This study performed a PSA to reduce the bias to the most extent and compare the effect of TEVAR for BTAI and pTBAD, intending to add more evidence to the clinical decision especially about BTAI in this TEVAR era. The BTAI group exhibited a more satisfying early outcome with no adverse events within 30 days postoperatively. Late mortality was similar in both groups, but the BTAI group showed a significantly lower rate of aortic-related reintervention. Regarding aortic remodeling, a remarkable higher rate of abdominal complete FL thrombosis was found in BTAI group than in pATBAD. Previously there was no study directly comparing BTAI and pTBAD due to the discrepancy of these two types of pathologies, such as the younger age distribution of BTAI patients. Therefore we perform this PSA study. After PSA, patient demographics and comorbidities turned into similar in both groups, which reduced the potential bias mainly caused by the older age distribution in the overall pATBAD cohort. The unmatched incidence of hypertension remained high in pATBAD, which was to be expected since it’s one of the crucial factors in AD pathogenesis.
In the present investigation, BTAI patients had an average duration from admission to surgery of 8.5 ± 6.6d (0–31 d), comparable with the 9.9 ± 5.4 d (1–23 d) of pATBAD patients. The intervention time of BTAI has been discussed for years. Society for Vascular Surgery 2011 guideline recommends an urgent repair for BTAI patients4. However, Ultee et al. found that early TEVAR on the day of admission was a risk factor for 30-day mortality19. Demetriades et al. and Marcaccio et al. both discovered a strong survival advantage with delayed repair, though with potentially higher morbidities of postoperative complications20, 21. European Society for Vascular Surgery 2017 guideline recommend delayed intervention for BTAI patients without large hematoma as IIa class of evidence6. In our BTAI cohort, only 3 patients underwent early repair on the day of admission, with one aortic rupture and 2 AD. Delayed TEVAR was performed in 92.7% of BTAI patients after the stability of the general condition. Favorable 30-day outcomes of BTAI patients were observed in our study with an absence of in-hospital mortality and complications, as well as a comparable overall length of stay in-hospital with the pATBAD group, further strengthening the current evidence of delayed repair for BTAI. Concerning endovascular procedures, the pATBAD group was found to have a significantly longer average SG coverage than the BTAI group, which could be explained by the difference of aortic lesion characteristics in two groups. There was a tendency toward higher incidence of spinal cord ischemia in the pATBAD group, yet no statistical significance was observed.
Previously Alberta et al.22 have compared aortic arch morphology among TBAD, BTAI, and descending thoracic aneurysm, discovering an overall smaller aortic diameter in BTAI patients, especially around zone 3. Theoretically, BTAI happened in the population with the originally healthy aorta. Therefore, the aortic morphology might differ from those of aortic dilative diseases. In our study, interpretations should be cautiously given about the result of SG proximal and distal diameters, which was slightly larger in the pATBAD group than the BTAI group, yet was not found to be significantly different. Hercules Low-Profile Thoracic SG was used only in the BTAI group in our center, which has smaller size of devices, providing more options in decision making process. It’s worth noting that hypovolemic aortic status was commonly presented in BTAI patients upon intervention, possibly leading to SG undersizing after fluid resuscitation, which could give rise to device-related complications such as SG migration or type I endoleak. Therefore, a slightly more oversizing rate was usually considered for BTAI patients. Paradoxically, excess oversizing could also result in severe incidences like RTAAD and bird-beak sign, which puts this issue in a dilemma and would require overall more comprehensive consideration. Combined with the above finding, the observation of similar SG diameters in both the groups could be attributed to the fact that most of the patients were transferred to our center from secondary or local hospitals after urgent management, whom were already corrected for hypovolemia. Besides, there was no post-operative RTAAD in BTAI group, yet four cases happened in pATBAD group (p = 0.3), which could be related to the suitable proximal oversizing rate adopted during our practice. Moreover, Alberta et al. found that the trauma patients were oversized more than the aneurysm patients at the distal landing zone (DLZ)23, which could raise the concerning of distal stent graft-induced new entry (SINE) due to the radial expanding force exerted by SG on distal healthy aorta in BTAI patients. Tapered SGs could be a more suitable choice for BTAI patients because of their segmented lesion. More extensive studies would be beneficial for probing into this focus.
Early and long-term outcomes were encouraging in this study. The pATBAD group appeared to have a significantly higher reintervention rate than the BTAI group during follow-up, which was coincidentwith the finding of previous studies24, 25. However, this was to be recalled that an unneglectable portion of patients were lost to follow-up despite the similar rate as previously report26. The possible reasons were the following: 1. As a high-volume tertiary center with advanced medical service, patients with the acute aortic syndrome were more likely to be transferred to our hospital at the time of onset but would prefer to receive CTA scan at local hospitals instead during follow-up, due to the potential cost of transportation or accommodation. 2. Young or middle-aged patients of BTAI with an originally healthy status itself could make them less compliant during follow-up. However, it could be assumed that patients who did not came back to our center for follow-up were most likely those without severe complications or without the need for reintervention. Therefore, the bias caused by loss of follow-up would actually affirm the conclusions deducted from the current results further. FL thrombosis was chosen as the parameter to assess aortic remodeling in this study. FL thrombosis was more favorable at distal aorta in BTAI group than pATBAD, which should be explained carefully since distal aorta was less involved in BTAI patients at the beginning with limited samples. However, this finding could still partially suggest that aortic lesion would rarely progress in BTAI patients, and the long-term efficacy of endovascular repair was satisfying in our cohort.
Results from our PSA indicated a favorable effect of TEVAR for BTAI patients, even superior to the pATBAD group. This study could provide more solid evidence for current clinical practice to support TEVAR for BTAI.
Our study had several limitations. First, this was an observational cross-sectional study from a single center with limited sample sizes, and the proportion of loss to follow-up was an inevitable weakness of such study design. Second, we were not able to adjust for all the potential confounding factors which could influence the comparison between two groups.