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a Center for Pediatric and Congenital Heart Diseases, Cleveland Clinic Foundation, Cleveland, Ohio
b Department of Vascular Surgery, Cleveland Clinic Foundation, Cleveland, Ohio
d Department of Cardiac Surgery, Cleveland Clinic Foundation, Cleveland, Ohio
c Creighton University–University of Nebraska Joint Division of Pediatric Cardiology, Omaha, Nebraska
Accepted for publication January 2, 2008.
* Address correspondence to Dr Greenberg, Department of Vascular Surgery/S61, Cleveland Clinic Foundation, 9500 Euclid Ave, Cleveland, OH 44195 (Email: greenbr{at}ccf.org).
| Dr Greenberg discloses that he has a financial relationship with Cook, Inc and Boston Scientific.
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Abstract |
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Methods: The database of patients undergoing thoracic endograft placement was reviewed to identify those with thoracic aneurysms after aortic coarctation repair. Clinical, operative, and radiographic data were assessed. Follow-up imaging included spiral computed tomography (CT) scans immediately after deployment, at 6 months, and yearly thereafter.
Results: Of 9 patients that were identified, 7 presented for elective repair and 2 were emergencies. The aneurysms measured 4.7 to 7.3 cm in diameter on spiral CT scans. Seven patients underwent carotid to subclavian bypass and subclavian ligation. Endografts were placed abutting the origin of the left common carotid artery. Seven patients were treated with Zenith endografts (Cook, Inc, Bloomington, IN), and 2 with TAG devices (W.L. Gore & Associates, Flagstaff, AZ). Left common carotid angioplasty and stenting was performed in 4 patients. No major complications occurred. A mean follow-up of 24 months (range, 6.4 to 48 months) demonstrated no late endoleaks, ruptures, conversions, or migration.
Conclusions: Placement of endovascular stent grafts is a less invasive approach for patients with thoracic aneurysm after aortic coarctation repair, provided there is no residual coarctation or arch hypoplasia. The potential to diminish the magnitude of the surgical procedure and consequences of aortic exposure in a reoperative field is promising and mandates further investigation.
Aneurysm formation is a significant complication after therapy for aortic coarctation (CoA). Aneurysms develop after surgical as well as transcatheter repair procedures of CoA. The reported prevalence of aneurysms after surgical repair of CoA is between 11% and 24%. The incidence is reported to increase with advancing interval after surgical or transcatheter therapy [1–3]. Older surgical techniques have been associated with development of aneurysms, as well as acute rupture and sudden death in long-term follow-up [4].
Although newer surgical techniques have supplanted older methods of open repair [1, 5], aneurysm development occurs independent of the surgical technique and has now been described after nearly every technique, including resection and end-to-end anastomosis, subclavian patch repair, and synthetic onlay patch repair [3, 6]. The reported incidence of aneurysms after transcatheter balloon procedures has varied greatly among different studies [2, 6–8], with some authors finding much higher incidences [9, 10]. The subset of patients treated for recurrent CoA with balloon dilation also share risk of later aneurysm formation of 0% to 14% [2].
Untreated, aneurysms may enlarge and result in rupture or aortic dissection. Although maximal aortic diameter remains the strongest predictor of rupture for nonspecific aneurysms, the unique morphology of post-CoA aneurysms causes skepticism with regard to the application of such data to the postoperative young patient population. The treatment of such problems can be complex given the inherent reoperative field (many patients have had multiple CoA repairs) with adherent pulmonary tissue, risk for aortobronchial fistula, the hypoplastic proximal arch, and the proximity of the lesion to the left common carotid artery, which may necessitate a staged approach using an elephant trunk graft technique. The potential advantage of an endovascular means of aneurysm exclusion in these circumstances is a marked reduction in the associated morbidity and mortality.
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Material and Methods |
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The determination of high risk for open repair was made after the patient was evaluated by a surgeon and interventionalist. In general, patients were considered high risk if they had undergone multiple prior repairs, had unfavorable body habitus, or if the anatomy of their aortic lesions mandated a two-stage (elephant trunk graft) approach. Several patients were treated with open surgical repair concurrently with enrollment into an endovascular treatment paradigm.
Devices
Zenith TX1 or TX2 thoracic endografts (Cook Inc, Bloomington, IN) and the TAG device (W. L. Gore & Associates, Flagstaff, AZ), were used for aneurysm exclusion. Zenith thoracic grafts are made from stainless steel Z-stents attached to a polyester fabric in a one-piece (TX1) or a two-piece (TX2) design. The device requires a 20F to 22F delivery system. The TAG device is an expanded polytetrafluoroethylene (ePTFE) graft with an outer self-expanding nitinol support structure. It is delivered through a 20F to 24F sheath. It can be used as a single device or multiple components can be overlapped to achieve the desired length.
Procedure and Device Delivery
General anesthesia was used in 7 of 9 patients. Procedures were performed in an endovascular operating room with a fixed imaging system (Siemens Angiostar or AXIOM Artis FA, Siemens AG, Erlangen, Germany). Graft lengths were designed using three-dimensional image processing on a vascular-based workstation (Aquarius, TeraRecon Inc, San Mateo, CA, or Leonardo, Siemens, Inc, Malvern, PA). The prosthesis diameters were intended to be 10% to 20% larger than the measured aortic diameters, and the device lengths exceeded the aneurysm length by at least 20 mm proximally and distally whenever possible.
In the setting of proximal disease, incorporation of the left carotid artery through a fenestration in the endograft enabled extension of the sealing and fixation zones. Femoral or iliac access was obtained after arterial exposure with an oblique incision in conjunction with a counter incision. A second brachial arterial access site was also used in all patients.
Heparin anticoagulation was used to maintain activated clotting time exceeding 300 seconds. Endografts were inserted over a stiff wire (Amplatz or Lunderquist Wire, Cook, Inc, Bloomington, IN) and deployed after ensuring accurate positioning with the aid of small-bolus angiography. Device conformity at the sealing locations was modified by selective ballooning. After deployment, a completion angiogram was performed.
The delivery system for nonfenestrated Zenith thoracic graft evolved into a braided sheath covering a nitinol-based cannula (Z-Track Plus), and the TAG was inserted through a 20F to 24F Check-flow sheath (Cook, Inc, Bloomington, IN). The Zenith devices incorporating a fenestration for the left common carotid artery included a preloaded catheter and wire that was used to selectively cannulate the left common carotid from within the device before graft deployment. This was snared from the brachial access to establish through and through access to align the carotid fenestration. A balloon-expandable stent was deployed in a retrograde fashion through a carotid–subclavian bypass graft accessed by way of a brachial puncture to ensure alignment of the fenestration with the carotid orifice.
Follow-Up
Four-view chest roentgenograms and spiral computed tomography (CT) scans were performed before the hospital discharge, at 1, 6, and 12 months of follow-up, and yearly thereafter. Measurements of aortic size and device migration were performed using three-dimensional imaging and centerline of flow techniques. Patients who required carotid stent placement in addition to their endovascular graft were maintained on clopidogrel for 30 days. Duplex ultrasound (DUS) scans were performed to assess carotid–subclavian bypass grafts, when necessary. Endovascular outcomes are reported in accordance with the most recent reporting standards document for endovascular aneurysm repair [11], and migration was assessed using a modification of this standard [12].
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Results |
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to ensure patency of that vessel because of potential device encroachment. One patient required placement of a Palmaz (Cordis Corp/Johnson & Johnson Health Care Systems Inc, Piscataway, NJ) stent in the mid arch for alignment. A single patient was treated with an arch fenestrated device to accommodate a hypoplastic arch that involved the left common carotid artery. Only one patient required an iliac conduit for graft introduction as a result of small iliac vasculature.
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Comment |
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Regardless of the cause, ruptures with subsequent deleterious outcomes have been noted in this relatively young patient population. Fatal rupture occurred in 38% of patients noted to have large aneurysms after CoA repair who did not undergo treatment [6]. Rupture and dissection can occur at smaller diameters in these patients than with other aneurysm types. Such observations mandate that follow-up studies be performed on all patients treated for CoA, yet the timing of aneurysm formation and thus the interval of requisite follow-up studies remain to be determined. Most surgeons advocate treatment of large aneurysms when the size exceeds 5 cm or the morphology is concerning for potential rupture (asymmetry or dissection). The surgical approach is dependent on the proximal and distal extent of the disease.
When the arch is involved, either aneurysmal or markedly hypoplastic, a staged approach is generally taken whereby a median sternotomy is performed and an elephant trunk graft is placed under hypothermic circulatory arrest. Subsequent completion of the elephant trunk graft is accomplished through a left lateral thoracotomy, but in postsurgical CoA repair patients, scar tissue from prior thoracotomy may be encountered.
Endovascular therapy is a relatively new treatment modality for thoracic aortic disease. Prospective studies evaluating endovascular repair of thoracic aortic aneurysms have been reported [14–16] with variable success. Many of these repairs are complex. The inherent tortuosity of the arch, proximity of the supraaortic trunk vessels, and hypoplastic nature of the proximal aorta can create technical difficulties. Access vessels may also be small, particularly with regard to the necessity of sheaths 20F or larger, creating the potential need for an iliac conduit [15]. Challenges with accurate device deployment, device migration [12], and aneurysm growth despite complete exclusion [16] have all been described.
The typically young ages of post CoA repair patients magnify these challenges. Iliac vessels in such patients are often small, and the proximity of the disease to the arch vessels mandates accurately placed devices with particularly durable systems to ensure stability and prolonged sealing.
The left subclavian artery was covered in every case in this series, although only 6 of the 9 patients underwent extraanatomic reconstructions (carotid–subclavian bypass grafting) before endograft deployment. Such a bypass graft, when performed before deployment, ensures retrograde access to the proximal left carotid system should the aortic device encroach on the vessel. Additional justification includes a higher likelihood of claudication in a young active population in contrast to older, perhaps less active patients with nonspecific or atherosclerotic aneurysms. However, the long-term patency of these bypass grafts has not been defined in a young and otherwise healthy population.
In all cases where there was a short proximal neck, which mandated graft material placement proximal to the ostium of the left common carotid artery, a scalloped fenestration was created to incorporate the left common carotid artery, allowing the graft material to traverse the entire arch to abut the innominate artery. A carotid–subclavian bypass was performed not only to avoid claudication but, more important, to provide retrograde brachial access to the left carotid system by traversing the bypass graft with catheters and wires. We used fenestrated grafts over other techniques such as carotid–carotid bypass grafting in an effort to avoid single-vessel cerebrovascular supply supplemented by the concept that a failed fenestration could always be treated with a subsequent extraanatomic bypass graft. Arch angulation in these young patients with prior CoA repairs tend to be rather steep, and thus, not all endovascular prostheses would be suitable for treatment of this pathology. Improvements in the delivery systems and devices were marked throughout enrollment of these patients. Flexibility was conferred by the use of braided delivery sheaths and nitinol cannulas. Owing to the conformational changes that are likely to occur, we tried to avoid balloon-expandable stents. Only 1 patient required such a stent to help align the proximal self-expanding stent graft with the arch angulation.
Although the endovascular approach offers advantages compared with open surgery in terms of dissection, physiologic response, recovery time, and length of stay, the durability of the endovascular approach remains in question. Devices with proximal barbs, which discourage migration, were preferentially used in this series for all but 2 emergency patients. Most of the devices were also tapered to conform to the patients’ anatomy (small proximal arch diameters of 22 to 32 mm) with larger distal aortic diameters (up to 40 mm). The overall device length was short (less than 20 cm) in all but one patient, who presented with aortobronchial fistula arising from either a proximal or distal anastomosis of a Dacron graft bypassing the narrowed aortic segment, to avoid any unnecessary risk of paralysis that has been noted with longer devices [17].
We believe from past experience that no average sized male patient should be left with a residual aortic size of less than 20 to 22 mm diameter, and for females, 18 to 20 mm [18]. Indeed, placement of small sized stent grafts in these patients may be contraindicated with the current devices owing to the risk of a "bird’s beak" deformity or collapse of devices within a too small aortic lumen. The endovascular approach should not be the first choice of therapy if a patient will be left with a significant residual stenosis from proximal aortic arch hypoplasia. We observed no cases of stenoses within the carotid stents placed during our follow-up assessments using both CT and DUS scans. Although the potential for such stenoses exists, it is likely that the incidence of de novo stenosis within a stent in a patient without atherosclerotic disease would be uncommon and likely with a low risk of emboli generation.
In 1 patient, an elephant trunk graft was placed before the endovascular repair. Arch involvement with concomitant coronary issues prompted this approach, which has been noted to be durable in more traditional aneurysm patients [18,19]. Finally, the treatment of presumed contaminated fields, such as the patient presenting with an aortobronchial fistula, may not eliminate the infectious source but is useful in rapidly ameliorating hemorrhage. The single patient in this series that had this problem presented in extremis, was treated urgently, and ultimately required extracorporeal membrane oxygenation for 5 days. Although a large postoperative lung abscess was noted (Fig 7), the abscess completely resolved over time and the patient remains well at more than 5 years after the endovascular procedure.
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Long-term follow-up using magnetic resonance imaging (MRI) or CT angiography is important in these patients. Either modality provides adequate information, but MRI could be advantageous owing to avoidance of repeated radiation exposure in this young population.
Although surgery may remain the standard of care for many years, endovascular techniques have been developed to treat failures of surgical techniques. Endovascular devices are currently limited to use in patients with appropriate anatomy who are willing to comply with follow-up studies.
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This article has been cited by other articles:
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  L. Botta, V. Russo, G. Oppido, M. Rosati, F. Massi, L. Lovato, R. Di Bartolomeo, and R. Fattori Role of endovascular repair in the management of late pseudo-aneurysms following open surgery for aortic coarctation Eur. J. Cardiothorac. Surg., October 1, 2009; 36(4): 670 - 674. [Abstract] [Full Text] [PDF]
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