Endovascular Hybrid Repair of True Ascending Aortic Aneurysms Using Double Graft Wrapping to Prepare a Landing Zone for Ascending Aortic Stent-Graft Placement: A Cohort Study

Abstract

Purpose: To describe a hybrid procedure that avoids cardiopulmonary bypass to treat patients with true ascending aortic aneurysms without a suitable proximal landing zone for endovascular repair. Material and Methods: Thirteen consecutive patients (mean age 75.9±6.5 years; 8 women) with true ascending aortic aneurysms were treated with the endovascular hybrid repair of true aortic aneurysms (EHTA) approach, which consists of a conventional sternotomy with double wrapping of the ascending aorta followed by staged stent-graft placement. Via sternotomy, a polypropylene mesh trimmed to downsize the aneurysm is placed around the dilated ascending aorta and sutured to the adventitia. A similarly trimmed polytetrafluoroethylene graft is placed loosely around the first wrap to avoid adhesions and secure the proximal landing zone. There is no need for cardiopulmonary bypass. A few days later, a standard thoracic stent-graft is deployed via either a transaxillary or transfemoral access; chimney or bypass grafts are used as needed to revascularize the supra-aortic vessels. Results: The ascending aortic diameter was reduced from a mean 5.7 cm (range 4.8–6.5) to 3.9 cm (range 3.2–4.3) after wrapping. The mean interval between surgery and stent-graft placement was 5 days. In this interval, 2 patients with significant reduction in the diameter of the ascending aorta elected to forego placement of a stent-graft. Of the 11 patients who underwent the full hybrid EHTA procedure, the ascending aortic stent-graft was combined with a chimney graft in the innominate artery in 4 cases. In 1 patient, a supra-aortic debranching procedure using a bifurcated Dacron graft to the innominate and left common carotid arteries was performed after wrapping with the polypropylene mesh. There was no mortality or neurological complication. A sternal wound infection required a prolonged hospital stay. At a mean follow-up of 13.8 months (range 3–24), there has been no death, type I endoleak, or sign of aneurysm enlargement on imaging. Conclusion: This technique permits complete endovascular exclusion of an ascending aortic aneurysm in a less invasive approach than standard open repair. Although this is only a small cohort of patients without long-term follow-up, it seems that this hybrid procedure is associated with low morbidity and mortality. It offers a beating-heart approach to treat true ascending aortic aneurysms in selected high-risk patients.

Keywords

aneurysm aortic wrapping arch stent-graft ascending aorta chimney technique debranching double wrap technique hybrid technique parallel grafts stent stent-graft

Introduction

There are numerous reports of stent-graft treatment of various ascending aortic pathologies, including type A dissections, false aneurysms, penetrating ulcers, and embolizing thrombus.^1–5 In the majority of patients with true ascending aortic aneurysms, open cardiac surgery with cardiopulmonary bypass is still the gold standard.⁶ In contrast to minimally invasive coronary bypass and valve repairs, beating-heart ascending aortic replacement to avoid pump-related complications is not an option in these patients. Moreover, most are not suitable for an endovascular repair because ascending aortic aneurysms typically have a conical configuration, so there is almost never a proximal landing zone to provide safe anchoring of a stent-graft.⁷ A less invasive approach, endovascular hybrid repair of true ascending aortic aneurysms (EHTA), permits hybrid treatment of these patients without the need for extracorporeal circulation. The basic principle of this technique is the creation of a landing zone by outer aortic double wrapping to downsize the aneurysm.

Materials and Methods

Study Design and Patient Sample

Of 19 patients with true ascending aortic aneurysms evaluated at our referral center between 2015 and 2018, 13 consecutive patients (mean age 76 years, range 67–87; 8 women) were treated with the EHTA technique involving aneurysm size reduction and staged stent-graft repair. The procedure is appropriate for patients unfit for open surgery with an ascending aortic aneurysm diameter >5.5 cm or rapid growth demonstrated on serial imaging and the explicit wish of the patient for definitive treatment. Patients were not candidates for the hybrid procedure if they required coronary artery bypass grafting or valve repair or had an aneurysm >6.5 cm in diameter. Patients with a limited life expectancy, congestive heart failure, prior sternotomy, incapacitating neurological disease, and/or aneurysm involvement of the sinotubular junction were also excluded. Patients appropriate for EHTA provided informed consent after being given details of alternative treatment options. Characteristics of the patients are given in Table 1. The mean baseline diameter of the ascending aortic aneurysms was 5.7 cm (range 4.8–6.5). Though the EHTA procedure was approved by the Catholic Hospital Group Institutional Review Board (approval number KEK1.9.2018), patient consent was waived for this retrospective review of anonymized data.

Table 1.

Demographics and Risk Factors for the 13 Study Patients.^a

Age, y	75.9±6.5 (67–87)
Women	8
COPD	6
Home oxygen	2
Renal insufficiency^b	3
Arrhythmia	6
Coronary artery disease	5
Hypertension	9
Smoking	7
Congestive heart failure	5
Aortic valve stenosis II°	1
Aortic valve incompetence II°	5

Abbreviation: COPD, chronic obstructive pulmonary disease.

Continuous data are presented as the mean ± standard deviation (range); categorical data are given as the number.

Creatinine >1.8 md/dL.

The treatment plan centered on creating a landing zone with a maximum diameter of 32 mm while at the same time reducing the aneurysm diameter to lessen shear stress and the risk of type A dissection. The operative team consisted of vascular surgeons, cardiac surgeons, anesthetists, and cardiologists. In all cases, a staged approach was used. Sternotomy and ascending aortic wrapping to create a landing zone and to downsize an aneurysm was performed first. A few days later, computed tomography angiography (CTA) was performed and a stent-graft was deployed, with endovascular debranching of the supra-aortic vessels if necessary.

Surgical Technique

A mini-full sternotomy as part of a trap door incision was used to expose the ascending aorta. Dissection was started at the level of the proximal landing zone as close as possible to the origin of the coronary arteries, which were identified and monitored with transesophageal echocardiography during the procedure. Special care was taken to avoid any injury of the pulmonary arteries. After circumferential dissection of the ascending aorta up to the level of the innominate artery, a 15×15-cm piece of nonabsorbable polypropylene mesh (Ethicon, Bridgewater, NJ, USA) used in hernia repair because of its high tensile strength was employed for the first wrap [outside the instructions for use (IFU) related to abdominal applications]. The mesh was trimmed to size according to the preoperative CT measurements and the planned aortic diameter goal; a trapezoidal shape was created to accommodate the shorter lesser curvature of the aneurysm. The mesh was placed circumferentially around the ascending aorta and fixed to the adventitia using interrupted monofilament sutures. After completion of the first layer, a second wrap consisting of a polytetrafluoroethylene graft (18-mm tube graft; W.L. Gore & Associates, Flagstaff, AZ, USA) was trimmed in similar fashion (Figure 1) and sutured loosely over the mesh layer. This technique was used to avoid adhesions between the posterior surface of the sternum and the ascending aorta in case a redo sternotomy was required at a later point in time. After closure of the pericardium and placement of a single mediastinal drain, the sternum was closed with wire in the usual fashion.

A CT scan (Figure 2) was performed on the second postoperative day. Centerline measurements were made to size the aortic stent-graft according to the length of the ascending aorta and the diameter of the proximal landing zone. Figure 3A shows the infolding typically found after wrapping.

Endovascular Technique

Within a few days after the wrapping procedure, stent-graft implantation was undertaken via a transfemoral and/or transaxillary approach. A stiff guidewire was placed into the left ventricle from the femoral access under fluoroscopic guidance; the entire procedure was under transesophageal ultrasound surveillance as well. If necessary, selective coronary angiography was performed.

In cases where the proximal portion of the aortic arch or most of zone 1 was still aneurysmal, a single or double parallel graft technique was used in conjunction with the ascending aortic stent-graft to maintain patency of the innominate artery (Figure 3B) and, if necessary, the left common carotid artery (Figure 4). Balloon-expandable chimney grafts (12-mm-diameter Lifestream; Bard Peripheral Vascular, Tempe, AZ, USA) were routinely deployed using a transaxillary access; when a periscope configuration was needed, a transfemoral approach was preferred. A 10-cm-long thoracic stent-graft (Medtronic, Minneapolis, MN, USA) was placed via a transfemoral access. The thoracic graft was advanced with its 1.5-cm-long nosecone through the valve into the left ventricle, monitoring the position of the tip of the graft at all times. The graft was deployed taking care that the bare springs did not obstruct the leaflets of the aortic valve.

When stent-grafts only were needed in the ascending aorta, tubular abdominal grafts (Endurant; Medtronic, Minneapolis, MN, USA) were preferred. The maximum length of one graft was 7 cm, and if necessary 2 stents could be placed into one another with generous overlapping. Because of the short delivery system, the 7-cm-long devices were deployed using a right-sided transaxillary approach.

Results

The double wrapping component of the EHTA procedure reduced the mean 5.7-cm diameter of the ascending aortic aneurysms to a mean 3.9 cm after wrapping (Table 2 and Figure 5). The mean operating time for the surgical component was 79.5±9.8 minutes (range 64–95). The mean interval between surgery and stent-graft placement was 5 days. In this interval, 2 patients with significant reduction in the diameter of the ascending aorta elected to forego placement of a stent-graft; both patients are under surveillance and no increase in aneurysm diameter has been seen. Of the 11 patients who underwent the full hybrid EHTA procedure, the ascending aortic stent-graft was combined with a chimney graft in the innominate artery in 4 cases. In 1 patient a supra-aortic debranching procedure using a bifurcated Dacron graft to the innominate and left common carotid arteries was performed after wrapping with the polypropylene mesh.

Table 2.

Pre- and Post-Wrapping Ascending Aortic Diameters and Adjunctive Procedures.^a

Ascending aortic diameters, cm
Preoperative	5.7±0.5 (4.8–6.5)
Postoperative	3.9±0.3 (3.2–4.3)
Procedures on the ascending aorta
Wrapping only	2
Wrapping + arch stent-graft	6
Wrapping + ascending stent-graft	5
Stent-graft + chimney	4
Unplanned chimney	1
Supra-aortic debranching	1
Wrapping procedure time, min	79.5±9.8 (64–95)

Continuous data are presented as the mean ± standard deviation (range); categorical data are given as the number.

There was no in-hospital mortality or neurological complication as verified by an independent neurology consultant (Table 3). The only major complication was a sternal wound infection and dehiscence in a patient who was on home oxygen treatment and corticosteroids. In this case, treatment with wound debridement and vacuum-assisted wound dressings prolonged the hospital stay to 24 days. At a mean follow-up of 13.8 months (range 3–24), there has been no death, type I endoleak, or sign of aneurysm enlargement on imaging.

Table 3.

Complications and Outcomes.^a

Endoleak	0
Prolonged chest tube	1
Stroke	0
Pneumonia	1
Acute kidney failure	0
Sternal infection	1
Arrhythmia	11^b
Length of ICU stay, d	2.1 (1–4)
Length of hospital stay, d	10.6 (7–24)
Discharge
Home	11
Rehabilitation facility	3
Mortality at mean 13 months	0

Abbreviation: ICU, intensive care unit.

Continuous data are presented as the median (absolute range); categorical data are given as the number.

Resolved.

Discussion

The majority of patients with true ascending aortic aneurysms are still treated with ascending aortic replacement either as a standalone procedure or in combination with aortic valve replacement or reimplantation of the coronary arteries. The majority of these patients do not have a proximal landing zone because of the conical configuration of the aneurysm. Almost all published reports of endovascular ascending repair describe patients with false aneurysms, dissections, or penetrating ulcers.^1–5 Ascending aortic repair requires a major cardiac surgical procedure with cardiopulmonary bypass. In contrast to minimally invasive coronary bypass and valve repair, there is no alternative to using extracorporeal perfusion, with its systemic and cerebral consequences in some high-risk patients.

The main technical problem preventing endovascular repair of ascending aortic aneurysm is the lack of a landing zone to permit secure fixation for the stent-graft. In contrast to other ascending aortic pathologies, a landing zone can be created in most true aneurysms only with a surgical banding procedure. Wrapping of the ascending aorta was first described in 1976⁸ and has achieved excellent long-term results.^9–11 The use of polypropylene mesh to reduce the aortic diameter not only lessens or eliminates the risk of rupture or dissection but also primarily lowers wall shear stress. The elasticity of the polypropylene permits fibroblast ingrowth and prevents adventitial tissue necrosis. An additional effect can be aortic root narrowing, rendering a mildly incompetent valve competent again.^12,13 In contrast to most cases in which ascending aortic wrapping has been described, we modified the technique by adding a PTFE cover to the polypropylene mesh to reduce adhesions and facilitate later open chest procedures should they become necessary. In our patients, the sternotomy was well tolerated, although some patients were suffering from pulmonary problems or required oxygen.

Recently, there is increasing interest in this wrapping technique in patients with type A dissections, either as a standalone procedure or in combination with stent-grafts.¹⁴ Gao et al¹⁵ described for the first time mesh wrapping in combination with a sandwich graft for acute type A dissection, with excellent intermediate-term results.

Wrapping of the ascending aorta can also be used as an adjunct to aortic valve repair.¹⁶ In a recent publication, Plonek et al¹⁷ described a beating-heart valve-sparing repair that they called the corset technique, in which wrapping included the aortic root. In contrast to our technique, a left ventricular draining vent was used to prevent ventricular dilatation, a problem that we did not see because of the short deployment time of the stent-graft when using the transvalvular technique. Theoretically, wrapping of the aortic arch and the origin of the innominate artery can be performed, but this will most likely only increase turbulence causing functional stenosis of the supra-aortic vessels. In zones 1 and 2, a surgical or endovascular solution is the preferred treatment option.

The hybrid technique described in our experience can be used in ascending aneurysms up to a diameter of 6.0 cm. Larger aneurysms should be treated with ascending repair if the patient is fit for pump-assisted cardiac surgery. In most cases, the length of the ascending aortic aneurysm can be a technical problem for an endovascular approach. All currently available off-the-shelf thoracic stent-grafts have a minimum length of 10 cm plus an additional 1.5 cm for bare springs (both arch stent-grafts currently under investigation have shorter bare springs, which is essential to avoid compromising aortic valve function.) Unless the aortic arch is aneurysmal as well, this length can obstruct the origin of the innominate artery. In some of our cases, a chimney graft with a periscope configuration was used when the aneurysm extended into zone 1 or 2.^18–21 The creation of a chimney-related gutter is the only disadvantage of this technique. Alternatively, branched or fenestrated grafts as well as in situ fenestrations can be options.

Another shortcoming of standard stent-grafts used outside of the IFU in the ascending aorta is the length of the nosecone, which must continuously be monitored during any manipulation close to the aortic valve or inside the left ventricle. Theoretically, a transapical approach would facilitate placement of the stent-graft, but it would require an intraoperative CT scan to take exact measurements for deployment of the stent-graft. It could be argued that the transapical approach adds to the complexity of the procedure, increasing perioperative morbidity and mortality.¹⁸

In one case wrapping of an aneurysm was combined with a debranching procedure, similar to the approach used by Uchida et al²² to combine banding of the aneurysmal ascending aorta with supra-aortic debranching for stent-graft fixation. The bifurcated Dacron graft was sutured to the aorta after partial clamping with a side-biting clamp, followed by stent-grafting of the ascending aorta and zone 1. While a single case does not provide sufficient data to recommend this procedure, Pecoraro et al²³ reported low perioperative morbidity and mortality and acceptable outcomes to 3 years in 26 patients.

The excellent results in our series, with no death up to 2 years and only a single major perioperative complication, may be attributable to the multidisciplinary approach in our high-risk cases. A thorough preoperative cardiology examination is necessary, including coronary angiography, as well as intraoperative transesophageal echocardiography monitoring during the procedures.

In some cases, wrapping with downsizing the diameter of the aneurysm by >20% creates folds in the ascending aorta (Figure 3A). We do not know the long-term effects of infolding on aortic remodeling over time. The creases most probably do not affect the stability of the aortic wall, but there is theoretically the possibility of thrombus formation in this area. The stent-graft enhances the stability of the aortic wall by pressure reduction as well as creating a smoother inner surface. The main disadvantage of any stent-graft in this location will be increased stiffness of the aortic wall with unknown long-term hemodynamic consequences, such as hypertensive disease. Long-term complications of the stent-graft, such as dislodgement and migration, of the device are still unknown. Notably, in one of our cases, a transaortic value intervention was performed 1 year after the hybrid procedure without any problems caused by the stent-graft.

Limitations

This retrospective study was limited by the small number of patients and thus cannot support any robust conclusions regarding the long-term performance of these procedures. Not all cases required a stent-graft after wrapping.

Conclusion

The technique described offers a less invasive approach to treating patients with true ascending aortic aneurysms. Although this is only a small cohort of patients without long-term follow-up, it seems that this technically straightforward procedure is associated with low morbidity and mortality. In the future, there will be dedicated grafts that permit a total endovascular solution, something like an endo Bentall procedure with branches for the coronary arteries and a prosthetic aortic valve as an anchoring point for the stent-graft.

Footnotes

Acknowledgements

The authors thank Mario Lachat for helping us with the technical aspects of the described procedure.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Ralf Kolvenbach

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