Ascending Aortic Length and Risk of Aortic Adverse events. The Neglected Dimension by Jinlin Wu, et al.J Am Coll Cardiol. 2019 Sep 13. pii: S0735-1097(19)36292-8.
For twenty years, aortic diameters have been used as the only aortic size criterion to define the threshold for prophylactic surgical repair in patients affected by ascending thoracic aortic aneurysm (ATAA). However, it is well-known that diameter alone is not enough for accurate risk stratification in these patients. In their very recent publication in JACC, Wu and colleagues aimed to evaluate the potential contribution to risk stratification of a neglected aortic dimension, the aortic length.
To this aim, the authors retrospectively included in the study a total of 522 adult patients with ATAA (age 65.8 ±13.6, 72.4% men) with available CT scans, ascending aortic diameters >3.5 cm and not affected by iatrogenic or traumatic dissection, type B aortic dissection, chronic aortic dissection, congenital aortic malformations or penetrating aortic ulcer or hematoma. Demographic and clinical data, and aortic adverse events (AAEs) (rupture, dissection and death) occurred during each patient follow-up (mean 42 months, range 5 days to 336 months) were also collected. Aortic size was measured in diastole from gated CT scans and described using the maximum diameter in the ascending aorta and, also, the ascending aortic length (AAL), defined as the distance between the aortic annulus and the innominate artery. These measurements were normalized by patient height to obtain the diameter height index (DHI) and the length height index (LHI). An aortic height index (AHI) was defined to account both for diameter and length as (DHI+LHI). Multiple statistical approaches and cross-validations were performed to assess the independent relation of aortic size parameters to the average yearly rate of adverse events.
Results shown aortic length to be related to the estimated probability of AAEs. Two AAL points with sharp increase in the estimated probability of AAEs were identified (11.5 to 12.0 cm and 12.5 cm to 13.0 cm). Also, patients with larger aortic length (AAL ≥13 cm or LHI ≥ 7.5 cm/m) presented almost 5-fold higher average yearly rate of AAEs compared to those with normal length (AAL< cm or LHI <5.5 cm/m). Similar results were obtained for aortic diameter and DHI. However, aortic length change was relatively immune to dissection (increase of 2.7% length vs 18% in aortic diameter after an acute type A dissection) and its combination with the aortic diameter in an AHI-based regression model showed better discrimination than a diameter- based model (AUC 0.810 vs 0.783, respectively; p=0.08). Based on these results, the authors conclude that including aortic length together with aortic diameter improves risk assessment in patients with ATAA and suggest an aortic length of 11 cm as a potential intervention criterion for ATAA.
This is a very complete study and, despite limitations in patients’ selection and methodology, the authors have clearly shown that clinical cardiology needs to move forward than aortic diameters when defining aortic size.