Does AAA Surgery Get the Complex Patients?

BY SHERRY BOSCHERT

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SEATTLE -- Since the advent of endovascular stent grafting for abdominal aortic aneurysms, more complex cases get sent to open surgery rather than all cases, yet outcomes after surgery haven't changed very much, Dr. Daniel P. Watson said.

A retrospective study of 371 open surgical repairs of abdominal aortic aneurysms at one hospital before it initiated a stent graft program and 375 open surgeries after the program started found no significant differences between groups in the type of surgical reconstruction, length of hospitalization, rates of major morbidities, or mortality, reported Dr. Watson of Riverside Methodist Hospital, Columbus, Ohio, and his associates.

Six surgeons handled the cases, which involved elective treatment of nonruptured aneurysms. (Another 283 other patients were treated with stent grafts during the last 6 years of the study period.) In the stent-graft era, the most common reason for sending a patient with abdominal aortic aneurysm to surgery was because of "a hostile proximal landing zone" in the aneurysm neck anatomy. That accounted for 41% of patients sent to surgery.

Other contraindications to stent-graft treatment in the cohort included thrombus in the aneurysm neck, an angled neck, or a neck diameter that was too large. Surgical patients in the pre-stent era generally were sicker than in the later period, with higher incidences of smoking, coronary disease, chronic obstructive pulmonary disease, and MI. Aneurysm sizes and American Society of Anesthesiologists risk categorizations of patients were similar between time periods.

There were significant differences between the two groups. Five percent of the early group and 23% of the later group required suprarenal aortic cross-clamp placement, and division of the renal vein was needed in 11% of the early group and 21% of the later group. Iliac aneurysms were present in 15% of the early group and 42% of the later group. Fewer patients in the early group had associated iliac occlusive disease (12%), compared with the later group (20%), they reported at the annual meeting of the Society of Interventional Radiology.

Despite the higher complexity of cases in the later group, the estimated blood loss per patient did not change significantly over time. Patients in both time periods spent 9 days in the hospital. More patients in the later group were discharged to an extended-care facility (26%) instead of to home, compared with 11% in the earlier group. Two percent in the early group and 3% in the later group died, an insignificant difference.

When asked to comment on this article, Dr. Patrick Ohara, a vascular surgeon from the Cleveland Clinic, stated, "The article reports that patients requiring open surgical repair of abdominal aortic aneurysms have become more complex to manage since the advent of endovascular aneurysm repair methods, yet the early postoperative mortality rates, estimated blood losses, and length of hospitalization associated with these more complex open operations have not changed.

"While these findings probably reflect improvements in surgical and anesthetic management, postoperative care, surgical technique or other factors, it is important to interpret the results with an understanding of the limitations of a retrospective, nonrandomized study.

"Although the authors state that the pre-stent era patients were sicker than those in the later period, they also report that the ASA risk categorization of patients was similar between the groups, an apparent inconsistency. Without prospective randomization, the results could easily be influenced by inherent selection bias. Furthermore, it is not specified whether the patients in each group were consecutively treated or whether any were excluded from treatment. Another important concern is the possibility of a Type II statistical error, which should also be considered when the comparisons fail to detect a significant difference between two treatment groups.

"Appropriate sample size calculations should determine whether the study actually has sufficient statistical power to detect a significant difference between the two groups, if it really exists. If there is insufficient power or sample size, the study results may be inconclusive.

"Nevertheless, the study might be interpreted to support the notion that both open and endovascular techniques may be viewed as complementary, rather than competitive, tools that, when appropriately applied, are each useful for the optimal treatment of patients with AAAs," he said

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