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Late Failure after Endovascular Repair of Descending Thoracic Aneurysms
Late Failure after Endovascular Repair of Descending Thoracic Aneurysms Rabih A. Chaer, MD, and Michel S. Makaroun, MD Although endovascular repair of descending thoracic aneurysm has been increasingly utilized as a minimally invasive alternative to open repair, the availability of late results remains quite limited, and what exists does not yet completely reflect the rapid evolution of devices, refinement in delivery systems and maturation of both institutional and general learning curves. Durability of endografts in the thoracic aorta continues to be defined as more long-term data emerge from the major device regulatory trials. This review describes the currently available published long-term results and describes some of the anecdotally reported modes of late failure associated with the technique. Semin Vasc Surg 22:81-86 © 2009 Elsevier Inc. All rights reserved.
T
HORACIC ENDOVASCULAR AORTIC repair (TEVAR) for descending thoracic aortic aneurysms (DTA) has become a mainstream technology with the release of commercial endografts. Most clinical information about TEVAR has originated from industry-sponsored nonrandomized comparisons to open repair of DTA, as well as single-center experiences or registry data that combine different pathologies and indications. This has allowed TEVAR to emerge in the last 5 years as an attractive option for the treatment of DTA, with very good early and mid-term results. Three commercial devices have completed their regulatory trials and are currently approved for use in the United States, although many more are in use throughout the world. One other device (Relay; Bolton Medical Inc., Sunrise, FL) is currently undergoing a phase II trial in the United States. Availability of late results, however, is quite limited, and what exists does not yet completely reflect the rapid evolution of devices, refinement in delivery systems, and maturation of both institutional and general learning curves. Most single-center and registry reports include a mixture of anatomic locations, stent-graft types, and varying degrees of urgency, making the evaluation of results somewhat difficult. The durability of TEVAR, therefore, continues to raise specific concerns, including late endoleaks, device migration and integrity, and component separation. Although only few late results have been published from the major device regu-
Division of Vascular Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA. Address reprint requests to Rabih A. Chaer, Division of Vascular Surgery, University of Pittsburgh Medical Center, 200 Lothrop Street, Suite A1011, Pittsburgh, PA 15213. E-mail [email protected]
0895-7967/09/$-see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1053/j.semvascsurg.2009.04.011
latory trials,1,2 late failures have certainly been encountered in clinical practice, some of which have been described in case reports. The purpose of this review is to report on the late failure modes after endovascular repair of DTAs from the limited published data as well as anecdotal evidence. Although reporting standards have been defined by the Ad Hoc Committee of the Society for Vascular Surgery and the American Association for Vascular Surgery in 2002,3 unfortunately, not all reports follow the guidelines accurately because of different study designs, endpoint definitions, and methods of data collection. In general, technical success is defined as delivery of the device to the intended location with satisfactory exclusion of the aneurysm with no type I or II endoleaks. Clinical success adds outcomes of aneurysm-related deaths, rupture, endoleaks, and reinterventions. Device migration seems to be less well-defined in the thoracic aorta than it is in the abdominal aorta, with different reporting methods utilized in the major device trials.1,4,5
Late Treatment Failures Mortality Although many reports give some insight on expectations for the mid-term, long-term data are scarce and are available from the Thoracic Aortic (endo)Graft (TAG) study reporting its 5-year results1 and for Zenith thoracic devices.2 The TAG trial has reported a survival advantage in favor of TEVAR to persist for at least 5 years because the difference reflects mostly the effect of the perioperative period with few, if any, later aneurysm-related mortalities in both open and TEVAR groups. All-cause late survival, however, shows minimal differences between open and endovascular modalities beyond 81
R.A. Chaer and M.S. Makaroun
82 1 year, mirroring the findings of randomized EVAR trials in the abdominal aorta. At 5 years, overall survival in the TEVAR and open groups was 68% and 67%, respectively, indicating similar late effectiveness for both procedures.1 Long-term follow-up with the Zenith TX1 and TX2 devices reported an overall survival of 70% at 60 months, with a mean follow-up of 36 months (range, 1 day to 78 months). Long-term freedom from aneurysm-related mortality, however, was ⬎90%, and appeared stable after the first-year follow-up. This long-term data included high-risk patients with mixed pathology, the majority being treated for descending thoracic aneurysms, and few for chronic aortic dissection, or fistulae.2 Other series of thoracic endografting have published long-term data.6,7 However, a significant proportion of patients in these series were treated for dissection and therefore excluded from this report. Late outcomes are not as encouraging in high-risk populations. A Stanford series of 103 patients, 60 of whom were deemed inoperable, reported a low 5-year survival estimate of 31%, in contrast to 78% for those who were open surgical candidates.8 This brings into question the appropriateness of any treatment in asymptomatic high-risk patients.
Late Neurologic Complications Neurologic complications can be devastating after DTA repair. Although stroke receives less attention than spinal cord ischemia (SCI), it is just as common and occurs with similar rates between open and endovascular repairs (range, 3% to 5%).6 Deployment of the proximal end of the endograft in zone 2 proximal to the left subclavian artery shows a strong association with perioperative stroke, likely secondary to manipulation of the arch with catheters, wires, balloons, and stent-grafts at the origin of cerebral vessels. The proximity of the endograft to the origin of the great vessels may serve as a nidus for embolization and stroke. The vast majority of neurologic complications, however, occur in the perioperative period. At 5 years, TAG patients were significantly less likely to have major adverse events, including neurologic complications, when compared to the surgical cohort, with no devicerelated strokes reported on long-term follow-up.1 Similarly, in the STARZ (Study of Thoracic Aortic Aneurysm Repair with the Zenith TX2 thoracic graft) trial, although five patients presented with a stroke in the perioperative period, the long-term risk of stroke was not increased.5 As was initially observed with the TAG study, which showed a marked reduction of paraplegia/paraparesis compared to open procedures (3% v 14%), the advantage of spinal cord protection with TEVAR was again evident when the data from all three US Food and Drug Administration trials were compared with open controls (6.2% v 13%; P ⬍ .007).1 If only devastating permanent paraplegia is considered, TEVAR at 1.6% versus 5.1% (P ⬍ .0037) for open operation is favored. Reduced incidence of SCI with TEVAR may be related to avoidance of thoracic aortic clamping and reduced hemodynamic disturbances at the spinal cord level due to lack of blood loss from intercostal backbleeding. It
should also be noted that SCI is not confined to the perioperative period. Delayed recurrent SCI and paraplegia after TEVAR have been reported, and have been shown to occur up to 1.5 years postoperatively.9,10 Several factors have been implicated, including hypotension, prior abdominal aortic aneurysm repair, length of aorta covered, use of an iliac conduit, and coverage of the hypogastric artery and the left subclavian artery. One additional mechanism that is unique in the pathogenesis of SCI after TEVAR is that coverage of critical intercostals may not necessarily result in immediate paraplegia because flow may be maintained through cross-collateral flow (ie, endoleak). When these endoleaks are sealed, the collateral flow is lost, which then may be followed by the neurologic deficit.10 Although the acute and late risk of SCI after TEVAR is low, it may be ongoing and dynamic, and depend on the integrity of the remaining collateral flow contributing to spinal perfusion.
Late Aneurysm and Device-Related Failures DTA is a degenerative process that may be limited to a part of the thoracic aorta at the time of treatment, but can progress over time to involve the undilated aorta chosen for sealing. The exact incidence of this problem is clearly dependent on the length of normal aorta covered and the life expectancy of the patient. Late degeneration of the landing zones should therefore be expected, and may lead to sac enlargement, migrations, type I endoleaks, and possible rupture. Moreover, tortuosity of the thoracic aorta and the high-flow patterns usually induce the endograft to settle into the larger convexities of the aneurysm cavity, which could result in both distal migration of the proximal end and proximal migration of the distal end with possible type I endoleaks. This tendency may be exacerbated by lengthening of the thoracic aorta over time,4 shortening the overlap zones and leading to type III endoleaks.
Endoleaks Early endoleak rates at the 30-day follow-up are inexplicably high in the VALOR (Vascular Talent Thoracic Stent Graft System for the Treatment of Thoracic Aortic Aneurysms) trial4 at nearly 26%, while they are far less in the TAG (3.6%)1 and STARZ (4.8%)5 studies as well as the EUROSTAR (European collaborators on Stent-graft Techniques for abdominal aortic Aneurysm Repair)) registry.11 This is mostly a definition issue because all endoleaks observed at any time prior to 30 days are included in the VALOR report, while only endoleaks at the 30-day follow-up are in the other two studies. At 1-year endoleaks were present in nearly 4% of TAG and TX2 patients and 12% of Talent patients. During longterm follow-up of the TAG study, approximately 4% of patients continued to have an endoleak at each yearly follow-up to 5 years.1 Distribution of endoleak type is also variable with the TAG study, reporting a majority of type I and III endoleaks, while the other two studies report a majority of type II endoleaks. This is again most likely a reporting issue, as the TAG study
Late failure after endovascular repair of descending thoracic aneurysms relied on investigator reports while the other two trials relied on a core laboratory. Late endoleaks (⬎30 days) were noted in 12 patients (7.5%) treated with the Zenith endograft. Other endoleaks detected were 10 type I (7 primary, 3 secondary), 14 type II (7 primary and 7 secondary), and 3 type III (1 primary and 2 secondary). However, associated sac enlargement was noted in only one patient at 4 years in the setting of a type III endoleak resulting from component separation. Freedom from primary endoleak was reported to be ⬎90% at 30 months by life-table analysis.2 Endoleaks were, in general, less frequent than comparable EVAR series with more type I and III endoleaks and less type II.
Sac Enlargement Aneurysm sac shrinkage is a good surrogate marker for successful repair of all aneurysms, including DTA. Sac enlargement is a concerning finding as it possibly indicates poor exclusion and pressurization of the sac. It may also introduce the potential for progressive outward traction in a larger cavity, resulting in possible stent-graft kinking or dislodgement. Sac enlargement rate of ⱖ5 mm is encountered more frequently with TEVAR than with abdominal EVAR and has been reported in 7% to 14% of patients at 1 year, with little variation between devices. The TAG pivotal trial has reported late results in a longitudinal cohort, and sac enlargement was noted in nearly 20% at 5 years. Shrinkage was observed in 50% and a stable sac was noted in the remaining patients.1 These rates may or may not apply to other grafts as the expanded polytetrafluoroethylene (ePTFE) material in the TAG study graft was somewhat porous with a sac behavior that resembled the original abdominal Gore Excluder. Both TAG and Excluder endografts were modified to a less porous ePTFE material, resulting in a much higher rate of sac shrinkage in the infrarenal position.12 Similarly, data from the confirmatory trial with the modified TAG device using the lowpermeability ePTFE has, so far, shown a lower incidence of sac enlargement at 2 years of 2.9% compared with 12.9% with the original device (P ⫽ .11). Long-term follow-up is obviously necessary. Aneurysm sac increase was observed in only two patients on long-term follow-up of a single institutional experience with the Zenith TX1 and TX2 thoracic devices.2 One patient had aneurysm growth noted at the 1-year follow-up visit, without evidence of endoleak or compromised fixation. She was monitored and the aneurysm had decreased in size at her 2-year visit, without evidence of sac expansion 3 years after treatment. Only one other patient had sac size increase that was detected at 4 years in the setting of a type III endoleak, requiring placement of an additional component to eliminate the endoleak.
83 early devices in association with neck dilation and stent-graft kinking.11,13 Current commercial devices tested in the US pivotal trials seem to have a low migration potential, ranging from 0.7 %to 3.9%. At 5 years, the TAG trial shows no late migration of ⬎10 mm by investigator reporting.1 Illustrating the variability in data sources, a core laboratory evaluation of a limited number of patients from the same study reports a freedom from migration of 97% at 12 months, 87% at 24 months, and 83% at 3 years.14 None of the migrations was clinically significant except for an early one associated with an arch aneurysm. Migration was noted on both ends of the devices with the Zenith device, with the TX2 trial reporting one cranial and two caudal migrations through 1 year.5 None of these was associated with endoleak or sac expansion or required an intervention. Morales et al2 assessed migration by centerline of flow distances from fixed landmarks (left common carotid and celiac arteries), where 14 patients had ⬎10 mm of distance change throughout follow-up. Any patient with detected changes of baseline central line length measurements underwent further image assessment, primarily using surface-rendering reconstruction to evaluate device position in relation to local landmarks. These analyses showed device movement had occurred in four patients (2.5%) at 6 months (distal) and 1 (proximal), 2 (distal), and 3 years (proximal) postoperatively, two required reintervention. Life-table analysis showed that 93% of patients in this series will be free of migration at the 5-year follow-up.
Device Integrity and Ruptures Early experience with TEVAR in high-risk individuals was associated with significant complication rates, with one study reporting a 13% stent fracture and 6% late rupture rates.15 Current devices suffer very few device-integrity issues and are expected to be ⬍2% in the marketed devices in the
Migration Late migration of the device has been reported to occur from 0% to 30% of patients.11 With TEVAR, migration can occur at both ends with distal migration of the proximal segment and proximal migration of the distal end frequently seen with
Figure 1 Thoracic endograft infection with air in the residual aneurysm sac, requiring open conversion.
R.A. Chaer and M.S. Makaroun
84 United States. The original TAG device showed fractures in the longitudinal wire in 14% of patients during 5 years of follow-up, with only one patient suspected of a type III endoleak receiving an endovascular repair. The wire has been removed from the modified device. No stent fracture, barb separation, stent-to-graft separation, or component separation was observed in the TX2 device in 1 year of follow-up.5 One patient had a distal bare stent strut entanglement that was detected at discharge. On long-term follow-up, however, barb fractures occurred in eight patients (5%),2 and all patients with noted barb fractures had only a single barb break. Fractures were detected in
three patients at 24 months, in two at 36 months, and in three at 60 months. Only one of the eight patients with barb fractures had evidence of device migration, which was noted at 2 years of follow-up and treated with a proximal extension. The remaining seven patients with barb fracture remained stable and did not require a reintervention. Three Talent devices were noted to have a fracture during follow-up, one in the connecting bar.4 One device was noted to have a fabric abrasion after explantation for rupture. This is the only known case of rupture among the 495 patients enrolled in the pivotal trials. The connecting bar has been removed from the modified investigational Val-
Figure 2 (A) Progressive enlargement of the landing zones over a period of 4 years following thoracic endovascular aortic repair for descending thoracic aortic aneurysms (TAA). (B) Proximal migration of the distal portion of the Talent endograft is noted (white arrow), resulting in component separation (black arrow) as compared to the completion angiogram from the initial repair in 2003. Relining of the endograft with proximal and distal extension of the landing zones was performed in 2007 using a TAG device.
Late failure after endovascular repair of descending thoracic aneurysms iant device. No graft thrombosis has been noted in all of these large devices.
Reinterventions Reintervention is defined as all procedures performed on patients referable to or as a consequence of the initial procedure. Early reinterventions have been noted in only 2.1% in the pivotal TAG cohort during the first year, but in 10.7% of the Talent study. Most reinterventions are for the treatment of endoleaks and several are endovascular in nature. TX2 reintervention rates through 1 year were similar between the two groups (4.4% TEVAR v 5.7% open).5 At long-term, data available from the TAG study showed a total reintervention rate of 3.6% of patients treated (2.1% for open repair).1 Two patients had a surgical conversion, one for an aorto-esophageal fistula and the second for an arch aneurysm and migration of the proximal device in a very large neck that did not meet inclusion and exclusion criteria. Both were during the first year of follow-up. Three patients had five endovascular revisions for endoleaks. Secondary procedures of any kind were noted during the 5-year follow-up in 15% of TAG patients and 32% of open surgical controls. While most secondary interventions following TAG were endoleak-related, those after open repairs were due to wound complications, tracheostomy, and gastrointestinal tract-related problems. The long-term data with the TX1 and TX2 devices showed that secondary interventions were required in 42 patients (26%). Indications included nine endoleaks, two aortobronchial fistulae, one aneurysm sac enlargement, three component separations, one compressed stent within an elephant trunk graft, and one patient with what was perceived to be a compromised proximal sealing segment with no endoleak. Endovascular techniques were used to treat all but one patient.2 Freedom from secondary intervention was reported to be ⬎60% at ⬎72 months follow-up.
85 required and may include proximal and distal extension or complete relining of the existing endograft to achieve an adequate seal (Fig 2B). Debranching of the aortic arch as well as coverage of the celiac axis may also be required. Elongation of the nonstented portion of the thoracic aorta after TEVAR has also been described. Up to 31% of patients from the VALOR trial were found to have ⬎1 cm elongation within 1 year of implantation and this may lead to migration or secondary interventions. Aortic length instability was associated with proximal and distal attachment site diameters larger than the adjacent normal aorta, suggesting that better patient selection or more extended aortic coverage beyond the ectatic segment may prevent this late problem. Proximity of the thoracic endograft to the origin of the great vessels in the aortic arch is usually well-tolerated in the acute setting. This is mainly a concern in patients with tenuous proximal landing zone who require coverage of the left subclavian artery, as the bare stents may potentially act as nidus for embolization and could increase the risk of longterm neurologic events. While this may be more common following treatment of aortic dissection of traumatic transection, it can occur following EVAR for DTA, especially in the setting of rupture. This can be managed with open conversion, hybrid intervention with arch debranching, or endovascular techniques with retrograde stenting of the origin of the involved great vessel into the aortic arch (Fig 3). Device-specific failures have been recognized and have lead to a modification of the current grafts. Fractured spines led to changing the TAG device and the fractured connecting bar in Talent led to the modified design of the Valiant graft. Several other modification have also been made to Valiant device, and the closed-web proximal device variant on the current design promises to avoid long-term complications, such as proximal aortic perforation by the uncovered stent
Other Complications Stent-graft infection is uncommon (Fig 1), and has been reported in the first year following implantation in two patients who required open conversion.16 Late graft infection requiring explanation after DTA repair has not been reported in the major device trials. Retrograde type A dissection has been reported at 1 week and 4 months after TEVAR, requiring open conversion.16 This is an unlikely late complication after TEVAR for DTA and may more occur commonly in patients treated for aortic dissection or from wire trauma. Aortoesophageal fistula is a well-described early and late complication of TEVAR and occurred in two patients at 3.5 and 49 months in one series, requiring open conversion.16 It was also described in the TAG trial in one patient who required debridement and drainage within the first year after implantation.1 Late enlargement of the landing zones has not been wellcharacterized, but can be expected with ongoing degeneration of the thoracic aorta (Fig 2A). Reintervention is often
Figure 3 Encroachment of the endograft scallop on the origin on the left common carotid artery (CCA) is seen in this patient initially treated for a ruptured thoracic aneurysm. The patient presented with a transient ischemic attack on late follow-up.
R.A. Chaer and M.S. Makaroun
86
References
Figure 4 Endograft collapse seen on late computed tomography follow-up after thoracic endovascular aortic repair for descending thoracic aortic aneurysms.
strut.17 This late failure may be more common, however, in patients treated for dissection, given the friability of the aortic wall. Other unusual late failures following TEVAR for DTA include stent-graft collapse (Fig 4), which is more commonly described in young patients with acute angulations of their aortic arch treated for aortic transaction.18 This late failure can be avoided by placing the proximal landing zone in a straight segment of the thoracic aorta. Although endovascular salvage may be possible, open conversion with arch debranching and proximal stent-graft extension may be a more durable alternative.
Conclusions Although reported data remain limited, the early advantages of TEVAR over open repair seems to be maintained on long-term follow-up. The incidence of late complications appears to be low, and device-related and aneurysmrelated adverse events are uncommon and anecdotal, especially with the new-generation devices. Careful patient selection and attention to technical details can prevent most late failures. Longer-term follow-up, however, is needed, with comparative data to evaluate the currently approved devices and the performance of different endografts in various anatomic and clinical situations.
1. Makaroun MS, Dillavou ED, Wheatley GH, Cambria RP; Gore TAG Investigators: Five-year results of endovascular treatment with the Gore TAG device compared with open repair of thoracic aortic aneurysms. J Vasc Surg 47:912-918, 2008 2. Morales JP, Greenberg RK, Morales CA, et al: Thoracic aortic lesions treated with the Zenith TX1 and TX2 thoracic devices: intermediateand long-term outcomes. Vasc Surg 48:54-63, 2008 3. Chaikof EL, Blankensteijn JD, Harris PL, et al: Reporting standards for endovascular aortic aneurysm repair. J Vasc Surg 35:1048-1060, 2002 4. Fairman RM, Farber M, Kwolek CJ, et al: Pivotal results of the Medtronic Vascular Talent™ Thoracic Stent Graft System for patients with thoracic aoric disease: the VALOR trial. J Vasc Surg 48:546-554, 2008 5. Matsumura JS, Cambria RP, Dake MD, Moore RD, Svensson LG, Snyder S: International controlled clinical trial of thoracic endovascular aneurysm repair with the Zenith TX2 endovascular graft: 1-year results. J Vasc Surg 47:247-257, 2008 6. Criado FJ, Abul-Khoudoud OR, Domer GS, et al: Endovascular repair of the thoracic aorta: lessons learned. Ann Thorac Surg 80:857-863, 2005 7. Fattori R, Nienaber CA, Rousseau H, et al: Results of endovascular repair of the thoracic aorta with the Talent Thoracic stent graft: the Talent Thoracic Retrospective Registry. J Thorac Cardiovasc Surg 132: 332-339, 2006 8. Demers P, Miller DC, Mitchell RS, et al: Midterm results of endovascular repair of descending thoracic aortic aneurysms with first-generation stent grafts. J Thorac Cardiovasc Surg 127:664-673, 2004 9. Kieffer E, Chiche L, Cormier E, Guegan H: Recurrent spinal cord ischemia after endovascular stent grafting for chronic traumatic aneurysm of the aortic isthmus. J Vasc Surg 45:831-833, 2007 10. Cho JS, Rhee RY, Makaroun MS: Delayed paraplegia 10 months after endovascular repair of thoracic aortic aneurysm. J Vasc Surg 47:625628, 2008 11. Leurs LJ, Bell R, Degrieck Y, Thomas S, Hobo R, Lundbom J: Endovascular treatment of thoracic aortic diseases: combined experience from the EUROSTAR and United Kingdom Thoracic Endograft registries. J Vasc Surg 40:670-679, 2004 12. Cho JS, Dillavou ED, Rhee RY, Makaroun MS: Late abdominal aortic aneurysm enlargement after endovascular repair with the Excluder device. J Vasc Surg 39:1236-1241, 2004 13. Resch T, Koul B, Dias N, Lindblad B, Ivancev K: Changes in aneurysm morphology and stent-graft configuration after endovascular repair of aneurysms of the descending thoracic aorta. J Thorac Cardiovasc Surg 122:47-52, 2001 14. Hassoun HT, Mitchell RS, Makaroun MS, Whiting AJ, Cardeira KR, Matsumura JS: Aortic neck morphology after endovascular repair of descending thoracic aortic aneurysms. J Vasc Surg 43:26-31, 2006 15. Ellozy SH, Carroccio A, Minor M, et al: Challenges of endovascular tube graft repair of thoracic aortic aneurysm: midterm follow-up and lessons learned. [see comment]. J Vasc Surg 38:676-683, 2003 16. Girdauskas E, Falk V, Kuntze T, et al: Secondary surgical procedures after endovascular stent grafting of the thoracic aorta: successful approaches to a challenging clinical problem. J Thorac Cardiovasc Surg 136:1289-1294, 2008 17. Panos A: Late retrograde aortic perforation by the uncovered part of an endograft: an increasing complication. Hellenic J Cardiol 48:115-116, 2007 18. Go MR, Barbato JE, Dillavou ED, et al: Thoracic endovascular aortic repair for traumatic aortic transection. J Vasc Surg 46:928-933, 2007
T
HORACIC ENDOVASCULAR AORTIC repair (TEVAR) for descending thoracic aortic aneurysms (DTA) has become a mainstream technology with the release of commercial endografts. Most clinical information about TEVAR has originated from industry-sponsored nonrandomized comparisons to open repair of DTA, as well as single-center experiences or registry data that combine different pathologies and indications. This has allowed TEVAR to emerge in the last 5 years as an attractive option for the treatment of DTA, with very good early and mid-term results. Three commercial devices have completed their regulatory trials and are currently approved for use in the United States, although many more are in use throughout the world. One other device (Relay; Bolton Medical Inc., Sunrise, FL) is currently undergoing a phase II trial in the United States. Availability of late results, however, is quite limited, and what exists does not yet completely reflect the rapid evolution of devices, refinement in delivery systems, and maturation of both institutional and general learning curves. Most single-center and registry reports include a mixture of anatomic locations, stent-graft types, and varying degrees of urgency, making the evaluation of results somewhat difficult. The durability of TEVAR, therefore, continues to raise specific concerns, including late endoleaks, device migration and integrity, and component separation. Although only few late results have been published from the major device regu-
Division of Vascular Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA. Address reprint requests to Rabih A. Chaer, Division of Vascular Surgery, University of Pittsburgh Medical Center, 200 Lothrop Street, Suite A1011, Pittsburgh, PA 15213. E-mail [email protected]
0895-7967/09/$-see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1053/j.semvascsurg.2009.04.011
latory trials,1,2 late failures have certainly been encountered in clinical practice, some of which have been described in case reports. The purpose of this review is to report on the late failure modes after endovascular repair of DTAs from the limited published data as well as anecdotal evidence. Although reporting standards have been defined by the Ad Hoc Committee of the Society for Vascular Surgery and the American Association for Vascular Surgery in 2002,3 unfortunately, not all reports follow the guidelines accurately because of different study designs, endpoint definitions, and methods of data collection. In general, technical success is defined as delivery of the device to the intended location with satisfactory exclusion of the aneurysm with no type I or II endoleaks. Clinical success adds outcomes of aneurysm-related deaths, rupture, endoleaks, and reinterventions. Device migration seems to be less well-defined in the thoracic aorta than it is in the abdominal aorta, with different reporting methods utilized in the major device trials.1,4,5
Late Treatment Failures Mortality Although many reports give some insight on expectations for the mid-term, long-term data are scarce and are available from the Thoracic Aortic (endo)Graft (TAG) study reporting its 5-year results1 and for Zenith thoracic devices.2 The TAG trial has reported a survival advantage in favor of TEVAR to persist for at least 5 years because the difference reflects mostly the effect of the perioperative period with few, if any, later aneurysm-related mortalities in both open and TEVAR groups. All-cause late survival, however, shows minimal differences between open and endovascular modalities beyond 81
R.A. Chaer and M.S. Makaroun
82 1 year, mirroring the findings of randomized EVAR trials in the abdominal aorta. At 5 years, overall survival in the TEVAR and open groups was 68% and 67%, respectively, indicating similar late effectiveness for both procedures.1 Long-term follow-up with the Zenith TX1 and TX2 devices reported an overall survival of 70% at 60 months, with a mean follow-up of 36 months (range, 1 day to 78 months). Long-term freedom from aneurysm-related mortality, however, was ⬎90%, and appeared stable after the first-year follow-up. This long-term data included high-risk patients with mixed pathology, the majority being treated for descending thoracic aneurysms, and few for chronic aortic dissection, or fistulae.2 Other series of thoracic endografting have published long-term data.6,7 However, a significant proportion of patients in these series were treated for dissection and therefore excluded from this report. Late outcomes are not as encouraging in high-risk populations. A Stanford series of 103 patients, 60 of whom were deemed inoperable, reported a low 5-year survival estimate of 31%, in contrast to 78% for those who were open surgical candidates.8 This brings into question the appropriateness of any treatment in asymptomatic high-risk patients.
Late Neurologic Complications Neurologic complications can be devastating after DTA repair. Although stroke receives less attention than spinal cord ischemia (SCI), it is just as common and occurs with similar rates between open and endovascular repairs (range, 3% to 5%).6 Deployment of the proximal end of the endograft in zone 2 proximal to the left subclavian artery shows a strong association with perioperative stroke, likely secondary to manipulation of the arch with catheters, wires, balloons, and stent-grafts at the origin of cerebral vessels. The proximity of the endograft to the origin of the great vessels may serve as a nidus for embolization and stroke. The vast majority of neurologic complications, however, occur in the perioperative period. At 5 years, TAG patients were significantly less likely to have major adverse events, including neurologic complications, when compared to the surgical cohort, with no devicerelated strokes reported on long-term follow-up.1 Similarly, in the STARZ (Study of Thoracic Aortic Aneurysm Repair with the Zenith TX2 thoracic graft) trial, although five patients presented with a stroke in the perioperative period, the long-term risk of stroke was not increased.5 As was initially observed with the TAG study, which showed a marked reduction of paraplegia/paraparesis compared to open procedures (3% v 14%), the advantage of spinal cord protection with TEVAR was again evident when the data from all three US Food and Drug Administration trials were compared with open controls (6.2% v 13%; P ⬍ .007).1 If only devastating permanent paraplegia is considered, TEVAR at 1.6% versus 5.1% (P ⬍ .0037) for open operation is favored. Reduced incidence of SCI with TEVAR may be related to avoidance of thoracic aortic clamping and reduced hemodynamic disturbances at the spinal cord level due to lack of blood loss from intercostal backbleeding. It
should also be noted that SCI is not confined to the perioperative period. Delayed recurrent SCI and paraplegia after TEVAR have been reported, and have been shown to occur up to 1.5 years postoperatively.9,10 Several factors have been implicated, including hypotension, prior abdominal aortic aneurysm repair, length of aorta covered, use of an iliac conduit, and coverage of the hypogastric artery and the left subclavian artery. One additional mechanism that is unique in the pathogenesis of SCI after TEVAR is that coverage of critical intercostals may not necessarily result in immediate paraplegia because flow may be maintained through cross-collateral flow (ie, endoleak). When these endoleaks are sealed, the collateral flow is lost, which then may be followed by the neurologic deficit.10 Although the acute and late risk of SCI after TEVAR is low, it may be ongoing and dynamic, and depend on the integrity of the remaining collateral flow contributing to spinal perfusion.
Late Aneurysm and Device-Related Failures DTA is a degenerative process that may be limited to a part of the thoracic aorta at the time of treatment, but can progress over time to involve the undilated aorta chosen for sealing. The exact incidence of this problem is clearly dependent on the length of normal aorta covered and the life expectancy of the patient. Late degeneration of the landing zones should therefore be expected, and may lead to sac enlargement, migrations, type I endoleaks, and possible rupture. Moreover, tortuosity of the thoracic aorta and the high-flow patterns usually induce the endograft to settle into the larger convexities of the aneurysm cavity, which could result in both distal migration of the proximal end and proximal migration of the distal end with possible type I endoleaks. This tendency may be exacerbated by lengthening of the thoracic aorta over time,4 shortening the overlap zones and leading to type III endoleaks.
Endoleaks Early endoleak rates at the 30-day follow-up are inexplicably high in the VALOR (Vascular Talent Thoracic Stent Graft System for the Treatment of Thoracic Aortic Aneurysms) trial4 at nearly 26%, while they are far less in the TAG (3.6%)1 and STARZ (4.8%)5 studies as well as the EUROSTAR (European collaborators on Stent-graft Techniques for abdominal aortic Aneurysm Repair)) registry.11 This is mostly a definition issue because all endoleaks observed at any time prior to 30 days are included in the VALOR report, while only endoleaks at the 30-day follow-up are in the other two studies. At 1-year endoleaks were present in nearly 4% of TAG and TX2 patients and 12% of Talent patients. During longterm follow-up of the TAG study, approximately 4% of patients continued to have an endoleak at each yearly follow-up to 5 years.1 Distribution of endoleak type is also variable with the TAG study, reporting a majority of type I and III endoleaks, while the other two studies report a majority of type II endoleaks. This is again most likely a reporting issue, as the TAG study
Late failure after endovascular repair of descending thoracic aneurysms relied on investigator reports while the other two trials relied on a core laboratory. Late endoleaks (⬎30 days) were noted in 12 patients (7.5%) treated with the Zenith endograft. Other endoleaks detected were 10 type I (7 primary, 3 secondary), 14 type II (7 primary and 7 secondary), and 3 type III (1 primary and 2 secondary). However, associated sac enlargement was noted in only one patient at 4 years in the setting of a type III endoleak resulting from component separation. Freedom from primary endoleak was reported to be ⬎90% at 30 months by life-table analysis.2 Endoleaks were, in general, less frequent than comparable EVAR series with more type I and III endoleaks and less type II.
Sac Enlargement Aneurysm sac shrinkage is a good surrogate marker for successful repair of all aneurysms, including DTA. Sac enlargement is a concerning finding as it possibly indicates poor exclusion and pressurization of the sac. It may also introduce the potential for progressive outward traction in a larger cavity, resulting in possible stent-graft kinking or dislodgement. Sac enlargement rate of ⱖ5 mm is encountered more frequently with TEVAR than with abdominal EVAR and has been reported in 7% to 14% of patients at 1 year, with little variation between devices. The TAG pivotal trial has reported late results in a longitudinal cohort, and sac enlargement was noted in nearly 20% at 5 years. Shrinkage was observed in 50% and a stable sac was noted in the remaining patients.1 These rates may or may not apply to other grafts as the expanded polytetrafluoroethylene (ePTFE) material in the TAG study graft was somewhat porous with a sac behavior that resembled the original abdominal Gore Excluder. Both TAG and Excluder endografts were modified to a less porous ePTFE material, resulting in a much higher rate of sac shrinkage in the infrarenal position.12 Similarly, data from the confirmatory trial with the modified TAG device using the lowpermeability ePTFE has, so far, shown a lower incidence of sac enlargement at 2 years of 2.9% compared with 12.9% with the original device (P ⫽ .11). Long-term follow-up is obviously necessary. Aneurysm sac increase was observed in only two patients on long-term follow-up of a single institutional experience with the Zenith TX1 and TX2 thoracic devices.2 One patient had aneurysm growth noted at the 1-year follow-up visit, without evidence of endoleak or compromised fixation. She was monitored and the aneurysm had decreased in size at her 2-year visit, without evidence of sac expansion 3 years after treatment. Only one other patient had sac size increase that was detected at 4 years in the setting of a type III endoleak, requiring placement of an additional component to eliminate the endoleak.
83 early devices in association with neck dilation and stent-graft kinking.11,13 Current commercial devices tested in the US pivotal trials seem to have a low migration potential, ranging from 0.7 %to 3.9%. At 5 years, the TAG trial shows no late migration of ⬎10 mm by investigator reporting.1 Illustrating the variability in data sources, a core laboratory evaluation of a limited number of patients from the same study reports a freedom from migration of 97% at 12 months, 87% at 24 months, and 83% at 3 years.14 None of the migrations was clinically significant except for an early one associated with an arch aneurysm. Migration was noted on both ends of the devices with the Zenith device, with the TX2 trial reporting one cranial and two caudal migrations through 1 year.5 None of these was associated with endoleak or sac expansion or required an intervention. Morales et al2 assessed migration by centerline of flow distances from fixed landmarks (left common carotid and celiac arteries), where 14 patients had ⬎10 mm of distance change throughout follow-up. Any patient with detected changes of baseline central line length measurements underwent further image assessment, primarily using surface-rendering reconstruction to evaluate device position in relation to local landmarks. These analyses showed device movement had occurred in four patients (2.5%) at 6 months (distal) and 1 (proximal), 2 (distal), and 3 years (proximal) postoperatively, two required reintervention. Life-table analysis showed that 93% of patients in this series will be free of migration at the 5-year follow-up.
Device Integrity and Ruptures Early experience with TEVAR in high-risk individuals was associated with significant complication rates, with one study reporting a 13% stent fracture and 6% late rupture rates.15 Current devices suffer very few device-integrity issues and are expected to be ⬍2% in the marketed devices in the
Migration Late migration of the device has been reported to occur from 0% to 30% of patients.11 With TEVAR, migration can occur at both ends with distal migration of the proximal segment and proximal migration of the distal end frequently seen with
Figure 1 Thoracic endograft infection with air in the residual aneurysm sac, requiring open conversion.
R.A. Chaer and M.S. Makaroun
84 United States. The original TAG device showed fractures in the longitudinal wire in 14% of patients during 5 years of follow-up, with only one patient suspected of a type III endoleak receiving an endovascular repair. The wire has been removed from the modified device. No stent fracture, barb separation, stent-to-graft separation, or component separation was observed in the TX2 device in 1 year of follow-up.5 One patient had a distal bare stent strut entanglement that was detected at discharge. On long-term follow-up, however, barb fractures occurred in eight patients (5%),2 and all patients with noted barb fractures had only a single barb break. Fractures were detected in
three patients at 24 months, in two at 36 months, and in three at 60 months. Only one of the eight patients with barb fractures had evidence of device migration, which was noted at 2 years of follow-up and treated with a proximal extension. The remaining seven patients with barb fracture remained stable and did not require a reintervention. Three Talent devices were noted to have a fracture during follow-up, one in the connecting bar.4 One device was noted to have a fabric abrasion after explantation for rupture. This is the only known case of rupture among the 495 patients enrolled in the pivotal trials. The connecting bar has been removed from the modified investigational Val-
Figure 2 (A) Progressive enlargement of the landing zones over a period of 4 years following thoracic endovascular aortic repair for descending thoracic aortic aneurysms (TAA). (B) Proximal migration of the distal portion of the Talent endograft is noted (white arrow), resulting in component separation (black arrow) as compared to the completion angiogram from the initial repair in 2003. Relining of the endograft with proximal and distal extension of the landing zones was performed in 2007 using a TAG device.
Late failure after endovascular repair of descending thoracic aneurysms iant device. No graft thrombosis has been noted in all of these large devices.
Reinterventions Reintervention is defined as all procedures performed on patients referable to or as a consequence of the initial procedure. Early reinterventions have been noted in only 2.1% in the pivotal TAG cohort during the first year, but in 10.7% of the Talent study. Most reinterventions are for the treatment of endoleaks and several are endovascular in nature. TX2 reintervention rates through 1 year were similar between the two groups (4.4% TEVAR v 5.7% open).5 At long-term, data available from the TAG study showed a total reintervention rate of 3.6% of patients treated (2.1% for open repair).1 Two patients had a surgical conversion, one for an aorto-esophageal fistula and the second for an arch aneurysm and migration of the proximal device in a very large neck that did not meet inclusion and exclusion criteria. Both were during the first year of follow-up. Three patients had five endovascular revisions for endoleaks. Secondary procedures of any kind were noted during the 5-year follow-up in 15% of TAG patients and 32% of open surgical controls. While most secondary interventions following TAG were endoleak-related, those after open repairs were due to wound complications, tracheostomy, and gastrointestinal tract-related problems. The long-term data with the TX1 and TX2 devices showed that secondary interventions were required in 42 patients (26%). Indications included nine endoleaks, two aortobronchial fistulae, one aneurysm sac enlargement, three component separations, one compressed stent within an elephant trunk graft, and one patient with what was perceived to be a compromised proximal sealing segment with no endoleak. Endovascular techniques were used to treat all but one patient.2 Freedom from secondary intervention was reported to be ⬎60% at ⬎72 months follow-up.
85 required and may include proximal and distal extension or complete relining of the existing endograft to achieve an adequate seal (Fig 2B). Debranching of the aortic arch as well as coverage of the celiac axis may also be required. Elongation of the nonstented portion of the thoracic aorta after TEVAR has also been described. Up to 31% of patients from the VALOR trial were found to have ⬎1 cm elongation within 1 year of implantation and this may lead to migration or secondary interventions. Aortic length instability was associated with proximal and distal attachment site diameters larger than the adjacent normal aorta, suggesting that better patient selection or more extended aortic coverage beyond the ectatic segment may prevent this late problem. Proximity of the thoracic endograft to the origin of the great vessels in the aortic arch is usually well-tolerated in the acute setting. This is mainly a concern in patients with tenuous proximal landing zone who require coverage of the left subclavian artery, as the bare stents may potentially act as nidus for embolization and could increase the risk of longterm neurologic events. While this may be more common following treatment of aortic dissection of traumatic transection, it can occur following EVAR for DTA, especially in the setting of rupture. This can be managed with open conversion, hybrid intervention with arch debranching, or endovascular techniques with retrograde stenting of the origin of the involved great vessel into the aortic arch (Fig 3). Device-specific failures have been recognized and have lead to a modification of the current grafts. Fractured spines led to changing the TAG device and the fractured connecting bar in Talent led to the modified design of the Valiant graft. Several other modification have also been made to Valiant device, and the closed-web proximal device variant on the current design promises to avoid long-term complications, such as proximal aortic perforation by the uncovered stent
Other Complications Stent-graft infection is uncommon (Fig 1), and has been reported in the first year following implantation in two patients who required open conversion.16 Late graft infection requiring explanation after DTA repair has not been reported in the major device trials. Retrograde type A dissection has been reported at 1 week and 4 months after TEVAR, requiring open conversion.16 This is an unlikely late complication after TEVAR for DTA and may more occur commonly in patients treated for aortic dissection or from wire trauma. Aortoesophageal fistula is a well-described early and late complication of TEVAR and occurred in two patients at 3.5 and 49 months in one series, requiring open conversion.16 It was also described in the TAG trial in one patient who required debridement and drainage within the first year after implantation.1 Late enlargement of the landing zones has not been wellcharacterized, but can be expected with ongoing degeneration of the thoracic aorta (Fig 2A). Reintervention is often
Figure 3 Encroachment of the endograft scallop on the origin on the left common carotid artery (CCA) is seen in this patient initially treated for a ruptured thoracic aneurysm. The patient presented with a transient ischemic attack on late follow-up.
R.A. Chaer and M.S. Makaroun
86
References
Figure 4 Endograft collapse seen on late computed tomography follow-up after thoracic endovascular aortic repair for descending thoracic aortic aneurysms.
strut.17 This late failure may be more common, however, in patients treated for dissection, given the friability of the aortic wall. Other unusual late failures following TEVAR for DTA include stent-graft collapse (Fig 4), which is more commonly described in young patients with acute angulations of their aortic arch treated for aortic transaction.18 This late failure can be avoided by placing the proximal landing zone in a straight segment of the thoracic aorta. Although endovascular salvage may be possible, open conversion with arch debranching and proximal stent-graft extension may be a more durable alternative.
Conclusions Although reported data remain limited, the early advantages of TEVAR over open repair seems to be maintained on long-term follow-up. The incidence of late complications appears to be low, and device-related and aneurysmrelated adverse events are uncommon and anecdotal, especially with the new-generation devices. Careful patient selection and attention to technical details can prevent most late failures. Longer-term follow-up, however, is needed, with comparative data to evaluate the currently approved devices and the performance of different endografts in various anatomic and clinical situations.
1. Makaroun MS, Dillavou ED, Wheatley GH, Cambria RP; Gore TAG Investigators: Five-year results of endovascular treatment with the Gore TAG device compared with open repair of thoracic aortic aneurysms. J Vasc Surg 47:912-918, 2008 2. Morales JP, Greenberg RK, Morales CA, et al: Thoracic aortic lesions treated with the Zenith TX1 and TX2 thoracic devices: intermediateand long-term outcomes. Vasc Surg 48:54-63, 2008 3. Chaikof EL, Blankensteijn JD, Harris PL, et al: Reporting standards for endovascular aortic aneurysm repair. J Vasc Surg 35:1048-1060, 2002 4. Fairman RM, Farber M, Kwolek CJ, et al: Pivotal results of the Medtronic Vascular Talent™ Thoracic Stent Graft System for patients with thoracic aoric disease: the VALOR trial. J Vasc Surg 48:546-554, 2008 5. Matsumura JS, Cambria RP, Dake MD, Moore RD, Svensson LG, Snyder S: International controlled clinical trial of thoracic endovascular aneurysm repair with the Zenith TX2 endovascular graft: 1-year results. J Vasc Surg 47:247-257, 2008 6. Criado FJ, Abul-Khoudoud OR, Domer GS, et al: Endovascular repair of the thoracic aorta: lessons learned. Ann Thorac Surg 80:857-863, 2005 7. Fattori R, Nienaber CA, Rousseau H, et al: Results of endovascular repair of the thoracic aorta with the Talent Thoracic stent graft: the Talent Thoracic Retrospective Registry. J Thorac Cardiovasc Surg 132: 332-339, 2006 8. Demers P, Miller DC, Mitchell RS, et al: Midterm results of endovascular repair of descending thoracic aortic aneurysms with first-generation stent grafts. J Thorac Cardiovasc Surg 127:664-673, 2004 9. Kieffer E, Chiche L, Cormier E, Guegan H: Recurrent spinal cord ischemia after endovascular stent grafting for chronic traumatic aneurysm of the aortic isthmus. J Vasc Surg 45:831-833, 2007 10. Cho JS, Rhee RY, Makaroun MS: Delayed paraplegia 10 months after endovascular repair of thoracic aortic aneurysm. J Vasc Surg 47:625628, 2008 11. Leurs LJ, Bell R, Degrieck Y, Thomas S, Hobo R, Lundbom J: Endovascular treatment of thoracic aortic diseases: combined experience from the EUROSTAR and United Kingdom Thoracic Endograft registries. J Vasc Surg 40:670-679, 2004 12. Cho JS, Dillavou ED, Rhee RY, Makaroun MS: Late abdominal aortic aneurysm enlargement after endovascular repair with the Excluder device. J Vasc Surg 39:1236-1241, 2004 13. Resch T, Koul B, Dias N, Lindblad B, Ivancev K: Changes in aneurysm morphology and stent-graft configuration after endovascular repair of aneurysms of the descending thoracic aorta. J Thorac Cardiovasc Surg 122:47-52, 2001 14. Hassoun HT, Mitchell RS, Makaroun MS, Whiting AJ, Cardeira KR, Matsumura JS: Aortic neck morphology after endovascular repair of descending thoracic aortic aneurysms. J Vasc Surg 43:26-31, 2006 15. Ellozy SH, Carroccio A, Minor M, et al: Challenges of endovascular tube graft repair of thoracic aortic aneurysm: midterm follow-up and lessons learned. [see comment]. J Vasc Surg 38:676-683, 2003 16. Girdauskas E, Falk V, Kuntze T, et al: Secondary surgical procedures after endovascular stent grafting of the thoracic aorta: successful approaches to a challenging clinical problem. J Thorac Cardiovasc Surg 136:1289-1294, 2008 17. Panos A: Late retrograde aortic perforation by the uncovered part of an endograft: an increasing complication. Hellenic J Cardiol 48:115-116, 2007 18. Go MR, Barbato JE, Dillavou ED, et al: Thoracic endovascular aortic repair for traumatic aortic transection. J Vasc Surg 46:928-933, 2007