Descending Aortic Replacement with Third-Part Left Axillary Artery Graft Perfusion

We introduce a unique perfusion method for open descending aortic repair through a left thoracotomy. Perfusion from femoral artery cannulation is generally adopted in descending aortic replacement surgery. However, in cases with shaggy or partially thrombosed chronic aortic dissection, retrograde perfusion alone has a high risk of embolization and alternative perfusion methods should be considered. Our perfusion method from the third part of the left axillary artery graft is safe, simple, and useful for avoiding postoperative cerebral complications. In the present study, we report the advantages and challenges of this graft-interposed perfusion via the distal left axillary artery for descending aortic replacement.


Introduction
In the current era of endovascular repair, the number of open descending or thoracoabdominal aortic replacements has remained the same [1]. Some cases with complications, such as poor landing zone, chronic dissection, or difcult access route, may occur, in which endovascular repair is inappropriate and open descending aortic replacement (DAR) is required [1,2]. Te desired outcomes for DAR surgery with low mortality rate, low stroke complications, and good long-term results are those reported by experienced surgeons [3][4][5][6]; however, shaggy aorta is one of the risk factors for embolic events [7]. Te establishment of the cardiopulmonary bypass (CPB) in DAR is considered a critical factor for safe surgery in shaggy aorta; however, the method for blood perfusion is still up for debate [8][9][10][11][12]. In this study, we have reported on the usefulness of DAR using the third part of the left axillary artery (LAx3) graft perfusion.

Technique
Te patient was given the right decubitus position, with the chest elevated to approximately 80°. Te patient's hips were positioned at about 45°. Te left arm was raised above the head, with the axillary artery positioned for easy access in front of the surgical feld (Figure 1(a)). In most cases, the left femoral artery and vein were exposed. At the same time, the third part of the left axillary artery (LAx3) was exposed. Te skin and subcutaneous tissue were incised, the axillary vein and median nerve were encountered, and the LAx3 was identifed beneath them. Low-dose heparin (activated clotting time: 200-250 sec) was administered. A 9 mm woven gelatin-coated polyester vascular graft, J-graft (Japan Lifeline, Tokyo, Japan), was anastomosed end-to-side to the LAx3. Te LAx3 graft was connected to the arterial line of the CPB.
A left lateral thoracotomy was carried out through the ffth intercostal space. Te ffth posterior and anterior ribs were incised for good exposure of the aorta. Te aorta was dissected free from the lung, esophagus, hemiazygos vein, ligamentum arteriosum, and recurrent laryngeal nerve. Specifcally, the proximal and distal anastomosis sites of the aorta were dissected free from their attachments to shorten the circulatory arrest time during anastomosis, and we ligated as many intercostal arteries as possible from outside the aorta.
After full heparinization, standard femoral arterial and venous cannulation was performed. In our series, CPB fow, with a cardiac index of 2.4 L/min per square meter, was obtained with the LAx3 graft perfusion. However, unless there was a risk of embolization from abdominal aortic atherosclerotic plaques or thrombi from the false lumen, concomitant femoral perfusion was used. In cases with a risk of embolization, femoral perfusion was only used for distal perfusion after clamping the mid-descending aorta.
After starting the CPB, the tape of the distal part of the LAx3 was slightly pulled to direct the blood fow to the proximal side. Core cooling was started. A venting cannula was usually inserted into the left atrium through the left upper pulmonary vein. However, in the case of moderate or severe preoperative aortic regurgitation, a venting cannula was preferably inserted through the apex of the heart into the left ventricle. When the heart fbrillates, potassium chloride (20-60 mEq) was administered from the CPB circuit to arrest the heart. Systemic cooling was considered adequate when the patient's nasopharyngeal temperature was about 25°C.
Before the circulatory arrest, the patient was placed in the Trendelenburg position. Ten, the CPB fow was arrested, and the venting tube was clamped. Te middescending aorta was clamped, and the arterial fow was started through femoral perfusion. Te aneurysm was incised. During open proximal anastomosis, the blood was kept above the aortic arch to prevent air from entering the neck vessels. After completing the anastomosis and careful de-airing, the proximal perfusion was restarted from the LAx3 graft or side branch of the aortic graft. Te rewarming was started gradually. Following the hemostasis of the residual intercostal arteries, distal anastomosis was carried out either with an open distal technique or clamping with the help of femoral perfusion.

Patient Selection. Between April 2017 and May 2022, 46
patients underwent open surgery for DAR at the Shonan Kamakura General Hospital. Among them, we retrospectively reviewed 13 patients who underwent DAR with LAx3 graft perfusion (Group LAx3) and another 33 patients who underwent DAR with femoral artery perfusion alone because it was considered safe with retrograde perfusion (Group F). Data were collected from computerized medical records. All data were processed using the R statistical program, version 3.4.4. Summary statistics were calculated using frequencies and proportions for categorical data and median values and interquartile range for continuous variables. Univariate analyses were performed using the t-test or Wilcoxon rank-sum test for continuous variables and the chi-square test or Fisher exact test for categorical variables. P values of <0.05 were considered statistically signifcant. Te study was approved by the institutional review board of the Shonan Kamakura General Hospital on October 31, 2022 (TGE02055-024). Te informed consent was obtained from all patients to participate in this study. Patient consent was obtained for the use of his photograph in this article (Figure 1(a)).

Results
Preoperative patient characteristics, operative data, and early outcomes are listed in Table 1, and there were no signifcant diferences between the groups LAx3 and F (Table 1). In Group LAx3, there was one in-hospital death (7.7%) due to DIC and no case of cerebral infarction. In Group F, there were two cases of cerebral infarction due to embolism from retrograde perfusion.

Discussion
As reported by Corvera and Fehrenbacher [3], the hypothermic open proximal technique is advantageous in descending or thoracoabdominal aortic artery replacement. We used this technique because it is simple and easy to anastomose. Te femoral artery is generally used as the blood perfusion route for DAR. However, in cases where retrograde blood perfusion through the diseased aorta is   [8], ascending aorta [9], right axillary artery [10], left common carotid artery [11], and left subclavian artery in the thoracic cavity [12], have been selected. Although each has been reported to have its advantages, all of them are somewhat complicated or give a poor visual feld when the patient is in the right decubitus position. In our institution, perfusion via the graft anastomosed to the LAx3 is the preferred alternative to femoral artery perfusion because this technique is simple and safe. Ogino et al. reported the usefulness of additional blood perfusion using a 10F-16F cannula inserted into the distal right axillary artery for total arch replacement through a median sternotomy [13]. However, there are no reports on the distal left axillary artery graft-interposed perfusion technique for DAR surgery. We adopted the graft-interposed perfusion method because it produces sufcient fow compared with the cannulation method. Blood can be safely delivered from the distal axillary artery without dispersing atheroma in the descending aorta (Figure 1(b)). Te advantages of the LAx3 perfusion are that it is situated behind the axillary vein and median nerve and can be easily exposed. It is located just in front of the surgical feld in the right decubitus position with the left arm raised. Tis artery has less atherosclerosis or calcifcation. Furthermore, the extension of aortic dissection is rare [14]. Hence, it is suitable for anastomosis. Additionally, the perfusion system does not interfere with the surgical feld (Figure 1(b)). Tere have been no postoperative wound infections or neurological complications in our series.
A necessary precaution in this technique is the fow volume. In our patients, we achieved full fow with axillary artery perfusion alone without complications. However, there is a possibility that fow might be insufcient when the axillary artery is narrow. In that case, concomitant femoral artery perfusion should be considered unless there is a risk of embolization from the diseased aorta. We believe that blood perfusion from the distal part of the axillary artery minimizes the turbulent jet in the aorta. However, if there are thrombi in the aortic arch, they might be dispersed. In such cases, perfusion from the left ventricular apex, ascending aorta, or right axillary artery might be an option.
Overall, in Group LAx3, there was one in-hospital death and no cases of cerebral infarction, paraplegia, and paraparesis (Table 1). Despite having several cases of shaggy aorta and thrombus in the false lumen, this outcome was more desirable as compared with previous reports [14]. In Group F, two cases of cerebral infarction occurred due to embolization despite of preoperative evaluation determining that retrograde blood perfusion was safe.
Currently, the criteria for selecting LAx3 perfusion are atheroma in the true lumen or nondissected aorta and thrombus in the false lumen with confrmed proximal entry.
Tis study has several limitations. Tis study was a retrospective analysis of a small cohort of DAR surgery; therefore, further studies with larger sample sizes are required to verify these observations. Future research should compare our results with other techniques used in a larger cohort of similar patients.

Conclusion
In selected cases for DAR surgery, our perfusion method with LAx3 graft is a safe and simple alternative to establish a CPB and might reduce the risk of cerebral complications.

Data Availability
Te data associated with the study are not publicly available but are available from the corresponding author upon reasonable request.