Limitations
This is a retrospectively designed study and is therefore prone to bias. We attempted to reduce bias by matching based on age, sex, race, body surface area, and hypertension. We also found no significant difference between cases and controls in many relevant areas, including smoking status (P =0.121), connective tissue disease (P =0.619), and bicuspid aortic valve (P >0.999). However, the two groups were not entirely similar, as there was a significantly greater prevalence of both diabetes and active malignancy in the control group. In a sensitivity analyses, adjusting for these two variables did not eliminate any of the significant effects we reported.
Blinding the researchers to case/control status was impractical since dissection pathology was obviously apparent in image analysis. In some cases, the dissection pathology contributed to greater difficulty in identifying landmarks and conducting measurements. This was particularly problematic in cases where root dilation resulted in an ambiguous STJ, which was noted in seven cases (10.4%). However, we did not eliminate these cases from analysis because it would complicate the case-control matching process and likely introduce a selection bias.
The major limitation of this study is the effect of dissection pathology on aortic length. Pre-dissection CT scans were not available for patients in our study, thus, it should be understood that the measurements reported here likely differ from the actual pre-dissection values.