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Division of Cardiovascular and Thoracic Surgery, Missouri Baptist Medical Center, St. Louis, Missouri
Accepted for publication July 21, 2008.
* Address correspondence to Dr Kouchoukos, Cardiac, Thoracic and Vascular Surgery, 3009 N. Ballas Rd, Ste 360C, St. Louis, MO 63131 (Email: ntkouch{at}aol.com).
| Abstract |
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Methods: Fifty-one patients with chronic expanding thoracic aortic dissections (48 type A, 3 type B with proximal extension) were treated with a single procedure using a bilateral anterior thoracotomy, hypothermic circulatory arrest, and reperfusion of the arch vessels first to minimize brain ischemia. Forty-six patients had previous operations: for acute type A aortic dissection (n = 36), aortic valve disease (n = 6), or coronary artery disease (n = 4). The ascending aorta and entire arch were replaced in all patients combined with varying lengths of the descending aorta.
Results: Hospital mortality was 3.9% (2 patients). Five patients (10%) required reoperation for bleeding. Two patients were discharged on ventilatory support and 2 on dialysis. No patient sustained a stroke, and paraplegia developed in one. The 5- and 7-year survival rates were 79% and 68%. Freedom from reoperation on the thoracic or abdominal aorta was 92% at 5 and 7 years postoperatively. Serial tomograms have documented substantial enlargement of the residual dissected aorta in only 2 patients (reoperated).
Conclusions: The technique is a safe and suitable alternative to the two-stage (elephant trunk technique) and hybrid procedures for treatment of chronic dissection with aneurysm of the thoracic aorta. It eliminates the risk of rupture in the interval between staged procedures and the risks associated with a second thoracic aortic procedure, and is associated with a low rate of reoperation on the remaining aorta.
| Introduction |
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The optimal surgical management of patients with these conditions who have substantial enlargement of the remaining ascending aorta, the aortic arch, and part or all of the descending thoracic aorta is not clearly established. Therapeutic options include staged procedures, commonly using the elephant trunk technique [9–11], hybrid procedures using endovascular grafts to exclude the descending thoracic aneurysmal segments at the time of or after graft replacement of the ascending aorta and aortic arch [12, 13], and one-stage procedures replacing all of the aneurysmal dissected aorta through one or several incisions [14–16].
We present here our experience with one-stage repair for patients with chronic type A aortic dissection and extensive enlargement of most or all of the remaining dissected thoracic aorta, using a bilateral anterior thoracotomy approach and early perfusion of the brachiocephalic arteries (arch-first technique) to minimize the duration of brain ischemia.
| Patients and Methods |
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The mean patient age was 58 years (range, 22 to 81 years), and 38 (74%) were men. Thirty-six patients had previously undergone repair of acute type A aortic dissection. A type A dissection developed in 10 patients, in 6 during or after aortic valve replacement or repair and in 4 after coronary artery bypass grafting (CABG). Three patients had type B aortic dissections that were initially managed with medical therapy and developed proximal extension of the dissection into the aortic arch and ascending aorta. The remaining 2 patients had chronic type A dissections that were initially managed without operation. Six patients (11.7%) had Marfan syndrome, and 1 (2%) had both Loeys-Dietz syndrome and type I Ehlers-Danlos syndrome.
Among the 46 patients undergoing reoperation, the mean interval between the initial and the second procedure was 73 months (median, 60; range, 3 to 249 months). The previous operations among the 36 patients with type A aortic dissection are reported in Table 1. At the time of reoperation, the dissection extended into the abdominal aorta in all but 1 patient.
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During the study interval, no patient with extensive aneurysmal dilatation of a chronically dissected aorta sufficient to require operation, but with the aneurysmal segment confined to the thoracic aorta, was managed by any other technique. Patients in whom the aneurysmal enlargement extended into the abdominal aorta were treated with staged procedures.
Operative Technique
Our current operative technique has been previously reported [14]. In brief, it involves use of a bilateral anterior thoracotomy through the fourth intercostal space, transverse sternotomy, peripheral venous cannulation through the right common femoral vein using a two-stage cannula with the tip positioned in the superior vena cava, and cannulation of both the right common femoral artery and the right axillary artery.
In our initial experience, a cuff of aortic tissue was excised around the brachiocephalic arteries, and this cuff was sutured to an opening in a collagen-impregnated polyester aortic graft during circulatory arrest [17, 18]. This technique was used in 26 patients. Our current and preferred technique, which was used in the most recent 25 patients, involves use of a branched aortic graft and perfusion of the brain through the axillary artery to minimize the duration of circulatory arrest [19]. Cerebral oxygen saturation in both hemispheres is monitored using the Invos Cerebral Oximeter (Somanetics Corp, Troy, MI).
After completion of the arch anastomosis by either of these techniques, the site for anastomosis of the graft to the descending thoracic aorta is selected. This is generally where the diameter of the aorta does not exceed 3 to 3.5 cm. A segment of the septum between the true and false aortic lumens of the distal aorta is excised to permit perfusion of both channels. Patent intercostal arteries above the seventh intercostal space are ligated. If the aorta is divided below this level, the distal aorta is beveled to preserve the lower intercostal arteries. After completion of the anastomosis and removal of air from the graft, flow to the lower body is established in the antegrade direction from the axillary artery, and rewarming is initiated.
During rewarming, aortic valve or aortic root replacement and CABG, if indicated, are performed. The proximal end of the aortic graft is sutured to the ascending aorta just above the level of the aortic commissures, to an existing ascending aortic graft, or to a newly inserted composite graft. Saphenous vein bypass grafts, if present, are anastomosed to the aortic graft.
Extent of Resection and Concomitant Procedures
The ascending aorta, the entire aortic arch, and varying lengths of the descending thoracic aorta were resected and replaced in all patients. The extent of descending thoracic aortic replacement and the concomitant procedures performed are summarized in Table 2.
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2 test was used to determine differences among variables. | Results |
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In-Hospital Morbidity
Reoperation for bleeding or for evacuation of clot from the left pleural space was required in 5 patients (10%). The intraoperative mean transfusion requirements were 8.9 ± 4.9 U of packed red cells, 7.2 ± 4.4 U of fresh frozen plasma, 5.5 ± 3.3 U of platelets, and 7.5 ± 11.9 U of cryoprecipitate.
Mechanical ventilatory support for more than 72 hours was required in 23 of the 50 operative survivors (46%), and 9 (18%) required tracheostomy. The mean duration of ventilatory support was 12 ± 20 days (median, 3; range, 1 to > 90 days). All but 2 patients were successfully weaned from mechanical support. Permanent left vocal cord paralysis occurred in 1 patient (2%).
Inotropic support with more than 5 µg /kg/min of dobutamine for more than 24 hours was required in 9 of the 50 operative survivors (18%). One patient required intraoperative insertion of a ventricular assist device for right ventricular failure. It was removed on the third postoperative day, and the patient made a full recovery.
Renal failure requiring ultrafiltration or hemodialysis occurred in 5 patients (10%). Three of these patients were successfully weaned, with return of serum urea and creatinine levels to baseline by the time of hospital discharge.
Permanent and transient neurologic dysfunction was evaluated according to the classification of Ergin and colleagues [20]. No strokes occurred. One patient sustained bilateral optic nerve injury resulting in blindness but without CT or MRI evidence for cerebral cortical infarction, and paraplegia also developed. Transient neurologic dysfunction occurred in 7 of the 50 operative survivors (14%) and resolved completely in all of them.
There were no deep chest wound infections. One patient required a femorofemoral artery bypass graft for postoperative occlusion of the left external iliac artery. One patient required exploration of a groin incision for arterial bleeding and also a left thoracotomy to treat a persistent chylothorax. One patient with Marfan syndrome required laparotomy for intraperitoneal bleeding resulting from spontaneous rupture of a branch of the splenic artery. The mean duration of the postoperative hospital stay was 23 days (median, 12; range, 11 to 71 days).
Late Mortality
During the follow-up interval, which extends to 117 months, 12 late deaths occurred between 2.4 and 100 months. The modes of death are summarized in Table 4. The mean duration of follow-up was 47 months. Thirty-two patients have been followed up for more than 3 years, 16 for more than 5 years, and 7 for more than 7 years. The 1-, 3-, 5- and 7-year survival rates are 90%, 88%, 79%, and 68%, respectively (Fig 3).
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The 1-, 3-, 5- and 7-year freedom from reoperation rates on the thoracic or abdominal aorta were 98%, 95%, 92%, and 92%, respectively (Fig 4).
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| Comment |
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Other studies have shown actuarial freedom from reoperation on the distal aorta at 10 years to be between 75% and 77% [3, 4, 6]. Younger age and the presence of Marfan syndrome are also associated with higher rates of reoperation [3, 6, 22]. In the series of Kazui and colleagues [4] and Shiono and colleagues [22], replacement of the entire aortic arch at the time of repair of the acute dissection was not associated with a lower incidence of reoperation on the distal aorta compared with less extensive resection. Freedom from reoperation on the distal aorta does not reflect the true frequency of aneurysm formation, because rupture of distal aneurysms has been noted in all published series. Lack of complete follow-up as well as the decision of some patients not to undergo reoperation are also factors that can affect the rate of reoperation [21].
Options besides a one-stage procedure for management of chronic dissecting aneurysms confined to the thoracic aorta that develop after successful initial repair, or after other surgical procedures, include a staged approach, commonly using the elephant trunk technique, and hybrid procedures [9–13, 23]. In four of the largest, recently reported series of elephant trunk procedures, which contain a substantial number of patients with chronic aortic dissection (31% to 39% of the total), the cumulative mortality for the two procedures and from deaths in the interval between the two procedures (commonly from aortic rupture) exceeded 20% [10, 11, 23, 24].
In the present study and in our previously reported series of single-stage procedures including other aortic pathology besides chronic dissection [14], the early mortality did not exceed that reported for the first stage of a two-stage procedure [10, 11, 23, 24]. In addition, the intraoperative transfusion requirements in our series were substantially less than those for the first-stage elephant trunk procedure reported by LeMaire and colleagues [11] and Safi and colleagues [25]. The prevalence of stroke, renal failure, and left recurrent laryngeal nerve injury did not exceed that reported for the first-stage procedure [10, 11, 23, 24].
Although our technique is not applicable in patients whose aneurysmal enlargement extends into the abdominal aorta, it represents a suitable alternative to staged procedures when the aneurysmal enlargement is confined to the thoracic aorta. Its use in the latter circumstance eliminates the risk of rupture of the remaining aneurysmal aorta in the interval between the first and second procedures, a common cause of death in this period, and the risks associated with a second procedure on the thoracic aorta [1, 10, 11, 23, 25].
The fate of the remaining chronically dissected descending thoracic aorta is of critical importance when the one-stage procedure we have described is used. Song and colleagues [26], using CT imaging, evaluated the long-term natural course of distal aortic dilatation in 51 patients who survived operation for acute DeBakey type I (type A) dissection. They followed up 27 of the 51 patients (53%) for more than 24 months, during which aneurysms (aortic diameter > 60 mm) developed in 8 patients (16%), and 3 died at 16, 21, and 71 months after onset of the acute dissection. In the follow-up interval, the incidence of aneurysmal change was 0% in the aortic arch, 15.7% at the upper descending thoracic aorta, 7.8% at the middle descending thoracic aorta, 2% at the lower descending thoracic aorta, and 2% at the abdominal aorta.
In our series, the upper descending thoracic aorta was replaced in all patients and the middle descending in 43 of the 51 patients (Table 2). Reoperation on the remaining dissected aorta was required in only 2 of the 49 hospital survivors in the follow-up interval, which extended to 117 months. Serial CT examinations have documented little or no increase in the diameter of the residual dissected aorta in the remaining patients. These findings, and the extremely low rate of aneurysm formation in the distal descending thoracic and abdominal aorta noted by Song and colleagues [26], suggest that more extensive replacement of these segments is unnecessary in most patients with chronic type A dissection. However, surveillance with serial imaging studies is essential and of particular importance in patients with Marfan syndrome and other genetically mediated conditions.
Stent grafting of the chronically dissected descending thoracic aorta at the time of reoperation on the ascending aorta and aortic arch (hybrid procedure) is another therapeutic alternative. To date, it has been used in only a small number of patients and follow-up is limited [12, 13, 27, 28]. Its role in the management of patients with chronic aortic dissection remains uncertain [29, 30]. Progressive thickening and stiffening of the septum between the true and false lumen and the presence of multiple fenestrations in the septum have brought into question the ability of stent grafts to induce complete thrombosis of the false lumen and remodeling in the descending thoracic aorta [30]. In the study of Shimono and colleagues [31], who used a transluminal stent graft placement technique for patients with acute and chronic aortic dissection, complete obliteration of the false lumen was observed in only 38.5% of patients with chronic dissection compared with 70% of those with acute dissection.
Because a higher incidence of spinal cord ischemic injury has been reported with extensive coverage of the descending thoracic aorta, several authors have recommended that the length of the stent graft be limited to the proximal 10 to 15 cm [10, 12, 27]. Stent graft collapse because of extremely small or stiff true lumens, endoleaks, torsion of the endograft, aortoesophageal fistula, new intimal tears, aneurysm formation, and late rupture are other reported complications that are unique to stent grafts and mandate lifelong imaging follow-up [30, 32–35]. Thrombosis of the false lumen distal to the implanted endograft can result in loss of perfusion to vital organs. Cost of the endografts is another consideration. In the United States at present, the minimal added cost of an endograft to a single-stage procedure would be $10,000.
In summary, our extended experience with the one-stage, arch-first technique for the management of chronic aortic dissection indicates that it is a safe and suitable alternative to the two-stage procedure and to current hybrid procedures based on currently available information. Our current and preferred technique for brain protection with axillary artery cannulation, a brief period of circulatory arrest, subsequent hypothermic brain perfusion, and use of a branched graft, has substantially reduced the duration of circulatory arrest of the brain. It obviates the need for direct cannulation of the brachiocephalic arteries and is safe, as evidenced by the absence of stroke and a low prevalence of temporary neurologic dysfunction. It has been associated with low hospital mortality, satisfactory long-term survival, and a low prevalence of reoperation on the distal aorta. It remains our treatment of choice for extensive chronic aortic dissection with aneurysmal dilatation confined to the thoracic aorta.
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