Section Two • Infrarenal Aortic Aneurysm
Chapter 5
Immediate Repair Compared with Surveillance of Small Abdominal Aortic Aneurysm
Aneurysm Detection and Management, Veterans Affairs Cooperative Study Group, Lederle FA, Wilson SE, Johnson GR et al. Immediate repair compared with surveillance of small abdominal aortic aneurysms. N Engl J Med. 2002 May 9;346(19):1437–44
Abstract
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 6 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% of the patients in the immediate-repair group and 61.6% 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% 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% 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%) as compared with the surveillance group (2.6%). Eleven patients in the surveillance group had rupture of abdominal aortic aneurysms (0.6% per year), resulting in seven deaths. The rate of hospitalization related to abdominal aortic aneurysm was 39% 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.
Expert Commentary by Samuel Eric Wilson, Samuel P. Arnot, and Juan Carlos Jimenez
When the Aneurysm Detection and Management (ADAM) Trial1 began, patient accrual in 1992 endovascular repair was still undergoing laboratory investigation. Publications by Volodos in 1986 from Russia, and Parodi, Argentina, in 1991 showed the promise and clinical feasibility of the minimally invasive technique. Some surgeons, however, worried that if endovascular aneurysm repair (EVAR) proved safer than open repair, as it did, there would be relaxation of the size limits for repair, i.e., small aneurysms would be repaired without evidence of benefit. Others thought that delay in repair, as would occur in an observation group, could lead to a higher postoperative morbidity and mortality as the patients aged or that ruptures were likely to occur even in small aneurysms. Guidelines from societies were indefinite. Given this clinical equipoise, the RAND Corporation along with the Society for Vascular Surgery advocated for clinical trial.
The principal goal of the ADAM trial was to determine if early repair of small abdominal aortic aneurysms (AAAs), soon after discovery, resulted in better life expectancy than observation with serial ultrasound until expansion or symptoms mandated repair.
Study Design This was a prospective, randomized, clinical trial of “immediate” open surgery (within 6 weeks of diagnosis) versus serial observations by ultrasound every 6 months for AAAs 4.0–5.5 cms in diameter. If symptoms occurred, size reached 5.5 cms, or diameter grew 1 cm in 1 year or 0.7 cms in 6 months patients under observation were referred for open surgery.
Sample Size 569 patients were randomized to immediate repair and 567 to surveillance.
Follow-Up Until threshold size for intervention was reached (5.5 cms), rapid expansion or symptoms occurred.
Inclusion/Exclusion Criteria Included were AAAs between 4 and 5.5 cms. The major exclusion criteria were previous aortic surgery, chronic obstructive pulmonary disease, recent myocardial infarct, and chronic renal failure.
Treatment Patients were randomized to early, open AAA repair or follow-up with ultrasound measurement of AAA diameter.
Results Early survival benefit in the surveillance group, primarily due to the higher 30-day postoperative mortality in the surgical group, but no difference in survival at 5 years and 10 years. Rupture rate in those patients under surveillance was less than 1%/year. A Cochrane Database analysis of the ADAM and UKSAT pooled data also found that there was no outcome difference according to age or diameter.2
Study Limitations Patients selected were good risk unlike the majority of patients likely to be encountered in practice. Some AAAs expanded rapidly with 30% reaching threshold size in 3 years and 40% by 4 years. Few women were study participants.
Relevant Studies The contemporaneous UK Small Aneurysm Trial (Greenhalgh) found essentially the same outcom...
