Midterm Change of Descending Aortic False Lumen After Repair of Acute Type I Dissection

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1 Midterm Change of Descending Aortic False Lumen After Repair of Acute Type I Dissection Kay-Hyun Park, MD, PhD, Cheong Lim, MD, PhD, Jin Ho Choi, MD, Euisuk Chung, MD, Sang Il Choi, MD, PhD, Eun Ju Chun, MD, PhD, and Kiick Sung, MD, PhD Departments of Thoracic and Cardiovascular Surgery and Radiology, Seoul National University Bundang Hospital, Bundang, and Department of Thoracic and Cardiovascular Surgery, Sungkyunkwan University School of Medicine, Samsung Medical Center, Seoul, Korea ADULT CARDIAC Background. Persistent false lumen in the descending aorta after repair of acute type I dissection adversely affects long-term prognosis. In this study, we investigated changes of the descending aortic false lumen during the midterm postoperative period. Methods. Postoperative computed tomographic (CT) images of 122 patients who underwent conventional ascending with or without arch replacement for acute type I dissection were reviewed. Patency and width of false lumen and maximal diameter of the aorta were compared between early and last follow-up images. Changes were analyzed separately in the thoracic and abdominal segments. Results. In early CT, thoracic false lumen was patent in 85 patients (69.7%), and abdominal false lumen was patent in 111 patients (91.0%). Among these, the false lumen remained patent after a mean interval of 33.6 months in 69 patients (81.1%) and 105 patients (94.6%), respectively. In 58 patients (47.5%), the descending aorta dilated by 1 cm or more. Dilatation occurred more frequently in the thoracic aorta and in patients with patent or wide false lumens, larger aortic diameter, Marfan syndrome, younger age, and male sex. Meanwhile, shrinkage of thoracic false lumen occurred in 36 patients (29.5%). Such shrinkage occurred in 23 of 24 patients (95.8%) who had thrombosed and narrow false lumens in the thoracic aorta. Conclusions. Early postoperative characteristics of false lumen were helpful for predicting both dilation and regression. Our data show not only a high incidence of descending aortic dilatation after repair of acute type I dissection, but also shrinkage of thoracic false lumen in some patients. These findings can be used as control data for determining the benefit of more extensive or new surgical approaches. (Ann Thorac Surg 2009;87:103 8) 2009 by The Society of Thoracic Surgeons Accepted for publication Sept 11, Address correspondence to Dr Park, Department of Thoracic and Cardiovascular Surgery, Seoul National University Bundang Hospital, 300 Gumi-dong, Bundang-gu, Seongnam-si, Gyeonggi-do, , Korea; drkhpark@yahoo.co.kr. After conventional surgery for DeBakey type I acute aortic dissection, the majority of patients have false lumen in the downstream aorta, which can adversely affect long-term prognosis [1 7]. Although many studies investigated the fate of descending aortic false lumen and the risk factors of aneurysmal dilatation [8 11], only a few looked at the difference or relationship between immediate postoperative characteristics and later longterm changes. In addition, many of the previous studies included the patients operated on with an old technique: anastomosis under aortic cross-clamping without circulatory arrest and replacing only the ascending aorta even in the presence of an arch tear. Thus, we do not have enough control data to determine the actual benefit of more aggressive or new approaches, such as routine replacement of the arch or insertion of frozen elephant trunk, which are expected to improve long-term prognosis [12 19]. In this study, we aimed to provide such control data by investigating the midterm change of the descending aortic false lumen and its difference according to immediate postoperative characteristics and level of the aorta. Patients and Methods Patients We retrospectively reviewed postoperative computed tomographic (CT) scan images in the patients who underwent surgery for DeBakey type I acute aortic dissection from 1997 through During the period, emergency surgery for Stanford type A acute dissection was performed by the first author in a total of 158 patients, and 150 (94.9%) of them could be discharged alive. Among these, we excluded the patients who had DeBakey type II dissection or intramural hematoma and included only the patients in whom CT scan was performed during hospitalization within 7 days after surgery and also in the late postoperative period (6 months or longer after surgery). The Institutional Review Board approved the study and waived the individual patient s consent. There were 122 patients, 72 male and 50 female. The mean age was 52.0 years (range, 24 to 82). Twenty patients had phenotypic manifestations of Marfan syndrome. All operations were performed within 3 days after 2009 by The Society of Thoracic Surgeons /09/$36.00 Published by Elsevier Inc doi: /j.athoracsur

2 ADULT CARDIAC 104 PARK ET AL Ann Thorac Surg DESCENDING AORTA AFTER TYPE I DISSECTION REPAIR 2009;87:103 8 symptom onset. Aortic resection and distal anastomosis of the prosthetic graft were done under deep hypothermic circulatory arrest in all patients. The extent of aortic replacement included the root in 39 patients (32.0%) and the transverse arch in 29 patients (23.8%). All intimal tears located in the arch were resected by replacing the entire or part of the arch (partial arch or hemiarch replacement). We did not insert an elephant trunk into the distal aorta during replacement of the arch. Equipment and Protocol of CT Scan The CT scan was done with a 16-slice (Mx 8000IDT; Philips Medical Systems, Best, the Netherlands) or 64- slice (Brilliance 64; Philips Medical Systems) multidetector row scanner. Images were acquired from the mandibular level to the level of acetabular roof at 5-mm intervals. To enhance the aorta, a bolus of 100 to 120 ml nonionic contrast material (Ultravist 370; Schering, Berlin, Germany) was intravenously injected at a flow rate of 4 ml/s, followed by flushing with 20 ml saline at the same flow rate. The enhanced image was acquired at 5 s after the signal density level in the ascending aorta reached the predefined threshold of 150 Hounsfield Units. Finally, additional 3-minute delay scanning was performed. Review of CT Images and Data Analysis For each patient, the early postoperative and the last of multiple follow-up images were reviewed. The interval Fig 2. Characteristics of the thoracic aortic false lumen (FL) in the early and the last computed tomography (CT) postoperative images. (TL true lumen.) between the surgery and the last CT examination ranged from 6 to 109 months (mean, 33.6; median, 26). False lumen patency was recorded at five levels in the early and the last images of each patient (Fig 1). Partially thrombosed false lumen was recorded as being patent. The five levels were grouped into two segments: thoracic (upper three levels) and abdominal (lower two levels). Thoracic aortic false lumen was recorded as patent if all or the upper two levels had patent false lumen. Abdominal aortic false lumen was recorded as patent if one of two levels had patent false lumen. Widths of true and false lumens were measured at the level where the external aortic diameter is largest in each segment. The review and the measurement were performed on the workstation provided with the CT scanner (Brilliance; Philips Medical Systems). The above characteristics were compared between the early and the last CT images. We also examined the difference in the incidence of aortic dilatation according to the false lumen characteristics and such factors as patient s age, sex, Marfan syndrome, and duration of follow-up. Statistical analyses were performed using SPSS 15.0 for Windows (SPSS Institute, Chicago, IL). The 2 or the Fisher exact test was used for comparing categorical variables and the Student t test was used for Fig 1. False lumen (FL) patency was recorded at five levels in each patient: the mid portion of the arch, bifurcation of the pulmonary artery, lower cardiac border, celiac trunk, and lower border of the left kidney. (A) Thoracic aortic false lumen was recorded as patent if all or upper two levels had patent false lumen, and abdominal aortic false lumen was recorded as patent if one of two levels had patent false lumen. (B) Partially thrombosed false lumen was recorded as patent. (C) Separately in thoracic and abdominal segments, widths of true and false lumens were measured at the level where the aortic diameter is largest. (T true lumen width; F false lumen width; T F diameter of the aorta.) Fig 3. Characteristics of the abdominal aortic false lumen (FL) in the early and the last computed tomography (CT) postoperative images. The abdominal aorta was not dissected in the remaining two patients. (TL true lumen.)

3 Ann Thorac Surg PARK ET AL 2009;87:103 8 DESCENDING AORTA AFTER TYPE I DISSECTION REPAIR 105 Fig 4. Later change of the descending aortic lesion according to early postoperative profile of the false lumen. (AAA abdominal aortic aneurysm; TAAA thoracoabdominal aortic aneurysm.) ADULT CARDIAC comparison of numerical variables. A p value less than 0.05 was considered statistically significant. Results Early Postoperative Features In the early postoperative period, the false lumen of the thoracic aorta was patent in 85 patients (69.7%), and thrombosis occurred in the remaining 37 patients (Fig 2). The false lumen of the abdominal aorta was more frequently patent, namely, in 91.0% (111 of 122) of the patients (Fig 3). The false lumen was wider than the true lumen in the thoracic aorta of 83 patients (68.0%) and in the abdominal aorta of 81 patients (66.4%). Patent false lumen was wider than the true lumen in the majority of cases; 82.4% (70 of 85) in the thoracic aorta and 72.1% (80 of 111) in the abdominal aorta. On the contrary, a significantly smaller portion of thrombosed false lumen was wider than the true lumen: 35.1% (13 of 37) in the thoracic aorta and 11.1% (1 of 9) in the abdominal aorta (p 0.05). Change of False Lumen During Follow-Up The proportion of patients who had patent false lumen in the last CT examination was not different from the results of early postoperative examination: 77 patients (63.1%) in the thoracic aorta and 105 patients (86.1%) in the abdominal aorta. The thoracic false lumen that had been patent early after surgery remained patent in 81.1% (69 of 85) of cases. In the abdominal aorta, patency of false lumen was maintained in higher proportion, namely, 94.6% (105 of 111). In the thoracic aorta, shrinkage of the false lumen occurred in 36 patients (29.5%). Such regression was most frequently observed in the patients who had completely thrombosed and narrow false lumen in the early postoperative period (23 of 24; 95.8%). In the abdominal aorta, the false lumen regressed in all of the few patients in whom it had been thrombosed early after surgery. On the contrary, thrombosed thoracic false lumen became patent during the follow-up in some patients, especially if it was wider than the true lumen (8 of 37, 21.6%). Dilatation of the Descending Aorta Dilatation of the descending aorta, defined as increase of maximal diameter by 1 cm or more during the follow-up period, occurred in 58 patients (47.5%). In 50 of those patients, the proximal thoracic aorta was involved in aneurysmal dilatation. The extent of dilatation was thoracic in 14, infrarenal in 2, and thoracoabdominal in 42 patients (Fig 4). A second operation for the descending aortic aneurysm was recommended for 22 patients in whom the maximal aortic diameter exceeded 5.5 cm (5.0 cm in case of Marfan syndrome). Nineteen patients underwent a second operation, and 17 of them survived. In 8 patients, the interval between the first and second operations was less than 1 year. Aortic dilatation was attributed to enlargement of the false lumen; when measured at the level where the maximal dilatation occurred, the true lumen width increased by only 1.5 mm (from 13.7 mm to 15.3 mm) whereas the false lumen width increased by 13.3 mm (from 19.0 mm to 32.4 mm) on the average. Aortic dilatation was significantly related with the false lumen characteristics (Table 1). Especially in the thoracic segment, dilatation of the aorta occurred more frequently if the false lumen was patent or larger than the true lumen, as depicted in Figure 4. Large diameter of the aorta was also a significant risk factor. Dilatation occurred in all patients with Marfan syndrome. Young age (50 years or younger) and male sex were other risk factors for aortic dilatation. With regard to the duration of follow-up, the incidence of aortic dilatation was relatively high (42.9%) among the patients who were evaluated less than 1 year after surgery. After 1 year, there was a tendency toward increasing incidence of aortic dilatation with longer follow-up.

4 ADULT CARDIAC 106 PARK ET AL Ann Thorac Surg DESCENDING AORTA AFTER TYPE I DISSECTION REPAIR 2009;87:103 8 Table 1. Incidence of Aortic Dilatation of 10 mm or More According to Risk Factors Variables Comment Incidence of Dilatation Level of the aorta Thoracic 50 of 122 (41.0%) Abdominal 29 of 122 (23.8%) False lumen patency a Patent 42 of 85 (49.4%) Thrombosed 8 of 37 (21.6%) False lumen width a Wider than true lumen 44 of 83 (53.0%) Narrower than true lumen 6 of 39 (15.4%) Maximal aortic diameter (mm) a 30 1 of 7 (14.3%) of 29 (27.6%) of 60 (40.0%) of 11 (54.5%) of 15 (60.0%) Age (years) of 24 (75.0%) of 27 (55.6%) of 30 (36.7%) of 33 (27.3%) 70 4 of 8 (50.0%) Sex Male 40 of 72 (55.6%) Female 17 of 50 (34.0%) Marfan syndrome Yes 20 of 20 (100%) No 38 of 102 (37.3%) Follow-up duration (years) 1 12 of 28 (42.9%) of 29 (31.0%) of 22 (50.0%) of 22 (50.0%) 5 15 of 21 (71.4%) a Refers to the thoracic aorta only. The result of our study is concordant with previous reports in that the majority of patients had patent false lumen in the descending aorta after surgery for acute type I dissection. Aneurysmal dilatation occurred in nearly half of the patients, and 15.6% underwent distal reoperation during the mean follow-up of 33.6 months. We confirmed the significance of previously reported risk factors of later aortic dilatation. Along with the importance of the false lumen patency, the size of the false lumen relative to that of the true lumen was also a significant risk factor. In previous studies, it was reported that 50% to 80% of patients had patent false lumen in the descending aorta after replacement of the ascending aorta for acute type A dissection [4, 5, 7]. Aneurysmal dilatation occurred in 15% to 60% within 10 years [4 6, 8, 9], and as many as 25% of patients required second surgery within 5 to 10 years [1, 3, 11]. In both type B and postoperative type A dissection patients, the risk of later aortic events was higher for the patients with patent false lumen, large initial aortic diameter, larger false lumen relative to the true lumen, Marfan syndrome, and young age [5, 8 11, 20 22]. The higher incidence of aortic dilatation among younger patients of our series can be partly explained by the fact that 15 of the 20 patients with Marfan syndrome were younger than 40 years. In addition, considering that most of our patients needed longterm antihypertensive medications postoperatively, we speculate that the impact of hypertension on aortic dilatation is greater in younger patients. As for the duration of follow-up, it is remarkable that the aorta dilated by 1 cm or more in more than 40% of patients who were followed for less than 1 year. Eight of them underwent second surgery soon after the CT examination. Based on this observation, we assume that aortic dilatation may be biphasic in some patients, in other words, rapid expansion in the early period and slow, progressive dilatation later on. Because residual intimal tear in the distal aorta is thought to be the major cause of continued false lumen patency [16, 23], some surgeons believe that more extensive aortic replacement could decrease the prevalence of patent false lumen. Some reported that the proximal thoracic false lumen was less frequently patent after arch replacement than after replacement of the ascending aorta only [2, 17, 24, 25]. In addition, some surgeons advocate insertion of a short elephant trunk during replacement of the arch to exclude small intimal tears adjacent to the anastomosis [16]. By this simple modification, complete thrombosis of the false channel in the proximal descending thoracic aorta could be achieved in 43.2% before discharge and in 100% at 3 years after surgery [18]. In the further modification, the elephant trunk is mounted on a self-expandable stent to allow insertion of a larger and longer prosthesis, thereby ensuring true lumen expansion and false lumen thrombosis [12]. It was reported that the so-called frozen elephant trunk technique resulted in complete thrombosis and shrinkage of the proximal thoracic false lumen in 90% to 100% and in 60% to 80% of cases, respectively [14, 15, 19]. However, the benefit of frozen elephant trunk has not been proven by randomized trials or case-control comparisons. For the present, the only way to assess the benefit would be a comparison with the historical data. We believe that our study provides control data for change of descending aortic false lumen after surgery performed in accordance with modern principles: open anastomosis under total circulatory arrest and resection of all arch tears. Some of our results back up the rationale of the frozen elephant trunk: (1) the false lumen in the thoracic aorta was patent and larger than the true lumen in nearly 70% of cases early after surgery; (2) patency of the false lumen was maintained later on in most of such cases; (3) aortic dilatation occurred frequently in them; and (4) the abdominal aorta remained relatively stable although the false lumen continued to be patent in most

5 Ann Thorac Surg PARK ET AL 2009;87:103 8 DESCENDING AORTA AFTER TYPE I DISSECTION REPAIR cases. In spite of such findings, we think that more data are needed about the rate and severity of complications [19, 26 28] before inserting frozen elephant trunk as a routine procedure because of our observation that nearly 20% of our patients had favorable false lumen characteristics early after surgery, namely, false lumen thrombosis and expansion of true lumen in the thoracic aorta. In most of them, false lumen regressed during the follow-up. Our study has several limitations. First, we did not review CT images taken at the same interval after surgery, and subsequently could not present the cumulative rate of aortic dilatation or thrombosis of previously patent false lumen. Second, the follow-up duration was not long enough to show long-term change of the descending aorta that remained stable early after surgery. Third, we could not compare the results of ascending aortic replacement and arch replacement because of the relatively small number of patients who underwent arch replacement. Such comparison might have showed different rates of false lumen patency according to extent of aortic replacement [2, 17, 24, 25]. Lastly, we did not review the preoperative images and their relationship with postoperative findings. The quality and format of preoperative CT images taken at different referring hospitals were variable, and some images were unavailable at the time of review. In conclusion, we confirmed the high incidence of descending aortic dilatation after repair of acute type I aortic dissection. However, we also found that the descending aortic lesion changed favorably in some patients. Early postoperative characteristics of the false lumen were helpful for predicting both favorable and unfavorable changes during later follow-up. Our results can be used as a control data for determining the benefit and indication of a more extensive or newer approach such as frozen elephant trunk. References 1. Geirsson A, Bavaria JE, Swarr D, et al. Fate of the residual distal and proximal aorta after acute type A dissection repair using a contemporary surgical reconstruction algorithm. Ann Thorac Surg 2007;84: Takahara Y, Sudo Y, Mogi K, Nakayama M, Sakurai M. Total aortic arch grafting for acute type A dissection: analysis of residual false lumen. Ann Thorac Surg 2002;73: Bachet J, Goudot B, Dreyfus GD, et al. Surgery for acute type A aortic dissection: the Hopital Foch experience ( ). Ann Thorac Surg 1999;67: Moore NR, Parry AJ, Trottman-Dickenson B, Pillai R, Westaby S. Fate of the native aorta after repair of acute type A aortic dissection: a magnetic resonance imaging study. Heart 1996;75: Ergin MA, Philips RA, Galla JD, et al. Significance of distal false lumen after type A dissection repair. Ann Thorac Surg 1994;57: Heinemann M, Laas J, Karck M, Borst HG. Thoracic aortic aneurysm after acute type A aortic dissection: necessity for follow-up. Ann Thorac Surg 1990;49: Yamaguchi T, Guthaner DF, Wexler L. Natural history of the false channel of type A aortic dissection after surgical repair: CT study. Radiology 1989;170: Zierer A, Voeller RK, Hill KE, Kouchoukos NT, Damiano RJ, Moon MR. Aortic enlargement and late reoperation after repair of acute type A aortic dissection. Ann Thorac Surg 2007;84: Yeh CH, Chen MC, Wu YC, Wang YC, Chu JJ, Lin PJ. Risk factors for descending aortic aneurysm formation in medium-term follow-up of patients with type A aortic dissection. Chest 2003;124: Kirsch M, Soustelle C, Houel R, Hillion ML, Loisance D. Risk factor analysis for proximal and distal reoperations after surgery for acute type A aortic dissection. J Thorac Cardiovasc Surg 2002;123: Immer FF, Krahenbuhl E, Hagen U, et al. Large area of the false lumen favors secondary dilatation of the aorta after acute type A aortic dissection. Circulation 2005;112(Suppl 1): 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: Mizuno T, Toyama M, Tabuchi N, Wu H, Sunanori M. Stented elephant trunk procedure combined with ascending aorta and arch replacement for acute type A aortic dissection. Eur J Cardiothorac Surg 2002;22: Liu ZG, Sun LZ, Chang Q, et al. Should the elephant trunk be skeletonized? Total arch replacement combined with stented elephant trunk implantation for Stanford type A aortic dissection. J Thorac Cardiovasc Surg 2006; 131: Uchida N, Ishihara H, Shibamura H, Kyo Y, Ozawa M. Midterm results of extensive primary repair of the thoracic aorta by means of total arch replacement with open stent graft placement for an acute type A aortic dissection. J Thorac Cardiovasc Surg 2006;131: Miyamoto S, Hadama T, Anai H, et al. Simplified elephant trunk technique promotes thrombo-occlusion of the false lumen in acute type A aortic dissection. Ann Thorac Cardiovasc Surg 2006;12: Ando M, Nakashima N, Adachi S, Nakaya M, Kawashima Y. Simultaneous graft replacement of the ascending aorta and total aortic arch for type A aortic dissection. Ann Thorac Surg 1994;57: Watanuki H, Ogino H, Minatoya K, et al. Is emergency total arch replacement with a modified elephant trunk technique justified for acute type A aortic dissection? Ann Thorac Surg 2007;84: Shimamura K, Kuratani T, Matsumiya G, et al. Long-term results of the open stent-grafting technique for extended aortic arch disease. J Thorac Cardiovasc Surg 2008;135: Bernard Y, Zimmermann H, Chocron S, et al. False lumen patency as a predictor of late outcome in aortic dissection. Am J Cardiol 2001;87: Marui A, Mochizuki T, Koyama T, Mitsui N. Degree of fusiform dilatation of the proximal descending aorta in type B acute aortic dissection can predict late aortic events. J Thorac Cardiovasc Surg 2007;134: Akutsu K, Nejima J, Kiuchi K, et al. Effects of the patent false lumen on the long-term outcome of the type B acute aortic dissection. Eur J Cardiothorac Surg 2004;26: Van Arsdell GS, David TE, Butany J. Autopsies in acute type A aortic dissection. Surgical implications. Circulation 1998; 98(Suppl 2): Bachet J, Teodori G, Goudot B, et al. Replacement of the transverse aortic arch during emergent operation for type A acute aortic dissection. J Thorac Cardiovasc Surg 1988;96: Kazui T, Kimura N, Yamada O, Komatsu S. Total arch graft replacement in patients with acute type A aortic dissection. Ann Thorac Surg 1994;58: ADULT CARDIAC

6 ADULT CARDIAC 108 PARK ET AL Ann Thorac Surg DESCENDING AORTA AFTER TYPE I DISSECTION REPAIR 2009;87: Usui A, Fujimoto K, Ishiguchi T, Yoshikawa M, Akita T, Ueda Y. Cerebrospinal dysfunction after endovascular stentgrafting via a median sternotomy: the frozen elephant trunk procedure. Ann Thorac Surg. 2002;74(Suppl): Easo J, Dapunt O, Natour E, Hoelzl P, Dangel G, Chavan A. Transfemoral stent-graft placement to treat a complication of the frozen elephant trunk procedure. J Endovasc Ther 2007;14: 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: INVITED COMMENTARY The less than 10% survival rate after repair of an acute type A dissection inspires interest in the fate of the survivors. Aneurysmal change of the residual false lumen brings on an unwelcome second or even third operation with no proper proximal clamp site. Recognition of aortic metamorphosis from its initial condition is essential to determine what the first procedure should be, so as to avoid falling into this morass afterward. The authors demonstrate here [1] that postoperative dilatation occurred more frequently in the thoracic aorta, in the young, and in the cases of patent or wide false lumen, larger aortic diameter, and Marfan syndrome. This result supports previous reports [2, 3]. Among these knotty conditions, surgeons can merely work out how to avoid leaving the false lumen patent in the thoracic aorta. Endoleak at the distal anastomosis or remaining entry (re-entry) in the descending thoracic aorta provides more opportunities for the false lumen to be patent. Therefore, it is consequential that application of the elephant trunk procedure, which reduces endoleak and increases the possibility of shielding an entry that may exist in the downstream aorta [4], improves long-term survival. In the past, one might have intervened in an acute dissection with ascending replacement of the aorta, thinking only of saving the patient s life immediately, not the mid-term outcome. Now the trend is toward total arch replacement, which offers excellent early outcomes and helps avoid future distal interventions or at least provides greater convenience if one is necessary. Furthermore, an ascending or partial arch replacement can not carry the elephant trunk, which prevents endoleak and reduces the likelihood of additional interventions in the descending aorta. Currently, the frozen elephant trunk, which has a stent graft distally as a trunk, is expected to enhance the value of the elephant trunk technique for dissections [5, 6]. Morphology after the repair of an acute type A dissection mirrors a type B aortic dissection. Tsai and colleagues [7] interestingly reported that partial thrombosis of the false lumen in an acute type B dissection has a worse prognosis than complete patency. In the present article, patent false lumen includes partial thrombosis. Subdivisions of patency (or thrombosis) may afford more significant and informative data for decision-making regarding the second intervention. Lately, thoracic endovascular aortic repair, like the proverbial little Dutch boy, has put its finger in the dike for us regarding complicated type B dissections [8]. Thoracic endovascular aortic repair can be the first approach for potentially troublesome distal lesions after repair of a type A dissection, followed by open graft replacement as the second approach, if necessary [9]. The elephant trunk provides a good proximal neck for both thoracic endovascular aortic repair and graft replacement. In short, no elephant trunk? No way. Shinji Miyamoto, MD Department of Cardiovascular Surgery Oita University 1-1 Idaigaoka Hasama-machi Yufu-shi, Oita, Japan smiyamot@med.oita-u.ac.jp References 1. Park K-H, Lim C, Choi JH, et al. Midterm change of descending aortic false lumen after repair of acute type I dissection. Ann Thorac Surg 2009;87: Zierer A, Voeller RK, Hill KE, et al. Aortic enlargement and late reoperation after repair of acute type A aortic dissection. Ann Thorac Surg 2007;84: Bernard Y, Zimmermann H, Chocron S, et al. False lumen patency as a predictor of late outcome in aortic dissection. Am J Coldiol 2001;87: Miyamoto S, Hadama T, Anai H, et al. Simplified elephant trunk technique promotes thrombo-occlusion of the false lumen in acute type A aortic dissection. Ann Thorac Cardiovasc Surg 2006;12: Jakob H, Tsagakis K, Tossios P, et al. Combining classic surgery with discending stent grafting for acute DeBakey type I dissection. Ann Thorac Surg 2008;86: Mizuno T, Toyama M, Tabuchi N, et al. Stented elephant trunk procedure combined with ascending aorta and arch replacement for acute type A aortic dissection. Eur J Cardio- Thorac 2002;22: Tsai TT, Evangelista A, Nienaber CA, et al. Partial thrombosisi of the false lumen in patients with acute type B aortic dissection. N Engl J Med 2007;357: Verhoye JP, Miller DC, Sze D et al. Complicated acute type B aortic dissection: Midterm results of emergency endovascular stent-grafting. J Thorac Cardiovasc Surg 2008;136: Chen IM, Shin CC. Extending hybrid approach to residual Stanford type A dissecting aortic aneurysm. Interact Cardio- Vasc Thorac Surg 2007;6: by The Society of Thoracic Surgeons /09/$36.00 Published by Elsevier Inc doi: /j.athoracsur