Investigation Of Stent Grafts Research Articles

Experience with Thoracic EndoVascular Aortic Repair (TEVAR) treatment of uncomplicated Stanford type B aortic dissection, 2022 Updates

There have been significant advances in the technique and application of endovascular repair of thoracic aortic pathology over the past 20 years. The Stanford type A and the complicated type B dissection patients require urgent/emergent intervention. In the last decade, earlier intervention has been pursued for uncomplicated type B dissections. The INvestigation of STent-grafts in Aortic Dissection (INSTEAD) Long term (XL) study showed that there was significant crossover from medical management to Thoracic EndoVascular Aortic Repair (TEVAR) at year 3, suggesting TEVAR might benefit this population long term. Today, the application of TEVAR, which was initially designed to address aneurysmal disease, has become a standard and Food and Drug Administrative (FDA) approved management option in dissections. Currently there are four FDA approved TEVAR devices in the United States for the treatment of the thoracic dissections, namely Gore, Medtronic, Cook, and Terumo. With each iteration, there are increased opportunities for customization and widespread use in individualized patient’s pathology. As the technology improves and the feasibility of the grafts expands, the complication rates continue to decline cementing the safety and efficacy of these thoracic aortic grafts. Two rare but catastrophic complications in spinal ischemia and retrograde Stanford type A aortic dissection are further discussed. With the success of the TEVAR, a new frontier of hybrid aortic surgery has developed. The debranching of the aortic arch vessels in order to advance the TEVAR proximal landing zones has been aggressively pursued. With the widespread growth of TEVAR technology it is apparent that complex aortic pathology can be safely repaired endovascularly. Article Details

Management of Uncomplicated Type B Aortic Dissection

Acute aortic dissection has an incidence of approximately half that of symptomatic abdominal and thoracic aneurysm of the aorta and more than twice the mortality of population-based controls. While urgent undelayed open surgery is the strategy of choice in proximal dissection, medical management has been the mainstay of treatment for uncomplicated distal or type B aortic dissection, but endovascular intervention is now considered a potential treatment option for all type B dissection due to its success in complicated cases. Endovascular repair can be technically demanding in aortic dissection, and timing of the repair can have a significant influence on anatomical and clinical outcome. Observational reports of feasibility and reasonable safety are flanked by only two randomised trials; the Acute Dissection Stent Grafting or Best Medical Treatment (ADSORB) trial demonstrated improved remodelling in acute dissection and the INvestigation of STEnt grafts in patients with type B Aortic Dissections (INSTEAD) trial showed better long-term survival in patients treated endovascularly in the subacute phase. Meta-analyses and other large clinical studies have demonstrated mixed results. Due to some risks associated endovascular repair and the requirement of specialist aortic care (which is not always available), a pragmatic approach for current management could involve high intensity serial imaging in the acute phase of a type B aortic dissection, thereby identifying complicated cases for early intervention and selection of patients at high risk of disease progression for deferred endovascular management in the subacute phase within 90 days.

Aortic Wall Enhancement Detected by Contrast Computed Tomography Scan Predicts Aortic Remodeling after Conservative Therapy for Acute Uncomplicated Type B Dissection

The Investigation of Stent Grafts in Aortic Dissection with extended length of follow-up trial showed that pre-emptive thoracic endovascular aneurysm repair (TEVAR) for the uncomplicated type B dissection (TBAD) in the subacute phase promotes aortic remodeling and avoids aortic-related death 5 years after onset. However, there are some patients with complete aortic remodeling (CAR) with optimal medical treatment (OMT) and severe complications after TEVAR such as retrograde type A dissection. Therefore, which patients should undergo pre-emptive TEVAR and optimal surgical timing are still under debate. We reported that aortic wall enhancement (AWE) after endovascular aneurysm repair for abdominal aortic aneurysm was associated with sac shrinkage. However, there is no report about the relationship between AWE and aortic dissection. Herein, we evaluated the relationship between AWE and acute TBAD. From March 2012 to May 2018, consecutive patients with acute TBAD were retrospectively collected. We retrospectively analyzed 35 patients with acute TBAD who were treated with OMT and without pre-emptive TEVAR in the subacute phase. AWE was defined as an increase of more than 20 Hounsfield units in mean computed tomography (CT) values, comparing images in delayed contrast-enhanced scans with those in plain scans evaluated within 3months from onset. The measurement points were all slices including the wall of the false lumen. The patients with traumatic dissection, type A dissection, acute complicated type B dissection, chronic (>12weeks) dissection, and those lost to follow-up within 3months from onset were excluded. The primary end point was spontaneous CAR under OMT, as determined by the latest contrast-enhanced CT scan. The median follow-up period from onset was 86weeks and there were 25 cases (71.4%) with AWE. Under OMT, CAR was observed in 20 patients (57.1%); this was significantly associated with abdominal branch dissection (6/15 [40%] vs. 2/20 [10%], P=0.050), number of tears more than 2 at onset (11/15 [73%] vs. 4/20 [20%], P=0.003), multiple tears at 1month after onset (9/15 [60%] vs. 4/20 [20%], P=0.020), maximal false lumen diameter at 1month after onset (14 vs. 8mm, P=0.025), and AWE within 3months of onset (7/15 [47%] vs. 18/20 [90%], P=0.010). Multivariate analysis demonstrated a significant difference with multiple tears at onset (P=0.014) and AWE within 3months of onset (P=0.047). AWE was associated with CAR under OMT for acute TBAD which is out of indication of pre-emptive TEVAR. Presence of AWE may be useful in predicting prognosis of TBAD.

Invited commentary

Treatment of dissection of the aorta remains one of the great challenges in vascular surgery, but one in which steady progress has been made. In years past, even making the diagnosis was difficult, and the best means of doing so was a matter of controversy. The universal availability of high-speed and high-quality computed tomography scanning now requires only a low index of suspicion before an accurate picture of the anatomic nature of the dissection can be defined. The clinical question, therefore, no longer is What is the diagnosis? but rather What is the best course of action? As vascular surgeons, we must remember that our fundamental rules about intervention in the case of a type B dissection were built on a risk-benefit ratio calculated when options for treatment involved medical management or the performance of a very substantial operation (open fenestration or emergency thoracoabdominal aortic replacement) that favored medical management the overwhelming percentage of the time. The availability of appropriate covered stent grafts, the development of intravascular ultrasound, and the availability of hybrid imaging and operative environments helped shift the calculation of the risk-benefit ratio dramatically toward intervention. We are still trying to define the role of intervention in the treatment of this pathologic process.1Ulug P. McCaslin J.E. Stansby G. Powell J.T. Endovascular versus conventional medical treatment for uncomplicated chronic type B aortic dissection.Cochrane Database Syst Rev. 2012; 11: CD006512PubMed Google Scholar, 2Nienaber C.A. Rousseau H. Eggebrecht H. Kische S. Fattori R. Rehders T.C. et al.Randomized comparison of strategies for type B aortic dissection: the INvestigation of STEnt Grafts in Aortic Dissection (INSTEAD) trial.Circulation. 2009; 120: 2519-2528Crossref PubMed Scopus (563) Google Scholar The classic anatomic division of vascular surgery territory from cardiothoracic surgery territory just distal to the left subclavian artery has been pushed proximally in the aorta by debranching procedures and snorkel/chimney adaptations to stent grafts. In spite of this advancing level of skill set and ingenuity, the treatment of the type A aortic dissection has been firmly in the hands of the cardiac surgeons, in which only incremental advances have been made in a maximally invasive operative technique, with outcomes leaving much room for improvement. Although the postmortem deployment of a surgeon-modified graft in a flow model using a nondiseased aortic arch specimen is a preliminary study, the endovascular approach to the treatment of this pathologic process is a logical extension of the ideas and skills developed from work done on type B dissections and the transcatheter aortic valve replacement procedures. Where will this lead us? Imagination and ingenuity have forged ahead of the availability of devices that will eventually be developed as standardized approaches become adopted. Will access to the ascending aorta be transapical, as in this report, or transfemoral or even transvenous/trans-septal? The invasiveness and outcomes of the open repair of type A dissections make the endovascular approach to the treatment of ascending aortic dissection a pursuit whose time is coming. Experimental evaluation of homemade distal stent graft fenestration for thoracic endovascular aortic repair of type A dissection by a transapical approachJournal of Vascular SurgeryVol. 68Issue 4PreviewThe use of off-the-shelf stent grafts for thoracic endovascular aortic repair of type A dissections is limited by variability in both the length of the ascending aorta and the location of the proximal intimal tear. This experimental study aimed to assess the feasibility of using a physician-modified thoracic aortic stent graft to treat acute type A dissection by a transapical cardiac approach. Full-Text PDF Open Archive

Editors' Commentary

Editors' Commentary

Part One: For the Motion. Level 1 Evidence is Necessary Comparing TEVAR and Medical Management of Uncomplicated Type B Aortic Dissection

Part One: For the Motion. Level 1 Evidence is Necessary Comparing TEVAR and Medical Management of Uncomplicated Type B Aortic Dissection

Part Two: Against the Motion. We do not Need Level 1 Evidence Comparing Best Medical Treatment with TEVAR in Patients with Uncomplicated Type B Aortic Dissection

Be it resolved that we do not need level 1 evidence comparing best medical treatment (BMT) with thoracic endovascular aortic repair (TEVAR) in patients with uncomplicated type B aortic dissection (BAD). There is reasonable level 1 evidence available for subacute/chronic type B dissection (Investigation of STEnt Grafts in Aortic Dissection [INSTEAD] trial 1 ) and we concede that the longterm results of this trial are needed to help clarify initial findings. We will argue instead that level 1 evidence for acute uncomplicated BAD and, consequently, the Acute Dissection Stent-graft Or Best medical treatment (ADSORB) trial, 2 was not required, nor has it resulted in clinically applicable information. Rather than focusing on whether all BADs should be treated with TEVAR or not, we need to determine which group of patients will find the most benefit. We are well on our way to understanding this without the need of a randomized trial. One core issue in the study of BADs is that many of its features are not uniformly defined.The only generally agreed upon definition is that Stanford type B or Debakey III aortic dissectionoriginatesinthedescendingthoracicaortawithout retrograde extension into the ascending aorta. BADs are considered complicated if they involve malperfusion or rupture, but studies are inconsistent on whether they include other symptoms, such as refractory hypertension and persistent pain. 3 Imaging findings such as an increase in periaortic hematoma and hemorrhagic pleural effusion clearly increase morbidity and mortality, but are inconsistently reported. 4 Historically, BAD is considered acute when it occurs within 14 days of symptom onset, while a dissection discovered after 2 weeks is considered chronic. In recent years, the term “subacute” has been used, further confounding the temporal classification. The INSTEAD trial is the only randomized controlled trial (RCT) of subacute or chronic type B dissections treated with TEVAR plus BMT versus BMT plus surveillance. 1 Conversely,the ADSORB trial,the 1-year results of which have recently been published, is the only RCT of acute type B dissections treated with TEVAR plus BMTversus BMT. 2 BMT generally involves lowering patients’ blood pressure to approximately 120 mmHg systolic over 80 mmHg diastolic. Beta blockade is usually first-line therapy and is supplemented by diuretics, angiotensin-converting enzyme inhibitors, calcium channel blockers, and sometimes ablockers in refractory cases. 5e7 TEVAR involves endograft

Patient outcomes and thoracic aortic volume and morphologic changes following thoracic endovascular aortic repair in patients with complicated chronic type B aortic dissection

True and false lumen changes and patient outcomes following thoracic endovascular aortic repair (TEVAR) for patients with stable type B dissection have been described by the The Investigation of Stent Grafts in Aortic Dissection (INSTEAD) trial. However, these changes have not been described in TEVAR patients treated for complications of chronic dissection. A single-institution study was conducted of 73 prospectively evaluated patients treated for complications of chronic type B dissection from 2002 to 2010. Spiral computed tomography reconstructions using M2S (Medical Media Systems, West Lebanon, NH) were analyzed for sequential changes in aortic volume and diameter during patient follow-up. Changes in aortic volume and diameter were tabulated as a percent change from preoperative values. Patient outcomes were determined by sequential evaluations postprocedure. TEVAR was successfully performed in 72 out of the 73 patients (99%). Indications for intervention were aortic enlargement (n = 62), failure of medical management (n = 7), and perforation (n = 4). The 30-day all-cause mortality rate was 14%; events were due to retrograde dissection (n = 4), cardiac-related (n = 4), and rupture (n = 2). Eleven out of the 72 patients (15%) required a secondary procedure for endoleak (n = 7) and persistent distal perfusion of the false lumen (n = 4). Mean percentage expansion of the thoracic true lumen was noted during the follow-up period: 38%, 46%, 71%, and 114% at 1-, 3-, 6-, and 12-month follow-up, respectively. Concomitant regression of the thoracic false lumen of -65%, -68%, -84%, and -84% was observed at the same intervals, respectively. Patients with an initial extension of the thoracic dissection into the infrarenal aorta (n = 46) had an increase in mean percentage change of aortic diameter and volume to 21% and 17% at 1 year, respectively. By contrast, in the patient group without infrarenal dissection (n = 14), the infrarenal aortic diameter and volume remained relatively unchanged at 3% and -0.9%, respectively, at 1-year postintervention. TEVAR is a potential treatment option for patients experiencing complications of chronic type B dissection. During follow-up, there is a predictable expansion of the thoracic true lumen and regression of the thoracic false lumen. These findings correlate with those of the INSTEAD trial, which demonstrated false lumen regression and true lumen expansion in a cohort of patients with stable type B dissection. However, many patients with extension of thoracic dissection into the infrarenal aorta demonstrate continued aortic dilation and, on occasion, the need for secondary intervention for persistent distal perfusion. Further analysis is needed in this subgroup of patients so as to better determine potential predictors and the clinical significance of post-TEVAR infrarenal expansion. Moreover, further investigations may support a role for secondary endovascular intervention in remedying persistent infrarenal aortic expansion after TEVAR for chronic dissection.

ADSORB: A Prospective Randomised Study on the Efficacy of Endovascular Grafting vs. Best Medical Treatment in Uncomplicated Acute Dissection of the Descending Aorta

Many of the arterial lesions that vascular surgeons treat are on the decline, and those that currently are may soon be offered more effective drug therapy. In contrast, dissections of the aorta are increasing and are likely to represent a significant future workload and challenge for vascular surgeons. Traditionally acute Stanford type B dissections of the aorta were managed by a variety of specialists, often cardiologists. Vascular surgeons only became involved where peripheral ischaemia supervened. Dake demonstrated the feasibility of placing endovascular stentgrafts in to dissected aortas. 1 This approach appeared to offer an attractive alternative to traditional open surgical approaches for complicated aortic dissection which carried high rates of complications. 2 Consequently stent-grafts have been used increasingly in this group of patients. 3 Early efforts to reduce mortality from acute type B dissection demonstrated that effective blood pressure control in the early stages reduced mortality. Medical therapy did not necessarily prevent long-term aortic related complications. The INSTEAD Trial attempted to answer the question whether there was any benefit from placing a stent-graft in type B aortic dissection in the subacute phase (2e52 weeks). 4 There was no reduction in aortic related mortality 2 years after the initial dissection but preliminary data from INSTEAD suggests that stent-grafting might be protective in the longer term (5 years). The next question is whether there would be any additional benefit (or harm) from stenting patients within the first 2 weeks of their initial uncomplicated type B dissection? There remains scope for improvement in the 10% in-hospital mortality when treated with medical therapy. 5 It is possible that stenting might reduce mortality. However, concerns remain (due in part to a lack of data) that stenting within the first 2 weeks may be associated with significant risks even when the aortic dissection is uncomplicated. It is for these reasons that we have been following the development of the ADSORB trial keenly since its inception in 2002. Recruitmenthasbeenslow,suggestingalackofclinicalequipoiseand the change of power calculation is regrettable but seems realistic if the triallists are to complete their study. It is a pity that the trial will not have the power to demonstrate significant differences in the more robustclinicalendpoints (aortic relatedorall-causemortality). It is not clear whether the primary trial composite endpoint of a variety of aortic related events (false lumen thrombosis, aortic dilatation >5 mm, aortic rupture) at 1-year will be a clinically relevant one for patients. In the INSTEAD Trial 20% of patients managed non-operativelyachievedfalselumenthrombosis.Itisquite possible that this group of patients receiving early stent-grafting in the ADSORBtrialmightnotderiveanybenefitatall(andmaybeharmed).

Editorial Comment: The primary entry tear location in acute type B aortic dissection as an adjunct in therapeutic decision-making

In the management of type B acute aortic dissection, most recent benchmarking has been proposed by the Investigation of Stent Grafts in Aortic Dissection (INSTEAD) trial [1]. In the case of uncomplicated dissection with optimal medical therapy alone, only 22% of these particular patients had to undergo secondary intervention or surgery at 2 years. This indicates that, in a benchmark trial, 78% of patients did well without developing the need for secondary reinterventions. However, per definition, the INSTEAD trial deals with chronic dissection, since the time delay from event to randomization was 6 weeks in average and >2 weeks in all patients. So, there is still a window of uncertainty about treatment modality in the early, acute period of dissection. For this early time frame, the data from the International Registry of Acute Aortic Dissection (IRAD) indicate that 24% of 515 patients with acute Type B dissection require emergent intervention for early complications within the acute phase of 14 days [2]. However, we still miss clear predictive parameters identifying patients at risk of a complicated course. The merit of the manuscript by Weiss et al. [3] in this issue is the fact that they provide a potential tool for further classification of patients into a higher risk group in the acute phase of dissection. They report that a primary entry tear at the concavity of the aortic arch and short distance between the primary entry tear and the left subclavian artery are frequently associated with the development of acute complications. Most promising is the fact that the authors postulate that this discrimination can be drawn at the first, diagnostic imaging study. When the entry tear was located at the convexity of the aortic arch, subsequent complications, needing intervention, developed in 20% of the patients. In contrast, when entry tear was located at the concavity of the arch, an impressive 89% of the patients required acute intervention. This potentially important information is somewhat confused by the fact that in total 56% of all studied patients finally developed complicated acute dissection. Remarkably, under the assumption of comparable definitions of complications, this is twice the incidence when compared with IRAD and by this weakens the broader applicability of the given decisive algorithm in daily routine. The pathophysiological background is that the supra-aortic branches on the convexity of the aortic arch serve as a natural anatomic barrier against retrograde propagation of the dissection process. A similar protective structure is missing at the concavity of the arch. In a porcine model of aortic dissection, this theory has been confirmed: when the entry was at the concavity of the aortic arch the retrograde propagation reached the ascending aorta in 16%, whereas the dissection stopped at the origin of the left subclavian artery when the entry was at the convexity of the aortic arch [4]. One might speculate, together with the authors, to deliberately go for an intervention in patients with an entry localized at the concavity of the aorta. Nevertheless, in the present paper, there remain two major concerns. First, if we start with endovascular intervention in otherwise uncomplicated Type B aortic dissections, in this specific high-risk group with an entry close to the left subclavian artery, we inevitably end up in the landing zones 1 or 2 of the aortic arch. This in turn carries a certain risk of stentgraft-induced retrograde type A aortic dissection [5]. For this particular mechanism, it will be a matter for future studies to show whether completely covered stentgrafts might reduce the risk of retrograde aortic dissection by avoiding bare springs. Secondly, the entry localization was analysed retrospectively when the patients were already classified as complicated or uncomplicated course, which carries the risk of bias in retrospective analysis. Despite a relatively large number of acute aortic syndromes referred to our interdisciplinary aortic centre and despite sophisticated imaging techniques, in many cases we are still uncertain about the exact localization of the primary entry tear. This decision, to accurately allocate the entry tear and, by this. Guide acute therapeutic strategy, may become even more difficult in the setting of clinical routine for less-experienced radiologists/surgeons on call. In conclusion, we appreciate the effort by Weiss et al. to identify the entry localization at the concavity of the aorta as a new risk factor for complication of acute type B aortic dissection. It initiates structured decision-making in the very early phase of a potentially devastating disease. Nevertheless, two questions have to be answered in the future. First, is prospective detection of the primary entry tear localization accurate and reproducible in broad clinical application? Secondly, is the risk of aggressive endovascular treatment of the distal aortic arch in otherwise uncomplicated dissections really justified?

Influence and Critique of the INSTEAD Trial (TEVAR Versus Medical Treatment for Uncomplicated Type B Aortic Dissection)

Endovascular stent-grafting represents a novel nonsurgical therapeutic concept for type B aortic dissection in both the acute and subacute/chronic settings with unknown impact on outcomes. In a prospective trial, 140 patients with clinically stable type B dissection were randomly subjected to elective stent-graft placement in addition to optimal medical therapy (n = 72) or to optimal medical therapy (n = 68) with surveillance (arterial pressure according to World Health Organization guidelines, ≤120/80 mm Hg) and recurrent computed tomography imaging. Primary endpoint was 2-year all-cause mortality, while aorta-related mortality, progression of disease (with need for crossover to stent-graft or additional endovascular or open surgery), and aortic remodeling were secondary endpoints. There was no difference in all-cause mortality at 2 years, with cumulative survival of 95.6% ± 2.5% with optimal medical therapy versus 88.9% ± 3.7% with thoracic endovascular aortic repair (TEVAR) (P = .15). Considering, however, that only 40% of the expected events occurred within 2 years (based on registry data), the trial turned out to be underpowered for all-cause mortality. Moreover, aorta-related mortality was also not different (P = .44) within the first 2 years of follow-up, and risk for the combined endpoints of aorta-related death (rupture) and progression (including conversion or additional endovascular or open surgery) was similar (P = .65); three neurological adverse events occurred in the TEVAR group (one paraplegia, one stroke, and one transient paraparesis) versus one paraparesis with medical treatment. Finally, and as expected, aortic remodeling (with true lumen recovery and thoracic false lumen thrombosis) occurred in 91.3% with TEVAR, but only in 19.4%with medical treatment alone (P < .001), suggestive of continued remodeling with TEVAR and failure of medical treatment to induce remodeling and healing of dissection. In conclusion, the data in the INSTEAD (Investigation of Stentgrafts in Aortic Dissection) trial show that in the setting of clinically stable, so-called uncomplicated type B aortic dissection, elective stent-graft placement on top of optimized medical management fails to improve survival and adverse events within an observation period of 2 years, despite favorable aortic remodeling.

Circulation: Clinical Summaries

<i>Circulation:</i> Clinical Summaries

The INvestigation of STEnt Grafts in Aortic Dissection (INSTEAD) Trial

In the present issue of Circulation , Nienaber et al1 report the results of a randomized comparison of strategies for type B dissection: the INvestigation of STEnt grafts in Aortic Dissection (INSTEAD) trial. This trial represents the first prospective randomized study of elective stent graft placement in survivors of uncomplicated chronic type B aortic dissection. The results have been eagerly anticipated by clinicians, particularly in light of recent analyses of the benefits of endovascular repair for abdominal aortic aneurysms2,3 and thoracic endovascular aneurysm repair (TEVAR) for the treatment of degenerative thoracic aneurysms.4–6 The authors are to be commended on providing Level 1 evidence to assist us in the management of chronic aortic dissection. The INSTEAD trial demonstrates that thoracic stent graft (TEVAR) placement failed to improve the rates of 2-year survival and adverse events when compared with optimal medical therapy (OMT). Although considerable attention to detail was paid by the authors in the design of this trial,7 several limitations exist that may preclude using these results to determine the final role of stent grafts in the management of chronic aortic dissection. Article see …

TEVAR for Acute Uncomplicated Aortic Dissection: Immediate Repair Versus Medical Therapy

Medical management remains the standard treatment modality for acute uncomplicated descending aortic dissections. Intervention (by either open surgery or an endovascular approach) is currently reserved for patients who present with or subsequently develop complications (ie, complicated dissections). Despite the success of medical therapy in the acute management of uncomplicated dissection, long-term morbidity and mortality are far from ideal. The introduction of thoracic endovascular aortic repair (TEVAR) has been associated with reductions in morbidity and mortality in the treatment of complicated dissections. There is limited data regarding TEVAR for acute uncomplicated dissections. Early results from the INSTEAD (Investigation of Stent Grafts in Patients with Type B Aortic Dissection) trial, a randomized trial for TEVAR in subacute/chronic uncomplicated dissections, were not favorable. The ADSORB (Acute Uncomplicated Aortic Dissection Type B: Evaluating Stent-Graft Placement or Best Medical Treatment Alone) trial, a randomized trial for TEVAR in acute dissections, is currently underway. Nonetheless, current data available, including multiple reports proposing a variety of predictive factors, suggest that there may be a subset of higher-risk patients with acute uncomplicated dissections who could benefit from TEVAR.

Role of Endovascular Therapies in the Management of Diverse Thoracic Aortic Pathology

Stent grafts are currently indicated for treatment of chronic aneurysmal disease of the descending thoracic aorta. At most centers of excellence, this technique has become the preferred treatment modality for this pathologic process. Many centers are also reporting excellent outcomes using a variety of debranching procedures to expand the anatomic limits of therapeutic intervention. These debranching procedures enable proximal extension of stent grafts into the transverse aortic arch and similarly enable distal extension into the visceral portion of the abdominal aorta. Thoracic aortic disease, however, is not limited to aneurysmal pathology. In our experience, at least half of all patients with major thoracic aortic pathology will have nonaneurysmal disease processes. Frequently, these patients are high-risk candidates for the performance of open surgical intervention. The reduced procedural morbidity and mortality observed with thoracic endovascular aortic repair when compared with open surgical intervention have catalyzed the investigation of stent grafts in the management of nonaneurysmal pathologic processes. This therapy has been successfully applied to a variety of diverse thoracic aortic pathologies, including aortic dissection, aortic transection, penetrating atherosclerotic ulcers, embolic lesions, and aortic coarctation. The focus of this article is on the latter 3 of these pathologies.

INvestigation of STEnt grafts in patients with type B Aortic Dissection: Design of the INSTEAD trial—a prospective, multicenter, European randomized trial

This study describes the design of an ongoing randomized trial initiated to compare the 2-year outcome of uncomplicated type B aortic dissection when treated by endovascular implantation of a Medtronic Talent stent graft adjunctive to best medical treatment versus best medical treatment alone. Patients older than 18 years with type B aortic dissection as diagnosed by computed tomography or magnetic resonance angiography are randomized to either a thoracic aortic endoprosthesis and antihypertensive treatment, called "stent grafting," or a tailored antihypertensive treatment, called "medical treatment." Only patients in a clinically stable condition and without spontaneous thrombosis of the false lumen after 14 days of the index dissection are considered eligible for study inclusion. Primary outcome measure is all-cause mortality. Secondary outcome variables include conversion to stent and/or surgery, induced thrombosis of the false lumen, cardiovascular morbidity, aortic expansion (>5 mm/y of maximum diameter including true and false lumina), quality of life, and length of intensive care unit and hospital stay. The study design calls for 136 patients to be randomized and monitored for 24 months. The INSTEAD trial is the first randomized trial investigating the role of endoluminal treatment of uncomplicated type B aortic dissection. By the end of December 2004, 125 patients were randomized, accounting for 92% of the target. Final results of the INSTEAD trial should be available in 2006.