Long-term outcomes of frozen elephant trunk for non-A non-B aortic dissection: a comparative analysis based on entry tear location

Introduction

Aortic dissection is a life-threatening condition with low incidence but extremely high mortality (1). Initially, the Stanford and DeBakey classifications were predominant in the field. However, with the introduction of the Type, Entry location, and Malperfusion (TEM) classification (2), which has been referenced in guidelines (3,4), it has gradually gained recognition among peers. The TEM classification integrates the extent of dissection, entry site location, and branch perfusion insufficiency into its diagnostic framework. A notable innovation in the TEM classification is the introduction of the non-A non-B aortic dissection (NANB-AD) category, which specifically describes aortic dissections confined to the aortic arch and descending aorta, without ascending aortic involvement. Due to aortic arch involvement, the surgical procedure presents significant technical challenges with greater trauma than endovascular approaches, carrying elevated perioperative risks (including stroke, reoperation, and infection) and uncertain long-term outcomes. However, its therapeutic efficacy in NANB-AD remains unclear (5). Therefore, based on our center’s accumulated experience, we conducted a 13-year follow-up study aimed at investigating the short-term and long-term outcomes of total arch replacement combined with frozen elephant trunk (TAR with FET) in treating NANB-AD with varying entry site locations. We present this article in accordance with the SUPER reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-aw-2195/rc).

Methods

The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study received approval from the ethical review board of Fuwai Hospital of the Chinese Academy of Medical Sciences (No. 2023-2084). Since this study is retrospective, patient consent was waived.

Study population and data collection

This retrospective study analyzed 63 consecutive patients who underwent TAR with FET for NANB-AD between 2010 and 2022 at Fuwai Hospital. During the same period, 1,672 patients with acute type A aortic dissection (TAAD) underwent TAR with FET at our center; these patients were not part of the present study cohort and were only used as a reference for the overall surgical volume. Malperfusion was assessed based on preoperative computed tomography (CT) findings and clinical symptoms. The cohort consisted of patients with acute NANB-AD, defined according to the TEM classification as dissection involving the aortic arch and the descending thoracic aorta while sparing the ascending aorta. The cohort was grouped based on the tear location identified through CT three‑dimensional reconstruction. Arch entry classification is characterized by an entry tear within the aortic arch with subsequent antegrade dissection extending into the descending aorta. If the tear extended across both the aortic arch and descending aorta, it was classified as an arch entry. Conversely, descending entry classification is defined by an entry tear positioned distal to the left subclavian artery origin, with retrograde dissection propagating into the aortic arch. Post-discharge surveillance protocol consisted of systematic follow-up evaluations at 3 months, 6 months, and annually thereafter. Both clinical assessment and CT examination were incorporated into each follow-up visit. Patient monitoring was maintained through a combination of direct clinical encounters and personal communications. In clinical practice, CT angiography was performed once per year during follow-up, unless earlier imaging was warranted by new symptoms or suspicion of disease progression. The follow-up period extended through August 2024.

Surgical techniques

Median thoracotomy and cardiopulmonary bypass (CPB) were universally performed on all patients. The choice of cannulation site (axillary, innominate, or femoral artery) was individualized based on patient-specific conditions. After establishing CPB, if aortic root pathology was present, appropriate surgical intervention was performed during the cooling phase. For example, in the Bentall procedure, the valved conduit is anastomosed to the aortic annulus before cerebral perfusion begins. Upon reaching the target core temperature (24–28 ℃), bilateral cerebral protection was achieved by inserting an additional perfusion cannula into the left common carotid artery, maintaining a total flow rate of 15 mL/kg/min. The FET (MicroPort Medical Co., Ltd., Shanghai, China) was deployed under direct visualization through the distal aortic anastomosis. The FET length (100/120/150 mm) was chosen according to patient height and the distance between the left common carotid artery and T8 vertebra, with consideration for spinal cord safety, positioning the distal anchor at T6–T7. The optimal deployment zone was selected between the left common carotid artery and the left subclavian artery. A four-branched Dacron graft (Boston Scientific Inc., Marlborough, Mass, USA) was then anastomosed end-to-end with both the distal aorta and the FET at Zone 3. Lower body perfusion was restored after inserting the arterial perfusion cannula into the dedicated perfusion branch of the Dacron graft. The procedure was completed by sequentially anastomosing the branches of the Dacron graft to the left subclavian artery, common carotid artery, innominate artery, and proximal aorta.

Definitions and outcomes

The primary outcome was mortality, while secondary outcomes included aorta-related reinterventions and activity of daily living (ADL). The TEM classification system was used to define and categorize aortic dissection and malperfusion (2). Thrombosis of the false lumen proximal to the stent is defined as the absence of false lumen at the stent level in the patient’s most recent follow-up CT imaging. In the descending-entry group, complete primary entry closure was assessed using this radiological criterion, that is, the absence of a residual false lumen at the stent level on postoperative CT. This finding was used as a surrogate marker of durable exclusion of the primary entry tear. Based on the WeChat questionnaires and telephone interviews, patients’ functional status was stratified into four ADL levels (6): Level 1—total loss of self-care capacity; Level 2—partial self-care requiring assistance; Level 3—complete self-care but unable to perform general physical work; Level 4—capable of standard physical labor.

The aortic morphological data were measured by iFlux Aorta (Beijing Duanliu Medical Technology Co., Ltd.). By straightening the aortic CT images, analyze the extent of aortic dissection and measure the morphological parameters of aortic length. The ascending aortic length (AAL) is defined as the distance of centerline between the aortic valve annulus and the innominate artery (7). The maximum diameter is determined using the aortic segmentation technique by identifying the cross-section with the largest area, which is then converted into an equivalent circular shape to obtain the maximum diameter (8).

Statistical analysis

Categorical variables were presented as frequencies with percentages and analyzed using the χ² or Fisher’s exact test, as appropriate. Continuous variables were assessed for normal distribution using the Kolmogorov-Smirnov test and were expressed as mean with standard deviation or median and interquartile range accordingly. Student’s t-test was applied to normally distributed variables, while the Mann-Whitney U test was used for nonnormally distributed variables. Kaplan-Meier curves were used to analyze long-term survival. The cumulative incidence of long-term reoperation was analyzed using the Gray-Fine regression model, with death considered a competing risk. Statistical analysis was assessed using R version 4.0.4 (The R Foundation for Statistical Computing, Vienna, Austria).

Results

Baseline characteristics

A total of 63 patients with NANB-AD underwent TAR with FET procedure and subsequent follow-up (Figure 1). The cohort comprised 31 patients (49.2%) in the arch entry group and 32 patients (50.8%) in the descending entry group (Figure 2). The study population included 48 males and 15 females with a mean age of 46.7 (11.2) years. Two patients (3.2%) had the history of cardiac surgery, and 9 patients (14.3%) were diagnosed with Marfan syndrome. Analysis of aortic morphology demonstrated a significant difference in ascending aorta length (AAL) between groups [102.3 (11.6) vs. 95.7 (13.2) mm, P=0.01]. No statistically significant differences were observed in other baseline characteristics, which are comprehensively presented in Table 1.

Figure 1 Patient flow diagram. TAR with FET, total arch replacement combined with frozen elephant trunk.

Figure 2 Representative CTA images illustrating primary entry tear locations in non-A non-B aortic dissection. (A) CTA of the aorta showing the entry tear in the aortic arch. (B) CTA of the aorta showing the entry tear in the descending aorta. CTA, computed tomography angiography.

Surgical details

As detailed in Table 2, concurrent procedures were performed in several patients: coronary artery bypass grafting in 10 patients (15.9%), extra anatomic bypass for lower-extremity in 9 patients (14.3%), and aortic root surgery in 18 patients (28.6%). The mean CPB time was 172.0 (49.4) minutes. The mean hypothermic circulatory arrest time was 18.8 (7.2) minutes, was a lowest core temperature of 26.3 (1.5) ℃. Intraoperative characteristics were well-balanced between the two groups (all P>0.05).

Early and long outcomes

Outcome characteristics were shown in Table 3. Two patients (3.2%) died postoperatively: one due to circulatory failure and one due to multiple organ failure. Two patients (3.2%) developed permanent neurological dysfunction but were discharged successfully. Following rehabilitation training, both patients achieved a level 3 on ADL assessment during follow-up. Six patients (9.5%) received continuous renal replacement therapy postoperatively, of whom one patient died due to multiple organ failure. Early postoperative complications did not differ significantly between the two groups (all P>0.05).

Complete follow-up was achieved for all patients, with a median follow-up duration of 4.0 years. Two patients (3.2%) experienced sudden death during follow-up, attributed to cardiovascular causes. Kaplan-Meier curve analysis revealed no statistically significant differences in long-term survival between the two groups (Figure 3). The 5-year survival rates of two groups were 96.8% and 93.8% for the arch entry and descending entry groups, respectively. Aortic-related reintervention was required in 5 patients (7.9%) across both groups (P=0.21), details shown in Table S1. Although the absolute number of aortic-related reinterventions was numerically higher in the arch entry group, this difference did not reach statistical significance and likely reflects the extent of distal aortic involvement at baseline rather than failure of proximal repair. Further competitive risk analysis was performed for aortic-related reintervention events and mortality (reintervention-P=0.27, Figure S1). Based on clinical experience, relevant criteria were included for univariate logistic regression analysis of in-hospital mortality. For every 1-hour increase in CPB time, the risk of mortality increased by 5% (Table S2). During follow-up, 54 patients (91.5%) were able to perform standard physical activities after surgery. No significant difference in ADL level was observed between the two groups (P=0.47, Figure S2).

Figure 3 Long-term follow-up survival curves of two groups.

Regarding imaging follow-up results, CT angiography was obtained in 58 (92.1%) patients, with a median radiological follow-up duration of 3.3 (1.8, 4.2) years. This high rate of radiological follow-up allowed consistent assessment of aortic remodeling and distal aortic events. False lumen thrombosis was observed in 54 patients (85.7%) with no statistically significant differences between the arch entry and descending entry groups. In the descending entry cohort, complete thrombosis of the false lumen proximal to the stent on the latest follow-up CT was considered a surrogate marker of durable primary entry closure, consistent with the definition in the Methods section. The median annual aortic diameter growth rate at the stent end was 0.33 (0, 0.83) mm/year, while the rate distal to the stent was 0.91 (0, 2.04) mm/year, with no statistically significant differences between the groups. These favorable proximal remodeling findings were in line with the low incidence of aorta-related reintervention during mid-term follow-up in both groups.

Discussion

Through this study, we demonstrated that different entry tear locations in NANB-AD yielded similar clinical outcomes following TAR with FET, addressing a significant knowledge gap in this field.

NANB-AD was first proposed by von Segesser in 1994 (9), representing a relatively rare subtype that accounts for approximately 3–11% of all aortic dissections (2,10-12). Due to arch involvement and the absence of ascending aortic disease, its management has long been controversial (13), and robust data on optimal therapy remained limited. Previous series have mainly reported outcomes of thoracic endovascular aortic repair (TEVAR) or TAR with FET in mixed NANB-AD populations. TEVAR combined with supra-aortic revascularization has been associated with acceptable early mortality but substantial rates of endoleak, retrograde type A dissection (RTAD), and aortic-related reintervention during follow-up (11,14). In contrast, small to medium-sized cohorts treated with TAR with FET have shown relatively low early mortality and favorable mid-term survival, suggesting that this approach may offer more durable aortic remodeling at the cost of higher initial invasiveness (15-18).

In our series of 63 patients—the largest cohort of NANB-AD treated with TAR with FET to date—early in-hospital mortality was 3.2%, and permanent neurological dysfunction occurred in 3.2% of patients. During a median follow-up of approximately 4 years, only 3.2% experienced all-cause death and 7.9% required aortic-related reintervention, resulting in a 5-year survival rate of 95%. These findings further support TAR with FET as an effective and durable treatment option for this challenging pathology. Another noteworthy feature of our cohort is the relatively young age at presentation. Although the onset age in our series is comparable to that reported in large-scale Chinese registries of aortic dissection, it is clearly lower than in many Western cohorts (19-21), consistent with the well-recognized epidemiological pattern that patients with aortic dissection in China tend to present at a younger age.

The present study also provided additional evidence supporting the use of TAR with FET in NANB-AD. This technique combined the advantages of open arch repair and endovascular stent grafting while mitigating some limitations of each approach (15,17,20). By excising or excluding the arch pathology and extending a stented graft into the proximal descending aorta, TAR with FET effectively addressed the large entry tears observed in NANB-AD (22), restored the true lumen in the proximal descending segment, and promotes false-lumen thrombosis and distal aortic remodeling. In the study, both the arch-entry and descending-entry groups achieved comparable long-term-outcomes, with no significant differences in aortic-related reintervention or distal aortic expansion rates. Two mechanisms may account for this: first, the remodeling effect of FET appears to play a more dominant role than differences in entry tear location; second, compared with classic type B dissection, entry tears in NANB-AD are typically located closer to the left subclavian artery, making them more amenable to reliable coverage by the stent graft portion of the FET (22).

Despite the broadly comparable outcomes between the two groups in our series, previous reports and our own data suggest that arch-entry NANB-AD may carry a higher intrinsic risk of distal aortic progression and late reintervention than descending-entry disease. Patients with arch-entry tears in our cohort tended to have more complex presentations, with a higher proportion of M2 and M3 malperfusion patterns, indicating more extensive branch-vessel involvement and more severe hemodynamic compromise before surgery. This is consistent with the findings of Kosiorowska et al., who reported that arch-entry non-A non-B dissections frequently present with rupture or organ malperfusion and often require urgent intervention, reflecting a less favorable anatomical and physiological substrate (18). In addition, in arch-entry NANB-AD, total arch replacement with FET, while effectively closing the proximal entry, may in some cases create a segment of false lumen that is proximally sealed but still perfused via residual distal re-entries. Such a locally confined yet persistently pressurized false-lumen configuration is prone to delayed thoracoabdominal aneurysmal enlargement and a greater need for secondary distal repair. By contrast, patients with descending-entry tears generally had smaller baseline diameters and more favorable distal anatomy, which may facilitate more stable downstream false-lumen thrombosis or partial thrombosis without progressive dilatation. Together, these factors may underlie the tendency toward higher aorta-related reintervention rates observed in arch-entry NANB-AD compared with descending-entry disease.

Our morphological analysis of NANB-AD revealed a significant finding: patients with entry tears located in the arch demonstrated longer ascending aortas compared to those with entry tears in the descending aorta (102.27 vs. 95.73 mm, P=0.01). This observation provides new insights into the anatomical characteristics of different NANB-AD subtypes. Della Corte’s study (23) reported that the mean AAL in acute TAAD was 115 mm, compared to 92 mm in normal subjects. Similarly, research in Asian populations (24) documented a median AAL in TAAD of 101 mm, which closely parallels our measurements in the arch entry group. However, ascending aorta length did not influence in-hospital mortality in our cohort. During follow-up, we incorporated ADL assessment to evaluate patients’ postoperative quality of life. We found that patients with NANB-AD who underwent TAR with FET achieved favorable quality of life outcomes (Figure S2). These findings reinforce our confidence in our surgical strategy for treating this challenging type of aortic dissection.

Limitation

There are several limitations in this study that warrant consideration. First, despite incorporating prospective follow-up, the investigation fundamentally remains a single-center retrospective study, which introduces potential selection bias. Second, although our cohort represents the largest and longest-duration study of NANB-AD treated with TAR with FET to date, the overall sample size remains relatively modest, potentially limiting statistical power for subgroup analyses. Third, in our institution, patients fulfilling the inclusion criteria for this study are routinely managed with surgical intervention; therefore, no comparable cohort of conservatively treated patients was available for analysis, and the absence of such a control group represents an important limitation.

Conclusions

This study demonstrated that TAR with FET serves as an effective surgical approach for treating NANB-AD, yielding low postoperative mortality and favorable aortic-related reintervention rates during long term follow-up. Importantly, our findings reveal that treatment outcomes remain consistent regardless of entry tear location, suggesting the versatility of this technique across different anatomical presentations of NANB-AD.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the SUPER reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-aw-2195/rc

Data Sharing Statement: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-aw-2195/dss

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-aw-2195/prf

Funding: This study was supported by the National Natural Science Foundation of China (No. 82400565) and Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences (CIFMS) (No. 2022-I2M-C&T-B-039).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-aw-2195/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study received approval from the ethical review board of Fuwai Hospital of the Chinese Academy of Medical Sciences (No. 2023-2084). Since this study is retrospective, patient consent was waived.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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