From the New England Society for Vascular Surgery
Late aortic remodeling persists in the stented segment after endovascular repair of acute complicated type B aortic dissection Mark F. Conrad, MD, MMSc, Stephanie Carvalho, BS, Emel Ergul, MS, Christopher J. Kwolek, MD, R. Todd Lancaster, MD, MPH, Virendra I. Patel, MD, MPH, and Richard P. Cambria, MD, Boston, Mass Objective: Thoracic endovascular aortic repair (TEVAR) for acute complicated type B aortic dissection (AD) promotes early positive aortic remodeling. However, little is known about the long-term effect of TEVAR on the dissected aorta, which is the goal of this study. Methods: Between August 2005 and August 2009, 31 patients with complicated type B AD were treated with TEVAR and had >1-year follow-up imaging. Computed tomography angiograms obtained at 1 month, 1 year, and long term (average, 42 months) were compared with baseline scans. The largest diameters of the stented thoracic aorta, stented true lumen, and stented false lumen were recorded at each time point, as were the values in the unstented distal thoracic aorta and the abdominal aorta. Changes over time were evaluated by a mixed effect analysis of variance model of repeated measures. Results: The average age of the cohort was 56 years, and 74% were male. Indications for TEVAR were as follows: 61% malperfusion, 32% refractory hypertension, 45% impending rupture, and 32% persistent pain; 58% had more than one indication. All patients were treated in the acute phase within 7 days of the initial presentation. The average length of aorta covered was 19 cm. Observation of the stented segment over time showed that the maximum diameter of the stented thoracic aorta was stable (P [ NS), the diameter of the stented true lumen increased (P < .001), and the diameter of the stented false lumen decreased (P < .001); 84% had complete false lumen obliteration across the stented aortic segment. Observation of the uncovered thoracic aorta over time showed that the maximum diameter increased (P [ .014), as did the visceral segment of the aorta (P < .001). The average growth of the visceral segment was 31% in patients with a patent false lumen vs 3% in those with a thrombosed false lumen (P [ .004). One patient had aneurysmal degeneration of the false lumen and required an additional endograft at 18 months. Conclusions: TEVAR of acute AD promotes long-term remodeling across the stented segment, with false lumen obliteration in 84% of patients. However, false lumen obliteration beyond the stented segment appears necessary to prevent late aneurysmal degeneration of the distal aorta. (J Vasc Surg 2015;62:600-5.)
Acute aortic dissection (AD) is the most common catastrophic event affecting the aorta, with an incidence exceeding that of ruptured abdominal aortic aneurysm. When it is uncomplicated, type B AD is managed medically because of the traditionally high morbidity and mortality rates associated with open graft replacement of the proximal descending thoracic aorta.1 However, when type B AD is complicated by the malperfusion syndrome, rapid aortic expansion, or rupture, emergent intervention is necessary to prevent death.2-4 Because patients with From the Division of Vascular and Endovascular Surgery, Department of Surgery, Massachusetts General Hospital, Harvard Medical School. Author conflict of interest: none. Presented at the Fortieth Annual Meeting of the New England Society for Vascular Surgery, Stowe, Vt, September 27-29, 2013. Correspondence: Mark F. Conrad, MD, MMSc, Massachusetts General Hospital, WACC 4, 15 Parkman St, Boston, MA 02114 (e-mail: [email protected]). The editors and reviewers of this article have no relevant financial relationships to disclose per the JVS policy that requires reviewers to decline review of any manuscript for which they may have a conflict of interest. 0741-5214 Copyright Ó 2015 by the Society for Vascular Surgery. Published by Elsevier Inc. http://dx.doi.org/10.1016/j.jvs.2015.03.064
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complicated type B AD often present in extremis, the mortality of open repair can be as high as 69%.5-8 These poor results have created an opportunity to pursue other methods of treatment in this high-risk population. In 1999, thoracic endovascular aortic repair (TEVAR) of complicated acute type B dissections with stent graft coverage of the proximal entry tear was described in two sentinel reports.9,10 These were met with early enthusiasm because it seemed intuitive that a less invasive method of sealing the proximal entry tear would lead to a lower morbidity and mortality in this high-risk cohort of patients. Indeed, a review of the Medicare database during the early years of TEVAR showed that in 2004 (the year before the first TEVAR device became commercially available in the United States), only 13% of interventions for dissection were performed with TEVAR, yet by 2007, this number had significantly increased to 43% (P < .0001).11 Since then, several prospective trials that focused on the use of TEVAR in patients with complicated type B AD have shown that the 30-day mortality is 5% to 16%.12-14 This is significantly lower than in the historical controls of open repair in this high-risk population, and in most aortic centers including those that participate in the International Registry of Acute Aortic Dissection (IRAD), TEVAR has
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become first-line therapy for anatomically suitable patients with complicated type B AD.1 The early favorable results achieved after TEVAR for complicated type B AD are encouraging, but it is unclear whether sealing of the proximal entry tear with a stent graft will prevent long-term aneurysmal degeneration and improve survival over best medical therapy in uncomplicated patients. The Investigation of Stent Grafts in Aortic Dissection (INSTEAD) trial randomized patients with subacute, uncomplicated type B AD into TEVAR and best medical therapy cohorts. There was no difference in 30day mortality between the groups, and the 2-year survival was actually lower in the TEVAR cohort (96% medical vs 89% TEVAR; P ¼ .15), probably secondary to a periprocedural mortality of 3%.15 However, the TEVAR cohort showed early positive aortic remodeling by 1 year of follow-up.15 Indeed, our previous cohort of patients who underwent TEVAR for acute complicated type B AD had similar results at 1 year, in which 90% of patients experienced false lumen thrombosis with stabilization of the total aortic diameter across the stented segment.16 Long-term data regarding aortic remodeling after TEVAR for acute type B AD are lacking. The goal of this study was to evaluate the long-term structural changes (aortic remodeling) in the thoracic aorta after TEVAR performed for acute complicated type B AD. METHODS The study cohort consisted of 31 patients who underwent TEVAR for complicated Stanford type B AD between August 2005 and August 2009 and had at least 1 year of follow-up imaging. Patients were considered to have a complicated course if they presented with the malperfusion syndrome, refractory hypertension, rupture or impending rupture, or intractable pain as previously defined.16 There were 15 patients treated as part of an industry-sponsored trial (TAG-0401); the remaining 16 TEVARs were performed at our institution. Demographic and clinical factors were collected retrospectively for each patient, as were long-term follow-up data. Comorbidities such as hypertension and chronic obstructive pulmonary disease were documented as part of the patient’s history regardless of current medications or past interventions. Renal insufficiency was defined as a baseline creatinine concentration of $1.5 mg/dL. The primary clinical end point was longterm anatomic follow-up based on serial computed tomography (CT) scanning. TAG-0401. The Gore TAG-0401 study is a prospective, nonrandomized, literature-controlled, multicenter trial of TEVAR of complex aortic diseases that enrolled patients between August 2005 and February 2007. There are three arms to the study, and 15 of the original 19 patients enrolled in the acute complicated type B AD arm had at least 1-year imaging follow-up and were included in the current patient cohort. The details of the 0401 trial have been previously published.12,16 In brief, all patients presented with acute complicated type B AD. Patients were imaged with non-contrast-enhanced and
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contrast-enhanced, thin-slice (1-2.5 mm) spiral CT with multiplanar reconstruction of the chest, abdomen, and pelvis to confirm study eligibility and for preprocedure planning. Patients were then observed with serial CT scans at 30 days, 6 months, 1 year, and yearly afterward with planned completion at 5 years. The protocol and procedures of the TAG-0401 trial were approved by the Food and Drug Administration and the individual Institutional Review Boards of each participating center. Patients or their surrogates signed a research informed consent before participation in this study. Operative details. The details of the performance of TEVAR at the Massachusetts General Hospital have been previously described.16 In brief, the procedures are performed in the endovascular operating suite equipped with digital subtraction angiography by participating vascular surgeons. All procedures were performed under general anesthesia, and spinal drains were placed at the discretion of the operating surgeon. Stent grafts were introduced into the aorta through a cutdown on the common femoral artery, and iliac conduits were used in patients with unsuitable iliac vessels for stent graft delivery (two patients in the Massachusetts General Hospital cohort). All patients underwent seal of the proximal entry tear at the level of the left subclavian artery with a covered stent graft, and the left subclavian artery was covered when necessary to obtain a 2-cm proximal seal zone. True lumen access was confirmed by intravascular ultrasound, and this was also used to define the relationship of the dissection flap to the visceral and renal arteries. Most patients were treated with a single endograft prosthesis, and additional pieces were placed only when the initial graft did not produce the desired result of coverage of the entry tear and expansion of the true lumen as determined by intraoperative intravascular ultrasound and angiography. Balloon angioplasty of the proximal seal zone was avoided if possible to prevent retrograde extension of the dissection into the aortic arch. Contrast angiography was performed sparingly and limited to hand injections of selected branch arteries to prove that the catheter or wire was beyond the dissection and in the true lumen of “normal” artery. This practice limits the load of contrast material during the procedure, thus avoiding further insult to the kidneys. Objective evidence of malperfusion was confirmed by the presence of a gradient between the aortic root and branch (not aorta) end-hole catheter pressures as described by Barnes et al.17 Bare-metal stents were placed at the origin of the visceral and renal vessels when necessary to ensure adequate end-organ blood flow. Anatomic follow-up. Follow-up CT angiography (CTA) of the chest, abdomen, and pelvis was performed at 1 month, 6 months, 1 year, and then yearly thereafter. Images from these scans were reviewed at each time point and compared with the baseline imaging obtained before the TEVAR procedure. Diametric measurements were obtained along the stented segment of the descending thoracic aorta. The measurements obtained included the largest diameter of stented aorta (SMAX), the largest
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diameter of the stented true lumen (STL), and the largest diameter of the stented false lumen (SFL) at each time point. The degree of false lumen thrombosis was also documented as none, partial, or complete, as appropriate. Measurements were also taken in the nonstented portion of the descending thoracic aorta and through the visceral segment. Statistics. Descriptive statistics were performed on the available variables for the entire study cohort (31 patients). Differences in aortic diameter measurements over time were determined by a mixed effect analysis of variance model of repeated measures. A P value of .05 was considered significant. RESULTS There were 31 patients during the study period who underwent TEVAR for acute type B AD and had at least 1-year imaging follow-up. The average age of the cohort was 56 years (range, 38-77 years), and 29 patients (94%) had a history of hypertension. Patient demographics associated with this cohort are summarized in Table I. All patients underwent TEVAR for complications related to their acute dissection, and 18 patients (58%) had more than one indication for intervention (Table II). The average length of aorta covered by stent grafts was 19.4 cm (range, 10-29 cm). An additional bare-metal stent was used in three patients (10%) to further expand the true lumen in the distal descending aorta, and bare-metal stents were used in visceral branches in six patients (19%; eight renal artery stents and one superior mesenteric artery stent). The left subclavian artery was covered to ensure an adequate proximal seal zone in 22 patients (71%). To be included in the study, patients had to be alive for at least 1 year after the indexed procedure and to have had CTA imaging follow-up. There were no late deaths in the cohort. The average time to the last follow-up CTA was 42 months (range, 14-98 months). The average SMAX rose slightly from baseline at 1 month, probably related to stent graft oversizing, but then returned to near baseline levels at 1 year and late scans (P ¼ NS; Fig 1). The average STL increased significantly from 18.8 mm at baseline to 32.4 mm at 1 month and then continued to increase over time (P < .001; Fig 2). The average SFL decreased significantly from 22 mm at baseline to 8.7 mm at 1 month, and it was 2.5 mm on long-term follow-up (P < .001; Fig 3). Complete obliteration of the false lumen was seen in 26 patients (84%) on the final CTA scan. There was one patient who experienced significant aortic growth and underwent reintervention for aneurysmal degeneration of the aorta. He initially presented with iliac and visceral ischemia and was treated with a single-piece 36-mm-diameter by 157-mm-length Cook Zenith stent graft (Cook Medical, Bloomington, Ind); 18 months later, he developed aneurysmal degeneration distal to the stent graft and underwent extension by 10 cm, with subsequent obliteration of the false lumen and stabilization of the aorta. When the unstented segment of the descending thoracic aorta was evaluated, only five patients (16%) had
Table I. Patient demographics Total cohort, No. (%) Age, years Male gender White race Hypertension Chronic obstructive pulmonary disease Coronary artery disease History of stroke Renal insufficiency DeBakey type IIIb dissection
55 23 24 29 5 2 8 5 26
(38-77) (74) (77) (94) (16) (6) (26) (16) (81)
Table II. Indication for thoracic endovascular aortic repair (TEVAR) Total cohort, No. (%) Malperfusion Refractory hypertension Rupture Uncontrolled pain Multiple indications (>1)
19 10 14 10 18
(61) (32) (45) (32) (58)
a maximum aortic diameter that was stable or decreased over time. The remaining 84% showed some growth compared with the initial postoperative study (29.9 mm at baseline vs 34.1 mm; P ¼ .014); the average maximum aortic diameter increased by 17.5%. The average true lumen of the unstented thoracic aortic segment increased over time as well, from 15 mm at baseline to 22.5 mm (P < .001), and the average true lumen increased by 11%. The average false lumen diameter in the unstented segment did not change over time (18 mm at baseline vs 15 mm; P ¼ NS; Fig 4). False lumen thrombosis had a significant effect on reduction of aortic growth as the visceral segment of patients with a patent false lumen showed significantly more growth than in patients with a thrombosed false lumen (31% patent false lumen vs 3% thrombosed false lumen; P ¼ .004). There were no visceral artery occlusions identified on follow-up imaging. DISCUSSION The goals of endovascular coverage of the entry tear of an acute complicated type B AD are to prevent early death from malperfusion or rupture and to slow late aneurysmal dilation of the aorta through the promotion of remodeling. Previous work from our group documented early (1-year) aortic remodeling after TEVAR for acute complicated type B AD.16 The current study is one of the first to show that this persists across the stented aortic segment during longer follow-up (average follow-up of 42 months) as evidenced by a significant increase in the STL, a significant decrease in the SFL, and overall stabilization of the SMAX. In addition, only one patient (3%) required intervention for aneurysmal degeneration during follow-up, and there were no late ruptures in this cohort. These results are in stark contrast to previous natural history studies of medically treated type B AD, wherein up to 40% of patients
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Fig 1. The average maximum aortic diameter along the stented segment was essentially unchanged from baseline through 42-month follow-up.
Fig 2. The average true lumen diameter along the stented segment of the aorta rose significantly from baseline to 1 month and then remained stable during long-term follow-up.
experienced rupture or aneurysmal degeneration in the first 4 years.18,19 It is likely that the continued positive effect that TEVAR has on the dissected aorta will make it the standard treatment for all patients who present with acute type B AD regardless of their classification as complex or uncomplicated. Support for the superiority of TEVAR over open repair or medical therapy alone in patients with acute complicated type B AD continues to grow. The Gore 0401 trial was a prospective, multicenter trial of TEVAR of aortic catastrophes. The complicated dissection arm of this trial contained 19 patients and showed a 30-day mortality of 16%, which was significantly lower than that achieved by the historical open controls (16% vs 24%; P ¼ .04).12 The Study of Thoracic Aortic Type B Dissection Using Endoluminal Repair (STABLE) was a prospective, multicenter trial that enrolled 40 patients with complicated type B AD who were treated with TEVAR within 90 days of symptom onset. This trial also showed favorable early results with a 30-day mortality of 5%.13 A review of the Medicare database showed that of 2701 patients treated with acute type B AD during a 4-year period, 31% were treated with TEVAR with a mortality of 9.1%, which was significantly lower than that of open repair (9.1% vs 21%; P < .001).11 In addition, the Society for Vascular Surgery Outcomes Committee pooled data from five centers with investigational device exemption studies of TEVAR for acute complicated type B AD and reported a 30-day mortality of 10.6%.14 Finally, two recently completed, industrysponsored trials of TEVAR for acute complicated type B AD, which in aggregate contain some 100 patients so managed, have reported similar early results, specifically an 8% 30-day mortality, wherein all patients were treated for rupture or malperfusion. It is likely that the mortality rate of TEVAR in patients with acute complicated type B AD should range between 5% and 10%, depending on the patient’s condition at presentation. The INSTEAD trial is a prospective, randomized, multicenter trial performed in Europe to assess the
treatment of subacute and chronic uncomplicated type B AD with either optimal medical therapy alone or optimal medical therapy in combination with TEVAR.20 Patients were randomized to medical therapy alone and TEVAR cohorts. There was no difference in survival between the two cohorts at 2 years. However, this served as a breakpoint between the groups as the 5-year survival was superior in the TEVAR cohort.21 Recent data from IRAD examined 1129 consecutive patients with acute type B AD, of whom 24.4% were treated with an early TEVAR. Similar to the INSTEAD trial, there was no difference in early survival between the two cohorts, but at 5 years, it was significantly higher in patients who had undergone TEVAR (84.5% vs 71%; P ¼ .018).22 Finally, in a recent natural history study of 298 patients with acute type B AD who were initially managed medically at our institution, the 6-year survival in patients who eventually required aortic intervention was significantly higher than in those who were treated with medical therapy alone (76.4% vs 59.3%; P ¼ .018). Although the exact mechanism for this survival advantage is unknown, there is a clear trend that favors TEVAR over medical therapy in patients with acute type B AD. Despite the early success of TEVAR in patients with acute complicated type B AD, medical therapy remains the standard of care for patients with uncomplicated dissections, mainly because of the high mortality associated with open repair of the proximal descending thoracic aorta in the acute setting3,23,24 and the fact that early results with medical management of uncomplicated dissections are excellent.20,23,25 However, the long-term consequence of medical management is aneurysmal degeneration and aortic rupture in up to 40% of patients.18,26 This is prevented by aortic remodeling around the stented segment of aorta. Eriksson et al27 evaluated 17 patients with DeBakey type IIIa dissections treated with TEVAR and showed an overall decrease in the maximum aortic diameter during an average follow-up of 2.9 years (44 mm to 39 mm; P ¼ .01). In the INSTEAD trial, the maximum aortic diameter of the patients treated with TEVAR showed minimal
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Fig 3. The average false lumen diameter along the stented segment of the aorta decreased significantly over time.
change during 5 years (44.1 mm at baseline to 44.5 mm at 5 years; P ¼ NS), whereas patients who were medically treated had an increase in maximum aortic diameter during 5 years (43.6 mm to 56.4 mm; P < .0001).21 In the current study, TEVAR led to aortic remodeling through stabilization of the maximal aortic diameter of the stented segment during an average follow-up of 4.2 years. The key to aortic remodeling is complete obliteration of the primary entry tear and the consequent promotion of false lumen thrombosis. Lombardi et al28 reported an increase in false lumen thrombosis over time from 0% at baseline to 43.5% at 2 years, and growth of the abdominal aorta was mainly attributed to false lumen expansion. In the INSTEAD trial, there was a dramatic decrease in the false lumen diameter from 29.3 mm to 10.4 mm, and complete false lumen thrombosis was confirmed in 90.6% of patients during 5 years.21 Hanna et al29 showed false lumen thrombosis in 72% of patients at an average follow-up of 33 months, and all patients who required late intervention had a patent false lumen. The obliteration of the false lumen in the current study led to a dramatic decrease in false lumen diameter from baseline to long-term followup, and 84% of patients had total false lumen obliteration. This had implications for the nonstented aorta as patients with a patent false lumen demonstrated an average growth of the unstented aorta of >30% vs 3% in patients whose false lumen had thrombosed. It has been suggested that further false lumen thrombosis may be promoted by extending stent coverage across the entire descending thoracic aorta with large, self-expanding bare-metal stents. Hofferbeth et al30 compared this technique to a cohort of patients treated with coverage of the proximal entry tear alone and found that patients with more descending thoracic aorta coverage were more likely to have complete false lumen thrombosis in the thoracic aorta (72% vs 46%) and abdominal aorta (40% vs 15%). There are several limitations to this study. The main one involves the fact that this is a combination of data from a multicenter trial and a single-institution experience. Although the trial data were prospective and controlled,
Fig 4. Changes in the maximum aortic, true lumen, and false lumen diameters in the unstented segment of the aorta from baseline to 42-month follow-up.
the addition of our own experience could inject bias into the results as 50% of the patients are now from a single institution. In addition, static measurement of maximum diameters may not be the best way to quantify structural changes in the aorta over time, but it remains the most clinically relevant because it provides the threshold for surgical intervention. Finally, aneurysmal degeneration occurs during a several-year period, and although TEVAR has clearly slowed the progression of this disease, longer anatomic follow-up will be necessary to determine if the remodeling phenomenon remains durable over the lifetime of these often young patients. CONCLUSIONS The management of acute type B AD has evolved during the last decade with the availability and early success of TEVAR coverage of the proximal entry tear. There is clearly an early mortality benefit of TEVAR in patients with complicated type B AD over open surgery and a trend toward improved 5-year survival for TEVAR over medical therapy. TEVAR appears to promote aortic remodeling over time as seen by obliteration of the false lumen and stabilization of the maximum aortic diameter. Total obliteration of the false lumen appears to be the key factor to aneurysmal prevention as aortic growth in the nonstented segment was significantly higher in patients with a patent false lumen. Indeed, the use of TEVAR in complicated acute dissection holds promise to reduce early and late complications. These results are sufficiently favorable to warrant consideration of the use of TEVAR in patients with uncomplicated acute type B dissection, and it is likely that this will be the standard of care in the future. AUTHOR CONTRIBUTIONS Conception and design: MC, CK, RL, VP, RC Analysis and interpretation: MC, CK, RL, VP, RC Data collection: MC, SC Writing the article: MC, SC, RC Critical revision of the article: MC, SC, RC
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Final approval of the article: MC, SC, EE, CK, RL, VP, RC Statistical analysis: MC, EE Obtained funding: Not applicable Overall responsibility: MC REFERENCES 1. Suzuki T, Mehta RH, Ince H, Nagai R, Sakomura Y, Weber F, et al. Clinical profiles and outcomes of acute type B aortic dissection in the current era: lessons from the International Registry of Aortic Dissection (IRAD). Circulation 2003;108(Suppl 1):II312-7. 2. Cambria RP, Brewster DC, Moncure AC, Steinberg FL, Abbott WM. Spontaneous aortic dissection in the presence of coexistent or previously repaired atherosclerotic aortic aneurysm. Ann Surg 1988;208:619-24. 3. Estrera AL, Miller CC 3rd, Safi HJ, Goodrick JS, Keyhani A, Porat EE, et al. Outcomes of medical management of acute type B aortic dissection. Circulation 2006;114:I384-9. 4. Tsai TT, Evangelista A, Nienaber CA, Myrmel T, Meinhardt G, Cooper JV, et al. Partial thrombosis of the false lumen in patients with acute type B aortic dissection. N Engl J Med 2007;357:349-59. 5. Cambria RP, Brewster DC, Gertler J, Moncure AC, Gusberg R, Tilson MD, et al. Vascular complications associated with spontaneous aortic dissection. J Vasc Surg 1988;7:199-209. 6. Coselli JS. Thoracoabdominal aortic aneurysms: experience with 372 patients. J Card Surg 1994;9:638-47. 7. Neya K, Omoto R, Kyo S, Kimura S, Yokote Y, Takamoto S, et al. Outcome of Stanford type B acute aortic dissection. Circulation 1992;86:II1-7. 8. Trimarchi S, Nienaber CA, Rampoldi V, Myrmel T, Suzuki T, Bossone E, et al. Role and results of surgery in acute type B aortic dissection: insights from the International Registry of Acute Aortic Dissection (IRAD). Circulation 2006;114:I357-64. 9. Mitchell RS, Miller DC, Dake MD, Semba CP, Moore KA, Sakai T. Thoracic aortic aneurysm repair with an endovascular stent graft: the “first generation.” Ann Thorac Surg 1999;67:1971-4; discussion: 1979-80. 10. Nienaber CA, Fattori R, Lund G, Dieckmann C, Wolf W, von Kodolitsch Y, et al. Nonsurgical reconstruction of thoracic aortic dissection by stent-graft placement. N Engl J Med 1999;340:1539-45. 11. Conrad MF, Ergul EA, Patel VI, Paruchuri V, Kwolek CJ, Cambria RP. Management of diseases of the descending thoracic aorta in the endovascular era: a Medicare population study. Ann Surg 2010;252:603-10. 12. Cambria RP, Crawford RS, Cho JS, Bavaria J, Farber M, Lee WA, et al. A multicenter clinical trial of endovascular stent graft repair of acute catastrophes of the descending thoracic aorta. J Vasc Surg 2009;50: 1255-64. e1-4. 13. Lombardi JV, Cambria RP, Nienaber CA, Chiesa R, Teebken O, Lee A, et al; STABLE investigators. Prospective multicenter clinical trial (STABLE) on the endovascular treatment of complicated type B aortic dissection using a composite device design. J Vasc Surg 2012;55: 629-40.e2. 14. White RA, Miller DC, Criado FJ, Dake MD, Diethrich EB, Greenberg RK, et al; Multidisciplinary Society for Vascular Surgery Outcomes Committee. Report on the results of thoracic endovascular aortic repair for acute, complicated, type B aortic dissection at 30 days and 1 year from a multidisciplinary subcommittee of the Society for Vascular Surgery Outcomes Committee. J Vasc Surg 2011;53: 1082-90. 15. Nienaber CA, Rousseau H, Eggebrecht H, Kische S, Fattori R, Rehders TC, et al; INSTEAD Trial. Randomized comparison of
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strategies for type B aortic dissection: the INvestigation of STEnt Grafts in Aortic Dissection (INSTEAD) trial. Circulation 2009;120: 2519-28. Conrad MF, Crawford RS, Kwolek CJ, Brewster DC, Brady TJ, Cambria RP. Aortic remodeling after endovascular repair of acute complicated type B aortic dissection. J Vasc Surg 2009;50:510-7. Barnes DM, Williams DM, Dasika NL, Patel HJ, Weder AB, Stanley JC, et al. A single-center experience treating renal malperfusion after aortic dissection with central aortic fenestration and renal artery stenting. J Vasc Surg 2008;47:903-10; discussion: 910-1. DeBakey ME, McCollum CH, Crawford ES, Morris GC Jr, Howell J, Noon GP, et al. Dissection and dissecting aneurysms of the aorta: twenty-year follow-up of five hundred twenty-seven patients treated surgically. Surgery 1982;92:1118-34. Juvonen T, Ergin MA, Galla JD, Lansman SL, McCullough JN, Nguyen K, et al. Risk factors for rupture of chronic type B dissections. J Thorac Cardiovasc Surg 1999;117:776-86. Nienaber CA, Zannetti S, Barbieri B, Kische S, Schareck W, Rehders TC. Investigation of stent grafts in patients with type B aortic dissection: design of the INSTEAD trialda prospective, multicenter, European randomized trial. Am Heart J 2005;149:592-9. Nienaber CA, Kische S, Rousseau H, Eggebrecht H, Rehders TC, Kundt G, et al; INSTEAD-XL trial. Endovascular repair of type B aortic dissection: long-term results of the randomized investigation of stent grafts in aortic dissection trial. Circ Cardiovasc Interv 2013;6:407-16. Fattori R, Montgomery D, Lovato L, Kische S, Di Eusanio M, Ince H, et al. Survival after endovascular therapy in patients with type B aortic dissection: a report from the International Registry of Acute Aortic Dissection (IRAD). JACC Cardiovasc Interv 2013;6:876-82. Tsai TT, Evangelista A, Nienaber CA, Trimarchi S, Sechtem U, Fattori R, et al. Long-term survival in patients presenting with type A acute aortic dissection: insights from the International Registry of Acute Aortic Dissection (IRAD). Circulation 2006;114:I350-6. Winnerkvist A, Lockowandt U, Rasmussen E, Radegran K. A prospective study of medically treated acute type B aortic dissection. Eur J Vasc Endovasc Surg 2006;32:349-55. Umana JP, Lai DT, Mitchell RS, Moore KA, Rodriguez F, Robbins RC, et al. Is medical therapy still the optimal treatment strategy for patients with acute type B aortic dissections? J Thorac Cardiovasc Surg 2002;124:896-910. Juvonen T, Ergin MA, Galla JD, Lansman SL, Nguyen KH, McCullough JN, et al. Prospective study of the natural history of thoracic aortic aneurysms. Ann Thorac Surg 1997;63:1533-45. Eriksson MO, Steuer J, Wanhainen A, Thelin S, Eriksson LG, Nyman R. Morphologic outcome after endovascular treatment of complicated type B aortic dissection. J Vasc Interv Radiol 2013;24: 1826-33. Lombardi JV, Cambria RP, Nienaber CA, Chiesa R, Mossop P, Haulon S; STABLE investigators. Aortic remodeling after endovascular treatment of complicated type B aortic dissection with the use of a composite device design. J Vasc Surg 2014;59:1544-54. Hanna JM, Andersen ND, Ganapathi AM, McCann RL, Hughes GC. Five-year results for endovascular repair of acute complicated type B aortic dissection. J Vasc Surg 2014;59:96-106. Hofferberth SC, Newcomb AE, Yii MY, Yap KK, Boston RC, Nixon IK, et al. Combined proximal stent grafting plus distal bare metal stenting for management of aortic dissection: superior to standard endovascular repair? J Thorac Cardiovasc Surg 2012;144:956-62; discussion: 962.
Submitted Jan 11, 2015; accepted Mar 20, 2015.
Late aortic remodeling persists in the stented segment after endovascular repair of acute complicated type B aortic dissection Mark F. Conrad, MD, MMSc, Stephanie Carvalho, BS, Emel Ergul, MS, Christopher J. Kwolek, MD, R. Todd Lancaster, MD, MPH, Virendra I. Patel, MD, MPH, and Richard P. Cambria, MD, Boston, Mass Objective: Thoracic endovascular aortic repair (TEVAR) for acute complicated type B aortic dissection (AD) promotes early positive aortic remodeling. However, little is known about the long-term effect of TEVAR on the dissected aorta, which is the goal of this study. Methods: Between August 2005 and August 2009, 31 patients with complicated type B AD were treated with TEVAR and had >1-year follow-up imaging. Computed tomography angiograms obtained at 1 month, 1 year, and long term (average, 42 months) were compared with baseline scans. The largest diameters of the stented thoracic aorta, stented true lumen, and stented false lumen were recorded at each time point, as were the values in the unstented distal thoracic aorta and the abdominal aorta. Changes over time were evaluated by a mixed effect analysis of variance model of repeated measures. Results: The average age of the cohort was 56 years, and 74% were male. Indications for TEVAR were as follows: 61% malperfusion, 32% refractory hypertension, 45% impending rupture, and 32% persistent pain; 58% had more than one indication. All patients were treated in the acute phase within 7 days of the initial presentation. The average length of aorta covered was 19 cm. Observation of the stented segment over time showed that the maximum diameter of the stented thoracic aorta was stable (P [ NS), the diameter of the stented true lumen increased (P < .001), and the diameter of the stented false lumen decreased (P < .001); 84% had complete false lumen obliteration across the stented aortic segment. Observation of the uncovered thoracic aorta over time showed that the maximum diameter increased (P [ .014), as did the visceral segment of the aorta (P < .001). The average growth of the visceral segment was 31% in patients with a patent false lumen vs 3% in those with a thrombosed false lumen (P [ .004). One patient had aneurysmal degeneration of the false lumen and required an additional endograft at 18 months. Conclusions: TEVAR of acute AD promotes long-term remodeling across the stented segment, with false lumen obliteration in 84% of patients. However, false lumen obliteration beyond the stented segment appears necessary to prevent late aneurysmal degeneration of the distal aorta. (J Vasc Surg 2015;62:600-5.)
Acute aortic dissection (AD) is the most common catastrophic event affecting the aorta, with an incidence exceeding that of ruptured abdominal aortic aneurysm. When it is uncomplicated, type B AD is managed medically because of the traditionally high morbidity and mortality rates associated with open graft replacement of the proximal descending thoracic aorta.1 However, when type B AD is complicated by the malperfusion syndrome, rapid aortic expansion, or rupture, emergent intervention is necessary to prevent death.2-4 Because patients with From the Division of Vascular and Endovascular Surgery, Department of Surgery, Massachusetts General Hospital, Harvard Medical School. Author conflict of interest: none. Presented at the Fortieth Annual Meeting of the New England Society for Vascular Surgery, Stowe, Vt, September 27-29, 2013. Correspondence: Mark F. Conrad, MD, MMSc, Massachusetts General Hospital, WACC 4, 15 Parkman St, Boston, MA 02114 (e-mail: [email protected]). The editors and reviewers of this article have no relevant financial relationships to disclose per the JVS policy that requires reviewers to decline review of any manuscript for which they may have a conflict of interest. 0741-5214 Copyright Ó 2015 by the Society for Vascular Surgery. Published by Elsevier Inc. http://dx.doi.org/10.1016/j.jvs.2015.03.064
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complicated type B AD often present in extremis, the mortality of open repair can be as high as 69%.5-8 These poor results have created an opportunity to pursue other methods of treatment in this high-risk population. In 1999, thoracic endovascular aortic repair (TEVAR) of complicated acute type B dissections with stent graft coverage of the proximal entry tear was described in two sentinel reports.9,10 These were met with early enthusiasm because it seemed intuitive that a less invasive method of sealing the proximal entry tear would lead to a lower morbidity and mortality in this high-risk cohort of patients. Indeed, a review of the Medicare database during the early years of TEVAR showed that in 2004 (the year before the first TEVAR device became commercially available in the United States), only 13% of interventions for dissection were performed with TEVAR, yet by 2007, this number had significantly increased to 43% (P < .0001).11 Since then, several prospective trials that focused on the use of TEVAR in patients with complicated type B AD have shown that the 30-day mortality is 5% to 16%.12-14 This is significantly lower than in the historical controls of open repair in this high-risk population, and in most aortic centers including those that participate in the International Registry of Acute Aortic Dissection (IRAD), TEVAR has
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become first-line therapy for anatomically suitable patients with complicated type B AD.1 The early favorable results achieved after TEVAR for complicated type B AD are encouraging, but it is unclear whether sealing of the proximal entry tear with a stent graft will prevent long-term aneurysmal degeneration and improve survival over best medical therapy in uncomplicated patients. The Investigation of Stent Grafts in Aortic Dissection (INSTEAD) trial randomized patients with subacute, uncomplicated type B AD into TEVAR and best medical therapy cohorts. There was no difference in 30day mortality between the groups, and the 2-year survival was actually lower in the TEVAR cohort (96% medical vs 89% TEVAR; P ¼ .15), probably secondary to a periprocedural mortality of 3%.15 However, the TEVAR cohort showed early positive aortic remodeling by 1 year of follow-up.15 Indeed, our previous cohort of patients who underwent TEVAR for acute complicated type B AD had similar results at 1 year, in which 90% of patients experienced false lumen thrombosis with stabilization of the total aortic diameter across the stented segment.16 Long-term data regarding aortic remodeling after TEVAR for acute type B AD are lacking. The goal of this study was to evaluate the long-term structural changes (aortic remodeling) in the thoracic aorta after TEVAR performed for acute complicated type B AD. METHODS The study cohort consisted of 31 patients who underwent TEVAR for complicated Stanford type B AD between August 2005 and August 2009 and had at least 1 year of follow-up imaging. Patients were considered to have a complicated course if they presented with the malperfusion syndrome, refractory hypertension, rupture or impending rupture, or intractable pain as previously defined.16 There were 15 patients treated as part of an industry-sponsored trial (TAG-0401); the remaining 16 TEVARs were performed at our institution. Demographic and clinical factors were collected retrospectively for each patient, as were long-term follow-up data. Comorbidities such as hypertension and chronic obstructive pulmonary disease were documented as part of the patient’s history regardless of current medications or past interventions. Renal insufficiency was defined as a baseline creatinine concentration of $1.5 mg/dL. The primary clinical end point was longterm anatomic follow-up based on serial computed tomography (CT) scanning. TAG-0401. The Gore TAG-0401 study is a prospective, nonrandomized, literature-controlled, multicenter trial of TEVAR of complex aortic diseases that enrolled patients between August 2005 and February 2007. There are three arms to the study, and 15 of the original 19 patients enrolled in the acute complicated type B AD arm had at least 1-year imaging follow-up and were included in the current patient cohort. The details of the 0401 trial have been previously published.12,16 In brief, all patients presented with acute complicated type B AD. Patients were imaged with non-contrast-enhanced and
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contrast-enhanced, thin-slice (1-2.5 mm) spiral CT with multiplanar reconstruction of the chest, abdomen, and pelvis to confirm study eligibility and for preprocedure planning. Patients were then observed with serial CT scans at 30 days, 6 months, 1 year, and yearly afterward with planned completion at 5 years. The protocol and procedures of the TAG-0401 trial were approved by the Food and Drug Administration and the individual Institutional Review Boards of each participating center. Patients or their surrogates signed a research informed consent before participation in this study. Operative details. The details of the performance of TEVAR at the Massachusetts General Hospital have been previously described.16 In brief, the procedures are performed in the endovascular operating suite equipped with digital subtraction angiography by participating vascular surgeons. All procedures were performed under general anesthesia, and spinal drains were placed at the discretion of the operating surgeon. Stent grafts were introduced into the aorta through a cutdown on the common femoral artery, and iliac conduits were used in patients with unsuitable iliac vessels for stent graft delivery (two patients in the Massachusetts General Hospital cohort). All patients underwent seal of the proximal entry tear at the level of the left subclavian artery with a covered stent graft, and the left subclavian artery was covered when necessary to obtain a 2-cm proximal seal zone. True lumen access was confirmed by intravascular ultrasound, and this was also used to define the relationship of the dissection flap to the visceral and renal arteries. Most patients were treated with a single endograft prosthesis, and additional pieces were placed only when the initial graft did not produce the desired result of coverage of the entry tear and expansion of the true lumen as determined by intraoperative intravascular ultrasound and angiography. Balloon angioplasty of the proximal seal zone was avoided if possible to prevent retrograde extension of the dissection into the aortic arch. Contrast angiography was performed sparingly and limited to hand injections of selected branch arteries to prove that the catheter or wire was beyond the dissection and in the true lumen of “normal” artery. This practice limits the load of contrast material during the procedure, thus avoiding further insult to the kidneys. Objective evidence of malperfusion was confirmed by the presence of a gradient between the aortic root and branch (not aorta) end-hole catheter pressures as described by Barnes et al.17 Bare-metal stents were placed at the origin of the visceral and renal vessels when necessary to ensure adequate end-organ blood flow. Anatomic follow-up. Follow-up CT angiography (CTA) of the chest, abdomen, and pelvis was performed at 1 month, 6 months, 1 year, and then yearly thereafter. Images from these scans were reviewed at each time point and compared with the baseline imaging obtained before the TEVAR procedure. Diametric measurements were obtained along the stented segment of the descending thoracic aorta. The measurements obtained included the largest diameter of stented aorta (SMAX), the largest
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diameter of the stented true lumen (STL), and the largest diameter of the stented false lumen (SFL) at each time point. The degree of false lumen thrombosis was also documented as none, partial, or complete, as appropriate. Measurements were also taken in the nonstented portion of the descending thoracic aorta and through the visceral segment. Statistics. Descriptive statistics were performed on the available variables for the entire study cohort (31 patients). Differences in aortic diameter measurements over time were determined by a mixed effect analysis of variance model of repeated measures. A P value of .05 was considered significant. RESULTS There were 31 patients during the study period who underwent TEVAR for acute type B AD and had at least 1-year imaging follow-up. The average age of the cohort was 56 years (range, 38-77 years), and 29 patients (94%) had a history of hypertension. Patient demographics associated with this cohort are summarized in Table I. All patients underwent TEVAR for complications related to their acute dissection, and 18 patients (58%) had more than one indication for intervention (Table II). The average length of aorta covered by stent grafts was 19.4 cm (range, 10-29 cm). An additional bare-metal stent was used in three patients (10%) to further expand the true lumen in the distal descending aorta, and bare-metal stents were used in visceral branches in six patients (19%; eight renal artery stents and one superior mesenteric artery stent). The left subclavian artery was covered to ensure an adequate proximal seal zone in 22 patients (71%). To be included in the study, patients had to be alive for at least 1 year after the indexed procedure and to have had CTA imaging follow-up. There were no late deaths in the cohort. The average time to the last follow-up CTA was 42 months (range, 14-98 months). The average SMAX rose slightly from baseline at 1 month, probably related to stent graft oversizing, but then returned to near baseline levels at 1 year and late scans (P ¼ NS; Fig 1). The average STL increased significantly from 18.8 mm at baseline to 32.4 mm at 1 month and then continued to increase over time (P < .001; Fig 2). The average SFL decreased significantly from 22 mm at baseline to 8.7 mm at 1 month, and it was 2.5 mm on long-term follow-up (P < .001; Fig 3). Complete obliteration of the false lumen was seen in 26 patients (84%) on the final CTA scan. There was one patient who experienced significant aortic growth and underwent reintervention for aneurysmal degeneration of the aorta. He initially presented with iliac and visceral ischemia and was treated with a single-piece 36-mm-diameter by 157-mm-length Cook Zenith stent graft (Cook Medical, Bloomington, Ind); 18 months later, he developed aneurysmal degeneration distal to the stent graft and underwent extension by 10 cm, with subsequent obliteration of the false lumen and stabilization of the aorta. When the unstented segment of the descending thoracic aorta was evaluated, only five patients (16%) had
Table I. Patient demographics Total cohort, No. (%) Age, years Male gender White race Hypertension Chronic obstructive pulmonary disease Coronary artery disease History of stroke Renal insufficiency DeBakey type IIIb dissection
55 23 24 29 5 2 8 5 26
(38-77) (74) (77) (94) (16) (6) (26) (16) (81)
Table II. Indication for thoracic endovascular aortic repair (TEVAR) Total cohort, No. (%) Malperfusion Refractory hypertension Rupture Uncontrolled pain Multiple indications (>1)
19 10 14 10 18
(61) (32) (45) (32) (58)
a maximum aortic diameter that was stable or decreased over time. The remaining 84% showed some growth compared with the initial postoperative study (29.9 mm at baseline vs 34.1 mm; P ¼ .014); the average maximum aortic diameter increased by 17.5%. The average true lumen of the unstented thoracic aortic segment increased over time as well, from 15 mm at baseline to 22.5 mm (P < .001), and the average true lumen increased by 11%. The average false lumen diameter in the unstented segment did not change over time (18 mm at baseline vs 15 mm; P ¼ NS; Fig 4). False lumen thrombosis had a significant effect on reduction of aortic growth as the visceral segment of patients with a patent false lumen showed significantly more growth than in patients with a thrombosed false lumen (31% patent false lumen vs 3% thrombosed false lumen; P ¼ .004). There were no visceral artery occlusions identified on follow-up imaging. DISCUSSION The goals of endovascular coverage of the entry tear of an acute complicated type B AD are to prevent early death from malperfusion or rupture and to slow late aneurysmal dilation of the aorta through the promotion of remodeling. Previous work from our group documented early (1-year) aortic remodeling after TEVAR for acute complicated type B AD.16 The current study is one of the first to show that this persists across the stented aortic segment during longer follow-up (average follow-up of 42 months) as evidenced by a significant increase in the STL, a significant decrease in the SFL, and overall stabilization of the SMAX. In addition, only one patient (3%) required intervention for aneurysmal degeneration during follow-up, and there were no late ruptures in this cohort. These results are in stark contrast to previous natural history studies of medically treated type B AD, wherein up to 40% of patients
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Fig 1. The average maximum aortic diameter along the stented segment was essentially unchanged from baseline through 42-month follow-up.
Fig 2. The average true lumen diameter along the stented segment of the aorta rose significantly from baseline to 1 month and then remained stable during long-term follow-up.
experienced rupture or aneurysmal degeneration in the first 4 years.18,19 It is likely that the continued positive effect that TEVAR has on the dissected aorta will make it the standard treatment for all patients who present with acute type B AD regardless of their classification as complex or uncomplicated. Support for the superiority of TEVAR over open repair or medical therapy alone in patients with acute complicated type B AD continues to grow. The Gore 0401 trial was a prospective, multicenter trial of TEVAR of aortic catastrophes. The complicated dissection arm of this trial contained 19 patients and showed a 30-day mortality of 16%, which was significantly lower than that achieved by the historical open controls (16% vs 24%; P ¼ .04).12 The Study of Thoracic Aortic Type B Dissection Using Endoluminal Repair (STABLE) was a prospective, multicenter trial that enrolled 40 patients with complicated type B AD who were treated with TEVAR within 90 days of symptom onset. This trial also showed favorable early results with a 30-day mortality of 5%.13 A review of the Medicare database showed that of 2701 patients treated with acute type B AD during a 4-year period, 31% were treated with TEVAR with a mortality of 9.1%, which was significantly lower than that of open repair (9.1% vs 21%; P < .001).11 In addition, the Society for Vascular Surgery Outcomes Committee pooled data from five centers with investigational device exemption studies of TEVAR for acute complicated type B AD and reported a 30-day mortality of 10.6%.14 Finally, two recently completed, industrysponsored trials of TEVAR for acute complicated type B AD, which in aggregate contain some 100 patients so managed, have reported similar early results, specifically an 8% 30-day mortality, wherein all patients were treated for rupture or malperfusion. It is likely that the mortality rate of TEVAR in patients with acute complicated type B AD should range between 5% and 10%, depending on the patient’s condition at presentation. The INSTEAD trial is a prospective, randomized, multicenter trial performed in Europe to assess the
treatment of subacute and chronic uncomplicated type B AD with either optimal medical therapy alone or optimal medical therapy in combination with TEVAR.20 Patients were randomized to medical therapy alone and TEVAR cohorts. There was no difference in survival between the two cohorts at 2 years. However, this served as a breakpoint between the groups as the 5-year survival was superior in the TEVAR cohort.21 Recent data from IRAD examined 1129 consecutive patients with acute type B AD, of whom 24.4% were treated with an early TEVAR. Similar to the INSTEAD trial, there was no difference in early survival between the two cohorts, but at 5 years, it was significantly higher in patients who had undergone TEVAR (84.5% vs 71%; P ¼ .018).22 Finally, in a recent natural history study of 298 patients with acute type B AD who were initially managed medically at our institution, the 6-year survival in patients who eventually required aortic intervention was significantly higher than in those who were treated with medical therapy alone (76.4% vs 59.3%; P ¼ .018). Although the exact mechanism for this survival advantage is unknown, there is a clear trend that favors TEVAR over medical therapy in patients with acute type B AD. Despite the early success of TEVAR in patients with acute complicated type B AD, medical therapy remains the standard of care for patients with uncomplicated dissections, mainly because of the high mortality associated with open repair of the proximal descending thoracic aorta in the acute setting3,23,24 and the fact that early results with medical management of uncomplicated dissections are excellent.20,23,25 However, the long-term consequence of medical management is aneurysmal degeneration and aortic rupture in up to 40% of patients.18,26 This is prevented by aortic remodeling around the stented segment of aorta. Eriksson et al27 evaluated 17 patients with DeBakey type IIIa dissections treated with TEVAR and showed an overall decrease in the maximum aortic diameter during an average follow-up of 2.9 years (44 mm to 39 mm; P ¼ .01). In the INSTEAD trial, the maximum aortic diameter of the patients treated with TEVAR showed minimal
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Fig 3. The average false lumen diameter along the stented segment of the aorta decreased significantly over time.
change during 5 years (44.1 mm at baseline to 44.5 mm at 5 years; P ¼ NS), whereas patients who were medically treated had an increase in maximum aortic diameter during 5 years (43.6 mm to 56.4 mm; P < .0001).21 In the current study, TEVAR led to aortic remodeling through stabilization of the maximal aortic diameter of the stented segment during an average follow-up of 4.2 years. The key to aortic remodeling is complete obliteration of the primary entry tear and the consequent promotion of false lumen thrombosis. Lombardi et al28 reported an increase in false lumen thrombosis over time from 0% at baseline to 43.5% at 2 years, and growth of the abdominal aorta was mainly attributed to false lumen expansion. In the INSTEAD trial, there was a dramatic decrease in the false lumen diameter from 29.3 mm to 10.4 mm, and complete false lumen thrombosis was confirmed in 90.6% of patients during 5 years.21 Hanna et al29 showed false lumen thrombosis in 72% of patients at an average follow-up of 33 months, and all patients who required late intervention had a patent false lumen. The obliteration of the false lumen in the current study led to a dramatic decrease in false lumen diameter from baseline to long-term followup, and 84% of patients had total false lumen obliteration. This had implications for the nonstented aorta as patients with a patent false lumen demonstrated an average growth of the unstented aorta of >30% vs 3% in patients whose false lumen had thrombosed. It has been suggested that further false lumen thrombosis may be promoted by extending stent coverage across the entire descending thoracic aorta with large, self-expanding bare-metal stents. Hofferbeth et al30 compared this technique to a cohort of patients treated with coverage of the proximal entry tear alone and found that patients with more descending thoracic aorta coverage were more likely to have complete false lumen thrombosis in the thoracic aorta (72% vs 46%) and abdominal aorta (40% vs 15%). There are several limitations to this study. The main one involves the fact that this is a combination of data from a multicenter trial and a single-institution experience. Although the trial data were prospective and controlled,
Fig 4. Changes in the maximum aortic, true lumen, and false lumen diameters in the unstented segment of the aorta from baseline to 42-month follow-up.
the addition of our own experience could inject bias into the results as 50% of the patients are now from a single institution. In addition, static measurement of maximum diameters may not be the best way to quantify structural changes in the aorta over time, but it remains the most clinically relevant because it provides the threshold for surgical intervention. Finally, aneurysmal degeneration occurs during a several-year period, and although TEVAR has clearly slowed the progression of this disease, longer anatomic follow-up will be necessary to determine if the remodeling phenomenon remains durable over the lifetime of these often young patients. CONCLUSIONS The management of acute type B AD has evolved during the last decade with the availability and early success of TEVAR coverage of the proximal entry tear. There is clearly an early mortality benefit of TEVAR in patients with complicated type B AD over open surgery and a trend toward improved 5-year survival for TEVAR over medical therapy. TEVAR appears to promote aortic remodeling over time as seen by obliteration of the false lumen and stabilization of the maximum aortic diameter. Total obliteration of the false lumen appears to be the key factor to aneurysmal prevention as aortic growth in the nonstented segment was significantly higher in patients with a patent false lumen. Indeed, the use of TEVAR in complicated acute dissection holds promise to reduce early and late complications. These results are sufficiently favorable to warrant consideration of the use of TEVAR in patients with uncomplicated acute type B dissection, and it is likely that this will be the standard of care in the future. AUTHOR CONTRIBUTIONS Conception and design: MC, CK, RL, VP, RC Analysis and interpretation: MC, CK, RL, VP, RC Data collection: MC, SC Writing the article: MC, SC, RC Critical revision of the article: MC, SC, RC
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Final approval of the article: MC, SC, EE, CK, RL, VP, RC Statistical analysis: MC, EE Obtained funding: Not applicable Overall responsibility: MC REFERENCES 1. Suzuki T, Mehta RH, Ince H, Nagai R, Sakomura Y, Weber F, et al. Clinical profiles and outcomes of acute type B aortic dissection in the current era: lessons from the International Registry of Aortic Dissection (IRAD). Circulation 2003;108(Suppl 1):II312-7. 2. Cambria RP, Brewster DC, Moncure AC, Steinberg FL, Abbott WM. Spontaneous aortic dissection in the presence of coexistent or previously repaired atherosclerotic aortic aneurysm. Ann Surg 1988;208:619-24. 3. Estrera AL, Miller CC 3rd, Safi HJ, Goodrick JS, Keyhani A, Porat EE, et al. Outcomes of medical management of acute type B aortic dissection. Circulation 2006;114:I384-9. 4. Tsai TT, Evangelista A, Nienaber CA, Myrmel T, Meinhardt G, Cooper JV, et al. Partial thrombosis of the false lumen in patients with acute type B aortic dissection. N Engl J Med 2007;357:349-59. 5. Cambria RP, Brewster DC, Gertler J, Moncure AC, Gusberg R, Tilson MD, et al. Vascular complications associated with spontaneous aortic dissection. J Vasc Surg 1988;7:199-209. 6. Coselli JS. Thoracoabdominal aortic aneurysms: experience with 372 patients. J Card Surg 1994;9:638-47. 7. Neya K, Omoto R, Kyo S, Kimura S, Yokote Y, Takamoto S, et al. Outcome of Stanford type B acute aortic dissection. Circulation 1992;86:II1-7. 8. Trimarchi S, Nienaber CA, Rampoldi V, Myrmel T, Suzuki T, Bossone E, et al. Role and results of surgery in acute type B aortic dissection: insights from the International Registry of Acute Aortic Dissection (IRAD). Circulation 2006;114:I357-64. 9. Mitchell RS, Miller DC, Dake MD, Semba CP, Moore KA, Sakai T. Thoracic aortic aneurysm repair with an endovascular stent graft: the “first generation.” Ann Thorac Surg 1999;67:1971-4; discussion: 1979-80. 10. Nienaber CA, Fattori R, Lund G, Dieckmann C, Wolf W, von Kodolitsch Y, et al. Nonsurgical reconstruction of thoracic aortic dissection by stent-graft placement. N Engl J Med 1999;340:1539-45. 11. Conrad MF, Ergul EA, Patel VI, Paruchuri V, Kwolek CJ, Cambria RP. Management of diseases of the descending thoracic aorta in the endovascular era: a Medicare population study. Ann Surg 2010;252:603-10. 12. Cambria RP, Crawford RS, Cho JS, Bavaria J, Farber M, Lee WA, et al. A multicenter clinical trial of endovascular stent graft repair of acute catastrophes of the descending thoracic aorta. J Vasc Surg 2009;50: 1255-64. e1-4. 13. Lombardi JV, Cambria RP, Nienaber CA, Chiesa R, Teebken O, Lee A, et al; STABLE investigators. Prospective multicenter clinical trial (STABLE) on the endovascular treatment of complicated type B aortic dissection using a composite device design. J Vasc Surg 2012;55: 629-40.e2. 14. White RA, Miller DC, Criado FJ, Dake MD, Diethrich EB, Greenberg RK, et al; Multidisciplinary Society for Vascular Surgery Outcomes Committee. Report on the results of thoracic endovascular aortic repair for acute, complicated, type B aortic dissection at 30 days and 1 year from a multidisciplinary subcommittee of the Society for Vascular Surgery Outcomes Committee. J Vasc Surg 2011;53: 1082-90. 15. Nienaber CA, Rousseau H, Eggebrecht H, Kische S, Fattori R, Rehders TC, et al; INSTEAD Trial. Randomized comparison of
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Submitted Jan 11, 2015; accepted Mar 20, 2015.
