Decision-making in aortic disease

This commentary refers to ‘Fate of the unoperated ascending thoracic aortic aneurysm: three-decade experience from the Aortic Institute at Yale University’, by J. Wu et al., https://doi.org/10.1093/eurheartj/ehad148 and the discussion piece ‘There is insufficient evidence to lower the threshold for prophylactic aortic surgery’, by O. Milleron et al., https://doi.org/10.1093/eurheartj/ehad690. We appreciate the insightful and thought-provoking comments1 regarding our suggestion that the surgical threshold for ascending thoracic aortic aneurysms be lowered from 5.5 to 5.0 cm.2 Early events in Kaplan–Meier curves: The rather modest drop-off in survival at the very inception of our Kaplan–Meier curves can be attributed to a variety of factors. (i) We use the first scan that permits diameter measurement as the starting point of our study. In some cases, this first scan was incidental, done for another reason, yet happened to disclose a large aneurysm with a poor prognosis. This scenario will appear as a rapid death in K–M analysis. (ii) Some patients presented to us with advanced disease, having borne the burden of aneurysm disease for many years, yet were not suitable for or refused surgery, contributing to early ‘drop-off’. (iii) Some patients presented with a lethal ascending aortic dissection and an incidental pre-dissection scan was used for the initial dimension. Analyses based solely on initial aortic measurement: Dr Milleron observes that aortic diameter may change during follow-up intervals. However, the rate of growth of the thoracic aorta is indolent (∼1 mm/year), and the likelihood of rapid growth is so low as to be almost mythical.2,3 Our analysis looks at outcomes in patients presenting to our offices at a specific time with a specific, finite aortic diameter. Our study elucidates long-term outcomes for those patients presenting with that diameter at that time—in order to permit a thoughtful management decision about their future from that time forward. All our patients undergo serial imaging over the years, and their risk profile is updated as needed based on the current diameter at the follow-up interval. We believe this is a logical approach. Surgical risk vs. natural risk of adverse events: Dr Milleron points out our finding that ‘the risk of aortic related events and death (AAE) is 0.3%, 1.4%, and 2% for aortas of diameter 45, 50, and 55 mm’. How then, he asks, can this justify a nearly equivalent surgical risk of 2%. This is easy to answer. The aortic risks are yearly, while exposure to the surgical risk is a unique, one-time experience. The risk of aortic events continues year after year, so that the risk rates, double, triple, quadruple, etc. with each passing year. For example, the cumulative risks of adverse natural aortic outcomes would be 1.5%, 7.0%, and 10% at the 5-year point. It is for the latter two ranges (50 and 55 mm) that we have, justifiably, recommended surgery. In addition, it is pivotal to emphasize that the aorta grows by about 8 mm at the very moment of dissection.4 This means that the aorta was 8 mm smaller than the measured immediate post-dissection sizes that we see clinically (Figure 1A). The 50 mm surgical threshold that we recommend provides accommodation for this crucial observation. (A) Eight consecutive yearly computed tomography scans of a single patient documenting the slow growth of the ascending aorta and a subsequent scan at the time of aortic dissection. Note the rapid 8 mm growth at the time of dissection. (B) Histogram of aortic size at the time of aortic dissection. Note the considerable cohort of acute Type A dissectors with aortas smaller than a 5.0 cm criterion. Reprinted with permission from Perez et al.5 (C) Summary graphic illustrating clinical decision-making in ascending aortic aneurysm disease. Reproduced with permission from Elefteriades et al.6 Also, it might be said that our 50 mm criterion is too conservative. Histograms of aortic diameter at the time of aortic dissection reveal that the 50 mm criterion ‘leaves behind’ a substantial proportion of afflicted patients, who have dissected at sizes <50 mm (Figure 1B). Indeed, the combined wisdom of world experts has endorsed our recommended ‘left-shift’ in the 2022 ACC/AHA Aortic Disease Guidelines.7 Furthermore, although size is a useful criterion, the decision to operate for ascending aneurysm is highly nuanced. We have recently recommended that 14 different factors be incorporated into the decision-making, only one of which is aortic diameter (Figure 1C). J.A.E. is Principal of Coolspine. All other authors have nothing to disclose.