No Advantage In Repairing Small Abdominal Aortic Aneurysms

NEW ORLEANS, LA – November 17, 2000 – Researchers reported here that major surgery to repair abdominal aortic aneurysms (AAA) smaller than 5.5 cm in size do not improve outcome more than by regular surveillance of patients.

In the Veterans Affairs’ Aneurysm Detection and management (ADAM) Study, Dr. Frank Lederle, professor of medicine at the University of Minnesota, in Minneapolis, and a clinician at the VA Medical Center, said about 1,136 veterans took part in the study which followed patients for an average of almost five years.

If imaging techniques discovered an AAA between 4.0 and 5.5 cm, patients were randomized to receive either surgery within six weeks or they were followed every six months by either ultrasound or computed tomography (CT) to assess the size of the aneurysm.

“Aortic aneurysm is the 13th leading cause of death in the United States,” Dr. Lederle said, “and most of these deaths are due to rupture of the AAA.” About 9,000 such deaths occur each year, he said.

However, doctors have debated at what point the aneurysm becomes so dangerous that the risk of rupture-which usually results in death- outweighs the risk of undergoing the difficult open AAA repair operation.

Dr. Lederle said the diameter of the AAA is the strongest known predictor of rupture, but small aneurysms are more common than the larger ones. In 1992, the Society for Vascular Surgery recommended elective surgery for patients with AAAs greater than 4 cm.

At the 73rd annual scientific sessions of the American Heart Association, Dr. Lederle said that after eight years, there were 141 deaths among the 569 patients who were placed in the surgery cohort, compared with 121 deaths among 567 patients in the surveillance cohort. The difference was not considered statistically significant, he said.

Since the study was conducted in VA centers, virtually all – 99 percent-of the patients in the study were men. The average age was 50 to 79 years, about 94 percent were white and about 42 percent had coronary artery disease.

During the course of the study, 92 percent of the patients originally assigned to surgery had, in fact, undergone the procedure, and despite the extensive operation, “mortality at 30 days was very low,” Dr. Lederle said. There was a 2.1 percent operative mortality in the surgery group, and a 1.5 percent mortality among those who were originally assigned to surveillance but who later went on to receive surgery. About 61 percent underwent the operation, including about 8.8 percent of patients who had surgery even though they were still within the protocol window for watchful waiting. Dr. Lederle said most of the protocol violations were patient initiated.

Overall, however, he said the ADAM study found “long-term survival is not improved by repair of AAA smaller than 5.5 centimeters when compared with imaging every six months, even when operative mortality is very low. Deferring repair until the AAA has enlarged to 5.5 cm does not increase operative mortality, and rupture is rare in AAA smaller than 5.5 cm.”