Endovascular aneurysm repair at 5 years: Does aneurysm diameter predict
outcome?
J Vasc Surg, 44 (5):
920--29; discussion 929-31 (November 2006)Abstract
OBJECTIVE: The appropriate size threshold for endovascular repair
of small abdominal aortic aneurysms (AAA) is unclear. We studied
the outcome of endovascular aneurysm repair (EVAR) as a function
of preoperative aneurysm diameter to determine the relationship between
aneurysm size and long-term outcome of endovascular repair. METHODS:
We reviewed the results of 923 patients treated in a prospective,
multicenter clinical trial of EVAR. Small aneurysms were defined
according to two size thresholds of 5.5 cm and 5.0 cm. Two-way analysis
was used to compare patients with small aneurysms (<5.5 cm, n = 441)
to patients with large aneurysms (> or =5.5 cm, n = 482). An ordered
three-way analysis was used to compare patients with small AAA (<5.0
cm, n = 145), medium AAA (5.0 to 5.9 cm, n = 461), and large AAA
(> or =6.0 cm, n = 317). The primary outcome measures of rupture,
AAA-related death, surgical conversion, secondary intervention, and
survival were compared using Kaplan-Meier estimates at 5 years. RESULTS:
Median aneurysm size was 5.5 cm. The two-way comparison showed that
5 years after EVAR, patients with small aneurysms (<5.5 cm) had a
lower AAA-related death rate (1\% vs 6\%, P = .006), a higher survival
rate (69\% vs 57\%, P = .0002), and a lower secondary intervention
rate (25\% vs 32\%, P = .03) than patients with large aneurysms (>
or =5.5 cm). Three-way analysis revealed that patients with small
AAAs (<5.0 cm) were younger (P < .0001) and were more likely to have
a family history of aneurysm (P < .05), prior coronary intervention
(P = .003), and peripheral occlusive disease (P = .008) than patients
with larger AAAs. Patients with smaller AAAs also had more favorable
aortic neck anatomy (P < .004). Patients with large AAAs were older
(P < .0001), had higher operative risk (P = .01), and were more likely
to have chronic obstructive pulmonary disease (P = .005), obesity
(P = .03), and congestive heart failure (P = .004). At 5 years, patients
with small AAAs had better outcomes, with 100\% freedom from rupture
vs 97\% for medium AAAs and 93\% for large AAAs (P = .02), 99\% freedom
from AAA-related death vs 97\% for medium AAAs and 92\% for large
AAAs (P = .02) and 98\% freedom from conversion vs 92\% for medium
AAAs and 89\% for large AAAs (P = .01). Survival was significantly
improved in small (69\%) and medium AAAs (68\%) compared to large
AAAs (51\%, P < .0001). Multivariate Cox proportional hazards modeling
revealed that aneurysm size was a significant independent predictor
of rupture (P = .04; hazard ratio HR, 2.195), AAA-related death
(P = .03; HR, 2.007), surgical conversion (P = .007; HR, 1.827),
and survival (P = .001; HR, 1.351). There were no significant differences
in secondary intervention, endoleak, or migration rates between small,
medium, and large AAAs. CONCLUSIONS: Preoperative aneurysm size is
an important determinant of long-term outcome following endovascular
repair. Patients with small AAAs (<5.0 cm) are more favorable candidates
for EVAR and have the best long-term outcomes, with 99\% freedom
from AAA death at 5 years. Patients with large AAAs (> or =6.0 cm)
have shorter life expectancy and have a higher risk of rupture, surgical
conversion, and aneurysm-related death following EVAR compared to
patients with smaller aneurysms. Nonetheless, 92\% of patients with
large AAAs are protected from AAA-related death at 5 years. Patients
with AAAs of intermediate size (5 to 6 cm) represent most of the
patients treated with EVAR and have a 97\% freedom from AAA-related
death at 5 years.