Early surgery did not reduce 6-year mortality in patients with small abdominal aortic aneurysms
ACP J Club. 1999 May-June;130:73. doi:10.7326/ACPJC-1999-130-3-073
The UK Small Aneurysm Trial Participants. Mortality results for randomised controlled trial of early elective surgery or ultrasonographic surveillance for small abdominal aortic aneurysms. Lancet. 1998 Nov 21; 352:1649-55.
In patients with small abdominal aortic aneurysms, does early elective open surgical repair reduce mortality better than regular ultrasonographic surveillance of aortic diameter?
Randomized, unblinded, controlled trial with up to 7 years of follow-up (mean 4.6 y).
93 hospitals in the United Kingdom.
1090 patients who were 60 to 76 years of age (mean age 69 y, 83% men); were fit for elective surgery; and had symptomless, infrarenal, abdominal aortic aneurysms 4.0 to 5.5 cm in diameter (mean diameter 4.6 cm). Exclusion criteria included being unfit for elective surgery and having a symptomatic aneurysm. Follow-up was complete.
Patients were allocated to early surgery (n = 563) or ultrasonographic surveillance of the aneurysm diameter (n = 527). Surgery was done according to normal local procedures. In the surveillance group, patients with aneurysms 4.0 to 4.9 cm were seen every 6 months, and those with aneurysms 5.0 to 5.5 cm were seen every 3 months; elective surgical repair was recommended to patients if the aneurysm diameter was > 5.5 cm, the growth rate was > 1 cm/y, the aneurysm became tender, or iliac or thoracic repair was needed.
Main outcome measure
Death from all causes.
Analysis was by intention to treat. In the surgery group, 517 of 563 patients (92%) had elective aneurysm repair with a prosthetic inlay graft; 452 of these patients (87%) had surgery ≤ 5 months after randomization (median time to surgery 1.8 mo). 38 (7%) patients in the surveillance group had surgery contrary to study protocol. By 6 years, mortality rates did not differ between the groups (hazard ratio 0.94, 95% CI 0.75 to 1.17, P = 0.56) (Table). Results were similar after adjustment for baseline factors and source of patient referral. The study had 80% power to detect a 9% difference at 5 years of follow-up.
Early, prophylactic, elective surgery did not reduce mortality compared with ultrasonographic surveillance of aortic diameter in patients with small, asymptomatic, abdominal aortic aneurysms.
Sources of funding: Medical Research Council and British Heart Foundation.
For correspondence: Professor J.T. Powell, Department of Vascular Surgery, Imperial College School of Medicine, Charing Cross Hospital, London W6 8RF, England, UK. FAX 44-181-846-7330.
Table. Early elective surgery vs ultrasonographic surveillance of aortic diameter for small abdominal aortic aneurysms*
|Outcome||Surgery||Surveillance||RRR (95% CI)||NNT|
|Death at 6 y||28.2%||28.5%||0.8% (-19.9 to 17.8)||Not significant|
*Abbreviations defined in Glossary; RRR, NNT, and CI calculated from data in article.
Theoretically, the optimal time at which an asymptomatic abdominal aortic aneurysm should be repaired is when the probability of perioperative death (if the patient has surgery) is approximately equal to the probability of death from a ruptured abdominal aortic aneurysm (if the patient does not have surgery). In this well-done study by the U.K. Small Aneurysm Trial Participants, no difference in mortality existed between patients who had immediate repair (mean aortic diameter 4.6 cm) and those who were followed with ultrasonography until the aneurysm reached 5.5 cm. Interestingly, 11 patients in the surveillance group died from a ruptured abdominal aortic aneurysm, and 8 patients in the surgery group died from perioperative complications. Thus, it seems reasonable to follow patients until the aneurysm reaches 5.5 cm, becomes symptomatic, or grows by more than 1 cm/y. A U.S. trial is also addressing this issue, and it is hoped that the results will be reported shortly (1).
Patients in the surveillance group had ultrasonography every 6 months, decreasing to every 3 months, for aneurysms between 5.0 and 5.5 cm. Thus, patients must be followed carefully to ensure that the results of surveillance ultrasonography are replicated in actual practice. Over a mean follow-up of 4.6 years, 61% of patients in the surveillance group eventually had surgery, indicating that in most cases surveillance delayed—not prevented—surgery. The 30-day perioperative mortality rate in the study was 5.8%, which is similar to mortality rates of other multicenter studies, and reinforces the fact that even in the 1990s, elective abdominal aortic aneurysm surgery is associated with considerable risk. The use of endovascular stents may reduce the perioperative mortality rate in the future, but experience to date has found similar mortality rates for stents and open repair (2-4). However, stents seem to be associated with less blood loss, shorter stays in intensive care and the hospital, and possibly less morbidity, although this has not been shown in a randomized trial.
The finding that patients with small aneurysms who receive immediate surgery incur more health care costs than those followed by surveillance is not surprising. However, it is not possible to reliably transfer the results of a costing study from one health care system to another. Unfortunately, few data about the amount of resources used by patients in the study (e.g., mean number of ultrasonograms and mean days in the hospital) were provided, which makes it difficult to compare treatments across regions. Further, patient-borne costs were not included, although these are unlikely to have been a major factor in the analysis.
The finding that patients in the surgery group had less bodily pain and more improved health perceptions than patients in the surveillance group is intriguing. One can hypothesize that patients in the surveillance group were more anxious that their aneurysm might rupture and, thus, had poorer health perceptions. Now that patients can be told that ultrasonographic surveillance leads to outcomes similar to those of early surgery, one wonders whether their health perceptions would also be similar. It is not clear why bodily pain should be improved in the surgery group.
It is likely that some patients will always prefer to have their aneurysm repaired earlier rather than later, whereas others will be comfortable to have their aneurysm followed for some time. Now that this excellent study has provided data about the outcomes of immediate surgery compared with ultrasonographic surveillance, the time seems right to develop a decision aid to give patients detailed information about the choices available to them and the consequences of those choices (5, 6). This will allow patients to participate fully in the decision about the timing of surgery and to make the choice that is right for them.
Andreas Laupacis, MD, MSc
Loeb Heart Research UnitOttawa, Ontario, Canada
2. May J, White GH, Yu W, et al. Concurrent comparison of endoluminal versus open repair in the treatment of abdominal aortic aneurysms: analysis of 303 patients by life table method. J Vasc Surg. 1998;27:213-20.
6. Barry MJ, Cherkin DC, Chang Y, Fowler FJ, Skates S. A randomized trial of a multimedia shared decision-making program for men facing a treatment decision for benign prostatic hyperplasia. DMCO. 1997;1:5-14.