Is the chimney graft technique a safe and feasible approach to treat urgent aneurysm and pseudoaneurysm of the abdominal aorta? An analysis of our experience and technical considerations

Abstract

The chimney graft (CG) technique, based on the deployment of a covered stent parallel to the aortic endograft, has been proposed to achieve a safe proximal fixation extending the sealing zone. We report our experience with the CG technique in an emergency setting. Between December 2010 and April 2012, 4 patients underwent the CG technique. The mean age was 79 (range 76–82 years) and 3 patients were men. The median aneurysm diameter was 64.7 mm (range 63–68 mm). Indications for CG were painful proximal para-anastomotic aneurysm in 2 cases and symptomatic juxtarenal aneurysm in the other 2. Target vessels were both the renal arteries. Technical success was achieved in 100% and no intraoperative complications occurred. No stent-related complications, or Type I endoleak, were detected. No death occurred during the postoperative course. Creatinine elevation was observed in 2 cases. At follow-up, no endoleaks or rupture occurred. One patient died of myocardial infarction 3 months after the procedure. The primary patency rate of covered stents was 100%. The CG technique seems to be safe and feasible with an excellent patency rate of covered stents and a low incidence of endoleaks. More evidence in the literature is needed to carry out a validation of this technique in an emergency.

INTRODUCTION

The chimney grafts (CGs) technique based on the deployment of covered stents into the target arteries alongside the aortic endograft has been advocated as a safe technique for aortic aneurysms involving critical side branches, particularly in emergent settings [1, 2].

We report a single-center experience using the CG to treat juxtarenal abdominal aortic aneurysm and proximal para-anastomotic abdominal aortic pseudoaneurysm involving renal arteries in emergency conditions.

MATERIALS AND METHODS

Between December 2010 and April 2012, 4 patients underwent urgent CG. Patients' demographics and clinical and surgical data are reported in Table 1. In all cases, a proximal landing zone >15 mm in length between the renal arteries' level and superior mesenteric artery was present. The mean aortic diameter was 64.7 cm (range 63–68 mm) and mean neck angulation was 30° (range 10–80°). Renal artery diameter and length were 6.12 (5.8–6.4 mm) and 5.2 (4.2–6.2 mm). In no cases was the superior mesenteric artery involved.

Table 1:

Patients and surgical data

Patient	Age	Sex	Comorbidities	Indication	Vessel involved	Symptoms	MB	CS	Outcome	Follow-up (months)
1	76	M	IHD, HYP, DM, COPD	JAA	LRA, RRA	Pain	Excluder	Viabahn	Good	12
2	78	F	IHD, COPD, HYP, CRF	PAAA	LRA, RRA	Contained rupture	TAG	Viabahn	Good	10
3	82	M	IHD, COPD, HYP, CRF, DM	PAAA	LRA, RRA	Rupture	TAG	Viabahn	Good	8
4	80	M	IHD, COPD	JAA	LRA, RRA	Pain	Excluder	Viabahn	Good	9

DM: diabetes mellitus; IHD: ischaemic heart disease; CRF: chronic renal failure; HYP: hypertension; COPD: chronic obstructive pulmonary disease; JAA: juxtarenal aortic aneurysm; PAAA: proximal para-anastomotic aortic aneurysm; LRA: left renal artery; RRA: right renal artery; MB: main body, CS: covered stent. FU: follow-up; TAG: thoracic aortic endograft.

CHIMNEY GRAFT TECHNIQUE

General anaesthesia was administered and both the femoral and proximal brachial arteries were exposed. After heparin administration (0.5 mg/kg), the renal arteries were cannulated by means of a 0.035-in., 260-cm long hydrophilic guidewire (Terumo Europe, Leuven, Belgium) over a vertebral catheter (Terumo) through a 7-Fr long introducer sheath (Cook Flexor, 90 cm, Cook Medical, Bloomington, IN, USA). The vertebral catheter was pushed down as far as possible into the renal artery, and a 7-Fr long introducer sheath was advanced 2–3 cm into the renal artery on a 0.035-in. extra-stiff Lunderquist, 0.035 guidewire (Cook).

The right renal artery was engaged through left brachial access and left renal artery through the right brachial access. A 0.035-in., 135-cm hydrophilic guidewire was placed into the superior mesenteric artery through the left femoral access. A Viabahn stent (W.L. Gore, Flagstaff, AZ, USA) 6 × 50 mm was placed at the renal level inside the same introducer and left in place. The aortic endograft was placed through the right femoral artery above the origin of renal level and deployed (Fig. 1). After control angiography, the two Viabahn stents were simultaneously deployed. A kissing balloon technique by means of a Tri-lobe, 34 mm in diameter (W.L. Gore) and Mustang balloons (Boston Scientific, MA, USA), 6 mm in diameter and 4 cm in length was carried out. Finally, the contralateral endograft was placed in the cases of juxtarenal aortic aneurysm (Excluder, W.L. Gore). In the cases of proximal para-anastomotic aortic aneurysm, a straight endograft was used (thoracic aortic endograft (TAG), W.L. Gore).

Figure 1:

Viabahn stents (measuring 6 × 50 mm were placed at the renal level inside the same introducer and left in place). The main body of TAG aortic endograft was placed through the right femoral artery above the origin of renal artery level and deployed. Computerized tomography angiography showed aortic endograft and bilateral Viabahn in both the renal arteries with exclusion of proximal para-anastomotic abdominal aortic pseudoaneurysm and no endoleak.

RESULTS

The operative time was 220 min (±41 min). Contrast media and fluoroscopic time were 101 ml (±41) and 87.5 min (±15.3). The mean intensive care unit stay was 1.7 (range 1–3 days), and mean hospital stay was 6.2 (range 6–7 days). No occlusion, misplacement, kinking of Viabahn and Type I endoleak were detected. Exclusion of the sac was achieved in all cases (Fig. 1). No patient died during the postoperative course, and no related procedural complications occurred. In 2 cases, worsening in renal function with creatinine elevation was observed. All patients received a dual antiplatelet therapy and computerized tomography angiography scan before discharge and at 6 months. At follow-up (2–12 months), no endoleaks were detected and no rupture occurred. Viabahn primary patency was 100%.

DISCUSSION

Although the CG technique seems to be a very safe approach in the management of complex aortic pathology, some technical issues need to be discussed. An important challenge has been the advancement of the covered stent in the renal arteries. Sheaths can be subjected to rotational and angular forces due to multiplanar changes of the aorta centerline between the brachial and renal arteries, which generally arise within 90° from the aorta in the cases of juxtarenal or proximal para-anastomotic aneurysms, making traceability and pushability difficult. Vessel calcification increases the rigidity and tortuosity of the vessel making the advancement of the stent graft into the target arteries difficult even in the cases of extra-stiff guidewire support, increasing the incidence of renal perforation [3]. We suggest a telescopic approach with the advancement of a 7-Fr introducer sheath into the renal artery as soon as possible on a 5-Fr vertebral catheter and extra-stiff guidewire.

Regarding the choice of materials, no consensus was reported between self-expanding and balloon-expanding covered stent for target arteries or the type of endoprosthesis [3, 4].

Balloon-expanding covered stent such as Advanta (Atrium, Medical Corporation, Hudson, USA) shows high radial force, visibility and precise release. However, we prefer a self-expanding covered stent such as Viabahn due to high flexibility, pullout force and kinking resistance with excellent conformability after endoprosthesis deployment resulting in optimal sealing of proximal neck avoiding compression or stent dislocation.

A correct planning of the diameter and length of the renal artery is mandatory to avoid misplacement, particularly during the ballooning of the covered stent with renal artery occlusion or compression of the same stent between the aorta and the endoprothesis. The self-expanding covered stent must be placed at the same level with the edge of the endoprosthesis to avoid competitive flow or ragged phenomenon with angulation and occlusion. We prefer ballooning first the endoprothesis and then the two Viabahn stents to achieve a more precise release.

Regarding endograft material, TAG or Excluder (W.L. Gore), is preferred. No data in the literature show the superiority of one endograft over the other, but to achieve a safe sealing, a 30% oversizing is mandatory [4, 5].

A guidewire into the superior mesenteric artery is useful for a prompt rescue procedure in the cases of inadvertent coverage.

Safety of the proximal sealing after the CG procedure and long-term patency of stents is still debated. Type I endoleak was reported in 7–15.6%, but in many cases seems at low flow due to narrow gutters without sac enlargement and spontaneous resolution [6, 7]. An appropriate choice of graft diameter with 30% oversizing leads to safe sealing in most cases. As reported in the literature, the patency rate of stents is 98% at 2 years, with better results in the cases of self-expanding covered stent [8]. The CG is associated with severe complications such as access-site lesion (5.4%), stroke (3.2%), myocardial infarction (2.1%) and renal failure (11.8%) [9]. Although CG appears to be a feasible and safe approach in the treatment of complex abdominal aortic with an important reduction in morbidity and mortality rates and ICU and hospital recovery, in our opinion it must be reserved only for very high-risk patients for open surgery. More evidence in the literature is needed to obtain a validation of this technique in emergencies.

Conflict of interest: none declared.