Ascending Aortic Length and Risk of Aortic Adverse Events: The Neglected Dimension

Background: Little information is available regarding the longitudinal changes of the aneurysmal ascending aorta. Objectives: This study sought to outline the natural history of ascending thoracic aortic aneurysm (ATAA) based on ascending aortic length (AAL) and develop novel predictive tools to better aid risk stratification. Methods: The ascending aortic diameters and lengths, and long-term aortic adverse events (AAEs) (rupture, dissection, and death) of 522 ATAA patients were evaluated using comprehensive statistical approaches. Results: An AAL of ≥13 cm was associated with an almost 5-fold higher average yearly rate of AAEs compared with an AAL of <9 cm. Two AAL “hinge points” with a sharp increase in the estimated probability of AAEs were detected between 11.5 and 12.0 cm, and between 12.5 and 13.0 cm. The mean estimated annual aortic elongation rate was 0.18 cm/year, and aortic elongation was age dependent. Aortic diameter increased 18% due to dissection while AAL only increased by 2.7%. There was a noticeable improvement in the discrimination of the logistic regression model (area under the receiver-operating characteristic curve: 0.810) due to the introduction of aortic height index (AHI) (diameter height index + length height index). The AHIs <9.33, 9.38 to 10.81, 10.86 to 12.50, and ≥12.57 cm/m were associated with a ∼4%, ∼7%, ∼12%, and ∼18% average yearly risk of AAEs, respectively. Conclusions: An aortic elongation of 11 cm serves as a potential intervention criterion for ATAA, which is even more reliable than diameter due to its relative immunity to dissection. AHI (including both length and diameter) is more powerful than any single parameter in this study.