic aneurysms (AAA) present as an emergency and require surgery; others remain asymptomatic. Treatment of asymptomatic aneurysms depends on a number of factors, one of which is size. The risk of rupture increases with aneurysm size. Large asymptomatic aneurysms (>6 cm diameter) are operated on; small aneurysms (<4 cm diameter) have regular ultrasound to monitor growth.

OBJECTIVES

The objective of this review was to compare the mortality, quality of life and cost effectiveness of early surgical repair with routine ultrasound surveillance in patients with an AAA of between 4-6 cm diameter.

SEARCH STRATEGY

Trials were identified through searching the Cochrane Peripheral Vascular Diseases Group trials register and the reference lists of relevant articles. The reviewers also contacted investigators in the field and hand searched recent conference proceedings.

SELECTION CRITERIA

Randomised controlled trials in which men and women with asymptomatic AAA of diameter 4-6 cm were randomly allocated to early surgery, or ultrasound surveillance at least once every 12 months. Outcome measures had to include mortality, quality of life or financial costs.

DATA COLLECTION AND ANALYSIS

Data were abstracted by one reviewer and checked by others. Due to the small number of trials at present no tests of heterogeneity or sensitivity analyses were performed.

MAIN RESULTS

Only one trial, the UK Small Aneurysm Trial, fulfilled the criteria for inclusion. This trial found no differences in mortality between the early surgery and surveillance groups at two, four and six years following randomisation (six years Peto OR 1.01 [95% CI 0.77-1.31]). Mean health service costs were higher in the surgery than the surveillance group, difference 1,064 pounds per patient [95% CI 796-1332]. Quality of life remained similar in the two groups but early surgery patients thought they were healthier and had less pain one year after randomisation. There were not enough patients in the trial to allow analysis of subgroups by, for example, age or aneurysm size.

REVIEWER'S CONCLUSIONS

The results from the one trial to date indicate that patients with asymptomatic AAA of 4-5.5 cm should normally have regular ultrasound surveillance accompanied by surgical intervention for aneurysms which grow rapidly (>1 cm per year) or reach 5.5 cm. The results are awaited of a major trial in progress in the USA.