Ann Thorac Surg 2009;87:773-777. doi:10.1016/j.athoracsur.2008.11.061
© 2009 The Society of Thoracic Surgeons
Original Articles: Adult Cardiac
Operative Strategy for Acute Type A Aortic Dissection: Ascending Aortic or Hemiarch Versus Total Arch Replacement With Frozen Elephant Trunk
Naomichi Uchida, MDa,*,
Hidenori Shibamura, MDa,
Akira Katayama, MDa,
Norimitsu Shimada, MDa,
Miwa Sutoh, MDa,
Hiroshi Ishihara, MDb
a Division of Cardiovascular Surgery, Hiroshima-city Asa General Hospital, Hiroshima, Japan
b Kajikawa Private Hospital, Hiroshima, Japan
Accepted for publication November 21, 2008.
* Address correspondence to Dr Uchida, Division of Cardiovascular Surgery, Hiroshima-city Asa General Hospital, 2-1-1, Kabe-minami, Asa-Kita-Ku, Hiroshima, 731-0293, Japan (Email: uchidacvs{at}yahoo.co.jp).
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Abstract
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Background: This report compares long-term results with total arch replacement with frozen elephant trunk (FET) to ascending aortic or hemiarch replacement (AHR) for acute type A aortic dissection.
Methods: The subjects were 120 consecutive patients, including 65 who received FET and 55 who had AHR for acute type A aortic dissection from 1997 to 2008. The late results after surgery were retrospectively compared between the FET and ARH groups.
Results: Three patients in the FET group died, and 2 patients in the AHR group died. In long-term follow-up (mean, 67 months), the survival rate after 5 years was 95.3% for the FET group and 69.0% for the AHR group (p = 0.03). The event rate for the thoracic aorta after 5 years showed a significant difference between the FET and AHR groups (95.7% versus 73.0%, p = 0.01). A false lumen at the proximal descending aorta was patent in 16 patients (29%) in the AHR group, but it was thrombosed in all in the FET group.
Conclusions: In patients with acute type A aortic dissection, it is possible to perform extensive primary repair using the FET technique with relative safety. FET may reduce the necessity for further operations to manage a residual false lumen.
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Introduction
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The conventional treatment for acute type A aortic dissection used to be replacement of the ascending portion of the aorta. Because the dissection involves the entire aorta, the pathology of residual false lumen of the downstream aorta plays an essential role in determination of prognosis. As long as the false lumen remains patent, the chances of survival might remain in jeopardy, and reoperation is inevitable. Therefore, it is expected that the long-term prognosis may be improved by performing a procedure that obliterates the residual false lumen in the descending thoracic aorta when treating type A acute aortic dissection [1–4].
Recently, intraoperative stent grafting for the distal thoracic aorta has been combined with total arch replacement when treating acute dissection by the elephant trunk technique (frozen elephant trunk [FET]) for the purpose of achieving complete thrombosis of the false lumen in the descending thoracic aorta and good results have been reported [5–7]. We have performed long-term follow-up by computed tomography at our institution after FET and have shown that good results are obtained. However, there has been no detailed assessment of the prognosis, such as the survival rate or a postoperative aortic event-free rate. In this study, we reevaluated the effect of FET by comparing long-term results between FET and ascending aortic or hemiarch replacement (AHR) in patients treated during the same period.
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Material and Methods
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The FET technique was approved by the Ethics Committee. The retrospective review of the records for publication was also approved by the Institutional Review Board. Informed consent was required in each case. We performed emergency surgery in 120 consecutive patients for acute type A aortic dissection within 48 hours of its onset between December 1997 and January 2008. All procedures were done by two surgeons (H.I., N.U.). We principally undertook resection of the intimal tear and open distal anastomosis as an operative procedure for acute type A aortic dissection. The AHR was performed for the tear-oriented surgery. However, the FET was added for secure anastomosis and early thrombosed closure of the false channel in the descending aorta. The surgeon finally selected which of two procedures to use, in large measure based on age and comorbidities.
The procedure was FET in 65 patients and AHR in 55 patients (Fig 1). The FET group had an average age of 64.4 years (range, 45 to 84), and the AHR group had an average age of 72.3 years (range, 45 to 87). The patients' preoperative profiles are shown in Table 1. There were 49 patients in the FET group and 8 in the AHR group less than 70 years old. The FET group included 17 patients with a distal entry in the descending thoracic aorta (DeBakey subtype III-D) and 10 patients with a true aneurysm of the distal arch. The AHR group included 5 patients with an intramural hematoma and 3 patients with preoperative catastrophic morbidities (severe cerebral stroke or dissection of the left main trunk). The anastomotic technique at the proximal site was the same for FET and AHR; a tube graft was inserted through the ascending aorta transected above the sinotubular junction and anastomosed to the sinotublar junction line, including aortic valve commissures by intermittent horizontal mattress sutures using 4-0 polypropylene with external Teflon (Impra Inc, subsidiary of L. R. Bard, Tempe, AZ) felt strip. Aortic valve replacement was not performed in this series.
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Fig 1. Postoperative three-dimensional computed tomography. (a) A patent false lumen at the aortic arch on computed tomography scans in the chronic period was not found in the frozen elephant trunk (FET) group, but 16 patients (29%) had a patent false lumen in the ascending aortic or hemiarch replacement (AHR) group. The false lumen remains patent from the distal descending aorta to the abdominal aorta. (b) The superior mesentric artery is supplied from the false lumen through reentry. (c) The false lumen has completely disappeared.
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To perform the FET, the size and length of the stent graft were determined by intraoperative measurement using a ball-shaped sizer that was inserted into the true lumen of the descending aorta through a transverse incision in the aortic arch under transesophageal ultrasound guidance. The distal border of the stent graft was positioned at the level of the main pulmonary trunk. The primary tear was located distal to the left subclavian artery (DeBakey subtype III-D) in 17 patients, and these primary tears were covered by the stent graft.
Late postoperative results were obtained for 115 patients after a mean follow-up period of 67 months (range, 3 to 124). The FET and ARH groups were retrospectively compared with the early and late results after surgery.
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Results
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The perioperative variables are summarized in Table 2. The operating time, extracorporeal circulation time, and selective cerebral perfusion time were all significantly shorter in the AHR group than in the FET group. Three patients in the FET group died of low output syndrome (n = 1) and deep infection (n = 2); 2 patients in the AHR group died of multiple organ failure with intestinal necrosis (n = 1) and brain damage (n = 1) within 30 days after the operation. Postoperative cerebral deficits were only recognized in patients who had cerebral complications before surgery; however, there were no new cerebral deficits and no spinal cord injury postoperatively. Visceral malperfusion was not recognized in the FET group, but developed in 3 patients who had persistent DeBakey subtype III-D dissection in the AHR group. One died of intestinal necrosis, and 2 had abdominal aortic fenestration performed 10 and 18 days after operation.
The late results are summarized in Table 3. Late death occurred in 3 patients of the FET group who had nondissection-related death. Nine patients died in the AHR group, including 3 of dissection-related death; there were 2 sudden deaths (12 and 21 months after operation) and 1 rupture of the descending thoracic aorta 59 months after operation. The 5-year survival rate was 95.3% in the FET group, and was significantly higher than the 69.0% in the AHR group (p = 0.03; Fig 2). Late aortic events in the thoracic aorta occurred in 2 patients of the FET group, including 1 patient with redissection of the annular aorta 85 months after operation and 1 additional operation on the descending thoracic aorta 20 months after operation. Late aortic events in the thoracic aorta were recognized in 3 patients of the AHR group, including 1 nonrescued rupture of the descending thoracic aorta, 1 emergency operation for impending rupture of the descending thoracic aorta 49 months after operation, and 1 transfemoral endovascular stent grafting procedure 26 months after operation. One patient of the AHR group required superior mesenteric artery noncovered stenting 2 months after discharge.
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Fig 2. The 5-year survival rate was 95.3% in the frozen elephant trunk (FET) group and was significantly higher than that of 69.0% in the ascending aortic or hemiarch replacement (AHR) group (p = 0.03).
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The overall 5-year aortic event rate including sudden death and abdominal aortic operation was significantly different between the FET and AHR groups (88.6% versus 70.3%, p = 0.02; Fig 3). The rate of events affecting the thoracic aorta over 5 years showed a significant difference between the FET and AHR groups (95.7% versus 73.0%, p = 0.01; Fig 4). A patent false lumen at the proximal descending aorta on computed tomography scans in the chronic period was not recognized in the FET group, but 16 patients (29%) had a patent false lumen in the AHR group (Fig 1). Five of these 16 patients had aortic events, consisting of 2 sudden deaths, 1 descending aortic rupture, 2 operations for dilation of the thoracic false lumen, and 1 stenting for superior mesenteric artery ischemia. In the FET group, the false lumen was completely thrombosed in the proximal descending thoracic aorta, and the thrombosed false lumen was absorbed within 1 year, except in 1 patient who had a residual entry in the middle descending aorta and an additional operation 20 months after FET for dilated descending aorta with a patent false lumen. Obliteration was recognized in all patients at the distal border of the stent graft, and absorption of thrombus was seen in 90% at the middle of the descending thoracic aorta within 1 year after operation.
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Fig 3. The overall 5-year aortic event rate was not significantly different between the frozen elephant trunk (FET) and the ascending aortic or hemiarch replacement (AHR) groups (88.6% versus 70.3%, p = 0.02).
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Fig 4. The aortic event rate of events affecting the thoracic aorta over 5 years showed a significant difference between the frozen elephant trunk (FET) and the ascending aortic or hemiarch replacement (AHR) groups (95.7% versus 73.0%, p = 0.01).
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Comment
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It is expected that the long-term prognosis can be improved by performing a procedure to obliterate the residual false lumen in patients with type A acute dissection of the descending thoracic aorta. A residual patent false lumen in the descending thoracic aorta is recognized in 50% to 70% of patients after ascending aortic or hemiarch replacement for acute type A aortic dissection and in approximately 30% even after total arch replacement. Approximately 13% to 25% of patients with a residual patent false lumen in the descending thoracic aorta required another operation within 5 years [8–11]. In particular, 30% of patients in whom an entry was not excluded required an additional operation within 1 year. Moreover, reoperation is often required for dilation of the false lumen distal to the proximal descending aorta in the late postoperative period [12–16]. Because anastomotic leakage or a small tear in the proximal descending thoracic aorta can exist after replacement of the ascending aorta or aortic arch, the false lumen is susceptible to dilation due to shear stress acting on the proximal descending aorta. Therefore, there have been recent reports about total replacement of the aortic arch during the first operation in such patients, even if the primary intimal tear is located in the ascending aorta. Kazui and coworkers [17] reported that when the descending thoracic aorta was repaired up to the midportion with a synthetic graft using the elephant trunk technique in the initial operation, subsequent dilation of the most susceptible parts of the residual false lumen was prevented. However, the diameter of the graft inserted with the elephant trunk procedure is likely to be smaller than that of a distally stented graft. A distally anchored stent graft allows both insertion of a larger diameter graft and a longer elephant trunk.
We principally undertook resection of the intimal tear and open distal anastomosis as an operative procedure for acute type A aortic dissection. The AHR was performed for the tear-oriented surgery. However, the FET was added for secure anastomosis and early thrombosed closure of the false channel in the descending aorta. The surgeon finally selected which of two procedures to use, in large measure based on age and comorbidities as follows. First, we aggressively performed FET in patients less than 70 years of age for the purpose of obtaining good long-term results, although it increases surgical invasion. We also selected FET for patients with narrowing of the true lumen, even if they were more than 70 years old; narrowing of the true lumen might lead to malperfusion of visceral branches. Visceral malperfusion often occurs if the distal false lumen remains patent with a residual tear. We expect that visceral malperfusion in the early postoperative period can be avoided by closure of the residual tear using the FET technique. Second, we used the FET technique for acute type A dissection with a dilated aortic arch (>4 cm) regarding long-term prognosis. Third, we recognized that the FET can close a distal entry in the descending thoracic aorta (so-called DeBakey subtype III-D). Conventionally, the distal aorta is anastomosed to exclude a primary entry distal to the recurrent laryngeal nerve when the primary entry is in the proximal descending thoracic aorta or the proximal aorta is anastomosed without excluding the primary entry when it is below the hilum of the lung, but we have experienced bleeding and rupture at the anastomotic region after surgery. We consider that FET makes it easy to control bleeding, and that the anastomosis may not fail because the entry is completely excluded by the stent graft. The findings of this study suggest that the FET technique is significantly able to prevent sudden death and reoperation on the descending thoracic aorta compared with the AHR operation.
Use of a stent graft for acute dissection has problems, such as the risk of intimal damage or selection of size, and is controversial [18, 19], but we want to emphasize that direct sizing through an incision in the aortic arch is very important. We insert a ball-shaped valve sizer into the true lumen of the descending aorta from the transverse incision under transesophageal ultrasound guidance and choose the correct size. Therefore, we have stent grafts of each size always ready. We minimize the danger of intimal damage by inserting a stent graft of the exact size under circulatory arrest, and have not experienced any new intimal tears after stent grafting so far during long-term follow-up. We only have experience of stent grafting for Marfan's syndrome in 1 case, and the long-term prognosis is unknown, so it seems that use of a stent graft for such patients needs careful consideration.
The risk of paraplegia caused by sacrificing the spinal arteries must be considered when a long synthetic vascular graft is inserted into the descending thoracic aorta. However, a recent report indicated that use of stent grafts for a true aneurysm causes most paraplegia, and obstruction or embolism of intercostal arteries by debris plays a role [20]. The importance of perfusion into the left subclavian artery is emphasized. Nevertheless, intercostal arteries are often patent after acute dissection, and it seems likely that blood flow occurs through reentry as shown by our computed tomography data even if the intercostal arteries have been dissected. In cases where many pairs of intercostal artery have been dissected, however, we plan to prevent delayed paraplegia by maintaining the blood pressure rather high to encourage early thrombosis of the false lumen due to compression by the stent graft.
Limitations of the Study
This is a retrospective study, and not randomized. The operative procedure of AHR or FET was finally selected by the surgeon in large measure based on the patient's age and preoperative comorbidities. A prospective and randomized study would be required to evaluate the precise advantage of FET for acute type A aortic dissection.
In conclusion, it is possible to perform extensive primary repair of the thoracic aorta for acute type A aortic dissection with relative safety by the FET technique. Moreover, the FET technique may reduce the necessity for further operations to manage a residual false lumen.
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References
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Abstract
Introduction
