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J Thorac Cardiovasc Surg 2006;132:361-368
© 2006 The American Association for Thoracic Surgery
Surgery for Acquired Cardiovascular Disease |
a Department of Vascular and Endovascular Surgery, Ruprecht-Karls University Heidelberg, Germany
b Department of Radiodiagnostics, Ruprecht-Karls University Heidelberg, Germany
d Department of Anaesthesiology, Ruprecht-Karls University Heidelberg, Germany
c Department of Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany.
Received for publication April 24, 2005; revisions received January 14, 2006; accepted for publication February 21, 2006. * Address for reprints: Dittmar Böckler, MD, Abteilung für Gefäßchirurgie, Chirurgische Universitätsklinik Heidelberg, Im Neuenheimer Feld 110, 69120 Heidelberg Germany. (Email: dittmar_boeckler{at}med.uni-heidelberg.de).
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Abstract |
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METHODS: Between 1997 and 2004, of 125 patients with acute and chronic aortic type B dissections, 88 were treated conservatively. Thirty-seven patients (29 male, mean age 58 years, range 30–82 years) underwent endovascular repair (30%) using 44 stent grafts of 3 different designs: Excluder (W. L. Gore & Associates, Inc, Flagstaff, Ariz), Talent (Medtronic Vascular, Santa Rosa, Calif), and Endofit (Endomed, Inc, Phoenix, Ariz). Indications for treatment were acute symptomatic type B dissection in 15 patients, chronic expanding aortic dissection greater than 55 mm in 14, rupture in 3, and simultaneous type A repair in 5 patients. Twenty-two operations were performed on an emergency basis. Patient characteristics, procedural variables, outcome, and complications were prospectively recorded. All patients underwent follow-up by computed tomography before discharge, at 6 and 12 months, and annually thereafter (mean follow-up: 24 months).
RESULTS: Correct deployment was achieved in 97% of cases. There were no instances of primary conversion, paraplegia, or stroke. Complete false lumen thrombosis was observed in 11 patients (44%). Perioperative complication rate was 22%. Thirty-day mortality rate in acute and chronic dissections was 19% and 0%, respectively. Freedom from aortic reintervention was 81%, 73%, and 68%, freedom from late rupture was 97%, 90%, and 80%, and overall success rate was 76%, 65%, and 57% at 1, 2, and 5 years, respectively. Results for patients with chronic dissections are significantly (P = .038) better than results in those with acute dissections.
CONCLUSIONS: Despite the minimally invasive approach, the complication and mortality rates for endovascular therapy of aortic dissections are still high. Frank reporting of these sequelae is if great importance to clarify the recent limitations of the method.
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Introduction |
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TopAbstractIntroductionPatients and MethodsResultsDiscussionLimitationsConclusionReferences |
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Aortic dissection is most often a catastrophic event which, if untreated, can be potentially life threatening. In a population-based longitudinal study, Meszaros and associates
1
report mortality rates of acute untreated aortic dissection of 22.7%, 50%, and 68% within 6 hours, 24 hours, and the first week, respectively. The International Registry of Acute Aortic Dissection (IRAD) study, with an overall mortality of 27.4%, confirmed that aortic dissection is a lethal disease.
2
Open surgical repair also is associated with high morbidity and mortality.
3
The advent of endovascular prostheses to treat descending thoracic aortic lesions offers an alternative approach in patients with dissections and severe comorbidities who are poor candidates for open surgery.
4,5
However, endoluminal treatment is not without complications.
6–8
Therefore, it is vital to report considerable complication rates and the midterm outcome after endografting. Hence, this report describes a continuing singe-center experience with endoluminal stent-graft repair in acute complicated and chronic expanding aortic type B dissections, focusing on limitations and complications of endovascular management.
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsDiscussionLimitationsConclusionReferences |
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Patients
Patient evaluation, selection, and endovascular procedures were performed by vascular surgeons. All patients with suitable aortic morphologic characteristics were offered a stent graft as our preferred alternative to open repair. Clinical characteristics, imaging, and procedural data were documented prospectively. Fifty-nine percent (n = 22) of all operations were emergency interventions.
For this study, the records of 29 men and 8 women (mean age 57 years, range 30–82 years) were reviewed. Patient characteristics, indications, stent-graft data, and results of treatment are summarized in Table E1. Fifteen patients had visceral, renal, or leg ischemia with true lumen collapse (TLC), and 3 had rupture of the false lumen (1 presenting with aortobronchial fistula [ABF] 2 years after initial uncomplicated dissection). Fourteen patients had chronic expansive aortic dissection (CEAD) greater than 55 mm of maximum diameter. All patients treated on an emergency basis had some degree of chest pain as the first presenting symptom. Five patients were treated by endografting after type A dissection repair: 2 immediate repairs in cooperation with cardiac surgeons (2 antegrade deployments necessitated by bleeding at the distal anastomosis of the arch repair) and 3 staged procedures necessitated by TLC with malperfusion syndrome (1 visceral, 1 renal ischemia) and due to chronic aneurysmal expansion and consecutive infrarenal aortic rupture via transfemoral access.
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10%) and only self-expanding endografts were implanted.
Device Details and Stent-Graft Placement
Six patients received more than 1 stent graft system simultaneously. Five patients received 2 devices and 1 patient received 3 devices. In total, 44 stent graft systems were implanted: 34 Excluder thoracic endoprostheses (TAG; W. L. Gore & Associates, Inc, Flagstaff, Ariz), 9 Talent endoluminal stent grafts (Medtronic Vascular, Santa Rosa, Calif), and 1 Endofit thoracic endoprosthesis (Endomed, Inc, Phoenix, Ariz) with lengths from 100 to 220 mm and diameters between 28 and 40 mm. The median stent graft–covered aortic segment was 169 mm (range 100–220 mm). Two surgeons equally qualified in endovascular experience performed all endovascular procedures with the patients under general anesthesia in an operating theater equipped with fluoroscopic and angiographic capabilities (series 9800; OEC Medical Systems, Inc, Salt Lake City, Utah) and a carbon-fiber operating table. Each patient received single-shot antibiotic therapy and 3000 units of heparin intravenously. With the exception of 1 patient (No. 30: antegrade approach during aortic arch repair), vascular access was obtained in 29 patients via the common femoral artery and in 7 patients by implanting a temporary 10-mm Dacron conduit to the common iliac artery because of small vessel size. The nondissected iliac/femoral artery, if iliac vessels were affected, was preferred for access. A 0.035-inch guide wire (Terumo, Frankfurt, Germany) was advanced and exchanged for a 7F calibrated angiography catheter. Digital subtraction angiography was performed with apnea followed by manual injection of 20 mL of nonionic contrast medium (Iopamidol [Solutrast 300], Byk Gulden, Konstanz, Germany). The aortic arch was rotated to about 45° in the left anterior oblique projection to adjust the parallax error for exact visualization of the proximal landing zones (minimum 15 mm). A sheath (up to 26F) was inserted over the guide wire and exchanged with a 0.035-inch, 260-cm Amplatz Super Stiff guide wire (Boston Scientific, Ratlingen, Germany) and passed to the aortic arch. Temporary adenosine-induced cardiac arrest with an average dose of 60 mg was used for precise endograft placement in 26 patients. Additionally, all patients were provided with external pacemakers. Ballooning was not performed. Transesophageal echocardiography was not used routinely during deployment, and there was no standby heart-lung machine. Completion angiography was performed to assess accurate placement and exclusion of the entry site of the dissection. Stent grafts were only deployed at the entry sites to depressurize the false lumen and to induce thrombosis. Stent grafting of longer aortic segments was avoided because of fear of paraplegia. To achieve a sufficient proximal anchoring zone in patients with CEAD and without any healthy landing zone, we performed one transposition of the left subclavian artery alone and polytetrafluoroethylene crossover bypass of both left common carotid and subclavian arteries in 2 patients before elective endografting.
Follow-up
Follow-up status between 1997 and 2004 is 100% complete and was performed in our department The follow-up protocol included postoperative contrast-enhanced CT scanning and plain chest radiography before hospital discharge, 6 months and 12 months after endografting, and annually thereafter. The mean follow-up is 24 months (range 0–56 months). Cause of death was obtained by medical reports or by contacting the primary care physician.
Definitions
By definition, acute type B dissection is present when diagnosis is made within 2 weeks after the initial onset of symptoms. Primary success was defined as insertion and accurate placement of the stent graft in the intended landing zone, successful immediate entry occlusion, and lack of immediate perioperative complications without any additional interventions. End points and criteria for late outcome were false lumen thrombosis of the thoracic aorta, lack of thoracic aorta expansion, and freedom from rupture. Endoleak is defined as radiologic evidence of blood flow outside the stent graft according to published guidelines, except persistent retrograde false lumen perfusion.
9
Reintervention is defined as any need for surgical or endovascular intervention on the treated aortic segment during follow-up. Treatment failure was defined as proximal type I endoleak, perioperative death, aortic reintervention, dissection-related death, and all sudden unexplained late deaths during follow-up.
Statistical Analysis
Comparison of acute and chronic dissections was done by the Wilcoxon signed-rank test. Kaplan-Meier life-table survival analysis was performed with XLSTAT V7.5.2 software (Addinsoft, New York, NY).
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Results |
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TopAbstractIntroductionPatients and MethodsResultsDiscussionLimitationsConclusionReferences |
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Reintervention
Freedom from aortic reintervention averaged 81%, 73%, and 68% at 1, 2, and 5 years: in acute cases, 82%, 73%, and 73%; in chronic cases, 80%, 74%, and 60% (P = .412) (Figure 3). During follow-up, no conversion (stent-graft explantation) was performed. One secondary proximal type I endoleak was diagnosed. In this patient (No. 17), initially treated for CEAD, a second proximal extension graft was inserted. The proximal endoleak persisted because of a disproportion of the different diameters of the endograft and aortic arch. She died of infrarenal false lumen rupture while she was scheduled for secondary conversion. A 78-year old man (No. 23) with ABF was treated by transfemoral coiling embolization of the false lumen to avoid conversion in a high-risk patient. He died 2 weeks later of another massive hemorrhage. One female patient with Marfan syndrome had chronic visceral aortic expansion and was treated with a hybrid procedure (case discussed later). Two more patients received aorto-biiliac bypass grafting 3 years after stent grafting.
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Chronic abdominal aortic expansion
Overall expansion rate was 32% (12/37) and 48% among survivors. Only 12 patients (acute, chronic) showed no enlarged aortic diameter during follow-up. Expansion by more than 30 mm but less than 50 mm was seen in 7 patients with continuing surveillance by CT scan. Five patients (3 chronic, 2 acute) developed aortic expansion of more than 50 mm over a 2-year period, and except for 1, all underwent open abdominal aortic bifurcated bypass grafting. One female patient (No. 19) with Marfan syndrome had progressive dilatation of the abdominal aorta after valve replacement and thoracic endografting of the distal arch. In a staged hybrid procedure, she was treated by extra-anatomic mesenteric and renal revascularization and endografting of the thoracoabdominal aorta (Figure 4).
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Discussion |
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TopAbstractIntroductionPatients and MethodsResultsDiscussionLimitationsConclusionReferences |
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The same authors published the only available study describing midterm results (4.5 years) of endovascular stent-graft repair of a thoracic aneurysm.
11
Although there are no long-term data to support definitive evidence, endovascular treatment is also proposed as an alternative therapy in patients with type B dissections. Whether stent grafting provides lasting protection from aortic rupture (especially false lumen rupture), from chronic aortic expansion, or from end organ ischemia still has to be determined. Therefore, we analyzed our midterm results for endovascular therapy on patients with type B aortic dissections.
The specific findings of this study highlight the problems and open questions of endovascular treatment in aortic dissections: The 30-day mortality rate of acute type B dissections after endograft implantation is still high (19%); in type A dissections it is as high as 57%. These disparate mortality rates likely pertain to patient selection bias and the acuity or pretreatment physiologic status of the patients. The high percentage of emergency interventions in this study (59%) and no diagnosis or delayed diagnosis of visceral ischemia in the prehospital time period may be a cause for patients dying of multiorgan failure despite technically successful entry closure. Many authors have published results on transluminal placement of endovascular stent grafts for the treatment of descending thoracic aortic dissections (Table 3).
12–14
Dake and associates
4
reported a series of 19 acute symptomatic dissections with 16% early mortality. This is in line with the 19% mortality in our own series. Early mortality in a third study from Palma and coworkers
15
published an early mortality of 6% in 58 patients, and of those, 35 had acute dissection but were asymptomatic. A comparative study of both therapy modalities, "endovascular versus conservative," for uncomplicated courses of asymptomatic patients is currently running. The excellent results achieved in 82 patients by Rehders and Nienhaber
16
are difficult to interpret because of a lack of differentiation between acute and chronic dissections, ruptures, and ischemia. Frequently, no difference between the results of asymptomatic and symptomatic patients has been made. Numerous retrospective studies with univariate and multivariate data analysis have been carried out to define those initial factors of the acute phase that determine the clinical course and the long-term prognosis.
5,17
Mesenteric ischemia has a major impact on outcome. Two of our patients died of multiorgan failure because of visceral ischemia and unresolved malperfusion persisting postoperatively. One 48-year-old male patient (No. 27), who was stent grafted with clinically asymptomatic abdomen but occlusion of the celiac trunk and superior mesenteric artery, developed severe colon ischemia and died despite early entry closure within 48 hours. Malperfusion remains a major challenge. If mesenteric ischemia is suspected, an aggressive posture toward laparotomy or laparoscopy is appropriate, even if endovascular revascularization has been achieved. Following laboratory values for potential markers of mesenteric infarction can be crucial. Four of our patients died because of delayed recognition.
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Thirty percent to 40% of all symptomatic patients have complications over the further clinical course.
1
Consequently, achievement of complete false lumen thrombosis and prevention of aortic growth and expansion is the main goal in the treatment of dissections. We observed complete or false lumen thrombosis only in 44% of patients and severe visceral aortic expansion over 50 mm in 5 patients. In the series reported by Kato and associates,
17
only 38.5% of chronic dissections showed complete obliteration during 27 months of follow-up. Patients after type A repair and residual type B dissections are also potential candidates for "hybrid" distal stent grafting. The 30-day mortality of this approach in our series of 57% is closely related to complications after type A repair, to a sick and small cohort of 5 patients, and needs skeptical judgment. The strategy of immediate hybrid repair of the ascending and descending aorta including technical considerations of antegrade versus retrograde stent-graft deployments needs definitive future evaluation.
Spinal cord ischemia after stent-graft repair of dissections varies between 3% and 10% in the literature,
19
0% in this study.
19
Potential factors for the lower incidence of spinal cord ischemia during endovascular repair are adequate collateral blood supply, no aortic crossclamping, short extension of stent graft–covered aorta, and deployment positioning far from the suggested origin of the artery of Adamkiewicz.
Sufficient proximal anchoring of 2 cm is necessary to avoid a proximal type I endoleak. To achieve this, coverage of the left subclavian or combined conventional transposition of the aortic arch branches may be necessary (Figure E2). We covered the left subclavian artery in 13 patients. One patient had clinically moderate dizziness and was observed without secondary intervention. Two patients had a proximal type I endoleak. Causes were incorrect endograft sizing and inflexible devices for the distal arch, which did not properly seal the proximal anchoring zone. Proximal tight fixation in the distal arch is mandatory and mostly makes covering the left subclavian artery necessary.
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An initial diameter of more than 4 cm and a persistent entry into the false lumen have been identified as determinants for CEAD. Surgical intervention rate and associated mortality is reported to be high (30%-40%).
20
Overall expansion rate was 32% (12/37), and 48% among survivors in this study underlines this significant sequelae.
Asymptomatic patients with an open false lumen, an initially large aortic diameter greater than 40 mm, and ongoing "open entry" face unfavorable prognostic factors.
21
The 1-year and 5-year survivals of asymptomatic patients under conservative medication amount to 94% and 86%, respectively. A comparison of these patients, however, to others who have undergone surgical therapy with a significantly higher risk is not permissible.
In a multicenter study comprising 465 patients, Hagan and associates
2
report a 3 times higher postoperative mortality rate (31.4%) as compared with the conservative patient group (10.7%). Lansmann and colleagues,
22
however, report a mortality of 0% with a fairly high associated complication rate of 47% in 34 patients with symptomatic type B dissection who had undergone surgery in the acute phase. In 1999, Nienhaber and colleagues
5
published a small study that was the first prospective study to compare transluminal and open surgery, constituting that stent-graft repair is a viable therapeutic option.
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Limitations |
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TopAbstractIntroductionPatients and MethodsResultsDiscussionLimitationsConclusionReferences |
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could prove the effectiveness of overstenting the intimal rupture site ("entry") for treatment of TLC. However, as long-term results are still lacking, it remains to be seen whether this circumstance can be classified as a criterion of success or aim of therapy. After 2 years, false lumen thrombosis rate was only 44%. Persisting perfusion of the false channel correlates with late complications CEAD and death due to rupture.
23,24
The meaning of patent false lumen in the further clinical course remains an open question. The term "true lumen collapse" (TLC) is difficult to interpret, as dissections are dynamic events with membrane movements, which can clearly be demonstrated by cine magnetic resonance imaging. The development of a specific endograft design for dissection therapy will become necessary. There is no ideal stent graft for dissections yet. The characteristics needed are gentle and flexible design, with no radial force and no bare springs. An important issue is the rigidity of the systems, which can cause penetration of the thin membrane. Of all the commercially available thoracic devices (Talent, Excluder, Endofit, and Zenith [Cook Incorporated, Bloomington, Ind]), we prefer the Excluder endoprosthesis, because of its access size and good flexibility. Finally, proof of the concept that endografts prevent long-term complications requires a prospective randomized trial. Our own therapy concept provides endovascular treatment in the symptomatic acute stage (any kind of ischemia, symptomatic TLC) or during the chronic course with aneurysmal expansion of more than 55 mm.
22
Therefore, only 23% of 110 patients with Stanford type B dissection were selected for endovascular surgery. |
Conclusion |
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TopAbstractIntroductionPatients and MethodsResultsDiscussionLimitationsConclusionReferences |
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The concept of endovascular treatment of type B dissections should be subjected to randomized evaluation to settle all the answers.
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Footnotes |
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References |
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