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The Stent Is Not to Blame: Lessons Learned With a Simplified US Version of the Frozen Elephant Trunk
The Stent Is Not to Blame: Lessons Learned With a Simplified US Version of the Frozen Elephant Trunk Ourania Preventza, MD, Joseph S. Coselli, MD, Jessica Mayor, MD, Katherine Simpson, MS, Julius Carillo, MD, Matt D. Price, MS, Lorraine D. Cornwell, MD, Shuab Omer, MD, Kim I. de la Cruz, MD, Faisal G. Bakaeen, MD, and Arin Jobe, MPH Division of Cardiothoracic Surgery, Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Department of Cardiovascular Surgery, Texas Heart Institute, and Division of Cardiothoracic Surgery, Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas; and Department of Thoracic and Cardiovascular Surgery, Cleveland Clinic, Cleveland, Ohio
Background. We analyzed trends, assessed outcomes and lessons learned, and investigated whether using a simplified US version of the frozen elephant trunk (FET) technique to treat complex arch pathology poses additional risk. Methods. From 2010 to 2015, we performed 129 consecutive ET procedures (traditional ET [t-ET], n [ 92 [71.3%]; FET, n [ 37 [28.7%]) for chronic dissecting (n [ 62 [48.1%]) and atherosclerotic aneurysms (n [ 67 [51.9%]). A stepwise logistic regression model using preoperative and intraoperative variables was created to analyze the outcomes. Results. Thirty-day mortality was 12.4% (t-ET, n [ 9 [9.8%]; FET, n [ 7 [18.9%]; p [ 0.24). The rate of persistent (at the time of discharge) stroke was 5.4% (t-ET, n [ 5 [5.4%]; FET, n [ 2 [5.4%]; p [1.00). The rate of persistent spinal cord deficit was 3.9% (t-ET, n [ 3
[3.3%]; FET, n [ 2 [5.4%]; p [ 0.62). In the multivariable analyses, the addition of FET was not an independent predictor of mortality, permanent stroke, or spinal cord deficit. Conclusions. With the advent of endovascular technology, there is a clinical shift toward increased use of FET to eliminate or facilitate the second surgical stage in treating patients with extensive aortic pathology. The addition of FET to the surgical armamentarium does not seem to pose additional risk (although larger studies are needed), but judicious use is advised nonetheless. A single-piece endoprosthesis for FET instead of a customized one should be considered.
E
recent experience and outcomes with both traditional ET (t-ET) and a simplified FET procedure that does not involve using a hybrid graft.
lephant trunk (ET) procedures are used to treat complex arch, descending thoracic aortic, and thoracoabdominal aortic pathology. The frozen elephant trunk (FET) technique is gaining wider acceptance, usually for patients whose descending thoracic or thoracoabdominal aorta is amenable to endovascular treatment. Currently, single-piece hybrid grafts designed for this purpose are being used in Europe and Asia [1–4]. Various techniques and modifications of the FET have been used [5–11]. Hemiarch with antegrade stent delivery [12, 13] does not involve implanting the head vessels and should be not confused with FET. Hybrid stent grafts for treating complex aortic pathology have not yet been granted US Food and Drug Administration approval. We report our
Accepted for publication March 27, 2017. Presented at the Sixty-third Annual Meeting of the Southern Thoracic Surgical Association, Naples, FL, Nov 9–12, 2016. Address correspondence to Dr Preventza, BCM 390, One Baylor Plaza, Houston, TX 77030; email: [email protected].
Ó 2017 by The Society of Thoracic Surgeons Published by Elsevier Inc.
(Ann Thorac Surg 2017;-:-–-) Ó 2017 by The Society of Thoracic Surgeons
Patients and Methods Over a recent period (2010 to 2015), 129 consecutive patients (Table 1) underwent proximal aortic repair by either t-ET (n ¼ 92) or the simplified FET procedure (n ¼ 37). Institutional Review Board approval for the study and waiver of consent were obtained by Baylor College of Medicine. Data were from a prospectively maintained aortic surgery database. The treated aortic pathology was atherosclerotic aneurysm (n ¼ 67) or chronic dissecting aneurysm (n ¼ 62). Outcome Dr Preventza discloses a financial relationship with Medtronic, W. L. Gore & Associates, Cook, and Gore; Dr Coselli with Medtronic, Gore, Cook, Vascutek Terumo, Bolton Medical, Glaxo Smith Kline, Edwards Lifesciences, and Vascutek Terumo.
0003-4975/$36.00 http://dx.doi.org/10.1016/j.athoracsur.2017.03.072
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Table 1. Preoperative Characteristics and Demographics Characteristics
Both Cohorts (n ¼ 129)
Age, years Male Hypertension Redo sternotomy Atherosclerotic aneurysm Chronic dissecting aneurysm Smoking Preoperative cardiac diseasea Prior COPD, restrictive CHF, NYHA III, IV Renal diseaseb History of stroke/TIA Diabetes mellitus Prior proximal aortic surgery Prior proximal aortic dissection Prior CABG surgery Prior thoracoabdominal surgery
65.0 89 111 70 67 62 62 48 46 42 23 19 10 68 61 8 2
(55–71) (69.0) (86.1) (54.3) (51.9) (48.1) (48.1) (37.2) (35.7) (32.6) (17.8) (14.7) (7.8) (52.7) (47.3) (6.2) (1.6)
t-ET (n ¼ 92) 64.0 68 78 55 38 54 40 33 29 26 14 18 5 53 53 7 0
(53.5–69.5) (73.9) (84.8) (59.8) (41.3) (58.7) (43.5) (35.9) (31.5) (28.3) (15.2) (19.6) (5.4) (57.6) (57.6) (7.6) (0.0)
FET (n ¼ 37) 68.0 21 33 15 29 8 22 15 17 16 9 1 5 15 8 1 2
(64–73) (56.8) (89.2) (40.5) (78.4) (21.6) (59.5) (40.5) (46.0) (43.2) (24.3) (2.7) (13.5) (40.5) (21.6) (2.7) (5.4)
p Value 0.029 0.057 0.51 0.047 0.0001 0.0001 0.10 0.62 0.12 0.10 0.22 0.015 0.15 0.079 0.0002 0.44 0.081
a
Preoperative cardiac disease was defined as preoperative myocardial infarction, coronary artery bypass graft surgery (CABG), percutaneous transluminal b coronary angioplasty, coronary artery disease, or pacemaker placement. Serum creatinine level 1.5 mg/dL or greater, history of hemodialysis, or history of renal insufficiency. Values are median (interquartile range) or n (%). CHF ¼ congestive heart failure; COPD ¼ chronic obstructive pulmonary disease; Association; t-ET ¼ traditional elephant trunk; TIA ¼ transient ischemic attack.
definitions were as follows: composite adverse outcome was defined as operative mortality, persistent neurologic event, or hemodialysis on hospital discharge. Operative times were described as follows: the circulatory arrest time was the total time of circulatory arrest with and without antegrade cerebral perfusion. The pure circulatory arrest time was the circulatory arrest time without antegrade cerebral perfusion. The cardiopulmonary bypass (CPB) time was the period of CPB, not including the antegrade cerebral perfusion or circulatory arrest time. The myocardial ischemia time was from the initiation of circulatory arrest or crossclamp placement until clamp removal. We have used this simplified FET technique in patients who were candidates for endovascular repair of aneurysm of the descending thoracic aorta (DTA)—initially sparely, and then more steadily as we became more familiar with the technique. The technique was used mainly as a stage I ET whenever a second stage was planned for thoracic endovascular aortic repair of the DTA aneurysm, and as a single-stage procedure to treat the total arch and the DTA. Because there is evidence for remodeling of the true lumen of the DTA after endovascular repair for chronic type III aortic dissection [14], we used FET for chronic dissecting arch aneurysm in cases in which we considered the dissecting aneurysm in the DTA to be amenable to endovascular treatment. We have not used yet this technique for acute type I aortic dissection, as it is our usual preference in these cases to perform aggressive hemiarch replacement and antegrade stent
FET ¼ frozen elephant trunk;
NYHA ¼ New York Heart
delivery [13], and not total arch repair as we perform in FET procedures.
Operative Technique For both t-ET and FET, we used the skirted ET Gelweave graft with the side arm (Vascutek Ltd, Ann Arbor, MI). We have previously described our technique of total arch replacement [15]. During circulatory arrest, the target nasopharyngeal temperature is 21 to 25 C. The head vessels are anastomosed with the island technique or a Y, double-Y (trifurcated), or single graft (Vascutek). In both the t-ET and FET procedures, the ET is approximately 8 to 10 cm and the skirt of the Dacron Gelweave graft is trimmed (Fig 1).
Fig 1. The skirt of the Dacron elephant trunk is trimmed.
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During the FET procedure, before the distal anastomosis, a soft glide wire is exchanged for a stiff Amplatz wire over a catheter (Fig 2). Over the stiff wire, the endograft is advanced under direct vision inside the ET [7]. The end of the stent graft is better visualized when we use the island technique (Fig 3A) to attach the head vessels than if we use the Y or double-Y graft (Fig 3B). When the end of the endograft is distal to the distal aortic anastomosis, the endograft is deployed (Fig 4). The main purpose of the endograft during the FET procedure is to keep the Dacron graft open and to facilitate the second stage of the procedure. At this stage, the endograft does not treat the entire DTA, and the length of the stent graft does not need to be more than 15 cm. Very early in our experience, we used longer stents with the intent to treat the entire aortic pathology (ascending aorta, arch, and DTA) in one stage, but we avoid using this technique because of concerns about spinal cord injury. The size of the stent graft that is used to construct the FET is selected according to the diameter of the distal DTA (with regard to what we think we will need to use in the second-stage completion ET) and the size of the skirted Dacron ET that we use to perform the distal anastomosis on the arch (a very large stent graft inside a small Dacron graft will not perform well). Although we have used various endografts (mainly, Gore-TAG [W. L. Gore & Associates, Flagstaff, AZ], n ¼ 34; Medtronic Valiant [Medtronic, Santa Rosa, CA], n ¼ 2; and Cook endograft [Cook Group, Bloomington, IN], n ¼ 1), we now prefer to use the comformable (CTAG) Gore endograft as FET inside the ET, for several reasons: the graft is delivered antegrade under direct vision, we can clearly see the end of the endograft inside the ET to place it accurately, no hybrid room or contrast is required, and using a sheath is not mandatory. After the endograft is delivered, we complete the distal aortic anastomosis and the anastomosis of the head vessels as a Y, double-Y, or island patch. Intraoperative data are provided in Table 2.
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Fig 3. The endograft is advanced under direct vision inside the elephant trunk for the construction of the aortic arch in (A) the island configuration or (B) the Y or double-Y graft configuration.
Differences in the distribution of preoperative, operative, and postoperative characteristics in the FET group versus t-ET group were tested with c2 analysis, or Fisher’s exact
test when necessary, for the categoric variables. The nonparametric Wilcoxon two-sample test was used for the continuous variables. Multivariable logistic regression models with stepwise variable selection were run to determine which preoperative and operative variables predicted adverse outcomes. Multicollinearity was checked with regression analysis. Statistical analyses
Fig 2. A soft glide wire is exchanged for a stiff Amplatz wire over a catheter.
Fig 4. The endograft is visualized at the level of the distal aortic anastomosis.
Statistical Analysis
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Table 2. Intraoperative Details Intraoperative Details
Both Cohorts (n ¼ 129)
Urgency Elective Emergent/urgent Concomitant procedures Aortic root replacement AV replacement/repair CABG Intraoperative PRBC Antegrade cerebral perfusion Head vessel configuration Y or double-Y graft Island Combination Operative times, minutes Cardiopulmonary bypass Myocardial ischemia Circulatory arrest Antegrade cerebral perfusion
t-ET (n ¼ 92)
FET (n ¼ 37)
p Value 1.00
113 (87.6) 16 (12.4)
80 (87.0) 12 (13.0)
33 (89.2) 4 (10.8)
20 8 13 105 129
16 2 9 73 92
4 6 4 32 37
(15.5) (6.2) (10.1) (81.4) (100)
71 (55.0) 44 (34.1) 14 (10.9) 140 99 63 63
(95.5–183) (78–135) (56–82) (56–82)
(17.4) (2.2) (9.8) (79.4) (100)
50 (54.4) 33 (35.9) 9 (9.8) 142 99 63 63
(95–185) (78–133) (55.5–82) (56–81.5)
(10.8) (16.2) (10.8) (86.5) (100)
21 (56.8) 11 (29.7) 5 (13.5) 138 104 64 64
(96–175) (79–146) (56–87) (56–87)
0.35 0.007 1.00 0.35 1.00 0.80 0.51 0.54 0.71 0.66 0.37 0.47
Values are n (%) or median (interquartile range). AV ¼ aortic valve; CABG ¼ coronary artery bypass graft surgery; traditional elephant trunk.
were performed with SAS version 9.1 (SAS Institute, Cary, NC). A p value less than 0.05 was considered significant.
Results Mortality and Composite Adverse Outcome Operative mortality was 15.5% (Table 3). Of the 20 patients who died, 12 (13.0%) underwent t- ET; among them, 7 underwent complicated redo procedures after prior proximal aortic surgery, 3 died of multiorgan failure (MOF), 1 died of stroke, and 1 underwent completion stage II ET during the same hospital stay to treat symptomatic extent II thoracoabdominal aortic aneurysm, and fatal MOF developed after the second procedure. Eight patients (21.6%) died after an FET procedure: 1 of stroke, 3 of MOF, and 2 of heart failure and inability to wean from extracorporeal membrane oxygenation. One patient had hemodynamic instability and cardiac arrest on postoperative day 12; he underwent cardiopulmonary resuscitation but died. Another patient had toxic megacolon during recovery and died of sepsis. No deaths were related to kinking or pseudocoarctation of the traditional ET graft or of the FET stent graft. Results of multivariable analysis for operative mortality and composite adverse outcome appear in Table 4.
Neurologic Events Ten patients (7.8%) had a persistent (5.4%) or transient stroke (2.3%), and 6 (4.6%) had persistent (3.9%) or transient (0.8%) paralysis or paraparesis. Three patients had both persistent spinal cord ischemia and stroke. The rate
FET ¼ frozen elephant trunk;
PRBC ¼ packed red blood cells;
t-ET ¼
of persistent stroke was 5.4% (n ¼ 7; t-ET, n ¼ 5 [5.4%]; FET, n ¼ 2 [5.4%]; p ¼ 1.00), and the rate of persistent spinal cord deficit was 3.9% (n ¼ 5; t-ET, n ¼ 3 [3.3%]; FET, n ¼ 2 [5.4%]; p ¼ 0.62). Two of the FET patients had persistent spinal cord deficit; in 1 patient, the procedure was intended to treat “mega aorta,” and the entire DTA was covered to a few centimeters above the celiac axis. This patient had MOF in addition to the spinal cord deficit, and the family withdrew support. The other patient had ischemic stroke and delayed persistent paraparesis, and the family withdrew support. Three patients had persistent spinal cord ischemia after t-ET, and 1 had transient spinal cord ischemia; this patient underwent stage II ET completion for symptomatic extent II thoracoabdominal aortic aneurysm during the same hospital stay and transient paraparesis developed postoperatively. Among the 5 patients who underwent t-ET and had persistent stroke, 3 partially recovered before discharge, 1 did not recover, and 1 died. Both FET patients who had ischemic strokes died. Because of the small number of events, multivariable analysis was performed for all neurologic events, both transient and permanent (n ¼ 13, 10.1%; Table 4).
Comment Extensive, two-stage aortic replacement by the ET procedure was first described in 1983 by Borst and colleagues [16], who used the procedure to facilitate the replacement of the descending and thoracoabdominal aorta. The ET procedure has greatly facilitated the second stage, but the cumulative risk incurred by performing two major operations [17–21] has inspired efforts to simplify or further
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Table 3. Short-Term Complications Both Cohorts (n ¼ 129)
Complication a
Composite adverse outcome Operative mortality 30-day mortality Ventilator support >48 hours All renal dysfunctionb Hemodialysis at discharge Total neurologic eventsc Total persistent neurologic events Persistent stroke Persistent spinal cord ischemia Tracheostomy Reoperation for bleeding Other postoperative complications Atrial fibrillation Pacemaker placement Deep venous thrombosis Myocardial infarction Hospital length of stay, days ICU length of stay, days
t-ET (n ¼ 92)
FET (n ¼ 37)
p Value
26 20 16 51 38 2 13c 10 7 5 23 11
(20.2) (15.5) (12.4) (39.5) (29.5) (1.6) (10.1) (7.8) (5.4) (3.9) (17.8) (8.5)
16 12 9 32 24 0 8 7 5 3 17 11
(17.4) (13.0) (9.8) (34.8) (26.1) (0.0) (8.7) (7.6) (5.4) (3.3) (18.5) (12.0)
10 8 7 19 14 2 5 3 2 2 6 0
(27.0) (21.6) (18.9) (51.4) (37.8) (5.4) (13.5) (8.1) (5.4) (5.4) (16.2) (0.0)
0.22 0.22 0.24 0.082 0.19 0.081 0.52 1.00 1.00 0.62 0.76 0.033
14 4 10 6 14.0 5
(10.9) (3.1) (7.8) (4.7) (9–27) (3–19)
9 2 7 4 13.5 5
(9.8) (2.2) (7.6) (4.4) (9–29) (3–19)
5 2 3 2 14 5.5
(13.5) (5.4) (8.1) (5.4) (10–25) (3–17)
0.54 0.32 1.00 1.00 0.82 0.72
a b Composite adverse outcome was defined as operative mortality, persistent neurologic event, or persistent hemodialysis at discharge. Postoperative c Three patients had both spinal cord ischemia and stroke. renal dysfunction with or without temporary or permanent hemodialysis.
Values are n (%) or median (interquartile range). FET ¼ frozen elephant trunk;
ICU ¼ intensive care unit;
t-ET ¼ traditional elephant trunk.
facilitate the second stage or to complete the entire repair in one stage [22]. Placing an endovascular prosthesis in the DTA was proposed by Kato and associates [23] and popularized by others [1–4, 11, 24, 25]. In the United
Table 4. Multivariable Regression Analysis for Entire Group Outcome Variable
p Value
OR
(95% CL)
0.038 0.0081
2.71 5.54
(1.06–6.95) (1.56–19.69)
0.034 0.011
3.03 1.01
(1.09–8.40) (1.00–1.01)
0.042 0.041
7.52 1.02
(1.07–52.76) (1.00–1.04)
0.015
6.33
(1.43–28.06)
0.024
1.03
(1.00–1.05)
a
Composite adverse outcome COPD Concomitant CABG Operative mortalityb COPD CPB time, per minute Total neurologic eventsc Emergent surgery Circulatory arrest time, per minute Total permanent neurologic eventsd Preoperative neurologic deficit Circulatory arrest time, per minute
a b Hosmer-Lemeshow p ¼ 0.87, c-index ¼ 0.68. Hosmer-Lemeshow c Hosmer-Lemeshow p ¼ 0.83, c-index ¼ p ¼ 0.50, c-index ¼ 0.74. d Hosmer-Lemeshow p ¼ 0.27, c-index ¼ 0.76. 0.67.
CABG ¼ coronary artery bypass graft; CL ¼ confidence limits; COPD ¼ chronic obstructive pulmonary disease; CPB ¼ cardiopulmonary bypass; OR ¼ odds ratio.
States, there is no approved single-piece device for the FET procedure, so we developed a simplified approach that involves placing a stent-graft inside the Dacron ET graft in the DTA. Among our patients, mortality was (nonsignificantly) higher with FET than with t-ET. In contrast, Leontyev and colleagues [26] reported slightly more overall mortality than we (18.1% versus 15.5%), possibly because their series included patients with acute type I aortic dissection [26]—the only predictor of mortality in that study. A study of data from the International E-Vita Open Registry (E-Vita Open and E-Vita Open Plus; JOTEC GmbH, Hechingen, Germany) showed 14% inhospital mortality among 57 patients who underwent FET for complex type B aortic dissection [27]. In a recent position paper by the Vascular Domain of the European Association of Cardiothoracic Surgery, inhospital mortality was reported as 1.8% to 17.2% [28]. The wide range of results can be explained by the heterogeneity of patients and the small size of individual series. In our multivariable analysis, preoperative pulmonary disease predicted mortality and composite adverse outcome, longer CPB time predicted mortality, and concomitant coronary artery bypass graft surgery predicted composite adverse outcome. Similar results have been shown in other series [29]. In addition, recognizing that longer CPB time is associated with mortality, we now are cooling patients to approximately 24 C, trying to avoid prolonged cooling, which increases CPB time. Spinal cord deficit has been described as the Achilles heel of the FET technique compared with t-ET. Very low
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frequencies similar to ours have been reported for the traditional ET procedure [18]. Even though no major differences were seen between our t-ET and FET patients with regard to spinal cord injury, one permanent injury occurred in a patient whom we treated for mega aorta in one stage. Using a distal landing zone beyond T7 to T9 for FET [30, 31] has been implicated in postoperative paraplegia or paraparesis by some investigators, but not by others [26]. With our FET method, we use endografts 10 to 15 cm in length. The main purpose of the endograft is to keep the Dacron graft open and to facilitate the second stage of the ET repair, not to treat the entire DTA pathology. In addition, when we perform standard thoracic endovascular aortic repair to treat the entire DTA, postoperatively our goal is to maintain the mean blood pressure at 90 mm Hg or more (usually 90 to 110 mm Hg). When we perform a total arch and ET procedure through median sternotomy, we prefer to keep the mean arterial pressure around 70 mm Hg because of the multiple anastomoses and the potential for bleeding, and we do not use cerebrospinal fluid drainage. In the literature, the spinal cord deficit rate is reported as 0% to 24% [28, 30–32]; again, this wide range is due to the small size of the individual series. Nonetheless, the one common theme among all series is the fear of spinal cord deficit. In our practice, we currently avoid treating the entire arch and DTA in one stage unless a second procedure would pose substantial risk. The stroke rate reported in the literature for the FET procedures varies between 2.5% and 20% [28]; the higher rates come from series involving acute type I aortic dissection [26]. Our stroke rates, although higher among the FET patients (perhaps because there were more atherosclerotic aneurysms in this cohort), did not differ significantly between the t-ET and the FET patients. Increasingly, we have been cooling patients to 24 C, and we avoid using single-stage repair to treat the entire aorta, because of concerns about spinal cord deficit. The procedure is performed in the regular and not the hybrid operating room, and there is no need for fluoroscopy or dye. We have not yet used this technique for acute type I aortic dissection, but we have used it for chronic type I aortic dissection. Regarding the dissection flap in t-ET procedures, the ET is usually placed inside a common aortic lumen. In the FET procedures, we have done it both ways, placing the FET inside a common aortic lumen and inside the true lumen. If the true lumen is too narrow and the dissection flap is too thick, that could potentially cause the stent graft to collapse or to narrow and obstruct the blood flow. Our study’s limitations are its retrospective design and the inherent biases thereof. Our purpose was to evaluate our most recent experience because surgical technique and methods are changing over time and can influence patients’ outcomes. The total neurologic event and spinal cord deficit rates, which would be of interest to readers, were based on small numbers, which make it difficult to make robust statements. The overall cohort, although large for a series of ET procedures in a short study period,
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is still too small; the study is not adequately powered to determine whether FET is associated with higher rates of death or other complications. Nevertheless, contemporary series that include both techniques are not often reported and are extremely important. The simplified US approach to FET had acceptable short-term results. Continuous refining of the operating technique is important, as is expanding the indications for use. Also, a single-piece endoprosthesis already in use outside the United States is currently in clinical trials in North America (https://clinicaltrials.gov/ct2/show/ NCT02724072). Judicious use of the FET technique is imperative, whether it involves a single-piece hybrid stent device or a custom-made device like the one described here. Larger studies will be needed to determine whether FET carries a higher risk for adverse outcomes than t-ET. Stephen N. Palmer, PhD, ELS, contributed to the editing of the manuscript.
References 1. Di Bartolomeo R, Di Marco L, Armaro A, et al. Treatment of complex disease of the thoracic aorta: the frozen elephant trunk technique with the E-Vita open prosthesis. Eur J Cardiothorac Surg 2009;35:671–6. 2. Kato M, Kuratani T, Kaneko M, Kyo S, Ohnishi K. The results of total arch graft implantation with open stent-graft placement for type A aortic dissection. J Thorac Cardiovasc Surg 2002;124:531–40. 3. Ma WG, Zhu JM, Zheng J, et al. Sun’s procedure for complex aortic arch repair: total arch replacement using a tetrafurcate graft with stented elephant trunk implantation. Ann Cardiothorac Surg 2013;2:642–8. 4. Shrestha M, Kaufeld T, Beckmann E, et al. Total aortic arch replacement with a novel 4-branched frozen elephant trunk prosthesis: single-center results of the first 100 patients. J Thorac Cardiovasc Surg 2016;152:148–59.e1. 5. Chen LW, Lu L, Dai XF, et al. Total arch repair with open triple-branched stent graft placement for acute type A aortic dissection: experience with 122 patients. J Thorac Cardiovasc Surg 2014;148:521–8. 6. Kawaharada N, Kurimoto Y, Ito T, et al. Hybrid treatment for aortic arch and proximal descending thoracic aneurysm: experience with stent grafting for second-stage elephant trunk repair. Eur J Cardiothorac Surg 2009;36: 956–61. 7. Preventza O, Al-Najjar R, LeMaire SA, Weldon S, Coselli JS. Total arch replacement with frozen elephant trunk technique. Ann Cardiothorac Surg 2013;2:649–52. 8. Reoma JL, Martin TD, Hess PJ, Beck AW. A novel technique for hybrid aortic arch reconstruction: the deployment cuff technique. Ann Thorac Surg 2014;97:1464–6. 9. Roselli EE, Rafael A, Soltesz EG, Canale L, Lytle BW. Simplified frozen elephant trunk repair for acute DeBakey type I dissection. J Thorac Cardiovasc Surg 2013;145(Suppl): 197–201. 10. Shimamura K, Kuratani T, Matsumiya G, et al. Hybrid endovascular aortic arch repair using branched endoprosthesis: the second-generation “branched” open stentgrafting technique. J Thorac Cardiovasc Surg 2009;138: 46–53. 11. Uchida N, Katayama A, Higashiue S, et al. A new device as an open stent graft for extended aortic repair: a multicentre early experience in Japan. Eur J Cardiothorac Surg 2016;49: 1270–8.
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12. Pochettino A, Brinkman WT, Moeller P, et al. Antegrade thoracic stent grafting during repair of acute DeBakey I dissection prevents development of thoracoabdominal aortic aneurysms. Ann Thorac Surg 2009;88:482–90. 13. Preventza O, Cervera R, Cooley DA, et al. Acute type I aortic dissection: traditional versus hybrid repair with antegrade stent delivery to the descending thoracic aorta. J Thorac Cardiovasc Surg 2014;148:119–25. 14. Nienaber CA, Kische S, Rousseau H, et al. Endovascular repair of type B aortic dissection: long-term results of the randomized investigation of stent grafts in aortic dissection trial. Circ Cardiovasc Interv 2013;6:407–16. 15. Preventza O, Garcia A, Cooley DA, et al. Total aortic arch replacement: a comparative study of zone 0 hybrid arch exclusion versus traditional open repair. J Thorac Cardiovasc Surg 2015;150:1591–600. 16. Borst HG, Walterbusch G, Schaps D. Extensive aortic replacement using “elephant trunk” prosthesis. Thorac Cardiovasc Surg 1983;31:37–40. 17. Estrera AL, Miller CC, Porat EE, Huynh TTT, Winnerkvist A, Safi HJ. Staged repair of extensive aortic aneurysms. Ann Thorac Surg 2002;74(Suppl):1803–5. 18. Etz CD, Plestis KA, Kari FA, et al. Staged repair of thoracic and thoracoabdominal aortic aneurysms using the elephant trunk technique: a consecutive series of 215 first stage and 120 complete repairs. Eur J Cardiothorac Surg 2008;34: 605–15. 19. LeMaire SA, Carter SA, Coselli JS. The elephant trunk technique for staged repair of complex aneurysms of the entire thoracic aorta. Ann Thorac Surg 2006;81:1561–9. 20. Safi HJ, Miller CC, Estrera AL, et al. Optimization of aortic arch replacement: two-stage approach. Ann Thorac Surg 2007;83(Suppl):815–8. 21. Svensson LG, Kim KH, Blackstone EH, et al. Elephant trunk procedure: newer indications and uses. Ann Thorac Surg 2004;78:109–16. 22. Rokkas CK, Kouchoukos NT. Single-stage extensive replacement of the thoracic aorta: the arch-first technique. J Thorac Cardiovasc Surg 1999;117:99–105.
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23. Kato M, Ohnishi K, Kaneko M, et al. New graft-implanting method for thoracic aortic aneurysm or dissection with a stented graft. Circulation 1996;94:II188–93. 24. Karck M, Chavan A, Hagl C, Friedrich H, Galanski M, Haverich A. The frozen elephant trunk technique: a new treatment for thoracic aortic aneurysms. J Thorac Cardiovasc Surg 2003;125:1550–3. 25. Palma JH, Almeida DR, Carvalho AC, Andrade JC, Buffolo E. Surgical treatment of acute type B aortic dissection using an endoprosthesis (elephant trunk). Ann Thorac Surg 1997;63: 1081–4. 26. Leontyev S, Borger MA, Etz CD, et al. Experience with the conventional and frozen elephant trunk techniques: a singlecentre study. Eur J Cardiothorac Surg 2013;44:1076–83. 27. Weiss G, Tsagakis K, Jakob H, et al. The frozen elephant trunk technique for the treatment of complicated type B aortic dissection with involvement of the aortic arch: multicentre early experience. Eur J Cardiothorac Surg 2015;47: 106–14. 28. Shrestha M, Bachet J, Bavaria J, et al. Current status and recommendations for use of the frozen elephant trunk technique: a position paper by the Vascular Domain of EACTS. Eur J Cardiothorac Surg 2015;47:759–69. 29. Iba Y, Minatoya K, Matsuda H, et al. Contemporary open aortic arch repair with selective cerebral perfusion in the era of endovascular aortic repair. J Thorac Cardiovasc Surg 2013;145(Suppl):72–7. 30. Flores J, Kunihara T, Shiiya N, Yoshimoto K, Matsuzaki K, Yasuda K. Extensive deployment of the stented elephant trunk is associated with an increased risk of spinal cord injury. J Thorac Cardiovasc Surg 2006;131:336–42. 31. Katayama K, Uchida N, Katayama A, et al. Multiple factors predict the risk of spinal cord injury after the frozen elephant trunk technique for extended thoracic aortic disease. Eur J Cardiothorac Surg 2015;47:616–20. 32. Pacini D, Tsagakis K, Jakob H, et al. The frozen elephant trunk for the treatment of chronic dissection of the thoracic aorta: a multicenter experience. Ann Thorac Surg 2011;92: 1663–70.
DISCUSSION DR TOMAS D. MARTIN (Orlando, FL): I would like to thank Dr Mayor and Dr Preventza and Dr Coselli for, number one, giving me the opportunity to discuss this paper and also for supplying me with the manuscript beforehand. I would then also like to compliment them and their group, as always, for another excellent paper and advancement toward what is a very complex problem. At least one comment. As most of you may see, the mortality rate in this type of an operation still is very high when we look at all of our aortic procedures we do. We looked at our results, which will be presented tomorrow, from the University of Florida, and indeed the mortality rate in these operations range anywhere from—and Dr Coselli could talk about this—some people report as low as like a 2% to 3% mortality rate on these operations, which I am not sure I believe, but probably from the major centers the mortality rate is going to run anywhere from 15% to 20%. It is still a very complex problem. So a couple of questions. Number one, maybe it is just my ignorance, but I am a little confused on some of the technical aspects, and the definition maybe of your circulatory arrest time—if you can tell me your circulatory arrest time, and cerebral ischemia time—and using your technique, was there a cerebral ischemia time? DR MAYOR: Not really. Our antegrade cerebral perfusion time and total circulatory arrest time, which included pure circulatory
arrest, were very similar. There was a difference of about a minute. DR MARTIN: Next. Your statistics relate that preoperative pulmonary disease is a predictor for mortality and you had a 40% incidence of respiratory failure in this series. We saw it actually in the last paper where they had a 48% incidence of prolonged ventilation. Yet what you used as your composite adverse outcomes rate only included dialysis, mortality, and neurologic events. Could you comment on maybe should we be including respiratory failure as one of these, because it is in a lot of series a predictor toward mortality. DR MAYOR: One thing is that distinguish these two entities. Our composite adverse outcomes being operative mortality, like you said, hemodialysis at discharge, permanent neurologic events, we consider these to be life altering, whereas in respiratory failure, you might have a prolonged hospital stay but usually it is not a permanent life-altering event. However, it would be something that we should probably consider in the future. DR MARTIN: I would just have to interject there that one of the biggest problems we all face are respiratory and many of those patients get tracheostomies and end up in long-term rehabilitation. So it is in some ways a life-altering problem.
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Next question. You did not use spinal drains. We have used spinal drains on all of our patients doing this, and I wonder if you had any comments on why you may or may not include that. DR MAYOR: That is an excellent question. It is well known that your group and other groups routinely use cerebrospinal fluid drains in these procedures. In our group, after discussion with our anesthesia colleagues, we fear complications with the combination of full heparinization and placement of cerebrospinal fluid drains, but perhaps it is something we should consider in the future. DR MARTIN: And last question or comment, maybe you or Dr Preventza or Dr Coselli could comment, in looking at your data, 50% of your patients had prior ascending aortic operations or aortic dissections; at least 50% had redo operations. Should we be considering as a group, not you at Baylor but we as a group, more extensive operations like was proposed in the last paper with maybe a debranching in some of these patients or a large percentage of these patients, which then would not necessitate coming back through the front to do this complex operation and most of the other operations might be addressed by endo procedures? DR MAYOR: So I have to answer that with both yes and no. We consider aggressive aortic procedures, including total arch procedures, usually in younger patients or patients with connective tissue disorders. In patients with acute type A dissections, our principal is to obtain survival, however that may be, and our approach is a hemiarch or a total arch if that is necessary. DR MARTIN: Great. Thank you, and I appreciate the privilege, and Dr Mayor is a second-year general surgery resident. You have done an excellent job. DR MAYOR: Thank you so much. DR PREVENTZA: If I may say, Jessica did an outstanding job and she is one of our second-year general surgery residents and she really wants to pursue a career in cardiothoracic surgery. So I hope that down at Baylor, Dr de la Cruz, Dr LeMaire, and Dr Coselli will be able to persuade her to pursue a career in cardiothoracic surgery, because she is really outstanding. DR MAYOR: Thank you. DR DAWN HUI (St. Louis, MO): Dr Mayor, can I ask you a couple of technical questions. It looks like you insert the CTAG graft after you have sewn in the majority of your graft. How is the visualization for determining if you have a good seal? Do you have any data on endoleaks at late follow-up?
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DR MAYOR: I will ask Dr Preventza for a little help with that one. DR PREVENTZA: The way actually that we do the frozen elephant trunk depends exactly on the time that we put the stent down into the proximal descending thoracic aorta. The video that we saw there is when the head vessels are implanted as an island. So in that particular case, we did a distal anastomosis, and then before suturing and doing the island anastomosis, we place the stent graft down into the proximal descending thoracic. The sequence of events when we place a Y graft or a doubleY graft is a little different, because then we perform the head vessel anastomosis first during the cooling, then we follow with the distal anastomosis, then we perform the antegrade stent delivery, and then we perform anastomosis of the innominate. So the sequence of events will actually change. It depends on the technique that we use. And with regard to the conformable Gore-TAG (CTAG), even though we have used different stent grafts as actually was mentioned, right now exclusively we use a CTAG for specific reasons, because we do the stent under direct vision, we do not use the hybrid operating room, and we are able actually to see the end of the stent graft when we deploy it. So it is just a matter of convenience and we think that it is easy to do. DR MARTIN: Can I make one last comment on the choice of graft. We have avoided the CTAG graft only because if you come back through a thoracotomy and have to sew to that graft at a later date, sewing to that very thin Gore-Tex, it is like a sprinkler system; it bleeds a lot. And so we have used the Dacron graft and have recently gone to the Medtronic device, because you can see through the sheath, as you put the sheath in you can see through it and you can see the back end of it. So the Medtronic, which is a Dacron device, is what we have gone to. We never use any fluro for our antegrade endograft, and we do not really need to because we are only going to put one device in. We are not worried where it really lands. You are only putting, at most, a 20cm device. So we are not trying to complete the whole thing. We agree that if you try to complete it, it is very difficult to do. So we do not do that. DR COSELLI: I was just going to say, Tom, in both those grafts you can see the portion toward the arch, and with the CTAG you are just expanding, you are not unsheathing it, so you can see it at all times. And truthfully, for the non–elephant trunk, you are sewing into the Gore material, and I agree with you, but in this circumstance, if you go back and have to suture, the graft sits almost entirely inside Dacron, so you would be suturing Gore as well as Dacron. So this is the one circumstance where that may not be the case.
Background. We analyzed trends, assessed outcomes and lessons learned, and investigated whether using a simplified US version of the frozen elephant trunk (FET) technique to treat complex arch pathology poses additional risk. Methods. From 2010 to 2015, we performed 129 consecutive ET procedures (traditional ET [t-ET], n [ 92 [71.3%]; FET, n [ 37 [28.7%]) for chronic dissecting (n [ 62 [48.1%]) and atherosclerotic aneurysms (n [ 67 [51.9%]). A stepwise logistic regression model using preoperative and intraoperative variables was created to analyze the outcomes. Results. Thirty-day mortality was 12.4% (t-ET, n [ 9 [9.8%]; FET, n [ 7 [18.9%]; p [ 0.24). The rate of persistent (at the time of discharge) stroke was 5.4% (t-ET, n [ 5 [5.4%]; FET, n [ 2 [5.4%]; p [1.00). The rate of persistent spinal cord deficit was 3.9% (t-ET, n [ 3
[3.3%]; FET, n [ 2 [5.4%]; p [ 0.62). In the multivariable analyses, the addition of FET was not an independent predictor of mortality, permanent stroke, or spinal cord deficit. Conclusions. With the advent of endovascular technology, there is a clinical shift toward increased use of FET to eliminate or facilitate the second surgical stage in treating patients with extensive aortic pathology. The addition of FET to the surgical armamentarium does not seem to pose additional risk (although larger studies are needed), but judicious use is advised nonetheless. A single-piece endoprosthesis for FET instead of a customized one should be considered.
E
recent experience and outcomes with both traditional ET (t-ET) and a simplified FET procedure that does not involve using a hybrid graft.
lephant trunk (ET) procedures are used to treat complex arch, descending thoracic aortic, and thoracoabdominal aortic pathology. The frozen elephant trunk (FET) technique is gaining wider acceptance, usually for patients whose descending thoracic or thoracoabdominal aorta is amenable to endovascular treatment. Currently, single-piece hybrid grafts designed for this purpose are being used in Europe and Asia [1–4]. Various techniques and modifications of the FET have been used [5–11]. Hemiarch with antegrade stent delivery [12, 13] does not involve implanting the head vessels and should be not confused with FET. Hybrid stent grafts for treating complex aortic pathology have not yet been granted US Food and Drug Administration approval. We report our
Accepted for publication March 27, 2017. Presented at the Sixty-third Annual Meeting of the Southern Thoracic Surgical Association, Naples, FL, Nov 9–12, 2016. Address correspondence to Dr Preventza, BCM 390, One Baylor Plaza, Houston, TX 77030; email: [email protected].
Ó 2017 by The Society of Thoracic Surgeons Published by Elsevier Inc.
(Ann Thorac Surg 2017;-:-–-) Ó 2017 by The Society of Thoracic Surgeons
Patients and Methods Over a recent period (2010 to 2015), 129 consecutive patients (Table 1) underwent proximal aortic repair by either t-ET (n ¼ 92) or the simplified FET procedure (n ¼ 37). Institutional Review Board approval for the study and waiver of consent were obtained by Baylor College of Medicine. Data were from a prospectively maintained aortic surgery database. The treated aortic pathology was atherosclerotic aneurysm (n ¼ 67) or chronic dissecting aneurysm (n ¼ 62). Outcome Dr Preventza discloses a financial relationship with Medtronic, W. L. Gore & Associates, Cook, and Gore; Dr Coselli with Medtronic, Gore, Cook, Vascutek Terumo, Bolton Medical, Glaxo Smith Kline, Edwards Lifesciences, and Vascutek Terumo.
0003-4975/$36.00 http://dx.doi.org/10.1016/j.athoracsur.2017.03.072
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Table 1. Preoperative Characteristics and Demographics Characteristics
Both Cohorts (n ¼ 129)
Age, years Male Hypertension Redo sternotomy Atherosclerotic aneurysm Chronic dissecting aneurysm Smoking Preoperative cardiac diseasea Prior COPD, restrictive CHF, NYHA III, IV Renal diseaseb History of stroke/TIA Diabetes mellitus Prior proximal aortic surgery Prior proximal aortic dissection Prior CABG surgery Prior thoracoabdominal surgery
65.0 89 111 70 67 62 62 48 46 42 23 19 10 68 61 8 2
(55–71) (69.0) (86.1) (54.3) (51.9) (48.1) (48.1) (37.2) (35.7) (32.6) (17.8) (14.7) (7.8) (52.7) (47.3) (6.2) (1.6)
t-ET (n ¼ 92) 64.0 68 78 55 38 54 40 33 29 26 14 18 5 53 53 7 0
(53.5–69.5) (73.9) (84.8) (59.8) (41.3) (58.7) (43.5) (35.9) (31.5) (28.3) (15.2) (19.6) (5.4) (57.6) (57.6) (7.6) (0.0)
FET (n ¼ 37) 68.0 21 33 15 29 8 22 15 17 16 9 1 5 15 8 1 2
(64–73) (56.8) (89.2) (40.5) (78.4) (21.6) (59.5) (40.5) (46.0) (43.2) (24.3) (2.7) (13.5) (40.5) (21.6) (2.7) (5.4)
p Value 0.029 0.057 0.51 0.047 0.0001 0.0001 0.10 0.62 0.12 0.10 0.22 0.015 0.15 0.079 0.0002 0.44 0.081
a
Preoperative cardiac disease was defined as preoperative myocardial infarction, coronary artery bypass graft surgery (CABG), percutaneous transluminal b coronary angioplasty, coronary artery disease, or pacemaker placement. Serum creatinine level 1.5 mg/dL or greater, history of hemodialysis, or history of renal insufficiency. Values are median (interquartile range) or n (%). CHF ¼ congestive heart failure; COPD ¼ chronic obstructive pulmonary disease; Association; t-ET ¼ traditional elephant trunk; TIA ¼ transient ischemic attack.
definitions were as follows: composite adverse outcome was defined as operative mortality, persistent neurologic event, or hemodialysis on hospital discharge. Operative times were described as follows: the circulatory arrest time was the total time of circulatory arrest with and without antegrade cerebral perfusion. The pure circulatory arrest time was the circulatory arrest time without antegrade cerebral perfusion. The cardiopulmonary bypass (CPB) time was the period of CPB, not including the antegrade cerebral perfusion or circulatory arrest time. The myocardial ischemia time was from the initiation of circulatory arrest or crossclamp placement until clamp removal. We have used this simplified FET technique in patients who were candidates for endovascular repair of aneurysm of the descending thoracic aorta (DTA)—initially sparely, and then more steadily as we became more familiar with the technique. The technique was used mainly as a stage I ET whenever a second stage was planned for thoracic endovascular aortic repair of the DTA aneurysm, and as a single-stage procedure to treat the total arch and the DTA. Because there is evidence for remodeling of the true lumen of the DTA after endovascular repair for chronic type III aortic dissection [14], we used FET for chronic dissecting arch aneurysm in cases in which we considered the dissecting aneurysm in the DTA to be amenable to endovascular treatment. We have not used yet this technique for acute type I aortic dissection, as it is our usual preference in these cases to perform aggressive hemiarch replacement and antegrade stent
FET ¼ frozen elephant trunk;
NYHA ¼ New York Heart
delivery [13], and not total arch repair as we perform in FET procedures.
Operative Technique For both t-ET and FET, we used the skirted ET Gelweave graft with the side arm (Vascutek Ltd, Ann Arbor, MI). We have previously described our technique of total arch replacement [15]. During circulatory arrest, the target nasopharyngeal temperature is 21 to 25 C. The head vessels are anastomosed with the island technique or a Y, double-Y (trifurcated), or single graft (Vascutek). In both the t-ET and FET procedures, the ET is approximately 8 to 10 cm and the skirt of the Dacron Gelweave graft is trimmed (Fig 1).
Fig 1. The skirt of the Dacron elephant trunk is trimmed.
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During the FET procedure, before the distal anastomosis, a soft glide wire is exchanged for a stiff Amplatz wire over a catheter (Fig 2). Over the stiff wire, the endograft is advanced under direct vision inside the ET [7]. The end of the stent graft is better visualized when we use the island technique (Fig 3A) to attach the head vessels than if we use the Y or double-Y graft (Fig 3B). When the end of the endograft is distal to the distal aortic anastomosis, the endograft is deployed (Fig 4). The main purpose of the endograft during the FET procedure is to keep the Dacron graft open and to facilitate the second stage of the procedure. At this stage, the endograft does not treat the entire DTA, and the length of the stent graft does not need to be more than 15 cm. Very early in our experience, we used longer stents with the intent to treat the entire aortic pathology (ascending aorta, arch, and DTA) in one stage, but we avoid using this technique because of concerns about spinal cord injury. The size of the stent graft that is used to construct the FET is selected according to the diameter of the distal DTA (with regard to what we think we will need to use in the second-stage completion ET) and the size of the skirted Dacron ET that we use to perform the distal anastomosis on the arch (a very large stent graft inside a small Dacron graft will not perform well). Although we have used various endografts (mainly, Gore-TAG [W. L. Gore & Associates, Flagstaff, AZ], n ¼ 34; Medtronic Valiant [Medtronic, Santa Rosa, CA], n ¼ 2; and Cook endograft [Cook Group, Bloomington, IN], n ¼ 1), we now prefer to use the comformable (CTAG) Gore endograft as FET inside the ET, for several reasons: the graft is delivered antegrade under direct vision, we can clearly see the end of the endograft inside the ET to place it accurately, no hybrid room or contrast is required, and using a sheath is not mandatory. After the endograft is delivered, we complete the distal aortic anastomosis and the anastomosis of the head vessels as a Y, double-Y, or island patch. Intraoperative data are provided in Table 2.
PREVENTZA ET AL SIMPLIFIED US VERSION OF FET TECHNIQUE
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Fig 3. The endograft is advanced under direct vision inside the elephant trunk for the construction of the aortic arch in (A) the island configuration or (B) the Y or double-Y graft configuration.
Differences in the distribution of preoperative, operative, and postoperative characteristics in the FET group versus t-ET group were tested with c2 analysis, or Fisher’s exact
test when necessary, for the categoric variables. The nonparametric Wilcoxon two-sample test was used for the continuous variables. Multivariable logistic regression models with stepwise variable selection were run to determine which preoperative and operative variables predicted adverse outcomes. Multicollinearity was checked with regression analysis. Statistical analyses
Fig 2. A soft glide wire is exchanged for a stiff Amplatz wire over a catheter.
Fig 4. The endograft is visualized at the level of the distal aortic anastomosis.
Statistical Analysis
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Table 2. Intraoperative Details Intraoperative Details
Both Cohorts (n ¼ 129)
Urgency Elective Emergent/urgent Concomitant procedures Aortic root replacement AV replacement/repair CABG Intraoperative PRBC Antegrade cerebral perfusion Head vessel configuration Y or double-Y graft Island Combination Operative times, minutes Cardiopulmonary bypass Myocardial ischemia Circulatory arrest Antegrade cerebral perfusion
t-ET (n ¼ 92)
FET (n ¼ 37)
p Value 1.00
113 (87.6) 16 (12.4)
80 (87.0) 12 (13.0)
33 (89.2) 4 (10.8)
20 8 13 105 129
16 2 9 73 92
4 6 4 32 37
(15.5) (6.2) (10.1) (81.4) (100)
71 (55.0) 44 (34.1) 14 (10.9) 140 99 63 63
(95.5–183) (78–135) (56–82) (56–82)
(17.4) (2.2) (9.8) (79.4) (100)
50 (54.4) 33 (35.9) 9 (9.8) 142 99 63 63
(95–185) (78–133) (55.5–82) (56–81.5)
(10.8) (16.2) (10.8) (86.5) (100)
21 (56.8) 11 (29.7) 5 (13.5) 138 104 64 64
(96–175) (79–146) (56–87) (56–87)
0.35 0.007 1.00 0.35 1.00 0.80 0.51 0.54 0.71 0.66 0.37 0.47
Values are n (%) or median (interquartile range). AV ¼ aortic valve; CABG ¼ coronary artery bypass graft surgery; traditional elephant trunk.
were performed with SAS version 9.1 (SAS Institute, Cary, NC). A p value less than 0.05 was considered significant.
Results Mortality and Composite Adverse Outcome Operative mortality was 15.5% (Table 3). Of the 20 patients who died, 12 (13.0%) underwent t- ET; among them, 7 underwent complicated redo procedures after prior proximal aortic surgery, 3 died of multiorgan failure (MOF), 1 died of stroke, and 1 underwent completion stage II ET during the same hospital stay to treat symptomatic extent II thoracoabdominal aortic aneurysm, and fatal MOF developed after the second procedure. Eight patients (21.6%) died after an FET procedure: 1 of stroke, 3 of MOF, and 2 of heart failure and inability to wean from extracorporeal membrane oxygenation. One patient had hemodynamic instability and cardiac arrest on postoperative day 12; he underwent cardiopulmonary resuscitation but died. Another patient had toxic megacolon during recovery and died of sepsis. No deaths were related to kinking or pseudocoarctation of the traditional ET graft or of the FET stent graft. Results of multivariable analysis for operative mortality and composite adverse outcome appear in Table 4.
Neurologic Events Ten patients (7.8%) had a persistent (5.4%) or transient stroke (2.3%), and 6 (4.6%) had persistent (3.9%) or transient (0.8%) paralysis or paraparesis. Three patients had both persistent spinal cord ischemia and stroke. The rate
FET ¼ frozen elephant trunk;
PRBC ¼ packed red blood cells;
t-ET ¼
of persistent stroke was 5.4% (n ¼ 7; t-ET, n ¼ 5 [5.4%]; FET, n ¼ 2 [5.4%]; p ¼ 1.00), and the rate of persistent spinal cord deficit was 3.9% (n ¼ 5; t-ET, n ¼ 3 [3.3%]; FET, n ¼ 2 [5.4%]; p ¼ 0.62). Two of the FET patients had persistent spinal cord deficit; in 1 patient, the procedure was intended to treat “mega aorta,” and the entire DTA was covered to a few centimeters above the celiac axis. This patient had MOF in addition to the spinal cord deficit, and the family withdrew support. The other patient had ischemic stroke and delayed persistent paraparesis, and the family withdrew support. Three patients had persistent spinal cord ischemia after t-ET, and 1 had transient spinal cord ischemia; this patient underwent stage II ET completion for symptomatic extent II thoracoabdominal aortic aneurysm during the same hospital stay and transient paraparesis developed postoperatively. Among the 5 patients who underwent t-ET and had persistent stroke, 3 partially recovered before discharge, 1 did not recover, and 1 died. Both FET patients who had ischemic strokes died. Because of the small number of events, multivariable analysis was performed for all neurologic events, both transient and permanent (n ¼ 13, 10.1%; Table 4).
Comment Extensive, two-stage aortic replacement by the ET procedure was first described in 1983 by Borst and colleagues [16], who used the procedure to facilitate the replacement of the descending and thoracoabdominal aorta. The ET procedure has greatly facilitated the second stage, but the cumulative risk incurred by performing two major operations [17–21] has inspired efforts to simplify or further
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Table 3. Short-Term Complications Both Cohorts (n ¼ 129)
Complication a
Composite adverse outcome Operative mortality 30-day mortality Ventilator support >48 hours All renal dysfunctionb Hemodialysis at discharge Total neurologic eventsc Total persistent neurologic events Persistent stroke Persistent spinal cord ischemia Tracheostomy Reoperation for bleeding Other postoperative complications Atrial fibrillation Pacemaker placement Deep venous thrombosis Myocardial infarction Hospital length of stay, days ICU length of stay, days
t-ET (n ¼ 92)
FET (n ¼ 37)
p Value
26 20 16 51 38 2 13c 10 7 5 23 11
(20.2) (15.5) (12.4) (39.5) (29.5) (1.6) (10.1) (7.8) (5.4) (3.9) (17.8) (8.5)
16 12 9 32 24 0 8 7 5 3 17 11
(17.4) (13.0) (9.8) (34.8) (26.1) (0.0) (8.7) (7.6) (5.4) (3.3) (18.5) (12.0)
10 8 7 19 14 2 5 3 2 2 6 0
(27.0) (21.6) (18.9) (51.4) (37.8) (5.4) (13.5) (8.1) (5.4) (5.4) (16.2) (0.0)
0.22 0.22 0.24 0.082 0.19 0.081 0.52 1.00 1.00 0.62 0.76 0.033
14 4 10 6 14.0 5
(10.9) (3.1) (7.8) (4.7) (9–27) (3–19)
9 2 7 4 13.5 5
(9.8) (2.2) (7.6) (4.4) (9–29) (3–19)
5 2 3 2 14 5.5
(13.5) (5.4) (8.1) (5.4) (10–25) (3–17)
0.54 0.32 1.00 1.00 0.82 0.72
a b Composite adverse outcome was defined as operative mortality, persistent neurologic event, or persistent hemodialysis at discharge. Postoperative c Three patients had both spinal cord ischemia and stroke. renal dysfunction with or without temporary or permanent hemodialysis.
Values are n (%) or median (interquartile range). FET ¼ frozen elephant trunk;
ICU ¼ intensive care unit;
t-ET ¼ traditional elephant trunk.
facilitate the second stage or to complete the entire repair in one stage [22]. Placing an endovascular prosthesis in the DTA was proposed by Kato and associates [23] and popularized by others [1–4, 11, 24, 25]. In the United
Table 4. Multivariable Regression Analysis for Entire Group Outcome Variable
p Value
OR
(95% CL)
0.038 0.0081
2.71 5.54
(1.06–6.95) (1.56–19.69)
0.034 0.011
3.03 1.01
(1.09–8.40) (1.00–1.01)
0.042 0.041
7.52 1.02
(1.07–52.76) (1.00–1.04)
0.015
6.33
(1.43–28.06)
0.024
1.03
(1.00–1.05)
a
Composite adverse outcome COPD Concomitant CABG Operative mortalityb COPD CPB time, per minute Total neurologic eventsc Emergent surgery Circulatory arrest time, per minute Total permanent neurologic eventsd Preoperative neurologic deficit Circulatory arrest time, per minute
a b Hosmer-Lemeshow p ¼ 0.87, c-index ¼ 0.68. Hosmer-Lemeshow c Hosmer-Lemeshow p ¼ 0.83, c-index ¼ p ¼ 0.50, c-index ¼ 0.74. d Hosmer-Lemeshow p ¼ 0.27, c-index ¼ 0.76. 0.67.
CABG ¼ coronary artery bypass graft; CL ¼ confidence limits; COPD ¼ chronic obstructive pulmonary disease; CPB ¼ cardiopulmonary bypass; OR ¼ odds ratio.
States, there is no approved single-piece device for the FET procedure, so we developed a simplified approach that involves placing a stent-graft inside the Dacron ET graft in the DTA. Among our patients, mortality was (nonsignificantly) higher with FET than with t-ET. In contrast, Leontyev and colleagues [26] reported slightly more overall mortality than we (18.1% versus 15.5%), possibly because their series included patients with acute type I aortic dissection [26]—the only predictor of mortality in that study. A study of data from the International E-Vita Open Registry (E-Vita Open and E-Vita Open Plus; JOTEC GmbH, Hechingen, Germany) showed 14% inhospital mortality among 57 patients who underwent FET for complex type B aortic dissection [27]. In a recent position paper by the Vascular Domain of the European Association of Cardiothoracic Surgery, inhospital mortality was reported as 1.8% to 17.2% [28]. The wide range of results can be explained by the heterogeneity of patients and the small size of individual series. In our multivariable analysis, preoperative pulmonary disease predicted mortality and composite adverse outcome, longer CPB time predicted mortality, and concomitant coronary artery bypass graft surgery predicted composite adverse outcome. Similar results have been shown in other series [29]. In addition, recognizing that longer CPB time is associated with mortality, we now are cooling patients to approximately 24 C, trying to avoid prolonged cooling, which increases CPB time. Spinal cord deficit has been described as the Achilles heel of the FET technique compared with t-ET. Very low
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frequencies similar to ours have been reported for the traditional ET procedure [18]. Even though no major differences were seen between our t-ET and FET patients with regard to spinal cord injury, one permanent injury occurred in a patient whom we treated for mega aorta in one stage. Using a distal landing zone beyond T7 to T9 for FET [30, 31] has been implicated in postoperative paraplegia or paraparesis by some investigators, but not by others [26]. With our FET method, we use endografts 10 to 15 cm in length. The main purpose of the endograft is to keep the Dacron graft open and to facilitate the second stage of the ET repair, not to treat the entire DTA pathology. In addition, when we perform standard thoracic endovascular aortic repair to treat the entire DTA, postoperatively our goal is to maintain the mean blood pressure at 90 mm Hg or more (usually 90 to 110 mm Hg). When we perform a total arch and ET procedure through median sternotomy, we prefer to keep the mean arterial pressure around 70 mm Hg because of the multiple anastomoses and the potential for bleeding, and we do not use cerebrospinal fluid drainage. In the literature, the spinal cord deficit rate is reported as 0% to 24% [28, 30–32]; again, this wide range is due to the small size of the individual series. Nonetheless, the one common theme among all series is the fear of spinal cord deficit. In our practice, we currently avoid treating the entire arch and DTA in one stage unless a second procedure would pose substantial risk. The stroke rate reported in the literature for the FET procedures varies between 2.5% and 20% [28]; the higher rates come from series involving acute type I aortic dissection [26]. Our stroke rates, although higher among the FET patients (perhaps because there were more atherosclerotic aneurysms in this cohort), did not differ significantly between the t-ET and the FET patients. Increasingly, we have been cooling patients to 24 C, and we avoid using single-stage repair to treat the entire aorta, because of concerns about spinal cord deficit. The procedure is performed in the regular and not the hybrid operating room, and there is no need for fluoroscopy or dye. We have not yet used this technique for acute type I aortic dissection, but we have used it for chronic type I aortic dissection. Regarding the dissection flap in t-ET procedures, the ET is usually placed inside a common aortic lumen. In the FET procedures, we have done it both ways, placing the FET inside a common aortic lumen and inside the true lumen. If the true lumen is too narrow and the dissection flap is too thick, that could potentially cause the stent graft to collapse or to narrow and obstruct the blood flow. Our study’s limitations are its retrospective design and the inherent biases thereof. Our purpose was to evaluate our most recent experience because surgical technique and methods are changing over time and can influence patients’ outcomes. The total neurologic event and spinal cord deficit rates, which would be of interest to readers, were based on small numbers, which make it difficult to make robust statements. The overall cohort, although large for a series of ET procedures in a short study period,
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is still too small; the study is not adequately powered to determine whether FET is associated with higher rates of death or other complications. Nevertheless, contemporary series that include both techniques are not often reported and are extremely important. The simplified US approach to FET had acceptable short-term results. Continuous refining of the operating technique is important, as is expanding the indications for use. Also, a single-piece endoprosthesis already in use outside the United States is currently in clinical trials in North America (https://clinicaltrials.gov/ct2/show/ NCT02724072). Judicious use of the FET technique is imperative, whether it involves a single-piece hybrid stent device or a custom-made device like the one described here. Larger studies will be needed to determine whether FET carries a higher risk for adverse outcomes than t-ET. Stephen N. Palmer, PhD, ELS, contributed to the editing of the manuscript.
References 1. Di Bartolomeo R, Di Marco L, Armaro A, et al. Treatment of complex disease of the thoracic aorta: the frozen elephant trunk technique with the E-Vita open prosthesis. Eur J Cardiothorac Surg 2009;35:671–6. 2. Kato M, Kuratani T, Kaneko M, Kyo S, Ohnishi K. The results of total arch graft implantation with open stent-graft placement for type A aortic dissection. J Thorac Cardiovasc Surg 2002;124:531–40. 3. Ma WG, Zhu JM, Zheng J, et al. Sun’s procedure for complex aortic arch repair: total arch replacement using a tetrafurcate graft with stented elephant trunk implantation. Ann Cardiothorac Surg 2013;2:642–8. 4. Shrestha M, Kaufeld T, Beckmann E, et al. Total aortic arch replacement with a novel 4-branched frozen elephant trunk prosthesis: single-center results of the first 100 patients. J Thorac Cardiovasc Surg 2016;152:148–59.e1. 5. Chen LW, Lu L, Dai XF, et al. Total arch repair with open triple-branched stent graft placement for acute type A aortic dissection: experience with 122 patients. J Thorac Cardiovasc Surg 2014;148:521–8. 6. Kawaharada N, Kurimoto Y, Ito T, et al. Hybrid treatment for aortic arch and proximal descending thoracic aneurysm: experience with stent grafting for second-stage elephant trunk repair. Eur J Cardiothorac Surg 2009;36: 956–61. 7. Preventza O, Al-Najjar R, LeMaire SA, Weldon S, Coselli JS. Total arch replacement with frozen elephant trunk technique. Ann Cardiothorac Surg 2013;2:649–52. 8. Reoma JL, Martin TD, Hess PJ, Beck AW. A novel technique for hybrid aortic arch reconstruction: the deployment cuff technique. Ann Thorac Surg 2014;97:1464–6. 9. Roselli EE, Rafael A, Soltesz EG, Canale L, Lytle BW. Simplified frozen elephant trunk repair for acute DeBakey type I dissection. J Thorac Cardiovasc Surg 2013;145(Suppl): 197–201. 10. Shimamura K, Kuratani T, Matsumiya G, et al. Hybrid endovascular aortic arch repair using branched endoprosthesis: the second-generation “branched” open stentgrafting technique. J Thorac Cardiovasc Surg 2009;138: 46–53. 11. Uchida N, Katayama A, Higashiue S, et al. A new device as an open stent graft for extended aortic repair: a multicentre early experience in Japan. Eur J Cardiothorac Surg 2016;49: 1270–8.
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12. Pochettino A, Brinkman WT, Moeller P, et al. Antegrade thoracic stent grafting during repair of acute DeBakey I dissection prevents development of thoracoabdominal aortic aneurysms. Ann Thorac Surg 2009;88:482–90. 13. Preventza O, Cervera R, Cooley DA, et al. Acute type I aortic dissection: traditional versus hybrid repair with antegrade stent delivery to the descending thoracic aorta. J Thorac Cardiovasc Surg 2014;148:119–25. 14. Nienaber CA, Kische S, Rousseau H, et al. Endovascular repair of type B aortic dissection: long-term results of the randomized investigation of stent grafts in aortic dissection trial. Circ Cardiovasc Interv 2013;6:407–16. 15. Preventza O, Garcia A, Cooley DA, et al. Total aortic arch replacement: a comparative study of zone 0 hybrid arch exclusion versus traditional open repair. J Thorac Cardiovasc Surg 2015;150:1591–600. 16. Borst HG, Walterbusch G, Schaps D. Extensive aortic replacement using “elephant trunk” prosthesis. Thorac Cardiovasc Surg 1983;31:37–40. 17. Estrera AL, Miller CC, Porat EE, Huynh TTT, Winnerkvist A, Safi HJ. Staged repair of extensive aortic aneurysms. Ann Thorac Surg 2002;74(Suppl):1803–5. 18. Etz CD, Plestis KA, Kari FA, et al. Staged repair of thoracic and thoracoabdominal aortic aneurysms using the elephant trunk technique: a consecutive series of 215 first stage and 120 complete repairs. Eur J Cardiothorac Surg 2008;34: 605–15. 19. LeMaire SA, Carter SA, Coselli JS. The elephant trunk technique for staged repair of complex aneurysms of the entire thoracic aorta. Ann Thorac Surg 2006;81:1561–9. 20. Safi HJ, Miller CC, Estrera AL, et al. Optimization of aortic arch replacement: two-stage approach. Ann Thorac Surg 2007;83(Suppl):815–8. 21. Svensson LG, Kim KH, Blackstone EH, et al. Elephant trunk procedure: newer indications and uses. Ann Thorac Surg 2004;78:109–16. 22. Rokkas CK, Kouchoukos NT. Single-stage extensive replacement of the thoracic aorta: the arch-first technique. J Thorac Cardiovasc Surg 1999;117:99–105.
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23. Kato M, Ohnishi K, Kaneko M, et al. New graft-implanting method for thoracic aortic aneurysm or dissection with a stented graft. Circulation 1996;94:II188–93. 24. Karck M, Chavan A, Hagl C, Friedrich H, Galanski M, Haverich A. The frozen elephant trunk technique: a new treatment for thoracic aortic aneurysms. J Thorac Cardiovasc Surg 2003;125:1550–3. 25. Palma JH, Almeida DR, Carvalho AC, Andrade JC, Buffolo E. Surgical treatment of acute type B aortic dissection using an endoprosthesis (elephant trunk). Ann Thorac Surg 1997;63: 1081–4. 26. Leontyev S, Borger MA, Etz CD, et al. Experience with the conventional and frozen elephant trunk techniques: a singlecentre study. Eur J Cardiothorac Surg 2013;44:1076–83. 27. Weiss G, Tsagakis K, Jakob H, et al. The frozen elephant trunk technique for the treatment of complicated type B aortic dissection with involvement of the aortic arch: multicentre early experience. Eur J Cardiothorac Surg 2015;47: 106–14. 28. Shrestha M, Bachet J, Bavaria J, et al. Current status and recommendations for use of the frozen elephant trunk technique: a position paper by the Vascular Domain of EACTS. Eur J Cardiothorac Surg 2015;47:759–69. 29. Iba Y, Minatoya K, Matsuda H, et al. Contemporary open aortic arch repair with selective cerebral perfusion in the era of endovascular aortic repair. J Thorac Cardiovasc Surg 2013;145(Suppl):72–7. 30. Flores J, Kunihara T, Shiiya N, Yoshimoto K, Matsuzaki K, Yasuda K. Extensive deployment of the stented elephant trunk is associated with an increased risk of spinal cord injury. J Thorac Cardiovasc Surg 2006;131:336–42. 31. Katayama K, Uchida N, Katayama A, et al. Multiple factors predict the risk of spinal cord injury after the frozen elephant trunk technique for extended thoracic aortic disease. Eur J Cardiothorac Surg 2015;47:616–20. 32. Pacini D, Tsagakis K, Jakob H, et al. The frozen elephant trunk for the treatment of chronic dissection of the thoracic aorta: a multicenter experience. Ann Thorac Surg 2011;92: 1663–70.
DISCUSSION DR TOMAS D. MARTIN (Orlando, FL): I would like to thank Dr Mayor and Dr Preventza and Dr Coselli for, number one, giving me the opportunity to discuss this paper and also for supplying me with the manuscript beforehand. I would then also like to compliment them and their group, as always, for another excellent paper and advancement toward what is a very complex problem. At least one comment. As most of you may see, the mortality rate in this type of an operation still is very high when we look at all of our aortic procedures we do. We looked at our results, which will be presented tomorrow, from the University of Florida, and indeed the mortality rate in these operations range anywhere from—and Dr Coselli could talk about this—some people report as low as like a 2% to 3% mortality rate on these operations, which I am not sure I believe, but probably from the major centers the mortality rate is going to run anywhere from 15% to 20%. It is still a very complex problem. So a couple of questions. Number one, maybe it is just my ignorance, but I am a little confused on some of the technical aspects, and the definition maybe of your circulatory arrest time—if you can tell me your circulatory arrest time, and cerebral ischemia time—and using your technique, was there a cerebral ischemia time? DR MAYOR: Not really. Our antegrade cerebral perfusion time and total circulatory arrest time, which included pure circulatory
arrest, were very similar. There was a difference of about a minute. DR MARTIN: Next. Your statistics relate that preoperative pulmonary disease is a predictor for mortality and you had a 40% incidence of respiratory failure in this series. We saw it actually in the last paper where they had a 48% incidence of prolonged ventilation. Yet what you used as your composite adverse outcomes rate only included dialysis, mortality, and neurologic events. Could you comment on maybe should we be including respiratory failure as one of these, because it is in a lot of series a predictor toward mortality. DR MAYOR: One thing is that distinguish these two entities. Our composite adverse outcomes being operative mortality, like you said, hemodialysis at discharge, permanent neurologic events, we consider these to be life altering, whereas in respiratory failure, you might have a prolonged hospital stay but usually it is not a permanent life-altering event. However, it would be something that we should probably consider in the future. DR MARTIN: I would just have to interject there that one of the biggest problems we all face are respiratory and many of those patients get tracheostomies and end up in long-term rehabilitation. So it is in some ways a life-altering problem.
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Next question. You did not use spinal drains. We have used spinal drains on all of our patients doing this, and I wonder if you had any comments on why you may or may not include that. DR MAYOR: That is an excellent question. It is well known that your group and other groups routinely use cerebrospinal fluid drains in these procedures. In our group, after discussion with our anesthesia colleagues, we fear complications with the combination of full heparinization and placement of cerebrospinal fluid drains, but perhaps it is something we should consider in the future. DR MARTIN: And last question or comment, maybe you or Dr Preventza or Dr Coselli could comment, in looking at your data, 50% of your patients had prior ascending aortic operations or aortic dissections; at least 50% had redo operations. Should we be considering as a group, not you at Baylor but we as a group, more extensive operations like was proposed in the last paper with maybe a debranching in some of these patients or a large percentage of these patients, which then would not necessitate coming back through the front to do this complex operation and most of the other operations might be addressed by endo procedures? DR MAYOR: So I have to answer that with both yes and no. We consider aggressive aortic procedures, including total arch procedures, usually in younger patients or patients with connective tissue disorders. In patients with acute type A dissections, our principal is to obtain survival, however that may be, and our approach is a hemiarch or a total arch if that is necessary. DR MARTIN: Great. Thank you, and I appreciate the privilege, and Dr Mayor is a second-year general surgery resident. You have done an excellent job. DR MAYOR: Thank you so much. DR PREVENTZA: If I may say, Jessica did an outstanding job and she is one of our second-year general surgery residents and she really wants to pursue a career in cardiothoracic surgery. So I hope that down at Baylor, Dr de la Cruz, Dr LeMaire, and Dr Coselli will be able to persuade her to pursue a career in cardiothoracic surgery, because she is really outstanding. DR MAYOR: Thank you. DR DAWN HUI (St. Louis, MO): Dr Mayor, can I ask you a couple of technical questions. It looks like you insert the CTAG graft after you have sewn in the majority of your graft. How is the visualization for determining if you have a good seal? Do you have any data on endoleaks at late follow-up?
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DR MAYOR: I will ask Dr Preventza for a little help with that one. DR PREVENTZA: The way actually that we do the frozen elephant trunk depends exactly on the time that we put the stent down into the proximal descending thoracic aorta. The video that we saw there is when the head vessels are implanted as an island. So in that particular case, we did a distal anastomosis, and then before suturing and doing the island anastomosis, we place the stent graft down into the proximal descending thoracic. The sequence of events when we place a Y graft or a doubleY graft is a little different, because then we perform the head vessel anastomosis first during the cooling, then we follow with the distal anastomosis, then we perform the antegrade stent delivery, and then we perform anastomosis of the innominate. So the sequence of events will actually change. It depends on the technique that we use. And with regard to the conformable Gore-TAG (CTAG), even though we have used different stent grafts as actually was mentioned, right now exclusively we use a CTAG for specific reasons, because we do the stent under direct vision, we do not use the hybrid operating room, and we are able actually to see the end of the stent graft when we deploy it. So it is just a matter of convenience and we think that it is easy to do. DR MARTIN: Can I make one last comment on the choice of graft. We have avoided the CTAG graft only because if you come back through a thoracotomy and have to sew to that graft at a later date, sewing to that very thin Gore-Tex, it is like a sprinkler system; it bleeds a lot. And so we have used the Dacron graft and have recently gone to the Medtronic device, because you can see through the sheath, as you put the sheath in you can see through it and you can see the back end of it. So the Medtronic, which is a Dacron device, is what we have gone to. We never use any fluro for our antegrade endograft, and we do not really need to because we are only going to put one device in. We are not worried where it really lands. You are only putting, at most, a 20cm device. So we are not trying to complete the whole thing. We agree that if you try to complete it, it is very difficult to do. So we do not do that. DR COSELLI: I was just going to say, Tom, in both those grafts you can see the portion toward the arch, and with the CTAG you are just expanding, you are not unsheathing it, so you can see it at all times. And truthfully, for the non–elephant trunk, you are sewing into the Gore material, and I agree with you, but in this circumstance, if you go back and have to suture, the graft sits almost entirely inside Dacron, so you would be suturing Gore as well as Dacron. So this is the one circumstance where that may not be the case.