Surgical treatment for retrograde type A aortic dissection after endovascular stent graft placement for type B dissection

Abstract

Retrograde type A aortic dissection (RTAD) is a life-threatening and underestimated complication of endovascular stent graft placement for type B dissection. Here, we retrospectively investigated our experience of surgical treatment for RTAD after endovascular stent graft placement for type B dissection. Between June 2006 and September 2011, nine patients with RTAD were transferred to our department for surgery. Total arch replacement was performed in six patients and three patients underwent subtotal arch replacement. Associated procedures consisted of ascending aorta replacement in nine patients, coronary artery bypass grafting in one patient and aortic valve plasty in two patients. All operations were performed under deep hypothermic circulatory arrest and selective antegrade cerebral perfusion. Cardiopulmonary bypass time was 158.33 ± 29.18 min. The myocardial ischaemic time was 78.11 ± 28.30 min. The antegrade cerebral perfusion time was 38.67 ± 12.34 min. The mean ventilation time was 45.63 ± 24.74 h. A tracheotomy was necessary in one patient. The ICU time was 7.00 ± 6.80 days and the in-hospital duration was 25.33 ± 11.95 days. There was no in-hospital mortality. The mean follow-up was 34.79 ± 19.37 months and eight patients are still alive. One patient was lost to follow-up. Surgical treatment for RTAD is a safe alternative and the results are encouraging.

INTRODUCTION

Although recent studies have demonstrated that medical therapy is the best therapeutic option for uncomplicated type B dissection, endovascular stent graft placement is still an effective alternative option in the treatment of some Stanford B aortic dissections [1–3]. However, despite its advantage of being less invasive, there are still some unavoidable early and late complications, including acute or delayed development of retrograde type A aortic dissection (RTAD) and acute stent dislocation caused by fractured wires and secondary leakage [4, 5]. In our hospital, Dong et al. [6] reported that the RTAD incidence reached 2.5% in 443 patients undergoing stent grafting for type B dissection, which was comparable with common complications of stent dislocation (0−3%).

In the present study, we report our experience with emergency surgical intervention for RTAD patients who present with life-threatening complications, including acute heart failure, cerebral malperfusion or aortic dissection rupture.

MATERIALS AND METHODS

Patient demographics and characteristics

Between June 2006 and September 2011, 419 consecutive patients underwent surgical treatment for type A aortic dissection (TAAD) at Zhongshan Hospital (Shanghai, China). Amongst them, nine patients were transferred to the Department of Cardiovascular Surgery for surgical treatment for RTAD after endovascular stent graft placement for type B dissection. The mean age of the patients was 56.67 ± 10.19 years (range 42–73 years) and 66% of the patients were male. Preoperative patient characteristics are listed in Table 1.

Table 1:

Preoperative characteristics in the nine RTAD patients

Variables	No or mean ± SD
Age, years	56.67 ± 10.19
Sex
Male	6
Female	3
Hypertension	8
DM	2
Previous CVA	1
PVD	1
COPD	0
Renal dysfunctiona	2
Location of the new tear
TPBS	3
Tip of original endovascular stent	3
Small curve of arch	3
Type of endovascular stent
TALENT (Medtronic)	3
VALIANT (Medtronic)	2
Hercules (Microport, Shanghai, China)	1
Zenith TX2 (COOK)b	3

DM: diabetes mellitus; CVA: cerebrovascular accident; PVD: peripheral vascular disease; COPD: chronic obstructive pulmonary disease; TPBS: tip of the proximal bare spring; RTAD: retrograde type A aortic dissection.

^aSerum creatinine >2.0 mg/ml.

^bWithout proximal bare spring.

Of these nine patients, eight were in acute phase and one in subacute phase. Total arch replacement is defined as involving the whole aortic arch, with reimplantation of the arch branch vessels either as an island or as individual branch grafts. The indications for total arch replacement were any one of the following conditions: (i) the primary tear was in the large curve of the transverse arch of the tip of the endovascular stents; (ii) malperfusion symptoms in the cerebral system; (iii) the presence of Marfan syndrome [7]. Six patients underwent total arch replacement because of new primary tears in the tip of the original endovascular stents (Fig. 1A). Subtotal aortic replacement was carried out on three patients (Fig. 1C and D). The concomitant operations, including ascending aorta replacement, were done for all nine patients, coronary artery bypass grafting for one patient (Fig. 1B) and aortic valve plasty for two patients. Surgical strategies are listed in Table 2.

Figure 1:

Diagram of operations performed on aortic arch and ascending aorta in nine patients presenting with RTAD: (A) total arch repair; (B) total arch repair and CABG (Aor-SVG-LAD); (C, D) subtotal arch repair.

Table 2:

Surgical strategy

Variables	Graft	No
Total arch replacement
Individual anastomosis	28/10/8/8/10 mm Datascope	6
	28/10/8/8/10 mm InterVascular
Subtotal arch replacement	30/10 mm, 28/10 mm, Datascope	3
	32 mm ALBOGRAFT
Concomitant procedures
Ascending aorta replacement		9
Aortic valve plasty		2
CABG	SVG	1

CABG: coronary artery bypass grafting; SVG: saphenous vein graft.

Surgical technique

Our technique for aortic dissection included total cardiopulmonary bypass, deep hypothermia, circulatory arrest and unilateral or bilateral selective cerebral perfusion (SCP). Circulatory arrest was initiated when the nasopharyngeal temperature reached 18–20°C. The right axillary artery was dissected for unilateral SCP. Bilateral cerebral perfusion was usually performed through the right axillary artery and left common carotid artery. In the early days, unilateral SCP was selected to combine with deep hypothermia circulatory arrest (DHCA) for cerebral protection. The flow rate and perfusion pressure were maintained at 8–10 ml/kg/min and 40–50 mmHg, respectively. Later, bilateral SCP combined with DHCA was widely performed. In this RTAD patient group, seven patients underwent unilateral SCP, while two patients underwent bilateral SCP.

We followed the ‘arch superiority’ principle during surgery. The wall of aortic dissection was completely removed around tears and proximal bare springs (Fig. 3A). If the original endovascular stent had bare springs, the proximal bare springs would be cut by wire scissors. The vascular graft was anastomosed distally with the endovascular graft, mimicking the ‘frozen elephant trunk’ procedure without the weaknesses of the surgical or interventional treatment alone [7]. The aortic root was strengthened by using the ‘sandwich method’ and then anastomosed with a proximal vascular graft.

Figure 3:

(A) New onset tears of intima locating at the tip of the proximal bare spring of the stent (arrow); (B) A four-branched graft was used for total arch reconstruction and anastomosed distally to the endovascular stent graft; (C) total arch reconstruction with a four-branched graft.

Statistical analysis

Data were collected from chart reviews and were entered into a dedicated Microsoft Excel table to calculate average and standard deviation.

RESULTS

Surgical data

Table 3 summarizes the surgical data, perfusion data and postoperative ICU information, including CPB time, myocardial ischaemic time, cerebral perfusion time, in-hospital time and ventilation time.

Table 3:

Perioperative data of the nine RTAD patients

	Mean ± SD	Range
Total cardiopulmonary bypass (min)	158.33 ± 29.18	120–209
Myocardial ischaemia (min)	78.11 ± 28.30	49–121
SCPa (min)	38.67 ± 12.34	20–54
Nasopharyngeal temperature (°C)	16.83 ± 2.03	12.2–19
Rectal temperature (°C)	21.54 ± 2.77	16–25
In-hospital time (day)	25.33 ± 11.95	8–46
ICU time (day)	7.00 ± 6.80	3–23
Ventilation time (h)	45.63 ± 24.74	15–72
RBC (ml)	1525 ± 592.66	600–2800
Serum (ml)	1060 ± 490.35	600–2000
Drainage of 1st day (ml)	460 ± 198.37	150–750

^a Unilateral SCP was performed in seven patients and bilateral SCP in two patient.

SCP: selective cerebral perfusion; ICU: intensive care unit; RBC: red blood cell.

The axillary artery was selected for arterial perfusion in seven patients; arterial perfusion was performed in two patients through both the axillary artery and the femoral artery.

Operative outcomes

There was no in-hospital mortality. Follow-up was completed with eight patients (88.89%), with a median follow-up duration of 34.79 ± 19.37 months (range, 1.5–51 months). One patient was lost to follow-up at 3 months.

Early outcomes

There were no early deaths. Complications consisted of severe hypoxemia requiring reventilation in one patient and tracheotomy in one patient. Both were successfully weaned from the ventilator after prolonged ventilation periods. Four patients had transient elevation of serum creatinine but did not need dialysis.

Late outcomes

With the exception of the patient lost to follow-up at 3 months, there were no late deaths. Twenty-eight months after operation, one patient was admitted to the Department of Vascular Surgery for endovascular stent placement because of secondary abdominal aortic dissection. New tears were observed at the levels of celiac trunk and iliac artery. One patient's condition required electrical conversion for atrial flutter within 1 month after discharge. Other patients had no new onset cerebral and cardiovascular complications.

Figure 2A–H shows the preoperative and postoperative follow-up of CT angiography in one patient in this group.

Figure 2:

CT angiography of one of the present nine RTAD patients: (A, B) preoperatively, CT angiography showing type B dissection. (B, C) Retrograde TAAD after endovascular stent graft placement for type B dissection. (E, F) Follow-up of CT angiography at 7 months, the false lumen thrombosis. (G, H) Follow-up of CT angiography at 42 months.

DISCUSSION

In the present study, we aim to systematically report our clinical experience of surgical treatment for RTAD after endovascular stent graft implantation for type B aortic dissection. RTAD is a life-threatening and catastrophic complication with a high mortality (42%) [2], and its incidence varied from 1.33 to 6.8% [2, 8, 9]. However, related literature on surgical treatment of the condition is limited to case reports and lacking systematic investigation.

By reviewing earlier reports, we found that most investigations focused mainly on aetiological factor analysis [2, 6, 9]. Dong et al. [6] and Eggebrecht et al. [2] concluded that the fragility of the aortic wall (Marfan syndrome, Ehler–Danlos syndrome), stent grafting-related causes (with or without a proximal bare spring, flexibility of stent grafts, oversizing of stent grafts), type I endoleak, combined with endovascular manipulation experience of surgeons, contributed to the occurrence of RTAD. In our current nine RTAD patients, eight patients were diagnosed with hypertension. One person developed RTAD within 1 week, three patients in 1 month, two patients in 2 months, one patient in 3 months, one patient in 24 months and one patient in 72 months. Seven patients developed RTAD within 3 months and the new onset tears were located on the tip of the proximal bare spring. This revealed RTAD, developed within 3 months, was highly related to stent grafting. There were also two excluded cases of TAAD after endovascular stent graft implantation which we did not think belonged to RTAD. One developed TAAD 3 years after endovascular stent graft implantation and the other after 5 years, and the new onset tears of both were located in the ascending aorta. In our study, two cases of RTAD developed 2 and 6 years after stent grafting. We assume that these cases were mainly caused by an abnormality of the aortic wall. Conversely, two patients were found to have a slight proximal type I endoleak revealed by angiogram and developed RTAD within 3 months after stent graft implantation. At the beginning of our experience, balloon inflation was routinely used to reduce type I endoleaks, but this procedure might be the cause of aortic wall injury.

Emergent surgical treatment is usually needed for RATD patients due to high mortality. The International Registry of Acute Aortic Dissection (IRAD) showed 70% patients would die within 1 week without intervention. Forty percent of patients would die with medical treatment alone, while surgical intervention could reduce that to ∼20% [10]. However, the INSTEAD study has demonstrated that stentgraft placement does not improve 1-year survival and adverse events for uncomplicated type B aortic dissection, despite favourable aortic remodelling [3].

Nine patients underwent urgent surgery. We hold the opinion that repairing the initial and new onset tear is the most critical step, and total or subtotal aortic arch replacement is necessary [11]. Surgical management of the proximal bare springs of the stent was quite difficult and related reported experiences are scarce. Contrary to simple descending aortic surgery, the implanted stent of RTAD could hardly be extracted through the arch. Therefore, some authors thought that the position of the proximal endovascular stent graft was hard to manage, thus making an arch replacement impossible [12]. In our group, three patients were initially implanted with Zenith TX2 (COOK) endovascular stents which did not have proximal bare springs. The proximal bare springs of the other six patients were all well managed. Four-branched arch graft technique combined with both axillary artery and femoral artery cannulation could ultimately reduce the DHCA and malperfusion times, and increase the versatility of surgery [13] (Fig. 3B and C).

No hospital mortality was observed, although a hospital mortality of 11 to 38% has been reported for acute type A dissection [14, 15]. The patients were followed-up by CT scan and echocardiography.

Limitations

There are some inevitable limitations of the present study. First, this is a retrospective observational study and the non-randomized design may have affected the results, including unrecognized confounding factors and bias. Secondly, this study represents one single-centre experience. There are surely some disparities among different centres and operators. Finally, the sample of this study is relatively small—only nine patients in this group. The main reasons are: some patients died intraoperatively of endovascular stent graft implantation, some just accepted medical therapy. Dong et al. [6] reported that just 72.7% (8 of 11) were transferred to the Department of Cardiac Surgery for surgical treatment.

CONCLUSIONS

Surgical treatment for RTAD after endovascular stent graft placement for type B dissection is a safe alternative, and the results are comparable to other open aortic reconstruction surgeries for TAAD.

Funding

This work was supported by the National Natural Science Foundation of China (grant 81000105).

Conflict of interest: none declared.