Contents
12.1 Introduction . . . . 133
12.2 Materials and Methods . . . . 133
12.2.1 Inoue Branched Stent-Graft . . . . 133
12.2.2 Inoue Stent-Graft Delivery System . . . . . 134
12.2.3 Aortic Arch Reconstruction with Single-Branched Stent-Grafts . . . . . 134
12.2.4 Aortic Arch Reconstruction with Double-Branched or Triple-Branched Stent-G rafts . . . . 135
12.2.5 Countermeasure Against Distal Embolization . . . . 135
12.2.6 Patients and Anatomic Criteria for Endovascular Repair . . . . 136
12.3 Outcome . . . . 137
12.3.1 Immediate Results and In-Hospital Course . . . . 137
12.3.2 Clinical Follow-Up . . . . 137
12.4 Conclusion . . . . 138
12.1 Introduction
Currently, the standard treatment of thoracic aortic an- eurysms is surgery with artificial graft replacement, for which perioperative mortality rates of 5±35% have been documented in multicenter reports [2, 3, 12, 14, 18, 19].
Despite recent progress of thoracic aortic surgery, com- plications are still prevalent in repair of aortic arch an- eurysms [3, 6, 15]. Endovascular stent-grafting of aortic aneurysms is an attractive alternative to conventional surgical therapy [1, 5, 17]. This approach potentially of- fers the benefits of remarkably reduced patient physical and psychic burden, shortened procedure time, reduced operative risk, and lower cost compared with conven- tional surgery. With regard to thoracic aortic aneurysm repair, Dake et al. [4] first demonstrated the clinical fea- sibility with Dacron-covered, self-expanding, stainless steel straight stent-grafts in 13 cases with descending thoracic aortic aneurysms. However, endovascular re- pair with straight stent-grafts is limited to the descend-
ing aortic aneurysms because the great vessels arising fromthe ascending aorta and transverse arch are oc- cluded by the stent-graft [13]. Therefore, the develop- ment of a branched stent-graft has been eagerly awaited for treating aortic arch aneurysms.
In 1996 we reported the first clinical application of a branched stent-graft for a patient with a type B dissec- tion originating just beyond the left subclavian artery [7]. The successful endovascular repair with the single- branched stent-graft led to the obliteration of the dis- section. Several modifications in stent-graft designs and catheter techniques enabled total arch reconstruction with a triple-branched stent-graft [10]. We describe herein our experience with the use of the Inoue branched stent-graft for the treatment of horizontal an- eurysms.
12.2 Materials and Methods
12.2.1 Inoue Branched Stent-Graft
The stent-graft is composed of crimped woven polyester graft material, the outside surface of which is encircled with multiple successive rings of nickel titanium wire [8]. The graft is extremely flexible to conform to the tortuous aortic arch. The first and second rings from the edge are covered by polyester graft fabrics to pro- vide effective, secure friction seals against the aortic wall. The middle rings prevent the graft from collapsing because of the outside pressure during long-termuse.
Although the graft rings are easily visible under fluoro- scopy, radiopaque gold markers are sutured to the two terminal rings and the center line along the greater cur- vature of the stent-graft to further facilitate graft visual- ization during the procedure.
As shown in Fig. 12.1, the branched stent-graft has a main graft body and short branches. The single- branched stent-graft, which has a branch extending into one of the great vessels arising fromthe aortic arch, is
Management of the
Horizontal Aorta with the Inoue Branched Stent-Graft
Kanji Inoue, Hiroaki Hosokawa, Kenichi Abe, Takeshi Kimura
12
mainly placed into the distal arch including the left subclavian artery and the descending thoracic aorta.
The double- and triple-branched stent-grafts have branches extended into two or three great vessels of the aortic arch.
The stent-graft is custom-made according to the state of the individual patient's pathology. Aortic arch aneurysms have highly complex anatomic characteris- tics; therefore, a precise stent-graft design is crucial to achieve complete aneurysm exclusion. The length, di- ameter, and taper of the stent-graft, and the landing zone are determined using a computer-assisted stent- graft design system. With the system, a suitable stent- graft can be designed by simulating the stent-graft in a three-dimensional aortic aneurysm model constructed from helical computed tomography images on a compu- ter display (Fig. 12.2). The main graft body is 22±
44 mm in diameter and 50±300 mm long. The side branch is 8±18 mm in diameter and 15±40 mm long.
connected to its distal end, which facilitates catching the tip by a snare wire inserted through the brachial ar- tery or the left carotid artery. The traction wire con- nected to the main graft body allows length adjustment by pushing it up after stent-graft deployment if spinal cord ischemia occurs. Reducing the length of the graft reduces the risk of spinal cord damage.
A 22-F or a 24-F delivery sheath is used for thoracic use.
12.2.3 Aortic Arch Reconstruction with Single-Branched Stent-Grafts
The endovascular catheter technique with a single- branched stent-graft is usually performed under local anesthesia in the angiography suite. Before the insertion of the stent-graft, a carrying wire is attached to the proximal end of the main graft body and a traction wire is also attached to each distal end of the main body and branch (Fig. 12.3). The main graft body and branch are individually constricted using a thread and a 0.020-mm nickel titanium wire in such a way that the stent-graft does not spontaneously expand after its re- lease fromthe sheath. A 10-F guiding catheter is then set over the traction wire connected to the branch. And then, a 3-F detachable tag wire is connected to the tip of the carrying catheter, which serves to lead the stent- graft toward the ascending aorta beyond the bend of the distal arch.
After initial arteriography, 200 U of heparin per kilo- gramof body weight is administrated and surgical ex- posure of the common femoral artery is made. A deliv- ery sheath is introduced into the descending thoracic aorta via the groin incision and then the detachable tag wire connected to the carrying wire is advanced through the sheath. A snare wire is then inserted into a 7-F guiding catheter which is inserted froma left bra- chial artery puncture site to capture the free end of the detachable tag wire. The constricted stent-graft is loaded into the cartridge, introduced into the sheath, posed of a woven Dacron fabric graft supported by multiple
rings of nickel titaniumwire
Fig. 12.2.A computer-assisted design system of stent-grafts for aortic aneurysms. A designed stent-graft can be virtually im- planted into the aortic aneurysm
and advanced into the descending aorta with the aid of the carrying wire, and released fromthe sheath. The stent-graft is further advanced toward the ascending aorta with the aid of the tag wire. Once the branch tip is placed near the left subclavian artery, the tag wire is detached fromthe carrying wire and removed, leaving the 7-F guiding catheter in the left brachial artery. Sub- sequently, the free end of the traction wire attached to the sidearmis folded back, inserted again into the 10-F guiding catheter which has been previously set, and ad- vanced to the distal arch so that its free end can be caught and pulled back using a snare wire which is in- serted through the 7-F guiding catheter froma left bra- chial artery puncture site. After confirmation of the lo- cation of the stent-graft with angiography, the stent- graft is deployed by removal of the 0.20-mm nickel tita- niumwires being used to constrict it. The main graft body and branch are fully dilated by means of balloon inflation. Finally, angiography is performed to assess technical adequacy, the carrying wire and traction wires are removed and then the arteriotomy site is repaired.
12.2.4 Aortic Arch Reconstruction with Double-Branched or Triple-Branched Stent-Grafts
The double-branched or triple-branched stent-graft is implanted in a manner similar to that of the single- branched stent-graft. Figure 12.4 shows the method of placing the triple-branched stent-graft. The procedure is performed under general or epidural anesthesia de- pending on the individual patient's clinical condition.
With the aid of its carrying system, the constricted stent-graft is delivered to the descending thoracic aorta via a 22-F or a 24-F sheath, released fromthe sheath, and then further advanced into the ascending aorta.
Then, each sidearmis positioned one by one into the aortic branch by pulling back each traction wire at-
tached to its tip with snare wires inserted frombilateral brachial artery and left carotid artery puncture sites.
Then, the main graft body is deployed, and subse- quently each branch is deployed. After all graft sections have been deployed, the stent-graft is pressed against the aortic and arterial walls by balloon inflation. At this point, adenosine is administered intravenously to in- duce temporary asystole, which reduces the risk of graft migration, when it is necessary.
12.2.5 Countermeasure Against Distal Embolization Although endovascular repair may be associated with lower morbidity and mortality than conventional surgi- cal approaches, the treatment has inherent complica- tions. Our prime concern of late has been cerebral vas- cular accidents. The cerebral incidents are most likely caused by cerebral embolization. Especially, our tech- nique needs catheter manipulation in diseased aortic arch containing mural thrombus and atherosclerotic debris. We have therefore developed a filter device to minimize the risk of massive embolization [16, 20].
The filter device is constructed of a polyester mesh with a nitinol wire ring. The filters are connected to a 0.014-in. wire which is used as a guidewire. There are two types of filter devices: detachable and undetachable (Fig. 12.5). Detachable ones are placed into the carotid arteries and detached fromthe guidewire so as not to interrupt catheter manipulation associated with stent- graft placement (Fig. 12.6). Undetachable ones are placed into the celiac axis, the superior mesenteric ar- tery, and the unilateral renal artery to protect visceral organs. After endovascular grafting is terminated, the filters are retrieved fromthe arteries (Fig. 12.7). Macro- scopic embolic particles were captured in the filters. In our preliminary clinical trial, the newly developed pro- tection device seemed to be effective and safe; however, further clinical data will be necessary to confirmits general utility.
Fig. 12.3.A constricted single-branched stent-graft and its de- livery system. A carrying wire is attached to the proximal end of the stent-graft and a traction wire is at each distal end of the stent-graft
Fig. 12.4.Technique of triple-branched stent-graft implantation.
The free end of a traction wire attached to the tip of the branches is caught by a snare wire
12.2.6 Patients and Anatomic Criteria for Endovascular Repair
Between November 1995 and March 2002, the procedure was attempted in 48 patients with aortic arch aneu- rysms. The mean age of the patients was 68 years (range, 21±87), with a male-to-female ratio of 5:1. Etiol- ogies included atherosclerosis in 26 patients, chronic aortic dissection in 15 patients, and posttraumatic or false aneurysmin seven patients. Because of the experi- mental nature of this procedure, it was mainly per- formed for high-risk surgical patients. The anatomic criteria are as follows:
1. For placement of a single-branched or a double branched stent-graft, both the proximal and the dis- tal landing zones should be at least 1 cmlong.
2. If a single-branched stent-graft is to be employed, ideally, the front part of the proximal landing zone (the segment between the origin of the left subcla- vian artery and the left carotid artery) and the back part of the proximal landing zone (the segment be- tween the origin of the left subclavian artery and the proximal aspect of the aneurysm) should each be more than 5 mm in length.
3. For placement of a triple-branched stent-graft, a proximal landing zone at least 3-cm long and a distal landing zone at least 1 cmlong must be present.
4. The caliber of the normal artery selected for sidearm implantation must be 8 mm or more in diameter.
Fig. 12.5.Newly designed filter device
Fig. 12.6.Fluoroscopic image after filter deployment in the car- otid arteries
Fig. 12.7.Macroscopic view of embolic particles captured by fil- ter devices
5. The caliber of the iliac and the femoral arteries must be sufficient to accept the delivery sheath.
6. Acute aortic dissections are excluded because the in- timal flap is flimsy and easily injured by the edge of the stent-graft. However, it usually thickens in the chronic phase. Patients with chronic type B aortic dissections are therefore suitable candidates even if they have very small true lumen with compression of the large false lumen.
7. Patients with connective tissue disorders (e.g., Mar- fan's syndrome) are excluded.
12.3 Outcome
12.3.1 Immediate Results and In-Hospital Course Single-branched stent-graft placement was technically successful in 86% (30/35 patients), double-branched in 67% (2/3 patients), and triple-branched in 70% (7/10) of patients (Fig. 12.8). The procedure was terminated before completion in nine patients, either because of a complication (one patient) or because the stent-graft did not pass through the delivery sheath used (eight pa- tients). There were three deaths in the perioperative period. The causes were rupture of the coiled external iliac artery, acute pancreatitis due to microemboliza- tion, and massive bleeding from the left carotid artery puncture site.
Other major complications included stroke in one patient, reversible neurological event in one patient, new aortic dissection in one patient, rupture of the ex- ternal iliac artery in one patient, and severe graft steno- sis in one patient. Of the major complications, the arte- rial rupture during the withdrawal of the delivery sheath was successfully managed by stent-grafting of the external iliac artery and the severe graft stenosis at the main graft body was corrected by deployment of metal stents.
12.3.2 Clinical Follow-Up
Follow-up for a period averaging 37 months (range, 4 months to 8.5 years) was available for 37 patients of the 39 patients in whomthe procedure was completed; one died of acute pancreatitis in the perioperative period and one was lost to follow-up. There were three proce- dure-related deaths. The causes were infection in one patient, rupture of the treated aneurysmin one patient, and heliumgas embolismduring secondary stent-graft intervention in one patient. Four late deaths occurred fromother causes (two due to pneumonia, one due to colon cancer, one due to rupture of a concomitant ab- dominal aortic aneurysm). Four patients had persistent endoleaks; three patients were successfully treated by additional catheter-based interventions.
Late graft disruption, which was caused by the defect of the graft fabric on the manufacturing process, oc- curred in eight patients. Of the eight patients, six re- ceived second stent-graft intervention; one died and five were successfully treated by the placement of an over- lapping stent-graft. Of the remaining two patients, one died of aneurysmrupture and the other declined further intervention. The other major complications in- cluded late graft thrombosis of the left subclavian ar- tery in one patient with freedomfromsymptoms and late endoleak in one patient. The leakage caused by a gap between the stent-graft and the aorta at the proxi- mal edge was eliminated by the placement of a straight stent-graft.
With regard to changes in the maximum diameter of the aneurysmsac as assessed by computed tomography, 18 of the 37 patients (49%) had a reduction (Fig. 12.9), 12 patients (32%) had no change, and seven patients (19%) had an increase (one with a persistent leak, two with late graft disruption, three with no demonstrable endoleak, one with residual reentries in a type B aortic dissection).
Fig. 12.8. Triple-branched stent-graft for treatment of aortic arch aneurysm.a Computed tomography (CT) image demon- strates a huge transverse aortic arch aneurysm.bCT image ob- tained after stent-graft placement shows complete exclusion of the aneurysm
a b
Fig. 12.9. Triple-branched stent-graft for treatment of aortic arch aneurysm.A CT image demonstrates a transverse aortic arch aneurysm.B CT image obtained 2 years after stent-graft placement shows aneurysm shrinkage
12.4 Conclusion
Endovascular repair with a branched stent-graft has the advantage of being remarkably less invasive compared with conventional surgical treatment and is applicable to complex aneurysms such as aortic arch aneurysms [9, 11]. Considering most of the patients in our series were at surgical high risk, the immediate and follow-up results of endovascular repair with the Inoue branched stent-graft appear to be favorable (Fig. 12.10). However, further technical refinements and extensive clinical trials will be needed before the procedure can become the primary treatment for horizontal aneurysms.
Acknowledgements.The authors thank Yuki Yoshida for the English translation of the manuscript.
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