Variants of reimplantation of supra-aortic branches of the aortic arch during the "frozen elephant trunk" procedure

• Козлов Б.Н.
• Панфилов Д.С.
• Пряхин А.С.
• Березовская М.О.

Резюме

Background. During the last decades, the dynamic development of thoracic aorta surgery has led to implementation of a hybrid technology known as the "frozen elephant trunk" procedure combining open prosthetic repair of the aortic arch and endovascular intervention on the descending thoracic aorta. This procedure has a series of technical peculiarities, including those related to restoration of the blood flow through the vessels of the aortic arch.

Objective. The study was aimed at assessing the effect of different variants of reimplantation of aortic arch branches on in-hospital outcomes of the "frozen elephant trunk" procedure.

Patients and methods. Our study included a total of 92 patients who from March 2012 to November 2021 underwent the "frozen elephant trunk" procedure using hybrid stent grafts. They were subdivided into 3 groups depending on the type of reimplantation of supra-aortic vessels: "island" technique (34 patients), partial debranching (34 patients), and total debranching (24 patients).

Results. The duration of artificial circulation (p=0.315) and the time cardiac arrest (p=0.586) in the analyzed groups were comparable. Statistically significant differences in the groups were obtained for the duration of the operative intervention (p=0.002). It was observed that in the group of total debranching, the time of surgical intervention was longer. The groups had no differences in the incidence of postoperative stroke, delirium and paraplegia, with a tendency towards an increase in respiratory complications (prolonged artificial pulmonary ventilation, tracheostomy) in the group of patients with total debranching of the supra-aortic vessels as compared with other groups of patients (p=0.065). 30-day mortality amounted to 7.2%.

Conclusion. Making the variant of reconstruction of supra-aortic branches during a hybrid intervention on the aortic arch more difficult was not associated with higher rates of postoperative complications, despite a statistically significant increase in the time of the intervention.

Ключевые слова:thoracic aorta; frozen elephant trunk; reimplantation of supra-aortic branches

Introduction

Over the past decades, the dynamic development of thoracic aorta surgery has led to implementation of a hybrid technology known as the "frozen elephant trunk" procedure combining open prosthetic repair of the aortic arch and endovascular intervention on the descending thoracic aorta [1], yielding promising results of this surgical technique in patients with both aneurysms and thoracic aorta dissection. This concerns not only a decrease in the postoperative mortality rates but also reduced frequency of open aortic reinterventions in the remote period of follow up [2-5].

Along with it, the "frozen elephant trunk" procedure has a series of technical peculiarities. An intrinsic part of this operation, as well as that of its predecessor - Borst procedure - is restoration of blood flow through the major vessels of the aortic arch. During aortic arch reconstruction, there exist 3 main methods of restoring blood flow through brachiocephalic arteries: en bloc vessel reimplantation (“island” technique), separate prosthetic repair of all arteries of the aortic arch (total arch debranching), and partial arch debranching, consisting in a combination of the "island" technique for the brachiocephalic trunk and left common carotid artery with separate reimplantation and/or prosthetic repair of the left subclavian artery [2]. In the world literature, there is no common opinion on a preferable choice of the variant of reconstruction of supra-aortic branches [2, 6]. Moreover, in some situations peculiarities of pathological alterations of the aortic arch dictate a method of choice of reconstruction of proximal portions of brachiocephalic arteries.

The purpose of this study was to retrospectively evaluate the effect of variants of restoring blood flow in the major branches of the aortic arch on in-hospital results of the "frozen elephant trunk" technique.

Patients and methods

Between January 2012 and November 2021, a total of 92 patients underwent the "frozen elephant trunk" procedure. The demographic data and clinical characteristics of the patients are shown in Table 1. Of these, 17 (19.5%) patients were operated on for thoracic aortic aneurysms. The majority of patients - 74 (80.5%) - were subjected to the operation due to aortic dissection: 45 (48.9%) patients had Stanford type A aortic dissection and 29 (30.9%) had type B aortic dissection. In acute thoracic aorta dissection, 48 (64.8%) patients were found to have a typical clinical course with neither malperfusion of visceral organs or extremities, hemodynamically significant pericardial effusion and/or cardiac tamponade. 26 (28.2%) patients were operated on for chronic aortic dissection.

All patients were subdivided into 3 groups, according to the type of reimplantation of supra-aortic vessels: "island" technique (34 patients), partial debranching (34 patients), and total debranching (24 patients). The choice of a variant of restoration of blood flow via brachiocephalic vessels was individual, determined during the operation and depending on anatomical peculiarities, degree of involvement of aortic tissues by the pathological process, level of anastomosis between the aorta and hybrid prosthesis, as well as technical possibilities. The sequence of surgical stages during the operation was similar in all patients.

Table 1. Clinical characteristics of patients

Note. BMI - body mass index; DM - diabetes mellitus; COPD - chronic obstructive pulmonary disease; CAD - coronary artery disease; GFR - glomerular filtration rate; LVEF - left ventricular ejection fraction.

The study groups were comparable by the main preoperative parameters analyzed.

The "frozen elephant trunk" procedure was performed in accordance with the accepted in our Clinic technique using hybrid stent grafts E-vita Open Plus (Jotec GmbH, Hechingen, Germany) and MedEng (CJSC Scientific Production Enterprise MedEng, Penza, Russia). Surgical interventions were carried out in conditions of moderate hypothermia (25-28° C) and unilateral antegrade cerebral perfusion (ACP) through the brachiocephalic trunk at the flow rate 8-10 ml/kg/min. In all operations, we implanted a hybrid prosthesis with the stent graft length 150 mm and diameter varying from 24 to 30 mm.

After achieving the target temperature and initiation of the circulatory arrest we opened the lumen of the aortic arch, implanted the stent graft into the descending aorta, fixing it to the aortic wall with uninterrupted suture. This was followed by reimplantation of supra-aortic vessels using one of the techniques discussed (see Figure). Once this stage completed, artificial circulation was restored with simultaneous warming up of the patient. During this period, we reconstructed the proximal portion of the aorta and if necessary performed accompanying cardiosurgical interventions.

Schematic presentation illustrating reimplantation of supra-aortic vessels: A - “island” technique; B - partial debranching (prosthetic repair of the brachiocephalic trunk and common left carotid artery on the common base + prosthetic repair of the left subclavian artery); C - total debranching.

Structured collection of patients data was performed in the database formed on the platform Microsoft Excel 2010 (Microsoft Cor., USA). The results were statistically processed using SPSS 23.0 for Windows (IBM Corp, Armonk, NY, USA), also checking for completeness and presence of data entry errors. Normality of distribution of quantitative parameters was checked using the Shapiro-Wilks test. The parameters obeying the normal distribution law were described by the mean (M) and standard deviation (SD) and presented as M±SD; in unknown law of distribution - by the median (Me) and 1^st and 3^rd interquartile intervals (Q₂₅-Q₇₅) as Me (Q₂₅; Q₇₅). Qualitative data were described by frequency (n) or its percentage (%). Statistical significance of differences in quantitative parameters in the compared groups was cheeked using the Kruskal-Wallis test. Statistical significance of differences in quantitative data was checked using the χ-squared criterion. All statistical parameters were regarded as significant if p<0.05.

The study was approved by the Local Ethics Committee (N 167 as of February 14, 2019). All patients gave written informed consent.

Results

The intraoperative data in the analyzed groups are shown in Table 2. Statistically significant differences in the groups were obtained only for the duration of operative intervention (p=0.002). It was noted that in the group of total debranching, the time of surgical intervention was significantly longer.

Schematic presentation illustrating reimplantation of supra-aortic vessels: A - "island" technique; B - partial debranching (prosthetic repair of the brachiocephalic trunk and common left carotid artery on the common base + prosthetic repair of the left subclavian artery); C - total debranching

Table 2. Intraoperative data

Note. AC - artificial circulation; APC - antegrade cerebral perfusion; CABG - coronary artery bypass grafting.

The duration of artificial circulation (p=0.315) and that of cardiac arrest (p=0.586) in the analyzed groups were comparable. Concomitant procedures were performed in 27 (29.3%) patients and included coronary artery bypass grafting (14.1%) and aortic valve repair (4.3%). Aortic root prosthetic repair using a composite valve transplant (Bentall-DeBono procedure) was performed in 10 (10.8%) patients.

The postoperative results are shown in Table 3. By the frequency of postoperative stroke, delirium and paraplegia, the groups had no significant differences, with a tendency towards increased respiratory complications (prolonged artificial pulmonary ventilation, tracheostomy) in the group of patients with total debranching of supra-aortic vessels as compared with other groups of patients. However, there was no statistically significant difference (p=0.065). The frequency of infectious complications, multiple organ failure and acute renal damage was comparable in the examined groups. 30-day mortality in the groups of island technique, partial and total debranching amounted to 1 (2.9%), 1 (2.9%) and 5 (20.8%), respectively, with an overall mortality rate of 7.2%.

Table 3. Postoperative data

Note. ICU - intensive care unit; APV - artificial pulmonary ventilation; MOF - multiple organ failure.

Discussion

Surgical treatment of thoracic aorta diseases is one of the currently important problems of contemporary heart surgery [7-12]. Significant lethality with no treatment promoted a decrease in surgical care for this cohort of patients [5, 6]. However, despite improved results of the intervention, on the background of optimizatation of surgical policy and technological support the frequency of postoperative complications remains at a high level [6-8]. The most urgent problem in surgery of the thoracic aorta, including hybrid surgery, remains the risk of postoperative complications, depending on the variant of reconstruction of the aortic arch vessels. Despite considerable world experience, the question concerning the effect of the technique of supra-aortic branches during the procedure of frozen elephant trunk technique on the hospital results is still open.

Amongst suggested methods of restoring blood flow through supra-aortic vessels, the simplest method of reimplantation from the point of view of surgical technique is the "island" technique. The main disadvantage of this approach consists in relatively high risk for aneurysmatic transformation of the residual tissue of the aortic arch in the remote period, which may lead to the necessity of repeat intervention [2, 9, 10]. On the contrary, debranching of supra-aortic branches excluding this disadvantage is a technically difficult variant of reimplantation of aortic arch vessels, which significantly increases the duration and complexity of the operation. Along with it, mention should be made that the results of the performed techniques largely depend on the operator’s experience and preference [2, 9].

Actively discussed in the literature is an opinion that additional manipulations with supra-aortic vessels are associated with a higher incidence rate of neurological deficit in the postoperative period [1, 2, 11, 12]. Thus, according to the data of the ARCH registry, separate reimplantation of the aortic arch vessels is acknowledged as a significant predictor of neurological deficit [2]. On the contrary, a series of publications demonstrated no increase in mortality and postoperative complications, including neurological in separate prosthetic repair of supra-aortic vessels compared with the island technique [9-11]. In our study, the incidence of stroke did not increase when performing total debranching of brachiocephalic arteries, with the overall frequency of persistent neurological deficit amounting to 4.2%. Moreover, no statistically significant differences in the frequency of neurological deficit, delirium or paraplegia in the analyzed groups were revealed (p=0.972). The obtained findings are in line with the results of other researchers. Thus, E.R. Charchyan et al. demonstrated that cerebral circulation impairments with persistent neurological deficit in the group of hybrid treatment were observed in 3.4% of patients [13]. Y. Okita et al. detected postoperative stroke in 3.5% of patients [14].

We noted that in the group of total debranching, surgical intervention was longer (averagely up to 400 min) owing to greater scope of the operation. It should be mentioned that separate prosthetic repair of aortic arch vessels in patients discussed in this study was associated with increased incidence of prolonged pulmonary ventilation in the postoperative period. However, this tendency was statistically insignificant.

30-day mortality amounted to 7.2%. The obtained data turned out to be comparable with the results of other research groups. Thus, in the work of Y. Okita et al., amongst 1005 patients operated on the aortic arch, in-hospital mortality amounted to 4.5% [14]. In the study of Y. Tanaka, amongst 423 operated on patients this parameter was 4.8% [15].

Study limitations. This study has a series of limitations inherent to a retrospective analysis of the obtained data. To them also belong an initially non-randomized design and single-center nature of our study. Apparently, performing such an analysis in a larger cohort of patients in the groups of comparison would make it possible to reveal statistically significant differences in the groups undergoing various methods of supra-aortic vessel reimplantation. The formulated conclusions are substantiated for an in-hospital period and should not be extrapolated to a longer follow-up period. The authors believe that it is necessary to continue studying the results of using the described herein surgical techniques, as well as to perform a multicenter, long-term, randomized study in order to more precisely compare therapeutic results of the "frozen elephant trunk" technique.

Conclusion

Making the variant of reconstruction of supra-aortic branches during a hybrid intervention on the aortic arch more difficult was not associated with higher rates of postoperative complications, despite a statistically significant increase in the time of the intervention.

References

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