Keywords aortic arch - endovascular - TEVAR - fenestration - physician-modified endograft
Introduction
Since the first implantation by Volodos in 1987, thoracic endovascular aortic repair
(TEVAR) has not just become an alternative but has been proven safe and effective,
replacing open surgery as the therapy of choice for a variety of thoracic aortic pathologies.[1 ] Left subclavian artery (LSA) coverage may be necessary in up to 40% of TEVAR cases
to achieve an adequate seal zone.[2 ] However, LSA occlusion may be related to a higher risk of downstream ischemic complications,
such as spinal cord ischemia, stroke, and left arm ischemia.[2 ]
[3 ]
[4 ]
A hybrid technique with surgical revascularization of the LSA has been the main option
for managing these patients in recent years.[5 ] However, revascularization may be related to morbidities such as nerve injury, lymphatic
leakage, graft infection, or stroke.[6 ]
[7 ]
[8 ]
Total endovascular approaches have improved over the years from options, such as the
chimney technique and in situ fenestrations, to more sophisticated endovascular solutions,
such as branched or fenestrated repair.[9 ]
[10 ] However, branched or fenestrated devices are not yet widely available for this region.
Widespread dissemination has been hampered by regulatory issues and the cost and time
required to manufacture the device.
Some of these issues may be overcome by modifying available endovascular grafts. The
term physician-modified endovascular graft (PMEG) was first used by Starnes in 2012,[11 ] and other authors have described encouraging initial experiences with thoracic endovascular
graft modifications for zone 2.[12 ]
[13 ] Herein, we present our initial experience with PMEG and early outcomes for a variety
of aortic arch diseases in zone 2, using a single fenestrated endograft to preserve
subclavian artery patency.
Materials and Methods
This series included six consecutive patients with various aortic pathologies who
underwent zone-2 TEVAR, using PMEG with a single fenestration to preserve LSA. Inclusion
criteria for the modified devices were as follows: preprocedural diagnosis of thoracic
aortic diseases with a neck length <20 mm from the LSA and ≥20 mm from the left common
carotid artery. A minimal distance of 8 mm between the left common carotid artery
and the LSA was necessary. All procedures were performed at the Ana Nery Hospital
of the Federal University of Bahia, Brazil. After thoroughly informing all patients
and their families about the off-label use of the graft and its risks and benefits,
they granted written informed consent.
Planning and Sizing
We used Horos version 3.3.6 (Horos Project, Annapolis, MD), a dedicated medical image
viewer, to plan the procedures. Centerline luminal reconstruction was performed, and
the distance between the left common carotid artery and the LSA were measured in the
outer curvature of the arch. Three-dimensional volume rendering reconstruction was
used to determine the best angle for arch visualization during the procedure.
Since the aim was to preserve LSA flow, a single fenestration was planned as previously
described by Zhu et al.[13 ] Oversizing ranging from 10 to 20% was planned for all cases.
Device Modification
All procedures were performed under general anesthesia. The endograft was modified
during anesthetic induction and common femoral dissection. The devices (Valiant Captivia,
Medtronic, Santa Rosa, CA) were unsheathed under sterile conditions on the back table,
without releasing the free-flow tip capture mechanism. A sterile marking pen was used
to mark the positions and a ruler was used to measure the fenestrations. An 8-mm circular
fenestration was made for the LSA using thermal cautery. This fenestration was reinforced
circumferentially with a 0.035-radiopaque wire (Anaconda, Vascutek, Scotland, United
Kingdom). Radiopaque marks were also used to mark the opposite side of the endograft
([Fig. 1 ]).
Fig. 1 Sequential images show the endograft fully unsheathed on the back table and the fenestration
site marked with a sterile pen (A ). The fenestration for the left subclavian artery was made using thermal cautery
(B ). The edge of the fenestration was reinforced using a radiopaque wire (C ). A 0.035 guidewire was passed through the sheath (D ) and exited the endograft through the fenestration (E ). The endograft was resheathed using umbilical tapes (F ) and a small groove was made in the tip of the introducer sheath (G ) to better accommodate the guidewire (H ).
A hole was made in the device's introducer sheath using a 21G needle. A 0.035 cm × 260 cm
guidewire (Road Runner, Cook Inc., Bloomington, IN) was passed through the needle
hole until it exited the sheath's extremity. It was then inserted into the endograft
and advanced through the fenestration. The endograft was resheathed with umbilical
tape and the preloaded guidewire emerged from the sheath under the tapered tip of
the introducer, where we made a small groove with a number 11 blade to better accommodate
the preloaded guidewire.
Surgical Technique and Device Implantation
The common femoral artery (CFA) and the left brachial artery (LBA) were exposed by
surgical incision, and the opposite CFA was accessed by puncture. Constant dialogue
was established with the anesthesia team, especially during endograft deployment to
ensure low blood pressure.
A guidewire was passed through the right CFA and exteriorized using a snare (One Snare,
Merit Medical, Jordan, UT) in the left upper limb to obtain a through-and-through
wire. An over-the-wire angioplasty balloon (Passeo-35, Biotronik, Bulach, Switzerland)
was introduced into the LBA access using the through-and-through wire, emerging from
the CFA. This balloon catheter was chosen for its length (130 cm), since it is longer
than diagnostic catheters. Using the same femoral introducer, an extra-stiff Lunderquist
0.035 cm × 260 cm (Cook Inc., Bloomington, IN) was positioned in the ascending aorta.
The PMEG was visualized under radioscopy to confirm the positioning of the radiopaque
marks and was then introduced over the Lunderquist wire until close to the femoral
artery. The preloaded wire was introduced trough the tip of the balloon catheter until
it exited in the left arm. The endograft was gently introduced up to the descending
thoracic aorta while the balloon catheter was retracted. An aortogram was obtained
with a pigtail catheter from other CFA. The graft was advanced up to the ascending
aorta and positioned exactly at the intended position. At this point, systolic blood
pressure was reduced and maintained under 70 mm Hg.
The proximal part of the graft was deployed and an 8-mm angioplasty balloon (Passeo-35,
Biotronik, Bulach, Switzerland) was advanced from the LBA through the fenestration
using the preloaded wire. The balloon was inflated to maintain the graft position
and the graft was fully deployed. The balloon was deflated, while a 7- or 8-Fr 90-cm
sheath (Flexor, Cook Inc., Bloomington, IN) was advanced through the fenestration
from the CFA, and a Lifestream covered stent (Bard, Tempe, AZ) was deployed 5- to
10-mm inside the endograft, aligning the hole. The positioning must be accurate to
avoid occluding the left vertebral artery. The proximal portion of the covered stent
was flared using a 12-mm standard angioplasty balloon. Finally, the angiography was
completed, demonstrating the patency of the supra-aortic branches and the TEVAR results
([Fig. 2 ]). If any proximal endoleak was seen, a compliant balloon was used to better accommodate
the endograft, while the 12-mm balloon was reinflated to maintain the covered stent
structure.
Fig. 2 Intraoperative images demonstrate the radiopaque marks in the resheathed endograft
in anterior (A ) and lateral (B ) views. Aortography demonstrates the aortic arch anatomy (C ). The endograft partially unsheathed and placement of an angioplasty balloon trough
the fenestration (D ). Angiography demonstrates the vertebral artery (E ) and a completion aortography shows the endograft positioning, the covered stent
patency, and no endoleak (F ).
Follow-up
Postoperative follow-up included routine visits to the outpatient department, and
contrast-enhanced computed tomography was scheduled after 30 days ([Fig. 3 ]). Early outcomes included immediate technical success and 30-day LSA patency, endoleaks,
and postoperative complications. Technical success was defined as successful implantation
of the fenestrated endograft into the thoracic aorta with appropriate covered stent
positioning through the fenestration into the LSA and no evidence of Type-1A endoleak.
Fig. 3 Three-dimensional computed tomography reconstructions show the preoperative image
of a Type B aortic dissection beginning close to the left subclavian artery (A ), and the postoperative image with the physician-modified endograft well positioned
in the distal arch, with patency of left subclavian artery, and no endoleak (B ).
Results
Patient Demographics
From November 2019 to August 2020, six patients (two women: 33%) underwent TEVAR with
PMEG using a single fenestration to preserve LSA patency. The mean age was 64.8 years
(range: 57–75 years). In this series, two operations were elective and four were urgent
repairs. The elective repairs included one patient with a right aberrant subclavian
artery who underwent a right subclavian-carotid bypass to avoid a bilateral bypass
and possible nerve injury. There were two chronic, one subacute, and one acute Type-B
aortic dissections, one penetrating aortic ulcer, and one intramural hematoma. All
dissections had surgical indication related to large diameters (>55 mm). The patient
operated on in the acute phase had refractory pain despite clinical treatment.
Endovascular Graft Configuration
The device used in all cases was a Valiant Captivia thoracic stent graft (Medtronic
Inc., Santa Rosa, CA). Three cases required two thoracic endografts, while the others
required only one. The diameter of all fenestrations was 8 mm, and the mean LSA diameter
was 9 mm (range: 8.8–9.5 mm). The mean diameter of the covered stents was 9.8 mm (range:
9–10 mm).
The median time it took to modify the devices was 54 minutes (range: 40–82 minutes).
The mean neck length from the left common carotid artery to the proximal portion of
the lesion was 28 mm (range: 21–40 mm).
Perioperative Data and Outcomes
The CFA was accessed to introduce the PMEG in five patients, and a cut-down left common
iliac conduit was used in one female patient due to small external iliac arteries.
Technical success was achieved in all cases, including successful placement of the
PMEG into the thoracic aorta with adequate covered stent positioning through the fenestration
into the LSA and no Type-1 endoleak. One case of LBA disruption occurred during manipulation
due to a small arterial diameter. An end-to-end reconstruction was immediately performed
with good results.
At 30-day follow-up, five patients were alive. Contrast-enhanced computed tomography
was performed in the five cases which showed LSA patency and no Type 1 endoleaks.
One patient, who was operated on for acute dilated Type B aortic dissection and refractory
pain, presented sudden death on the second day after surgery. Echocardiography showed
no retrograde dissection, and we had no opportunity to perform a computed tomography
or a cardiac catheterization. The cause of death was unclear, and we could not rule
out other causes related to the aorta.
There have been no reports of left arm ischemia, paraplegia, conversion to open surgery,
or secondary open procedures. No patients required surgical LSA revascularization.
Discussion
The Society for Vascular Surgery Committee on Aortic Disease began recommending routine
LSA revascularization in 2009.[5 ] This approach has been extensively debated in the literature with respect to distal
aortic arch diseases, since it often requires multiple surgical interventions and
longer operative times. Some arguments in favor of this approach are the prevention
of stroke, spinal cord ischemia, and left arm ischemia.[4 ]
[6 ]
[14 ] Nevertheless, some groups still use a selective approach, occluding a varying percentage
of LSA in their series,[3 ]
[5 ]
[15 ] especially those performed in urgent situations.
In a retrospective analysis, Delafontaine et al[3 ] found lower pulmonary and neurological complications for endovascular LSA revascularization
than the conventional open technique. Thus, this complete endovascular solution for
the treatment of aortic arch diseases in zone 2 represents important progress for
aortic surgery.
Chimney and in situ laser fenestration techniques have been used with reasonable results.[9 ]
[16 ]
[17 ] Hogendoorn et al[16 ] evaluated the chimney technique in different aortic arch pathologies and found a
variable occurrence of endoleaks. Parallel grafts can involve gutters, which may cause
Type 1A endoleaks, a constant concern when using this technique. Therefore, longer
sealing zones are required to achieve better graft apposition. Another related concern
is the patency of the covered stent due to possible compression by the endografts,
which may require angioplasty with bare stents, thus requiring attention during follow-up.[9 ]
Off-the-shelf branched devices have already been tested in selected studies but are
not yet widely available.[18 ]
[19 ] Recently, some authors have described the use of PMEG with a single fenestration
to preserve LSA patency, employing similar approaches.[12 ]
[13 ] This case series represents our initial experience with PMEG to treat zone-2 aortic
arch diseases. There was a 100% immediate technical success rate, which was maintained
in early follow-up, with LSA patency in all cases and no Type-1A endoleaks. There
were no strokes, left arm ischemia, or paraplegia.
Stroke remains one of the major concerns in aortic arch endovascular repair. In the
majority of cases, cerebral events are related to atheromatous embolisms in calcified
aortic arches. Arch manipulation can be minimized by using preloaded wires, lower
profile devices, adequate patient selection criteria, and rigorous planning. Such
factors can reduce the incidence of these potentially disastrous complications. Wires
and graft manipulation in the aortic arch and the potential for air embolism are significant
technical factors related to the procedure. The graft sheath should always be irrigated
abundantly with saline solution. Some authors have advocated the use of carbon dioxide
before saline infusion to reduce the amount of air captured in the endograft.[20 ]
The technique described here is based on the use of a single fenestration for the
LSA. Thus, as a general concept for fenestrations, we only used this approach when
the LSA originated from a nondilated aorta. This approach should be avoided in aneurysms
involving the LSA origin; branched techniques should achieve better results in these
patients.
Tortuosity is intrinsic to the aortic arch, so the precise positioning of the graft
in this area is challenging. To overcome this issue, we based our technique on rigorous
planning and certain mechanisms to achieve better accuracy, such as radiopaque marks
to enhance visualization of the graft position, and a preloaded guidewire. Preprocedural
computed tomography can predict the majority of traps that might occur during surgery,
including problems with access vessels, descending aorta tortuosity, true and false
lumen identification, and choosing the best view of the arch for the most suitable
sealing zone.[21 ] Suturing a radiopaque wire circumferentially to the fenestration edge is important
to enable a better connection between the fenestration and the covered stent. It is
also crucial for identifying the position of the PMEG in the aortic arch, since the
movements made in the device's grip are not regularly transmitted to its distal extremity.
A radiopaque mark on the opposite side of the fenestration is another valuable modification
that could help prevent rotational misalignment.
PMEG durability is a matter of concern for every group that works with these devices.
In a systematic review, Georgiadis et al[22 ] compared the use of PMEG and off-the-shelf devices in the thoracoabdominal region
of 308 patients (936 target vessels) and found no significant adverse events, as well
as similar safety and effectiveness in both groups. Other authors working with PMEGs
for the aortic arch demonstrated durable and safe results in the midterm follow-up.[23 ] However, careful long-term follow-up is required due to potential late complications
involving durability and migration of the main endograft and the covered stent.[24 ]
Limitations
The technique presented in this initial study has certain limitations regarding aortic,
subclavian, and access vessel anatomy. Aortic aneurysms or subclavian dilations involving
the LSA origin preclude the use of this technique due to potentially poor apposition
between the LSA and the fenestration. Aortic and iliac vessel tortuosity and narrowing
can also involve potential issues. Branched endografts and lower profile devices are
required to address these conditions. We believe that more complex cases involving
zones 0 and 1 should be managed with similar techniques, that is, one fenestration
combined with cervical debranching or more fenestrations for total endovascular repair.
Conclusions
PMEG with a single fenestration is a feasible option for treating distal arch diseases
that require sealing in zone 2. This therapeutic approach is valuable because it preserves
LSA patency, reducing the number of procedures and the risks related to open revascularization.
Although the number of patients in our sample is small and the long-term durability
of this procedure is still unknown, our results encourage the use of this endovascular
approach, and we hope that advances in endovascular surgery will lead to off-the-shelf
devices suitable for most cases. Shifting to a single endovascular procedure to maintain
LSA patency should lead to more liberal LSA preservation with total endovascular techniques.
