Aortic arch-clamping technique without open distal anastomosis for extended ascending aortic aneurysms

Introduction

Currently, operative intervention for high-risk ascending aneurysms with a size ≥4.5 or >5.5 cm is recommended in several guidelines (1,2). The treatment strategy for an aneurysm in the proximal aorta is relatively advanced and has achieved satisfactory clinical outcomes. However, when the aneurysm involves the distal ascending aorta or proximal arch, proximal aortic replacement alone is insufficient to eliminate the entire lesion, which may increase the risk of more extensive reoperation (3,4). Open distal anastomosis (ODA) is a classic surgical method for proximal arch aneurysms, and several studies have indicated that ODA may reduce the incidence of long-term reintervention compared to proximal aortic replacement alone (5-7).

Nevertheless, ODA inevitably requires selective cerebral perfusion and hypothermic circulatory arrest (HCA), which may lead to postoperative organ injury, coagulopathy, and neurologic dysfunction (7-9). Due to the risks associated with ODA, some researchers have proposed new surgical techniques to avoid the application of HCA during the operation, but the clinical results are limited (10-12). At our institution, the aortic arch-clamping (AAC) technique has been used to treat ascending aneurysms that extend to the proximal arch. The present study compared the short- and mid-term prognoses of the AAC group with those of the ODA group, aiming to clarify the application value of the AAC technique. We present this article in accordance with the STROBE reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1133/rc).

Methods

The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by the Ethics Committee of the Beijing Anzhen Hospital, Capital Medical University (No. 2020061X) and individual consent for this retrospective analysis was waived.

Study population

Between January 2015 and February 2022, 306 patients with ascending aneurysms involving the proximal arch underwent elective proximal aortic replacement and distal ascending aorta replacement. Patients under 18 years of age, as well as those with a bovine arch, distal aortic arch dilation, aortic dissection or rupture, or severe calcification of the aorta or femoral artery, were excluded. After exclusion criteria screening, 230 participants were included in the research cohort.

Preoperative transthoracic echocardiography and computed tomography angiography (CTA) confirmed all patients’ diagnoses. Based on the surgical approach, the patients were divided into the ODA group (n=113) or the AAC group (n=117).

Surgical techniques

At our institution, distal ascending aorta replacement is performed when the diameter is ≥4 cm. Near-infrared spectroscopy (YN-9002, ENO, Anhui, China) was used to assess the changes in cerebral perfusion-oxygenation during the operation.

The details of the AAC procedure have been described previously (13): the innominate artery and proximal aortic arch were fully dissociated, and a thick suture was placed around the aortic arch between the innominate artery and the left common carotid artery to mark the clamping site for the aortic clamp. Cardiopulmonary bypass (CPB) was established through the right femoral artery, and cooling was initiated. Mild hypothermia [the lowest rectal temperature (RT) ranging from 28 to 32 ℃] was employed to balance organ protection with surgical efficiency. After proximal aortic surgery was completed, the aortic arch was clamped between the left common carotid artery and the innominate artery (zone 1 arch). Then, the innominate artery was clamped, and an additional anastomotic distance of approximately 1 cm was obtained by removing the atraumatic clamp on the distal ascending aorta. To ensure sufficient perfusion of the right side of the cerebrum, the atraumatic clamp on the innominate artery was removed to check for back-bleeding. The distal aortic anastomosis and vascular graft termination were then cut in a matching oblique fashion, and the continuity of the aorta was reconstructed by continuous sutures using a 4-0 polypropylene suture. The greater curvature of the aortic arch was anastomosed proximal to the innominate artery orifice, and the lesser curvature was anastomosed with the aortic arch, which was contralateral to the left common carotid artery orifice. Perfusion flow throughout the CPB was maintained at 60–80 mL/kg/min.

The details of the ODA procedure have also been described previously (14). CPB was established through the right axillary artery, and the cooling target was set to a RT of 25 ℃. After the proximal surgery, the perfusion flow was adjusted to 5–10 mL/kg/min. The arch branch vessel was clamped, and the atraumatic clamp on the ascending aorta was removed. Antegrade cerebral perfusion (ACP) with moderate HCA was initiated. The aortic continuity was reconstructed using the same anastomotic technique and site as the AAC procedure.

Definitions and follow-up

The primary endpoint was composite adverse events, including mortality, permanent neurological dysfunction (PND), Kidney Disease: Improving Global Outcomes (KDIGO) stage of acute kidney injury (AKI) ≥3, and ventilation time >24 h. Operative mortality was defined as 30-day or in-hospital mortality. PND was defined as a new stroke lesion confirmed by head CT and/or brain magnetic resonance imaging. Transient neurological dysfunction (TND) was defined as postoperative transient psychiatric symptoms without positive imaging findings, such as confusion, dysphoria, delirium, and apathy. Hepatic dysfunction was defined as the peak value of either alanine aminotransferase or aspartate aminotransferase exceeding 100 IU/L within 48 hours after surgery (15). Respiratory failure was defined as the inability to maintain adequate gas exchange, requiring reintubation or the application of noninvasive ventilatory support following initial extubation. AKI is diagnosed by a postoperative serum creatinine increase of ≥1.5 times the baseline value in the first 7 days, and the stage of AKI was based on the KDIGO criteria. Reintervention included aortic-related reoperation or interventional procedures. Cross-clamp time refers to the duration from the application of the aortic clamp to the completion of aortic reconstruction and the restoration of blood flow.

All patients were recommended to have a CTA review within 30 days after surgery and a CTA or an echocardiography review at 3, 6, and 12 months after the operation and yearly thereafter. The patients were followed up regularly through outpatient service, telephone, and WeChat.

Statistical analysis

Frequencies and percentages were used to summarize categorical variables, and Fisher’s exact test or Chi-squared analysis (with continuity correction) was used to compare them. The mean (standard deviation) or median (interquartile range) represented continuous variables. The differences in continuous variables were compared using the Student’s t-test or the Kruskal-Wallis test.

To minimize selection bias and control latent confounders, propensity score matching (PSM) was used to adjust for baseline data (16). Propensity scores were created for each patient using a logistic regression model based on 18 covariates, which are listed in Table 1 and concomitant procedures. The AAC group were matched to the ODA group in a 1:1 ratio utilizing a greedy-nearest-neighbor algorithm with a caliper of 0.1. The quality of the match was evaluated using the standardized mean difference (SMD), and a maximum SMD of 0.1 or even 0.15 was considered acceptable (17).

Univariate and multivariable logistic regression analyses were performed to analyze the impact of the AAC technique on the incidence of composite adverse events, AKI, ventilation time >24 h, hepatic dysfunction, and neurological complications (PND + TND). The multivariable logistic regression analysis included the variables from the univariate analysis with P values less than 0.1. The Kaplan-Meier method was used to estimate the survival function, and the log-rank test was used to assess differences between these two groups (AAC vs. ODA). The probability of reintervention was estimated using cumulative incidence curves; the cumulative incidence with the competing risk of death was compared by using Gray’s test. Statistical analysis was performed using SPSS, version 26.0 and R 4.2.1.

Results

Study population characteristics

Before PSM, the proportion of males in the AAC group was higher compared to the ODA group (74.4% vs. 59.3%, P=0.02), and the AAC group had a greater prevalence of alcohol consumption and diabetes (32.5% vs. 19.5%, P=0.04; 16.2% vs. 3.5%, P=0.003, respectively). The aortic root diameter of AAC group was significantly wider than that of ODA group (3.97 vs. 3.97 cm, P=0.03), but the middle ascending aorta diameter was significantly narrower than that of ODA group before PSM (5.55 vs. 5.77 cm, P=0.04). After PSM, 2 groups of 67 patients were obtained. There was no substantial mean difference (absolute SMD <0.15) in the baseline data between the 2 groups, and a love plot of the SMD for the matched variables is presented in Figure S1. A summary of the baseline data is shown in Table 1. The propensity-score distribution was quite similar in the 2 groups after matching (Figure S2).

Intraoperative data

The treatment of the proximal aorta and the combined operation were comparable in both groups. The AAC group had significantly shorter CPB times (120 vs. 156 minutes, P<0.001) and higher nasopharyngeal and RTs (30.3 vs. 24.5 ℃, P<0.001; 30.6 vs. 25.6 ℃, P<0.001, respectively) than the ODA group but the cross-clamp time (78 vs. 88 minutes, P=0.08) was similar to that in the ODA group (Table 2). The median HCA time in the ODA group was 15 minutes. Compared to the ODA group, the amount of blood product transfusion was significantly lower in the AAC group before PSM. However, there was no significant difference in intraoperative blood transfusions between the two groups after PSM.

Postoperative outcomes

The postoperative outcomes in the different groups are summarized in Table 3. In contrast with the AAC group, the incidences of AKI, TND, ventilation time >24 h, and composite adverse events were significantly higher in the ODA group (AKI, 32.8% vs. 7.5%, P=0.001; TND, 9.0% vs. 0%, P=0.04; ventilation time >24 h, 19.4% vs. 6.0%, P=0.04; composite adverse events, 13.4% vs. 1.5%, P=0.02). In the AAC group, patients had shorter in-hospital time (16 vs. 18 days, P=0.02). Between the two groups, there was no significant difference in operative mortality rate (0% vs. 1.5%, P>0.99) or incidences of PND (4.5% vs. 0%, P=0.24). In the multivariable logistic regression analysis (Tables 4,5), AAC was an independent protective factor for composite adverse events, ventilation time >24 h, and AKI [composite adverse events, odds ratio (OR): 0.05, 95% confidence interval (CI): 0.01–0.39, P=0.005; ventilation time >24 h, OR: 0.33, 95% CI: 0.12–0.92, P=0.03; AKI, OR: 0.21, 95% CI: 0.08–0.54, P=0.001].

Midterm outcomes

By September 2022, the clinical follow-up of all operative survivors was completed. The mean follow-up time was 4.0 (2.2) years (maximum 7.6 years). During follow-up, there were 7 deaths and 6 reoperations in the entire cohort, and 217 patients survived without reoperation (Figure 1). No patients with arch redilation were found during follow-up, and the details of the death and reoperation patients are summarized in Table S1. There was no discernible difference between the two groups in terms of mid-term mortality or cumulative incidence of reintervention with competing risk of death (P=0.44; P=0.91, respectively) (Figure 2).

Figure 1 Competing risks analysis of death, reoperation, and survival without reoperation.

Figure 2 Mid-term outcomes diagram of patient mortality and reintervention. (A) Kaplan-Meier plots of overall survival by group in unmatched patients. (B) Kaplan-Meier plots of overall survival by group in matched patients. The difference was assessed with the log-rank test. Freedom from all-cause death between the two groups was not statistically significant. (C) The cumulative incidence of reintervention with all-cause death as a competing risk in unmatched patients. (D) The cumulative incidence of reintervention with all-cause death as a competing risk in matched patients. The difference was assessed with Gray’s test. The difference in reintervention between two groups was not statistically significant. ODA, open distal anastomosis; AAC, aortic arch-clamping.

Discussion

In the current research, we evaluated the application value of the AAC technique. AAC significantly reduced the incidence of postoperative composite adverse events and had a significant protective effect on AKI and ventilation time >24 hours. In addition, the AAC technique had a shorter CPB time and a higher nasopharyngeal temperature, which may reduce the risk of postoperative hepatic dysfunction and neurological complications (Figure 3). However, we found that mid-term mortality and reintervention were not significantly different between the AAC and ODA groups.

Figure 3 The short-term efficacy of the AAC technique was better than the ODA technique in patients with ascending aortic aneurysms extending to the proximal arch. *, P<0.05; **, P<0.001; ns, not significant. ODA, open distal anastomosis; AAC, aortic arch-clamping; AKI, acute kidney injury; TND, temporary neurological dysfunction; PND, permanent neurological dysfunction; IABP, intra-aortic balloon pump.

Current guidelines have indicated surgical indications for proximal aortic aneurysms and aortic arch aneurysms (1,18). However, surgical indications for distal ascending aortic aneurysm or proximal aortic arch aneurysm are lacking in the guidelines, and whether to perform hemiarch replacement depends on the experience of the cardiac surgeon at each institution. At our center, the surgical threshold for patients with aneurysms involving the proximal arch is 4.0 cm. According to our mid-term follow-up results, there was no aortic arch-related reintervention in the AAC or ODA groups, which may indicate that 4.0 cm is sufficient as the surgical threshold. In a report by the Malaisrie’s team (6), an additional hemiarch replacement was performed when the distal ascending aorta reached 4.0 cm, and 177 patients who underwent the ODA technique during hemiarch replacement had no reoperation related to the aortic arch during follow-up, which may support our opinion.

The ODA combined with moderate HCA technique is a classic surgical procedure for distal ascending aortic aneurysm. Compared with deep HCA, moderate HCA greatly reduces the cooling and rewarming time of CPB and significantly reduces the risk of coagulopathy and neurological complications caused by prolonged CPB and deep hypothermia (19,20). The ODA technique inevitably has a period of organ ischemia, although mild HCA has been applied in aortic arch surgery in many centers (21,22). It is difficult to determine the tolerance time of the liver, kidney, spinal cord, and other terminal organs to hypothermia ischemia. The balance between temperature and circulatory arrest time needs to be clarified further by prospective randomized controlled studies with large sample sizes. The significant advantage of the AAC technique is that it adequately addresses proximal arch lesions while avoiding the need for HCA application. Due to the continuous perfusion of distal organs, the lowest RT in the AAC group was set at mild hypothermia, which significantly shortened the CPB time and avoided the complications associated with hypothermia.

Clinically, we found that aortic aneurysms more often involved the proximal aortic arch, while aneurysms throughout the aortic arch were relatively rare, which may be related to the shear force caused by hemodynamics (23). In the AAC technique, additional anastomotic distance is achieved by changing the position of the aortic arch clamp during the operation. The clamping position effectively avoids the aneurysm lesion and allows us to conduct tension-free sutures, which is similar to the ODA technique. In addition, the AAC technique does not require clamping of the common carotid artery and the left subclavian artery, which avoids dissociating the distal aortic arch and reduces the possibility of recurrent laryngeal nerve damage. This is very important for hospitals with small volumes and relatively inexperienced doctors, who no longer have to struggle to save precious HCA time.

In our institution, unilateral ACP was used for both groups. The optimal cerebral protection strategy continues to be debated. According to a meta-analysis involving 28 studies, there is no significant difference in the efficacy of unilateral ACP and bilateral ACP in operations involving the aortic arch (24). In a study involving 307 people, Professor Yang pointed out that postoperative stroke and mortality risks were similar in patients with unilateral ACP and bilateral ACP. As a simple and effective technique, unilateral ACP is more often recommended for application (25). Another study noted that the prognosis of patients with unilateral ACP on the left and right sides did not differ significantly, and both results were satisfactory (26). In our center, the axillary artery was used in the ODA group, and the femoral artery was used in the AAC group. We performed preoperative evaluations of the cerebral arteries, including the Circle of Willis, using MRI or CT angiography. This comprehensive assessment was crucial for determining the feasibility of unilateral cerebral perfusion. Additionally, during operations, we ensured the adequacy of cerebral perfusion by checking the back-bleeding from the contralateral cerebral blood vessel and performing near-infrared spectroscopy monitoring. The incidence of PND in the ODA group and in the AAC group was 4.5% and 0%, respectively, indicating that unilateral ACP effectively avoided postoperative neurological complications. However, the incidence of TND in the ODA group was substantially higher than that in the AAC group (9% vs. 0%, P=0.03). Logistic regression showed that the lowest NT, smoking and intraoperative fresh frozen plasma infusion were significant factors indicating neurological complications. Furthermore, the AAC technique reduces the risk of air embolism by avoiding the need for intraoperative HCA, which may be another factor contributing to ideal postoperative neurologic outcomes in this group of patients.

Although no significant difference in the amount of intraoperative blood transfusion between the two groups after PSM, the application of the AAC technique holds promise for reducing intraoperative blood transfusion requirements. Prolonged CPB leads to coagulopathy and increased consumption of coagulation factors, which can increase the risk of massive intraoperative bleeding. In addition, HCA can also increase the risk of platelet dysfunction, resulting in difficulty achieving intraoperative hemostasis (19,27). The transfusion of blood products will lead to the release of substances such as circulating free hemoglobin, iron, and platelet-related bioactive mediators, which can further activate the inflammatory response, leading to an increased risk of other related adverse events (28,29).

In this study, the incidences of prolonged postoperative mechanical ventilation and AKI increased significantly in the ODA group. According to the results of the multivariable analysis, AAC was a significant protective factor for these two adverse events. In addition to the fact that HCA induces ischemia-reperfusion injury and prolongs CPB time, transfusion-related kidney and lung injuries may be the underlying causes according to our previous studies (28,29). The interaction of different mechanisms eventually leads to the recurrence of the events mentioned above. The ability of the AAC technique to avoid this interaction may be another application value of this technique.

The AAC technique has some contraindications, such as porcelain aortic aneurysm and aortic dissection. When CTA showed calcified plaque in the aortic arch, intraoperative transesophageal echocardiography is required to confirm the plaque position further. In addition, aortic dissection is a dynamic process, and it is difficult to determine whether there is an intimal tear in the distal arch during the operation by preoperative evaluation. If a residual arch intimal tear is not treated, it may increase the risk of reoperation (30). Furthermore, unlike central aortic or axillary artery cannulation which ensures continuous antegrade flow, femoral artery cannulation results in retrograde flow. This carries the potential risk of displacing atherosclerotic plaques or emboli from the descending aorta, potentially leading to organ infarction such as stroke. A study of our center has also demonstrated an evident increase in neurological complications among patients with aortic dissection even when utilizing combined cannulation strategies (31). Therefore, patients with server aortic atherosclerosis or aortic dissection require special attention.

Limitations

There are potential limitations in this study. First, the results may be affected by the lack of randomization in this single-center retrospective study. Second, the baseline data differed between the two groups, and even after the PSM analysis, potential selection bias in our population could not be entirely avoided. Additionally, the choice of surgical method was primarily based on the surgeon’s preference, which may have introduced additional selection bias. Last, the incidences of death and reoperation events were too low to identify risk factors, and long-term mortality and reintervention risks need further follow-up.

Conclusions

The AAC technique allows for distal ascending aorta replacement without HCA or selective cerebral perfusion. Our study showed that the AAC technique significantly improves clinical outcomes, with satisfactory mid-term results. For ascending aneurysms extending to the proximal arch, the AAC technique should be considered because of its simplicity, safety, and effectiveness.

Acknowledgments

Funding: This work was supported by Beijing Major Science and Technology Projects from Beijing Municipal Science and Technology Commission (Nos. Z191100006619094 and Z221100007422112).

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1133/rc

Data Sharing Statement: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1133/dss

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1133/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-24-1133/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 (as revised in 2013). The study was approved by the Ethics Committee of the Beijing Anzhen Hospital, Capital Medical University (No. 2020061X) and individual consent for this retrospective analysis 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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