Medline ® Abstracts for References 2,3,5-14

Decision-making in regard to elective repair of abdominal aortic aneurysms (AAA) requires careful assessment of factors that influence rupture risk, operative mortality, and life expectancy. Individualized consideration of these factors in each patient is essential, and the role of patient preference is of increasing importance. It is not possible or appropriate to recommend a single threshold diameter for intervention which can be generalized to all patients. Based upon the best available current evidence, 5.5 cm is the best threshold for repair in an "average" patient. However, subsets of younger, good-risk patients or aneurysms at higher rupture risk may be identified in whom repair at smaller sizes is justified. Conversely, delay in repair until larger diameter may be best for older, higher-risk patients, especially if endovascular repair is not possible. Intervention at diameter<5.5 cm appears indicated in women with AAA. If a patient has suitable anatomy, endovascular repair may be considered, and it is most advantageous for older, higher-risk patients or patients with a hostile abdomen or other technical factors that may complicate standard open repair. With endovascular repair, perioperative morbidity and recovery time are clearly reduced; however, there is a higher reintervention rate, increased surveillance burden, and a small but ongoing risk of AAA rupture. There is no justification at present for different indications for endovascular repair, such as earlier treatment of smaller AAA. Until long-term outcome of endoluminal repair is better defined and results of randomized trials available, the choice between endovascular and open repair will continue to rely heavily on patient preference.

PURPOSE: The purpose of this study was to investigate the hypothesis that abdominal aortic aneurysm (AAA) expansion may be slowed by beta-adrenergic antagonists.

METHODS: One hundred twenty-one patients with infrarenal AAA were monitored with serial aortic ultrasound examinations. Eighty-three patients received no beta-blockers (group I), and 38 patients received beta-blockers (group II). Values are expressed as mean +/- SD.

RESULTS: The mean follow-up was 43 +/- 29 months with 5.5 +/- 3.4 ultrasound examinations per patient. The expansion rate among all AAA was 0.38 +/- 0.44 cm/yr. Large aneurysms (>or = 5 cm) expanded significantly faster than small aneurysms (p = 0.02) in patients not treated with beta-blockers. Among patients with large AAA, those receiving beta-blockers had a significantly reduced mean expansion rate; 0.36 +/- 0.20 versus 0.68 +/- 0.64 cm/yr, (p<0.05). Although rupture rates were lower in group I (5%) versus group II (13%), this difference was not statistically significant. Thirty-four patients in a poor-risk category with AAA were monitored greater than 5 cm in diameter. Ten of these AAA ruptured. The mean expansion rate was significantly greater in those patients with ruptured AAA versus those patients with AAA that did not rupture; 0.82 +/- 0.74 versus 0.42 +/- 0.41 cm/yr (p = 0.04).

CONCLUSIONS: In patients not undergoing beta-blocker therapy, large AAA expand at a significantly greater rate than smaller AAA. Large aneurysms that rupture show more rapid expansion than those AAA that do not rupture. We have demonstrated a significantly reduced rate of expansion of large AAA in patients receiving beta-blockade.

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.

BACKGROUND: Early elective surgery may prevent rupture of abdominal aortic aneurysms, but mortality is 5-6%. The risk of rupture seems to be low for aneurysms smaller than 5 cm. We investigated whether prophylactic open surgery decreased long-term mortality risks for small aneurysms.

METHODS: We randomly assigned 1090 patients aged 60-76 years, with symptomless abdominal aortic aneurysms 4.0-5.5 cm in diameter to undergo early elective open surgery (n=563) or ultrasonographic surveillance (n=527). Patients were followed up for a mean of 4.6 years. If the diameter of aneurysms in the surveillance group exceeded 5.5 cm, surgical repair was recommended. The primary endpoint was death. Mortality analyses were done by intention to treat.

FINDINGS: The two groups had similar cardiovascular risk factors at baseline. 93% of patients adhered to the assigned treatment. 309 patients died during follow-up. The overall hazard ratio for all-cause mortality in the early-surgery group compared with the surveillance group was 0.94 (95% CI 0.75-1.17, p=0.56). The 30-day operative mortality in the early-surgery group was 5.8%, which led to a survival disadvantage for these patients early in the trial. Mortality did not differ significantly between groups at 2 years, 4 years, or 6 years. Age, sex, or initial aneurysm size did not modify the overall hazard ratio.

INTERPRETATION: Ultrasonographic surveillance for small abdominal aortic aneurysms is safe, and early surgery does not provide a long-term survival advantage. Our results do not support a policy of open surgical repair for abdominal aortic aneurysms of 4.0-5.5 cm in diameter.

Information is incomplete about the rate of expansion of abdominal aortic aneurysms and the risk of rupture in relation to their size. To address these questions, we conducted a population-based study. Of the 370 residents of Rochester, Minn., with an aneurysm initially diagnosed from 1951 through 1984, 181 had the aneurysm documented by ultrasound examination. Among the 103 patients who underwent more than one ultrasound study, the diameter of the aneurysm increased by a median of 0.21 cm per year. Only 24 percent had a rate of expansion of 0.4 cm or more per year. Among the 176 patients who had an unruptured aneurysm at the time of the initial ultrasound study, the cumulative incidence of rupture was 6 percent after 5 years and 8 percent after 10 years. However, the risk of rupture over five years was 0 percent for the 130 patients with an aneurysm less than 5 cm in diameter and 25 percent for the 46 patients with an aneurysm 5 cm or more in diameter. All 16 patients who had ruptures had aneurysms that were 5 cm or more in diameter at the time of the rupture. These population-based data challenge the clinical perception that aneurysms typically expand at a rate of 0.4 to 0.5 cm per year. Our data also suggest that for aneurysms less than 5 cm in diameter the risk of rupture is considerably lower than has been reported previously. However, the risk of rupture is substantial for aneurysms 5 cm or more in diameter.

BACKGROUND: Whether elective surgical repair of small abdominal aortic aneurysms improves survival remains controversial.

METHODS: We randomly assigned patients 50 to 79 years old with abdominal aortic aneurysms of 4.0 to 5.4 cm in diameter who did not have high surgical risk to undergo immediate open surgical repair of the aneurysm or to undergo surveillance by means of ultrasonography or computed tomography every six months with repair reserved for aneurysms that became symptomatic or enlarged to 5.5 cm. Follow-up ranged from 3.5 to 8.0 years (mean, 4.9).

RESULTS: A total of 569 patients were randomly assigned to immediate repair and 567 to surveillance. By the end of the study, aneurysm repair had been performed in 92.6 percent of the patients in the immediate-repair group and 61.6 percent of those in the surveillance group. The rate of death from any cause, the primary outcome, was not significantly different in the two groups (relative risk in the immediate-repair group as compared with the surveillance group, 1.21; 95 percent confidence interval, 0.95 to 1.54). Trends in survival did not favor immediate repair in any of the prespecified subgroups defined by age or diameter of aneurysm at entry. These findings were obtained despite a low total operative mortality of 2.7 percent in the immediate-repair group. There was also no reduction in the rate of death related to abdominal aortic aneurysm in the immediate-repair group (3.0 percent) as compared with the surveillance group (2.6 percent). Eleven patients in the surveillance group had rupture of abdominal aortic aneurysms (0.6 percent per year), resulting in seven deaths. The rate of hospitalization related to abdominal aortic aneurysm was 39 percent lower in the surveillance group.

CONCLUSIONS: Survival is not improved by elective repair of abdominal aortic aneurysms smaller than 5.5 cm, even when operative mortality is low.

BACKGROUND: Independent risk factors for abdominal aortic aneurysm (AAA) have not been clearly defined in multivariable analyses of large patient populations.

OBJECTIVE: To identify factors that are independently associated with AAA and to determine the prevalence of previously unrecognized AAA in defined demographic and risk groups.

DESIGN: Cross-sectional screening study.

SETTING: 15 Department of Veterans Affairs medical centers.

PARTICIPANTS: 73451 veterans who were 50 to 79 years of age and had no history of AAA.

MEASUREMENTS: The results of ultrasonographic screening for AAA and a prescreening questionnaire were analyzed using multiple logistic regression.

RESULTS: An AAA of 4.0 cm or larger was detected in 1031 participants (1.4%). Smoking was the risk factor most strongly associated with AAA; the odds ratio (OR) for AAAs of 4.0 cm or larger compared with normal aortas (infrarenal aortic diameter<3.0 cm) was 5.57 (95% CI, 4.24 to 7.31). The association between smoking and AAA increased significantly with the number of years of smoking and decreased significantly with the number of years after quitting smoking. The excess prevalence associated with smoking accounted for 78% of all AAAs that were 4.0 cm or larger in the study sample. Female sex (OR, 0.22 [CI, 0.07 to 0.68]), black race (OR, 0.49 [CI, 0.35 to 0.69]), and presence of diabetes (OR, 0.54 [CI, 0.44 to 0.65]) were negatively associated with AAA. A family history of AAA was positively associated with AAA (OR, 1.95 [CI, 1.56 to 2.43]) but was reported by only 5.1% of participants. Other independently associated factors included age, height, coronary artery disease, any atherosclerosis, high cholesterol levels, and hypertension.

CONCLUSIONS: Abdominal aortic aneurysm is associated with multiple factors. Smoking was the risk factor most strongly associated with AAA and may be responsible for most clinically important cases of previously undiagnosed AAA.

BACKGROUND: Persons with abdominal aortic aneurysm are more likely to have a higher prevalence of risk factors for and clinical manifestations of cardiovascular disease. It is unknown whether these factors explain the high mortality rate associated with abdominal aortic aneurysm.

OBJECTIVE: To describe the risk for mortality, cardiovascular mortality, and cardiovascular morbidity in persons screened for abdominal aortic aneurysm.

DESIGN: Longitudinal cohort study.

SETTING: Four communities in the United States.

PARTICIPANTS: 4734 men and women older than 65 years of age recruited from Medicare eligibility lists.

MEASUREMENTS: Abdominal ultrasonography was used to measure the aortic diameter and the ratio of infrarenal to suprarenal measurement of aortic diameter in 1992-1993. Abdominal aortic aneurysm was defined as aortic diameter of 3 cm or greater or infrarenal-to-suprarenal ratio of 1.2 or greater. Mortality, cardiovascular disease mortality, incident cardiovascular disease, and repair or rupture were assessed after 4.5 years.

RESULTS: The prevalence of aneurysm was 8.8%, and 87.7% of aneurysms were 3.5 cm or less in diameter. Rates of total mortality (65.1 vs. 32.8 per 1000 person-years), cardiovascular mortality (34.3 vs. 13.8 per 1000 person-years), and incident cardiovascular disease (47.3 vs. 31.0 per 1000 person-years) were higher in participants with aneurysm than in those without aneurysm; after adjustment for age, risk factors, and presence of other cardiovascular disease, the respective relative risks were 1.32, 1.36, and 1.57. Rates of repair and rupture were low.

CONCLUSIONS: Rates of total mortality, cardiovascular disease mortality, and incident cardiovascular disease were higher in participants with abdominal aortic aneurysm than in those without aneurysm, independent of age, sex, other clinical cardiovascular disease, and extent of atherosclerosis detected by noninvasive testing. Persons with smaller aneurysms detected by ultrasonography should be advised to modify risk factors for cardiovascular disease while under surveillance for increase in the size of the aneurysm.

In the physical examination of abdominal aortic aneurysm (AAA), the only maneuver of demonstrated value is abdominal palpation to detect abnormal widening of the aortic pulsation. Palpation of AAA appears to be safe and has not been reported to precipitate rupture. The best evidence on the accuracy of abdominal palpation comes from 15 studies of patients not previously known to have AAA who were screened with both abdominal palpation and ultrasound. When results from these studies are pooled, the sensitivity of abdominal palpation increases significantly with AAA diameter (P<.001), ranging from 29% for AAAs of 3.0 to 3.9 cm to 50% for AAAs of 4.0 to 4.9 cm and 76% for AAAs of 5.0 cm or greater. Positive and negative likelihood ratios with 95% confidence intervals (CIs) using a cutoff point for AAAs of 3.0 cm or greater are 12.0 (95% CI, 7.4-19.5) and 0.72 (95% CI, 0.65-0.81), respectively, and for AAAs of 4.0 cm or greater are 15.6 (95% CI, 8.6-28.5) and 0.51 (95% CI, 0.38-0.67). The positive predictive value of palpation for AAA of 3.0 cm or greater in these studies was 43%. Limited data suggest that abdominal obesity decreases the sensitivity of palpation. Abdominal palpation specifically directed at measuring aortic width has moderate sensitivity for detecting an AAA that would be large enough to be referred for surgery but cannot be relied on to exclude AAA, especially if rupture is a possibility.

BACKGROUND: A family history of abdominal aortic aneurysm has been reported to increase the risk for developing the disease.

OBJECTIVE: To determine the risk for abdominal aortic aneurysm in first-degree relatives of patients with the disease.

DESIGN: Cross-sectional ultrasonographic screening study.

SETTING: University Central Hospital, Helsinki, Finland.

PATIENTS: 238 of 325 living first-degree relatives of patients having surgery for abdominal aortic aneurysm (age>50 years; 98 men and 110 women) and 281 controls (135 men and 149 women) without a family history of abdominal aortic aneurysm.

MEASUREMENTS: Ultrasonography was used to measure aortic diameter in 101 male relatives and 140 female relatives (241 of the 325 persons at risk [74%]) and in 281controls.

RESULTS: Three siblings had already undergone surgery for abdominal aortic aneurysm. Eleven siblings (all brothers) (11 of 101 [10.9%]) had ultrasonographic evidence of abdominal aortic aneurysm (aortic diameter>30 mm). In the control group, 2 men (1.5%) and 2 women (1.3%) had an aneurysm. Thirty siblings and no controls had dilatation of the abdominal aorta (aortic diameter, 20 to 29 mm). Neither the age nor the sex of the proband affected risk for developing abdominal aortic aneurysm among first-degree relatives. Family history increased the risk for an aneurysm by 4.33-fold (95% CI, 1.32-fold to 14.23-fold), male sex increased the risk by 12.21-fold (CI, 2.63-fold to 56.64-fold), and age (by decade) increased the risk by 1.93-fold (CI, 1.15-fold to 3.25-fold).

CONCLUSION: Aging brothers of patients with known abdominal aortic aneurysm have the highest risk for developing the disease; the prevalence of the disease in siblings older than 60 years of age is 18%.