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Ann Thorac Surg 2006;81:1570-1577
© 2006 The Society of Thoracic Surgeons


Original article: Cardiovascular

Midterm Outcome in 158 Consecutive Gore TAG Thoracic Endoprostheses: Single Center Experience

Grayson H. Wheatley, III, MD a , Ahmet Tayfun Gurbuz, MD b , Julio A. Rodriguez-Lopez, MD a , Venkatesh G. Ramaiah, MD a , Dawn Olsen, PA a , James Williams, BS a , Edward B. Diethrich, MD a , *

a Department of Cardiovascular Surgery, Arizona Heart Institute, Phoenix, Arizona
b Department of Cardiovascular Surgery, Anadolu Saglik Merkezi, Kocaeli, Turkey

Accepted for publication June 24, 2005.

* Address correspondence to Dr Wheatley, Arizona Heart Institute, 2632 N 20th Street, Phoenix, AZ 85006 (Email: gwheatley{at}azheart.com).

Presented at the Forty-first Annual Meeting of The Society of Thoracic Surgeons, Tampa, FL, Jan 24–26, 2005.


Adult cardiac surgery: The Annals of Thoracic Surgery CME Program is located online at http://cme.ctsnetjournals.org. To take the CME activity related to this article, you must have either an STS member or an individual non-member subscription to the journal.

 

    Abstract
 Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 Discussion
 References
 
BACKGROUND: Despite recent improvements in surgical technique, some patients with descending thoracic aortic pathologies are unable to undergo open surgical repair due to significant comorbidities and/or unfavorable thoracic aortic anatomy. Some of these patients might be able to tolerate a less invasive approach, such as endoluminal grafting. We reviewed our consecutive clinical experience with the Gore TAG endoprosthesis (W. L. Gore & Assoc, Flagstaff, AZ) for the endovascular exclusion of assorted descending thoracic aortic pathologies in higher surgical risk patients.

METHODS: After obtaining institutional review board approval, 158 high surgical risk patients underwent attempted delivery of a Gore TAG thoracic endoprosthesis between February 2000 and July 2004. Indications for study enrollment were atherosclerotic aneurysm (n = 76), aortic dissection (n = 36), penetrating aortic ulcer (n = 15), contained rupture (n = 11), pseudoaneurysm (n = 10), traumatic aortic injury (n = 5), aortobronchial fistula (n = 4), and aortic coarctation (n = 1).

RESULTS: The device was successfully delivered in 156 (98.7%) patients. Mean patient age was 72 ± 12.1 years. Three (1.9%) patients developed transient paraparesis after graft deployment and 1 (0.6%) patient developed paraplegia. While postimplantation endoleaks were observed in 18 (11.5%) patients, only 12 patients required reintervention. Thirty-day mortality was 3.8% (6 of 156). Mean follow-up was 21.5 ± 18.8 months, and the overall mortality was 17.3% (27 of 156).

CONCLUSIONS: Endoluminal grafting of multiple types of descending thoracic aorta pathologies with the Gore TAG thoracic endoprosthesis is feasible and safe in higher surgical risk patients. Additional studies and long-term follow-up of these patients are warranted.

Numerous pathologies of the descending thoracic aorta (DTA), including atherosclerotic aneurysms, chronic dissections, pseudoaneurysms, and traumatic injuries are amenable to open surgical repair [1]. Recent advances in surgical technique such as distal aortic perfusion, cerebrospinal fluid drainage, and intercostal artery reimplantation have enabled patients with increased comorbidities and/or challenging aortic anatomy to undergo surgical resection with improved outcomes and morbidity [2]. However, many patients with significant comorbidities and/or unfavorable thoracic aortic anatomy are denied open surgical repair because of their increased surgical risk. Without treatment, these patients have a diminished life-expectancy and alternative therapeutic options are needed [3].

Endovascular deployment of an endoluminal graft (ELG) is emerging as a potentially important treatment strategy for disorders of the thoracic aorta [4–6]. In addition to being less invasive, endovascular exclusion of DTA aneurysms offers the possibility of decreased early patient morbidity [7]. In March 2005, the Gore TAG thoracic endoprosthesis (TAG; W. L. Gore and Associates, Flagstaff, AZ) became the first thoracic ELG to receive market approval for the treatment of DTA aneurysms by the Circulatory System Devices Panel of the United States Food and Drug Administration. Although the device was approved exclusively for use in DTA aneurysms, pathologies other than atherosclerotic aneurysms of the DTA may also be amenable to treatment with ELGs [8, 9]. In order to assess the feasibility and safety of an endovascular approach for higher open surgical risk patients, we reviewed our consecutive clinical experience for the treatment of assorted DTA pathologies using the TAG endoprosthesis as part of an investigational single-center protocol.


    Patients and Methods
 Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 Discussion
 References
 
Study Population
After obtaining institutional review board approval, nonrandomized patients with pathologies of the DTA were prospectively enrolled in a single-site investigational device exemption clinical study between February 2000 and July 2004. All patients received TAG endoprostheses under the investigational protocol, were fully informed, and consented prior to implantation of the ELG. A number of clinical and anatomic characteristics were used to select patients. Enrollment in the study was limited to patients who were deemed to be at "high surgical risk," meaning that they have comorbidities and/or thoracic aortic pathologies that place them at prohibitive risk for open repair, and, without intervention, an adverse event could be anticipated within days or weeks were included. In some cases, the relative risk of surgery was compared with the anticipated procedural risk of ELG, and given the patient's significant comorbidities, patients were offered ELG repair. Select study inclusion and exclusion criteria are summarized in Table 1.


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Table 1. Select Inclusion and Exclusion Criteria for Study Enrollment
 
Endoprosthesis Description
The TAG endoprosthesis is a nitinol-supported expanded polytetrafluoroethylene (PTFE) ELG. The ELG is available in diameters of 26 to 40 mm and in 10-, 15-, and 20-cm lengths. The profile of the device depends on the diameter of the ELG, and requires a 20 French (Fr), 22 Fr, or 24 Fr introducer sheath. The ELG is constrained within a PTFE sleeve, and has a unique self-expanding deployment mechanism, which allows graft expansion to begin centrally and propagates in both an antegrade and retrograde direction simultaneously (Fig 1). This type of deployment allows rapid intraluminal expansion of the device and minimizes the displacing forces relating to high arterial blood flow. An overlap of at least 3 cm is recommended when more than one ELG of differing diameters is deployed, or 5 cm if the deployed devices are of the same diameter. Intraluminal profiling and further expansion of deployed ELGs was selectively performed using a specially designed Gore Tri-lobed Balloon (W. L. Gore), which permits intraluminal blood flow to continue distally during balloon inflation.


Figure 1
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Fig 1. Gore TAG thoracic endoprosthesis. Endoluminal graft deployment starts centrally, and progresses in an antegrade and retrograde direction simultaneously.

 
Two versions of the TAG endoprosthesis were used during the study period. Between February 2000 and May 2001, 57 patients (group I) received a device which contained two longitudinal nitinol spines for columnar support. Although no adverse clinical events were identified, the device manufacturer voluntarily elected to suspend patient enrollment in May 2001 due to a limited number of device spine and stent fractures. Between February 2003 and July 2004, 101 patients (group II) received the slightly modified TAG endoprosthesis. This device lacked the longitudinal nitinol spines and the middle layers of the PTFE were reworked to add rigidity and assist with tracking and delivery of the device.

ELG Delivery and Deployment
All ELG procedures were performed in an endovascular suite by cardiovascular surgeons using standard endovascular techniques. Recommended preoperative imaging included contrast-enhanced computed tomography (CT) of the chest, abdomen, and pelvis. If no preoperative CT scans were available, or the CT images were of limited value, contrast angiography and/or intravascular ultrasound (IVUS) were performed. In addition, IVUS was routinely used to position the guidewire into the true aortic lumen in cases of aortic dissection and identify areas of fenestration. Occasionally, intraoperative transesophageal echocardiography imaging was used to augment the other imaging modalities. The ELG diameter was oversized compared with the native aortic landing zone diameter by 10% to 20%, as recommended by the device manufacturer.

In a majority of patients, the common femoral artery (CFA) was surgically exposed and used for device delivery. A common iliac artery approach was utilized when neither femoral artery was able to accommodate the introducer sheath. In this situation, a retroperitoneal incision was used. The introducer sheath was then delivered through a 10-mm Dacron graft which had been anastomosed to the common iliac artery or distal aorta. Once vascular access was obtained, 70 units/kg of heparin were intravenously administered, and an activated clotting time of greater than 200 seconds was maintained throughout the endovascular procedure. Prior to ELG deployment, systemic blood pressure was reduced to less than 100 mm Hg by the anesthesiologist to minimize device migration during deployment. No attempt was made to limit heart rate. The ELG was carefully deployed after exact location of the great vessels, primary entry tear, and/or the diseased aortic segment was confirmed. To minimize endoleaks and ensure secure placement of the ELG, proximal and distal landing zones of 2 cm of normal aorta were required. Sometimes this necessitated covering the origin of the left common carotid artery and/or the left subclavian artery with an ELG. Both final ELG position and postdeployment endoleaks were assessed using contrast aortography. Patients who were endotracheally intubated prior to the procedure were extubated at the completion of the procedure.

All patients were observed in an intensive care unit setting for a minimum of 12 hours after ELG implantation. Hemodynamic parameters, pulse oximetry, and telemetry were monitored continuously. Frequent neurologic assessments were performed. To optimize spinal cord perfusion, systolic blood pressures were maintained at or above 140 mm Hg for the first 48 hours after ELG implantation. Cerebrospinal fluid (CSF) drainage was reserved for patients who developed severe neurologic deficits, or in high risk patients such as those with prior abdominal aortic aneurysm repair and needing deployment of an ELG below the level of T8. Routine contrast-enhanced CT angiography of the chest, abdomen, and pelvis was obtained prior to discharge in patients with adequate renal function. Patients were discharged when they were medically stable.

Patient Follow-Up
After discharge, patients were seen within two weeks to assess the incision sites and to evaluate the patient's overall health status. Computed tomographic scans, plain radiographs, and physical examinations were obtained at 1, 6, and 12 months and yearly thereafter. A 3-month visit with a CT scan was also included in patients with an early endoleak identified at 1 month. All significant medial events that resulted in either an unplanned increase in the level of care, permanent sequelae, or death were recorded.


    Results
 Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 Discussion
 References
 
Patient Characteristics
One hundred fifty-eight patients were enrolled in the study. Anatomic indications for study enrollment were atherosclerotic aneurysm (n = 76), aortic dissection (n = 36), penetrating aortic ulcer (n = 15), contained rupture (n = 11), pseudoaneurysm (n = 10), traumatic aortic injury (n = 5), aortobronchial fistula (n = 4), and aortic coarctation (n = 1) (Table 2). With regard to the patients with type III thoracic aortic dissections who were treated with an ELG, 61.1% (n = 22) were for acute dissections and 38.9% (n = 14) were for chronic dissections. Indications for intervention were intractable pain (n = 20), end-organ ischemia (n = 10), or impending rupture as evidenced by contrast extravasation or associated hemothorax (n = 6). The study population had a mean age of 72 ± 12.1 years (23 to 91 years), and the additional demographics of the study patients are listed in Table 3.


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Table 2. Anatomic Indications for Study Inclusion
 

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Table 3. Preoperative Characteristics and Associated Comorbidities of Study Patients
 
ELG Deployment and Vascular Access
Successful deployment of the TAG endoprosthesis was accomplished in 156 of 158 patients (98.7%). A total of 218 ELGs were deployed in 156 patients. The number of ELGs deployed per patient varied based on aortic pathology and DTA anatomy. One device was used in 106 (67.9%) patients, 2 devices were used in 42 (26.9%) patients, 3 devices were deployed in 7 (4.5%) patients, and 1 (0.6%) patient required the deployment of 4 devices. The most frequently deployed ELG size was 34 mm (n = 71, 32.6%). Table 4 summarizes the number of each device size that was successfully deployed.


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Table 4. Endoluminal Graft Size Deployed
 
As per previously published criteria [10], the aorta was divided into standard anatomic regions in order to characterize the location of the proximal landing zone (Fig 2). Two of 156 (1.3%) patients had bovine arch anatomy, and required the proximal landing zone of their ELG to be in zone 1. Twenty-six of 156 (16.6%) patients had the proximal landing zone of their ELG located in zone 2. The most common proximal landing zone was zone 3 (n = 117, 75%). The proximal landing zone included zone 4 in 11 of 156 (7.1%) patients.


Figure 2
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Fig 2. Proximal landing zones of the aorta. Z0 = ascending root to the distal aspect of the innominate artery origin. Z1 = distal to the innominate artery origin including the left common carotid artery origin. Z2 = distal to the left common carotid artery origin including the left subclavian artery origin. Z3 = proximal third of the descending thoracic aorta distal to the left subclavian artery origin. Z4 = remainder of the supradiaphragmatic descending thoracic aorta [10].

 
Our treatment strategy relating to ELG coverage of the left common and subclavian arteries evolved throughout the study. Of the 57 patients in group I, 8 (14%) patients required coverage of their left common carotid artery and/or subclavian artery with an ELG to achieve adequate exclusion of their aortic pathology. Each of these patients received either a preoperative or perioperative carotid-subclavian bypass or carotid transposition. However, in group II (n = 101), we reserved preoperative or perioperative bypass for patients in which it was (1) necessary to preserve the left internal mammary artery, and/or (2) the left vertebral artery was critical to posterior cerebral circulation. No preoperative or perioperative bypasses or transpositions were performed in this group of patients. Two of 101 (2%) patients in group II required subsequent bypass for left upper extremity ischemia.

The two failures of device deployment occurred in patients in group I, and were all related to iliac artery size and vessel tortuosity. Of the 55 (96.5%) patients in group I (n = 57) who underwent successful device deployment, 47 (85.5%) patients had the ELG delivered through the CFA, while 8 (14.5%) patients had the device delivered through an iliac artery conduit. In group II (n = 101), CFA device delivery was accomplished in 85 (84.2%) patients, and an iliac artery conduit was necessary in 7 (6.9%) patients. Additionally, in this group, a sheathless "bareback" delivery through the CFA was utilized in 9 (8.9%) patients with small, noncalcified access vessels. We did not experience any difficulties with the bareback approach. Two patients experienced iliac artery perforation during introduction of the ELG through a CFA approach. In one patient, the iliac artery was repaired and the procedure was completed. In the other patient, the iliac artery was repaired and the procedure was terminated secondary to significant iliac artery tortuosity.

Patient Mortality and Morbidity
Thirty-day mortality for the entire study population of high surgical risk patients was 3.8%. In group I, 2 (3.5%) patients expired within 30 days of ELG deployment. The first patient expired on postoperative day (POD) 3 from multisystem organ failure and visceral embolization of atherosclerotic debris after ELG repair of a ruptured DTA aneurysm. The second patient experienced an iliac artery rupture during ELG deployment secondary to a CFA introducer sheath. The iliac artery was promptly repaired, but a brief episode of hypotension during the case in a patient with known coronary artery disease resulted in a subsequent acute myocardial infarction and death on POD 1.

Group II 30-day mortality was 4% (n = 4). The first mortality in this group occurred in a patient who had previously undergone ELG repair of a DTA dissection with a Talent thoracic stent graft (Medtronic, Inc, Minneapolis, MN). Approximately 9 months after ELG repair, the patient developed hematemesis and was diagnosed with an aortoesophageal fistula at the level of the prior ELG. The fistula was successfully closed using two TAG endoprostheses as part of this study protocol. However, the patient developed abdominal pain with associated metabolic acidosis approximately three weeks post-ELG deployment. Acute mesenteric ischemia was discovered at the time of the patient's exploratory laparotomy. One of the TAG endoprosthesis had become infected and migrated distally in the aorta and covered the celiac and superior mesenteric arteries. The patient expired on post-ELG deployment day 23. The second mortality (POD 23) resulted from multisystem organ failure in a patient who underwent open conversion for a persistent proximal endoleak on POD 2. The third mortality occurred on POD 7 after an open conversion for an introducer sheath perforation of a contained DTA aneurysm rupture. This patient experienced a cerebrovascular accident, and eventually expired from respiratory and renal failure. The final mortality (POD 10) occurred in a patient who underwent simultaneous repair of DTA and infrarenal abdominal aortic aneurysms. This patient developed internal bleeding and expired from an acute myocardial infarction.

Endoleaks occurred in a total of 18 (11.5%) patients. Seven (12.7%) patients in group I developed endoleaks. Six patients in this group developed an endoleak after ELG repair of a DTA aneurysm and one patient had a dissection repaired. Eleven (10.9%) patients in group II developed endoleaks. Seven patients with endoleaks received ELGs in this group for DTA aneurysms, and 4 patients were treated for dissections. There were a total of 11 (61%) patients with a type I endoleak, 4 (22.2%) patients with a type II endoleak, 1 (5.6%) patient with a type III endoleak, 1 (5.6%) patient with both a type I and II endoleak and 1 (5.6%) patient with both a type II and III endoleak. Thirty days post-ELG deployment, an endoleak remained in 9 patients: 6 for aneurysms and 3 for dissections. In this subset of patients, 4 (44.4%) had a type I endoleak, 4 (44%) had a type II endoleak, and 1 (11.1%) had a type III endoleak. Of the 36 patients in the study treated for an aortic dissection, 5 (13.9%) developed an endoleak. After POD 30, 3 (8.3%) patients with aortic dissections had residual endoleaks (all 3 patients with distal type I endoleaks).

Spinal cord neurologic events occurred in 4 (2.6%) patients. Bilateral lower extremity weakness developed immediately postoperatively in one patient. This patient received intravenous steroids, and the weakness resolved completely within 72 hours. Mild bilateral lower extremity weakness developed within the first 24 hours postoperatively in another patient. This patient was observed, and the weakness completely resolved prior to discharge. Another patient developed generalized weakness starting one week postoperatively. After a month of observation and therapy, the patient almost fully recovered except for some lack of control of bowel and bladder function. The final patient who suffered a neurologic event developed bilateral lower extremity paraplegia several hours postoperatively after ELG deployment for an acute DTA dissection. Cerebrospinal fluid drainage was instituted along with intravenous steroid therapy and elevation of the patient's systolic blood pressure. This patient incompletely recovered, and was left with permanent bowel and bladder incontinence.

Open surgical conversions were required in 4 (2.6%) study patients. In one of these patients the conversion was emergent. This conversion resulted from an introducer sheath perforation of a contained DTA aneurysm rupture. Another patient required open surgical conversion on POD 2 for inadequate proximal sealing of the ELG. Both of these patients have been previously mentioned as morbidities. Another patient underwent successful open removal of an infected ELG approximately 6 months postdeployment. This patient originally had an ELG placed for repair of an aortobronchial fistula, which resulted from a previous interposition graft, and the ELG subsequently became infected. Finally, another patient successfully underwent ELG removal along with aortic resection and repair of an expanding DTA aneurysm sac 3 years post-ELG deployment.

Thirteen endovascular reinterventions were necessary in 12 patients. An endoleak was corrected in 9 patients with an additional ELG deployment. One patient developed a new penetrating aortic ulcer, which was identified as part of the routine follow-up imaging studies, and required deployment of an additional ELG. Another patient developed an ELG infection and was not an open surgical candidate, and the original graft was excluded with deployment of a new ELG. Finally, a patient required deployment of two new ELGs due to both proximal and distal expansion of the aneurysm.

Average patient follow-up was 21.5 ± 18.8 months. Table 5 summarizes all of the postoperative complications. Seven patients of 156 (4.5%) experienced either a cerebral vascular accident (n = 4) or a transient ischemic attack (n = 3) within 30 days postoperatively. There were 27 (17.3%) total deaths during the follow-up period, with 21 (13.5%) of the deaths occurring after 30 days. The Kaplan-Meier survival graph is shown in Figure 3. Deaths occurred in patients who had received an ELG for the following indications: elective atherosclerotic aneurysm (n = 16), aortic dissection (n = 8), ruptured atherosclerotic aneurysm (n = 2), and traumatic aortic injury (n = 1). Among the 21 deaths after 30 days, mortality resulted directly from patient comorbidities in 10 patients. These comorbidities included coronary artery disease (n = 2), renal failure (n = 2), respiratory failure (n = 2), urosepsis (n = 1), lung cancer (n = 2), and metastatic prostate cancer (n = 1). Despite attempts at multiple inquiries of family members and referring physicians, the cause of death was unknown in 9 patients. Two patients expired after a prolonged duration of postprocedure respiratory failure and ventilator dependence. There was one death due to device migration.


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Table 5. Total Postoperative Complications
 

Figure 3
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Fig 3. The Kaplan-Meier survival graph of all 156 patients treated with an endoluminal graft.

 

    Comment
 Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 Discussion
 References
 
Endovascular approaches for the thoracic aorta have emerged as a relatively less invasive treatment alternative for thoracic aortic disorders. The short-term benefits of this technique have been demonstrated [11, 12]. It is usually well-tolerated in elderly patients and is associated with both shorter stays in the intensive care unit and decreased blood transfusion requirements [13]. Perioperative mortality and paraplegia risk compare favorably to open surgical repair rates [13, 14].

Vascular access issues are just as important as proximal and distal landing zone concerns with regard to an endovascular approach. Careful preoperative planning is critical in limiting and preventing introducer sheath vascular injuries. Although we experienced only 2 vascular access injuries in this study, these injuries can occur in as high as 10% to 15% of patients undergoing endovascular procedures [14, 15]. Most of the currently available devices require 22 Fr or 24 Fr introducer sheaths for delivery, and future generations of ELGs will be able to be delivered through smaller sheaths. Introducer sheath delivery through a 10-mm Dacron conduit into the iliac artery is an effective option in patients with small or severely calcified femoral arteries. Patients with thoracic aortic disorders do not tolerate this complication well, and therefore, prompt recognition and repair of vascular access injuries is important.

Management of the left common carotid and subclavian arteries is changing with regard to endovascular therapies of the thoracic aorta. In this study, we initially performed a bypass procedure preoperatively or perioperatively when it was necessary to deploy an ELG that covered either of these vessels. However, recent studies have shown that this might not always be necessary [17]. In the second part of the study, we found that very few patients developed signs of vascular ischemia when an ELG covered the left common carotid or subclavian arteries. This approach appears to be safe, and an expectant approach with regard to this issue does not seem to add increased patient morbidity. In fact, the morbidity from not performing the bypass procedure may be less than the morbidity related to the surgical bypass procedure itself.

In this study, we noted a 2.6% incidence of spinal cord ischemia, which compares favorably with other studies [11, 13]. Only one patient was left with a serious permanent deficit, and this patient was at high risk for neurologic injury secondary to their aortic pathology (acute type B dissection). We used CSF drainage selectively in this study, but recognize that this adjunctive therapy might have a role in high risk candidates for endovascular therapy, such as those who have had prior abdominal aortic aneurysm repair. In our experience, the two most significant factors associated with neurologic events are prior abdominal aortic aneurysm repair and need for deployment of a thoracic ELG at or below the level of T8. When we placed a spinal drain, we maintained a spinal cord pressure below 14 mm Hg by draining CSF every 2 hours as needed. Future studies will need to address this issue and possibly risk stratify patients preoperatively for their neurologic risk prior to endovascular therapy to minimize the risk of this serious complication. The risk stratification criteria for endovascular patients may be different than those for open surgical patients.

All patients with DTA dissections had successful coverage of the proximal entry point. There were no visceral or end-organ ischemic issues, although one patient with an acute dissection developed paraparesis postoperatively. When treating patients with either acute or chronic dissections, it is important to identify, either through preoperative CT scan or intraoperative IVUS or aortogram, the distal fenestration. This fenestration will permit vessel filing off the false lumen after the proximal false lumen thromboses after ELG placement. We did not find it necessary to create a fenestration in any of the patients. Careful patient selection will possibly enable more patients with acute and chronic DTA dissections to be treated with ELGs. Additional study is necessary.

Thirty-day mortality in this study (3.7%) was lower compared with the 9% mortality rate reported by Mitchell [4] and 19% mortality rate reported by Neuhauser and colleagues [18]. Freedom from treatment failure is also an important indicator of graft durability during midterm follow-up. Dake and colleagues [19] reported a 53% freedom from treatment failure in an early experience and 69% of patients were free from treatment failure in the series reported by Ishida and colleagues [14]. The low treatment failure rate in this study is most likely related to both a low incidence of associated ELG endoleaks and a low reintervention rate. Similarly, our stroke rate of 4.5% (n = 7) is appreciatively lower than 10% reported in prior studies [4]. This is possibly related to our attempts to minimize manipulation of guidewires and ELG devices in the aortic arch.

We acknowledge limitations to this study. First, although patients were prospectively enrolled in this study, they were nonrandomized. Many of the patients in this study are not candidates for open surgical therapy, and therefore a randomized study using this same patient population would need to compare endovascular therapy against medical therapy. However, the natural history of patients with thoracic aneurysms greater than 6 cm has been reported to be poor [3]. Second, this is a single-site investigational device exemption study. To understand better the safety and efficacy of endovascular therapies for the thoracic aorta, it would be necessary to conduct a multicenter prospective randomized trial. Patients are already being enrolled in a phase II study using the TAG endoprosthesis for DTA aneurysms [6]. However, this study does not look at the use of an ELG for aortic pathologies other than aneurysms or in high surgical risk patients. Finally, the average follow-up in our study population was 21.5 ± 18.8 months. The mechanical stresses in the thoracic aorta, which result from repeated expansion and contraction of the ELG in the presence of intense systolic pressures, are quite different than the mechanical stresses impacting the infrarenal abdominal aorta. To make any significant conclusions regarding the durability of any type of endovascular therapy for thoracic aortic pathologies, it will be necessary to obtain longer term follow-up information. Finally, we acknowledge that the cause of late death was unable to be ascertained in several patients in this study (n = 9). This information is obviously important in assessing the efficacy of endovascular approaches for the thoracic aorta. Our patient referral pattern is unique and encompasses a national pool of patients. Despite numerous contacts with surviving family members and referring physicians, we were unable to obtain the cause of late death and, although unlikely in a patient population with significant comorbidities, we cannot rule out ELG associated mortality in this subgroup.

In conclusion, this study suggests that a wide variety of aortic pathologies are amenable to endovascular therapy. Careful attention to vascular access for sheath delivery is important, and complications associated with vascular access are in general poorly tolerated by these patients. The midterm results of this approach in high risk surgical patients compare favorably with traditional open surgical repairs. This procedure can be performed with a low incidence of neurologic complications (spinal cord ischemia or stroke). The TAG endoprosthesis performed extremely well with regard to delivery, deployment, and efficacy of treatment. Endovascular therapies for the thoracic aorta are in the early stages of development, and we believe that additional studies and continued surveillance of treated patients are necessary [16].


    Discussion
 Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 Discussion
 References
 
DR O. H. FRAZIER (Houston, TX): It was a very nice presentation. To me it was unclear how you distinguish between patients that you would use this technique and approach in contradistinction to an open repair, and I wonder how many patients you had during this same period that you utilized an open repair?

DR GURBUZ: Thank you, Dr Frazier. The protocol states all the patients that received the second version of the device at least had to be high risk, that means they were at prohibitive risk for an open repair, as well as there was a chance for an adverse event if the repair wasn't done soon, in a matter of days to weeks. The other patients received an open repair.


    References
 Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 Discussion
 References
 

  1. Svensson LG, Labib SB. Aortic dissection and aortic aneurysm surgery Curr Opin Cardiol 1994:191-199.
  2. Safi HJ, Miller CC, Huynh TT, et al. Distal aortic perfusion and cerebrospinal fluid drainage for thoracoabdominal and descending thoracic aortic repairten years of organ preservation. Ann Surg 2003;238:372-380.[Medline]
  3. Pitt MP, Bonser RS. The natural history of thoracic aortic aneurysm diseasean overview. J Card Surg 1997;12(suppl 2):270-278.[Medline]
  4. Mitchell RS, Miller DC, Dake MD, et al. Thoracic aortic aneurysm repair with an endovascular stent graftthe "first generation.". Ann Thorac Surg 1999;67:1971-1974.[Abstract/Free Full Text]
  5. Ramaiah V, Rodriguez-Lopez JA, Diethrich EB. Endografting of the thoracic aortasingle center experience with technical considerations. J Card Surg 2003;18:444-453.[Medline]
  6. Makaroun MS, Dillavou ED, Kee ST, et al. Endovascular treatment of thoracic aortic aneurysmsresults of the phase II multicenter trial of the GORE TAG thoracic endoprosthesis. J Vasc Surg 2005;41:1-9.[Medline]
  7. Destrieux-Garnier L, Haulon S, Willoteaux S, et al. Midterm results of endoluminal stent grafting of the thoracic aorta Vascular 2004;12:179-185.[Medline]
  8. Thompson CS, Ramaiah VG, Rodriquez-Lopez JA, et al. Endoluminal stent graft repair of aortobronchial fistulas J Vasc Surg 2002;35:387-391.[Medline]
  9. Demers P, Miller DC, Mitchell RS, et al. Stent-graft repair of penetrating atherosclerotic ulcers in the descending thoracic aortamid-term results. Ann Thorac Surg 2004;77:81-86.[Abstract/Free Full Text]
  10. Tse LW, MacKenzie KS, Montreuil B, Obrand DI, Steinmetz OK. The proximal landing zone in endovascular repair of the thoracic aorta Ann Vasc Surg 2004;18:178-185.[Medline]
  11. Cambria RP, Brewster DC, Lauterbach SR, et al. Evolving experience with thoracic aortic stent graft repair J Vasc Surg 2002;35:1129-1136.[Medline]
  12. Thompson CS, Gaxotte VD, Rodriguez-Lopez JA, et al. Endoluminal stent grafting of the thoracic aortainitial experience with the Gore Excluder. J Vasc Surg 2002;35:1163-1170.[Medline]
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