Abstract Body (Do not enter title and authors here): Background:
The incidence of ascending thoracic aortic aneurysms (aTAA) is approximately 5-10/100000 individuals/year. Estimates of acute rupture or dissection range from 1.6-4/100000 individuals/year with a mortality rate for untreated dissection up to 50% within 48 hours. Current guidelines recommend surgical intervention for aTAAs ≥ 55mm in diameter. Risk factors that contribute to aTAA growth and mortality include diabetes, age, and smoking history however, not much investigation has been done to evaluate protective factors.

Objective:
To evaluate clinical factors that reduce three-year and five-year all-cause mortality in a veteran population who have dilated ascending aortas or ascending thoracic aortic aneurysms (aTAA) and who did not undergo repair within three or five years.

Methods:
We conducted a cohort study of 887 patients followed for aTAA (diameter ≥ 4.0cm) at a Veterans Affairs hospital. Patients who died of any cause before repair within 3 or 5 years of aTAA identification or had 3 or 5 years of follow-up without repair were further analyzed. 57 pertinent factors (including social, genetic, cardiac risk factors, aneurysm size, medications, etc.) were evaluated in univariate logistic regression models of three and five-year all-cause mortality. Variables with univariate p<0.2 were combined in a multivariate logistic regression model. P<0.05 was considered statistically significant.

Results:
In the 3-year model, 392 had ≥3 years follow-up without aTAA surgical repair. 35 out of 392 patients (8.9%) died within 3 years. The only statistically significant variable that reduced mortality was history of angiotensin receptor blocker (ARB) use (OR 0.24, p=0.042). In the 5-year model, 274 had ≥5 years follow-up without aTAA surgical repair. 68 out of 274 patients (24.8%) died within 5 years. Similarly, history of ARB use (OR 0.22, p=0.003) was the only pertinent variable. For both models, the results were independent of age, history of diabetes, valve disease, CHF, and stroke.

Conclusion:
Among modifiable risk factors, at both 3 and 5 years, history of ARB was associated with reduced mortality (13% mortality compared to 27% at 5 years) and should be further investigated.