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Ann Thorac Surg 2007;83:1059-1066
© 2007 The Society of Thoracic Surgeons
a Departments of Angiography and Interventional Radiology, Medical University of Vienna, Vienna, Austria
b Department of Cardio-Thoracic Surgery, Medical University of Vienna, Vienna, Austria
c Department of Emergency Medicine, Medical University of Vienna, Vienna, Austria
Accepted for publication October 24, 2006.
* Address correspondence to Dr Schoder, Department of Angiography and Interventional Radiology, Medical University of Vienna, Waehringer Guertel 18-20, A-1090 Vienna, Austria (Email: maria.schoder{at}meduniwien.ac.at).
| Abstract |
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Methods: Twenty-eight patients with acute type B-dissection who were treated by stent graft repair presented with rupture (n = 1), contained rupture (n = 2), compromised branch vessels (n = 14), pleural effusion (n = 11), rapid aortic diameter progression (n = 5), persistent pain (n = 3), refractory hypertension (n = 10), and an aortic diameter of more than 4 cm (n = 4). Taking into account the perfusion status of the false lumen, diameter changes were monitored in the thoracic aorta at the level of the stented segment (L1), distal to the stent graft (L2), and at the level of the celiac trunk (L3).
Results: Severe complications in 9 patients (32%) resulted in 3 deaths for a 30-day mortality rate of 10.7%. Primary sealing of the entry tear was achieved in 86%. At all levels, the true lumen diameter increased significantly after stent graft placement. At the 1-year follow-up, the false lumen in L1 was thrombosed in 90% and the mean difference of diameter reduction was highly significant. In L2, complete false lumen thrombosis occurred in 60% with a significant diameter decrease. In L3, the false lumen thrombosed in only 22%, and the mean difference of false lumen diameter increase reached significance at the 2-year follow-up.
Conclusions: Ninety percent of patients were treated successfully with thrombosis of the false lumen in the stented segment. False lumen perfusion distal to the stent graft resulted in diameter increase in several patients leaving these segments an area of concern.
| Introduction |
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Closure of the primary entry tear by endovascular repair may lead to thrombosis of the false lumen with remodelling of the true lumen in the acute and chronic setting. Furthermore, lowering the pressure in the false lumen may restore the perfusion in the compromised aortic branch vessels. In recent years, encouraging technical results after endovascular repair of acute type B dissection have been reported [1321]; however, reports on the true and false lumen changes after endovascular therapy during a longer-term follow-up remain limited [13, 20, 22, 23].
The purpose of this study was to assess the clinical outcome and technical success in endovascular repair of acute type B aortic dissections. The significance of true and false lumen diameter changes in the thoracic and abdominal aorta was also evaluated at the long-term follow-up.
| Material and Methods |
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Endovascular repair of thoracic aortic diseases was introduced at Medical University of Vienna as an alternative treatment to surgical repair in high-risk patients in 1996. The local Institutional Review Board gave approval and consent for this retrospective study. Written informed consent was obtained from all conscious patients. In one unconscious patient, the treatment decision was made collaboratively with cardiothoracic surgeons and interventional radiologists.
Confirmation of dissection was based on contrast-enhanced computed tomography (CT) angiography (CTA) using a multidetector scanner (Somatom Volume Zoom; Siemens, Erlangen, Germany). CT scanning ranged from the supraaortic vessels to the common femoral arteries. Routine post acquisition image processing from each CT scan included three-dimensional reconstructions consisting of multiplanar reformations (MPR), curved planar reconstructions (CPR), and a maximum intensity projection (MIP).
Dissections extended down into one (n = 10, 36%) or both iliac arteries (n = 11, 39%), to the renal arteries (n = 3, 13%), to the superior mesenteric artery (SMA; n = 1, 4%), or were limited to the thoracic aorta (n = 3, 13%). The primary intimal tear was located just distal to the left subclavian artery in 26 (93%) patients, whereas in 2 patients, the entry tear was in the middle third of the descending aorta. The false lumen was patent in all patients. Thirty branch vessels were compromised by either an exclusively dynamic process (n = 17) or a combination of a dynamic and a static process. In 12 patients (42.9%), either one branch vessel (renal artery in 10, celiac trunk in 1) or two branch vessels (renal artery and superior mesenteric artery) originated from the false lumen.
Twenty-four symptomatic patients with more than one complication were selected for endovascular therapy because of rupture (n = 1), contained rupture (n = 2), compromised branch vessels (n = 14), pleural effusion (n = 11), rapid aortic diameter progression (n = 5), persistent pain (n = 3), and refractory hypertension (n = 10). Specific patient characteristics with dissection related complications are listed in Table 1. Four clinically asymptomatic patients demonstrating an aortic diameter of more than 40 mm and marked compression of the true lumen were treated to prevent further aortic dilation. Owing to the severity of their symptoms, 9 patients (32%) required emergent (within hours) stent graft implantation after CT diagnosis of an acute type B dissection. Another 11 patients were treated within 7 days. Mean time to treatment was 101 hours (range, 1 to 312 hours).
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All procedures were performed in an angiosuite that is equipped with digital subtraction angiography (Multistar T.O.P., Siemens, Erlangen, Germany). All patients were under general anesthesia. Antibiotic prophylaxis was administered intravenously in all patients before the procedure. In patients without rupture, 5000 IU of heparin sodium was given after the access site (common femoral or external iliac artery) was surgically exposed.
A 5F pigtail catheter was positioned into the ascending aorta through right-sided percutaneous brachial access to perform an angiogram before stent graft deployment. Gaining access to the true lumen from the iliac route required adjunctive maneuvers in 2 patients. Approaching from the true lumen via brachial access, a pigtail catheter was advanced down to the aortic bifurcation. Subsequently, a 260-cm-long steerable hydrophilic guidewire (Terumo Europe N.V., Leuven, Belgium) was advanced to the iliac artery and snared with an Amplatz gooseneck snare (ev3, Plymouth, MN). A diagnostic catheter was then introduced from the femoral site over the through-and-through wire up to the aortic arch to facilitate placement of the superstiff guidewire (Back-up Meier, Boston Scientific, Natick, MA).
After deployment of the device, an angiogram was performed to evaluate the position of the stent graft relative to supraaortic arch vessels, to confirm closure of the proximal entry tear, to ascertain the true lumen diameter along the aorta, and to document the perfusion status of the branch vessels.
Follow-up Imaging
CTA examinations were routinely performed within 3 days after the procedure, at 3, 6, and 12 months, and yearly thereafter. To assess the extent of the dissection, the diameter of the true and false lumen, and the perfusion status of the false lumen and the branch vessels, the entire aorta and the iliac arteries were included.
Statistical Analysis
Continuous variables are expressed as means and ± standard deviation. For exact analysis of diameter changes of the true and false lumen, preprocedural and follow-up CT examinations were reevaluated. Measurements were obtained at the same levels perpendicular to the line of the intimal flap and at the maximum diameter in three selected aortic segments: stented aortic segment (L1), thoracic aorta distal to the stent graft (L2), and the abdominal aorta at the level of the celiac trunk (L3).
Diameter changes were evaluated for significance between the preprocedural and first postprocedural images. For statistical analysis of diameter changes for long-term follow-up, a 1-year and 2-year CTA examination was required. Differences of aortic measurements were tested for significance using the
2 test for proportions. Significance level was set at p < 0.05. Statistical analysis was performed using SPSS 13 statistical software (SPSS Inc, Chicago, IL).
| Results |
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Proximal overstenting led to sealing of the entry tear in 1 patient, and in the second patient, the perfusion of the false lumen from the entry tear decreased steadily and was sealed completely at the 1-year follow-up. Two patients (patient 19 and 21) with partial covering of the LSA demonstrated residual flow into the false lumen from the proximal entry tear at the last follow-up. For further proximal overstenting, transposition of the left common carotid artery would be necessary in these 2 patients. One of these patients refused further interventions, and the second patient has a stable thoracic aortic diameter. Consequently, these patients remain under close observation.
Expansion of the true lumen after stent graft deployment resulted in a satisfactory perfusion of compromised vessels in 83% (Fig 1). Additional stenting was necessary in five (17%) arteries (2 visceral arteries, 2 renal arteries, 1 iliac artery) to alleviate persistent obstruction of the true lumen by extension of the intimal flap beyond a vessels origin.
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Further serious complications in the 25 surviving patients were spinal cord ischemia in 2 (7.1%). In patient 11, who sustained permanent paraplegia, the LSA was completely overstented and the stent graft covered Th-8 distally. In patient 6, who had incomplete transient paraplegia, the LSA was partially covered and the device was fixed distally at the level of the ninth thoracolumbar vertebrae. Intentional occlusion of the LSA led to ischemia of the left upper limb requiring secondary transposition of LSA in 1 patient. A retrograde type A dissection that developed in another patient was treated successfully with surgery. Dissection-related infarction of the intestines required a partial small bowel resection and a right-sided hemicolectomy in one patient. Temporary hemodialysis was necessary in 3 patients who had dissection-related acute renal failure.
Follow-Up Analysis of the True and False Lumen
Mean CT follow-up of surviving patients was 859 ± 546 days (range, 40 to 2107 days). The first postprocedural CT examination was completed in 25 patients. Twenty patients were available for the 1-year CT follow-up analysis, and 14 patients had CT examinations at 24 months, 8 at 36, 4 at 48, and 2 at 60 months.
l1-stented thoracic aortic segment
At the first postprocedural CT, a complete thrombosis of the false lumen was seen in 15 (60%) patients. The mean difference of true lumen diameter increase was highly significant (p < 0.0001) between the preprocedural and postprocedural measurements (Fig 2,
Table 2).
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l2-thoracic aortic segment distal of the stent graft
At the first postprocedural CT a complete thrombosis of the false lumen was observed in 5 patients (20%) and the mean difference of true lumen diameter increase was statistically significant (p = 0.0005; Fig. 3,
Table 2).
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l3-abdominal aorta-level of celiac artery
At the first postprocedural CT, none of the 22 patients demonstrated a thrombosis of the false lumen; however, the true lumen showed a statistically significant mean difference of diameter increase (p = 0.0009; Fig 4,
Table 2).
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| Comment |
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The effectiveness of surgical or endovascular repair for aortic dissection is dependent on closure of the entry tear, reexpansion of the true lumen, and clotting of the false lumen. Our experience, as well as that in other studies [13, 15, 16, 18, 19, 21, 24], indicates that stent graft repair is an effective approach even in the emergent treatment of patients with a complicated acute type B dissection. In addition to relief of acute symptoms, stent graft placement may prevent aneurysmal degeneration of the thoracic aorta by thrombus formation in the false lumen.
The in-hospital mortality rate in this patient series was 10.7%, which is similar to the 7% to 20% reported in literature [13, 16, 18, 19, 24, 25]. Although these data indicate a superior survival compared with surgery, the serious condition of this category of patients is also reflected in a complication rate of up to 36% as reported by Kato and colleagues [25] and in the 30% occurrence in our patients, corresponding to the study by Eggebrecht and colleagues [20].
As a procedure-related complication, we observed permanent paraplegia in 1 (3.6%) patient. This compares favorably with reported rates in patients who underwent surgery [8, 9, 26]. Another serious procedure-related complication was a retrograde type A dissection occurring in 2 patients who were treated with a Talent endoprosthesis with a free flow design on the proximal cage, resulting in one death. The cause may be related to the limited flexibility of the currently available devices that produce forced wall stress at the outer curvature leading to intimal injuries, which is also reported in previous experiences [24, 27, 28].
Intentional overstenting of the LSA without previous revascularization is described as a feasible and well-tolerated procedure in a few series [17, 21, 29, 30]. However, 1 of our 3 patients with complete LSA occlusion, without previous revascularization, sustained acute arm ischemia that necessitated LSA transposition. Nonserious ischemic arm symptoms in 13.6% of patients were also reported in the study of Görich and associates [29]. Moreover, in the series of Tiesenhausen and colleagues [31], 3 (37.5%) of 8 patients with partial or complete occlusion of the LSA sustained vertebrobasilar symptoms. As reported in the literature, bilateral vertebral artery occlusion, which can be also simulated by overstenting of a dominant LSA and an additional severely stenotic or hypoplastic right vertebral artery, caused irreversible neurologic problems in 23% of patients [32]. Therefore, to rule out patients for whom LSA revascularization might be essential, both the carotid and vertebral arteries should be evaluated before intentional overstenting.
Branch vessels may be compromised by a dynamic or static obstruction, or a combination of both [13, 33]. In a study by Dake and colleagues [13], restoration of blood flow was sufficient after stent graft repair in all branch vessels that were compromised exclusively by a dynamic process. In vessels also affected by a static component, deployment of an uncovered stent within the true lumen of the obstructed artery was necessary in 60% of the patients. In accordance with this, all our patients with a dynamic obstruction of arteries could be treated by stent grafting alone. An additional stent deployment was necessary in five vessels (17%) with an obstruction caused by direct extension of the flap beyond the vessels origin. Infradiaphragmatic vessels originating from the false lumen did not suffer from malperfusion after occlusion of the entry tear. An adequate blood supply was provided by existing natural fenestrations of the intimal flap allowing communication between the true and false lumen, which has also been shown in other series [13, 34].
Recent studies have reported patient outcome during the chronic phase in type B dissections that have only been treated with medical therapy [2, 5]. Akutsu and associates concluded [2] that patients with a thrombosed false lumen had a significantly better outcome in terms of dissection-related death and dissection-related events in the chronic phase. In addition, they found that a higher incidence of dissection-related death in patients with the most dilated aortic segment located at the distal arch. Marui and colleagues [5] reported that during the chronic phase, the event-free rate at 1 year was 97% in type B dissections with a thrombosed false lumen and an aortic diameter of less than 40 mm. Conversely, dissections with a patent false lumen and an aortic diameter of 40 mm or more had an event-free rate of only 43% at the same instant. With respect to these findings, the advantage of endovascular treatment of acute type B dissections is not limited to treatment of complications, but might also prevent adverse events during the chronic phase.
Primary closure of the entry tear after stent grafting was reported in 89% to 100% [16, 17, 19, 21, 24, 35] and was achieved in 85.7% of our patients. In our series, complete thrombosis of the false lumen in the stented aortic segment (L1) as well as in the thoracic aorta distally to the stent graft (L2) was observed in 90% and 60%, respectively. A significant reduction of the false lumen diameter was also achieved in these patients. In dissections with a patent false lumen in L2, the false lumen increased without reaching statistical significance at the 2-year follow-up. However, the maximal aortic diameter increased significantly over the same time period.
Thrombosis of the false lumen occurred in the abdominal aorta (L3) in 22% of our patients, a rate consistent with the findings of other studies that reported false lumen thrombosis in the abdominal aorta in 0% to 10% [13, 20, 36]. This circumstance can be explained by the presence of reentries, as mentioned previously. In contrast to the results of Czermak and associates [23], who found no substantial volume change in the abdominal aorta, we showed that the mean difference of diameter increase of a patent false lumen was remarkable at the L3 level at the 1-year follow-up and reached statistical significance at the 2-year follow-up. There was a clear tendency for diameter decrease at this level with a thrombosed false lumen.
A limitation of this study is the small sample size, which did not allow us to draw final conclusions from our results. However, closure of the entry tear and stabilization of the true lumen presents a promising alternative treatment to conventional surgery for relief of life-threatening dissection related complications. Furthermore, aortic segments with a thrombosed false lumen had no substantial diameter changes during the follow-up period. False lumen perfusion distal of the stent graft resulted in substantial diameter increase in several of our patients leaving these segments an area of great concern.
| Acknowledgments |
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| References |
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