Servier – Phlebolymphology

1.1.1 Thoracic aorta: open, endo, or hybrid

Can we stratify the operative risk of TEVAR?
M. Thompson

Even though thoracic endovascular aortic repair (TEVAR) presents a lower short-term mortality and morbidity than traditional open surgery, it is still associated with a high morbimortality rate (10% to 15%) and a high rate of all-cause death at follow-up. Considering these facts, the author developed a system to stratify patient-specific risk to aid in preoperative planning.

The MOTHER database (Medtronic endOvascular THoracic Endovascular Registry) gathered data from five prospective clinical trials and a single institutional series. Rates of perioperative adverse events were calculated, as were mid-term death and reintervention rates. Different statistical tests were applied to construct models using preoperative variables to predict perioperative and mid-term adverse events as well as to determine discrimination and goodness of fit of the models.

Of 670 patients that underwent TEVAR for thoracic aneurysm, 5% died, 5% had a stroke, and 3% developed spinal cord injury (SCI) postoperatively. Independent predictors of 30-day death were age, nonelective surgery, and the need for >2 devices (C statistic=0.71). Stroke was predicted by female sex, previous stroke, coverage of the left subclavian artery, and the need for >2 devices (C statistic=0.77). SCI was predicted by female sex, smoking, previous stroke, nonelective surgery, and the need for >2 devices (C statistic=0.72). Aortic reintervention was predicted by aneurysm length, maximum diameter, and iliac tortuosity and a high-risk cohort could be identified. Patients could be successfully divided into tertiles of risk using the mid-term all-cause death model.

The study indicated that the mid-term outcomes of TEVAR are defined by associated comorbidities and mode of admission. Nonaortic mortality is high in the mid-term for patients with thoracic aortic aneurysm, and managing modifiable risk factors appears vital. The author concluded that TEVAR results in excellent mid-term protection from aortic-related mortality. Improved patient selection and better postoperative risk-factor management may help to improve the high all-cause death rate seen in aneurysm patients at follow-up.

These models predict important outcomes following TEVAR and are relatively accurate. External validation of this risk stratification system is required before it can be introduced into clinical practice.

Objective assessment of current stent grafts: which graft for which lesion?
L. Canaud

The first decade of thoracic endovascular aortic repair (TEVAR) has demonstrated good short- and mid-term outcomes, supporting endovascular repair as the procedure of choice for patients presenting with thoracic aortic diseases. Presently, four thoracic stentgrafts have achieved the CE (Conformité Européenne) marking: Valiant (Medtronic Vascular, Santa Rosa, CA, USA), Zenith TX2 thoracic stent-graft (Cook Medical, Bloomington, IN, USA), TAG (W.L. Gore & Associates, Flagstaff, AZ, USA), and the Relay Stent-graft (Bolton Medical, Sunrise, FL, USA). These stent-grafts have different features in terms of stent-graft design (polytetrafluoroethylene [PTFE] vs Dacron, stent framework) and delivery system. Knowledge of stent-graft conformability, radial force, and accuracy of the delivery system is crucial to prevent devastating complications such as stentgraft collapse, type I endoleak, retrograde ascending aortic dissection (RTAD), and inadvertent coverage of the supra-aortic trunks.

In this context, the author presented an experimental study performed using a benchtop pulsatile flow model and human cadaveric aortas in order to assess the conformability of the latest generation of thoracic stent-grafts as a function of oversizing and increasing aortic arch angulation. He further reported a comprehensive review of the literature combined with a review of his single center experience to identify devicerelated complications.

The experimental study demonstrated that the requirement for close conformability has influenced the design of next-generation devices. Manufacturers have modified devices and/or deployment systems to specifically address this problem. When compared with the results of the author’s previous experimental test, these alterations have resulted in a marked improvement in the performance of commercially available stent-graft systems.

Concerning the performed literature review and regarding RTAD, inappropriate stentgraft oversizing, particularly in patients with aortic wall fragility, should be avoided. Iteration of stent-graft design will be important in reducing the incidence of RTAD, but the present study suggests that the presence of a bare proximal stent does not lead to an increased rate of RTAD. Considering the thoracic stent-graft collapse, accurate assessment of aortic arch anatomic features, as well as the choice and sizing of the device, may prevent this complication. Prevention of the risk of inadvertent coverage of the supra-aortic trunks is based on the choice of a stent-graft with a controlled delivery system.

The author concluded that improvement in the performance of commercially available stent-graft systems combined with a proper knowledge of the different features of these stent-grafts would prevent most device-related complications.

Ascending aorta: is the endovascular approach realistic? How I do it.
T. Kölbel

The standard treatment for pathologies of the ascending aorta is currently still open surgery; it is a dissection, aneurysm, or rupture. Meanwhile, the open approach is associated with considerable morbidity and mortality rates. Even though thoracic endovascular aortic repair (TEVAR) is now considered the preferred approach for the descending thoracic aorta, technical and anatomical challenges persist for endovascular repair of the more proximal sections of the aorta, rendering TEVAR a more exceptional indication. Present problems of TEVAR from a downstream access for the ascending aorta include: (i) inability to advance, control, and deploy the endograft due to iliac and aortic pathology (including severe tortuosity); (ii) hemodynamic forces; (iii) the need to place a stiff guidewire into the left ventricle; and (iv) the shortness of currently available stent-graft introducing systems. To overcome these limitations, alternative retrograde access techniques have been developed including subclavian access, conduits to iliac arteries, infrarenal, and thoracic aorta. In the author’s opinion, antegrade access and transapical stent-graft deployment might be an alternative access in patients unfit for or at a high risk for open surgery or retrograde access. Described originally by MacDonald et al (J Vasc Surg. 2009;49:759-762), the transapical access, through a mini thoracotomy (same approach performed for transcatheter aortic valve implantation [TAVI]), has the following potential advantages: (i) avoidance of downstream access problems; (ii) short distance with excellent trackability, pushability, and rotational control; (iii) nearly unlimited profile; (iv) instant decompression of the pericardial tamponade; and (iv) availability, as transapical access is a standard technique for TAVI in many cardiovascular centers. Meanwhile, remaining issues subsist regarding TEVAR in the ascending aorta: pulsatility of the arch, proximal seal, unknown impact on AV, selection of the patients and specifically designed grafts still to come.

Aortic arch: tips and tricks for total endovascular repair.
T. Resch

The author presented, in this lecture, some pertinent points that can lead to a successful endovascular repair of the entire aortic arch. He emphasized the importance of the planning in a 3D workstation, looking carefully at the ascending aorta, the coronaries, the aortic valve, the cervical vessels’ landing zone, the access, the aortic tortuosity, and the presence of a previous device. He finished by stating that total endovascular arch repair is feasible, but it implies an important learning curve with regard to patient selection and stent-graft implants.

Hybrid techniques for the arch: are they effective and durable?
P. Cao

The author presented his group experience from 2005 to 2014 in hybrid techniques for aortic arch repair. A total of 136 patients were treated with the following landing zone distribution: Z0, 25; Z1, 60; Z2, 51. The perioperative outcome rates at 30 days were 5.1% mortality, 2.9% stroke, 2.2% spinal cord ischemia, 3.6% type I endoleak, and 3.6% retrograde type A dissection. The long-term outcomes regarding the vascular surgical reconstruction were also presented, with only 3.7% of reinterventions. As such, the author concluded that aortic arch debranching repair relies on a number of procedural options that need to be tailored to patient characteristics, mode of admission, and the center’s experience. He also argued that: (i) hybrid arch procedures present a persistent high risk of perioperative mortality, mostly in landing zone 0; (ii) retrograde dissection may complicate total surgical debranching, especially in a dissected aorta; (iii) total endovascular procedures (chimney techniques) are currently subject to a high rate of gutter type I endoleak and should be reserved for emergencies; (iv) embolization procedures are not always effective; and (v) tailored endografts seem to provide promising results.

1.1.2 Controversy: Timing of TEVAR for uncomplicated acute type B aortic dissection

Early intervention is the best choice.
J. Brunkwall

The author started his argumentation by reminding the audience of the complications of an acute type B dissection, such as rupture, malperfusion (renals, intestines, spine, and lower limbs), uncontrolled hypertension, and aneurysm formation. He stated that malperfusion is associated with high mortality rates.

By performing thoracic endovascular aortic repair (TEVAR) in an acute setting of uncomplicated type B dissection (time from symptom onset to treatment ≤14 days), the author argued that it is possible to obtain remodeling with “restitutio ad integrum,” reducing the risk of complications, the number of reinterventions, and the mortality rate at 5 years (prevention of late aortic-related death). According to the paper “The IRAD Classification System” (Booher AM et al; IRAD Investigators. Am J Med. 2013;126:730. e19-24), an International Registry of Aortic Dissection (IRAD) with a total of 665 type B dissections, endovascular treatment provided the best cumulative survival from time of symptom onset to 60 days. Although the placement of an endograft in the acute setting increases the risk for retrograde type A dissection, distal malperfusion, stroke, and paraplegia. The interim results of the ADSORB trial (Acute Dissection Stentgraft OR Best medical treatment) further demonstrated that TEVAR is safe in the acute phase of uncomplicated type B dissection, being able to significantly reduce the mortality at 30 days in comparison with medical treatment alone. He further stressed that five treatment crossovers occurred within a few days after randomization in the medical treatment group (n=30; results not published yet).

The author concluded that acute type B dissection is life threatening, that the first 14 days are critical, and that early treatment is not dangerous, being even able to save lives.

Delayed TEVAR is much preferable.
M. Thompson

The author started his reply by pointing out the pitfalls of the ADSORB trial (Acute Dissection Stentgraft OR Best medical treatment), especially with regard to the way it was powered, decreasing from the 250 patients initially needed to the 60 actually recruited. He further argued that deferred thoracic endovascular aortic repair (TEVAR) resulted in fewer peridissection complications, delivering the same protection from late aortic death.

In fact, in the most recent systematic review (Canaud L et al. Ann Surg. 2014 Jan 16, Epub ahead of print) that gathered data from 38 reports (totaling 9594 patients), the overall incidence of retrograde type A dissection after TEVAR was 1.7%, with a mortality rate reaching 33.6%. The odds ratio of retrograde type A dissection for an acute aortic dissection was 10.0 (95% confidence interval [CI], 4.7-21.9) and 3.4 (CI, 1.3-8.8) for chronic aortic dissection.

Additionally, he presented the results of the VIRTUE registry, describing the mid-term clinical and morphological results of TEVAR in patients with type B aortic dissection (Virtue Registry Investigators. Eur J Vasc Endovasc Surg. 2011;41(2):159-166). The VIRTUE registry is a prospective, multi-center clinical trial, which enrolled patients with complicated acute (<15 days), subacute (15 to 92 days), and chronic (>92 days) type B aortic dissections treated with the Valiant endograft. One hundred patients were enrolled and the clinical outcomes were described at a 3-year follow-up. 3-year allcause mortality (18%, 4%, and 24%), dissection-related mortality (12%, 4%, and 9%), aortic rupture (2%, 0%, and 4%), retrograde type A dissection (5%, 0%, and 0%), and aortic reintervention rates (20%, 22%, and 39%) were defined for patients with acute (50), subacute (24), and chronic (26) dissections, respectively. Analysis of aortic morphology observed that patients with subacute dissection demonstrated a similar degree of aortic remodeling to patients with acute dissection. As such, retention of aortic plasticity in the subacute group appears to lengthen the therapeutic window for the treatment of uncomplicated type B dissection.

Finally, he concluded that TEVAR could be performed in a subacute setting, with similar long-term results with significantly less acute complication rates.

Discussion

During the discussion regarding this controversy, some argued that performing thoracic endovascular aortic repair (TEVAR) in an acute setting of uncomplicated type B dissection is similar to carotid surgery in symptomatic patients: in fact, early surgery has been shown to be essential to reduce the high risk of stroke in the first few weeks after a transient ischemic attack or minor stroke, even at the cost of a higher complication rate.

In the end, the voting was favorable to M. Thompson.

Malperfusion and acute type B dissection: what is the best strategy?
T. Mastracci

The publication of long-term outcomes from the INSTEAD XL trial (INvestigation of STEnt grafts in Aortic Dissection with eXtended Length of follow-up) provided adequate data to perform TEVAR in uncomplicated dissection, promoting aortic remodeling, and changing the natural history of the disease. However, complicated dissections, especially those that present with malperfusion, remain a challenging clinical problem that can be lethal very early in the presentation of the disease. In the International Registry of Aortic Dissection (IRAD) database, visceral ischemia was the cause of death in 15.9% of patients (Booher AM et al; IRAD Investigators. Am J Med. 2013;126:730.e19-24). The author stated that malperfusion can be dynamic or static, and can have a variety of etiologies including intimal dissection and complete occlusion of branch vessels, intimal tear of the dissection flap causing interrupted flow, or dissection flap collapse during systole, making the treatment of malperfusion a challenge. As such, the author argued that endovascular surgeons must have a good understanding of the disease, as well as the likely clinical scenario based on individual patient characteristics.

The endovascular approach to malperfusion has included a variety of techniques, but most will agree that modern solutions are a combination of thoracic stenting, branch vessel stenting, and fenestration. The thirty-day mortality, in centers that have reported this, ranges from 0% to 25%, representing a heterogeneous group of patients and approaches, and making it challenging to gain insight into the best approach based on the reported literature alone. Where a good proximal landing zone exists, the author’s center favors placement of a thoracic stent as the first-line approach to malperfusion. This addressed the issue of altered flow dynamics in the true lumen, which is, in the author’s experience, commonly the cause of malperfusion. The author added that changing the flow dynamics between the true lumen and the false lumen, and not radial force alone, is the reason why proximal thoracic grafting is successful. When a primary thoracic stent does not completely resolve malperfusion and the large intimal tears above the celiac artery have been adequately covered, the author’s group adopts an approach of selective recanalization and stenting of branch vessels. Their experience with this method describes 61 patients with malperfusion over an 11-year span (Ryan C et al. J Vasc Surg. 2013;57:1283-1290). Malperfusion in these patients occurred in at least one territory (including spinal cord, 7/61 [12%]; mesenteric, 37/61 [61%]; renal, 45/61 [73%]; and lower extremity, 38/61 [62%]), but 43/61 patients had >1 bed effected malperfusion and 54/61 patients included mesenteric or renal involvement. Most patients were treated <24 hours after presentation (36/61, 59%). Thoracic stents were used in all patients, and branch vessel stenting was also required in 41% (25/61). Mortality was inversely associated with male sex (hazard ratio [HR], 0.42; 95% confidence interval [CI], 0.18-0.96; P=0.04), quitting smoking (HR, 0.31; 95% CI, 0.1-0.99; P=0.047), and positively associated with left subclavian artery occlusion (HR, 2.97; 95% CI, 1.09-8.11; P=0.034). The 30-day/in-hospital mortality was 21.3%. The 6-month, 1-year, and 5-year survival was 75% (95% CI, 65% to 87%), 71% (95% CI, 61% to 84%), and 56% (95% CI, 43% to 74%), respectively.

The author concluded that understanding of this lethal disease is still limited, but it appears that endovascular techniques may improve outcomes compared with medical management.

Acute type B dissection. Is closure of the proximal tear sufficient?
J-M. Alsac

Thoracic endovascular aortic repair became the treatment of choice for aortic dissections concerning the descending thoracic aorta because of its less invasive and reproducible character. The placement of a covered stent-graft on the proximal tear of the dissection redirects blood flow in the true lumen and treats most complications that may occur during the acute phase. However, the existence of other distal entry tears often leads to reperfusion downstream of the stent-graft, which maintains a circulating flow in the false lumen of the dissection.

In case of visceral malperfusion during the acute phase of the dissection, a higher pressure in the false lumen of the dissected aorta may lead to a “dynamic” compression of the true lumen where the most collateral for visceral arteries arise. To promote the true lumen expansion and perfusion vs the false lumen pressure, the Zenith Dissection Endovascular System (Cook medical, Bloomington, IN, USA.) proposes a composite device with noncovered metal stents that extend into the thoracoabdominal aorta, below the proximal thoracic aortic stent-graft. In the author’s group experience in the systematic treatment for dynamic malperfusion complicating acute dissections, the Zenith Dissection Endovascular System achieved satisfactory clinical results, safely and effectively, in the short-term. However, the long-term impact of this composite treatment on aortic remodeling remains to be determined (Alsac JM et al. J Vasc Surg. 2014;59:645-650).

Regarding mid-term evolution of aortic dissections, a persisting circulating flow in the false lumen of the dissection often promotes aneurysmal degeneration of the thoracoabdominal aorta. To avoid distal perfusion of the false lumen, the author proposed to adjunct a retrograde endovascular fenestration of aortic dissection flap to obtain a seal at the distal portion of the aortic stent-graft using the DEFINITE technique (Distal Endovascular Fenestration INsIde Thoracic Exclusion).

The author concluded that closure of the proximal tear in type B aortic dissections is efficient, validated, reproducible, but not always sufficient (50%), especially for extensive dissections. In this setting, adjunct procedures on distal tears may be required (extensive stent-graft, spot stenting, distal stabilization with a bare metal stent, and the DEFINITE technique). These combined endovascular options could limit the frequent aneurysmal evolution of aortic dissection and its fatal complications.

Chronic type B dissection. What is wrong with TEVAR?
R. Gibbs

Chronic type B dissection is defined as a dissection lasting for more than 6 weeks. The author presented some data from the Interdisciplinary Expert Consensus Document on Management of Type B Aortic Dissection (Fattori R et al. J Am Coll Cardiol. 2013;61:1661- 1678). As such, concerning the outcomes of endovascular treatment for chronic type B dissection, the perioperative mortality is 0% to 7.5%, and the mid-term mortality is 8%. As a result, it is advocated that interventional treatment (either endovascular or, when contraindicated, open surgery) should be reserved for recurrence of symptoms, aortic aneurysmal dilation (>55 mm), or a yearly increase of >4 mm after the acute phase. The uncomplicated chronic type B dissections should be left under medical therapy and an imaging surveillance protocol (at 6 weeks and annually thereafter).

1.1.3 Thoracoabdominal segment

When to use branched or fenestrated stent grafts, when to use chimney?
E. Ducasse

Since its first implementation in 1999, fenestrated endovascular aortic repair (fEVAR) has demonstrated excellent early and mid-term results. Meanwhile, the author stressed that fEVAR is not for emergent cases (even if it is possible to consider homemade grafts). He added that some technical points are also required such as: adequate bilateral iliac access (18F to 24F are required in contralateral access for fenestration catheterization, even though a double 7F puncture is possible); ostia of the target vessels are in the landing/sealing zone; targeted arteries have no important angulation, kinking, or stenosis.

Branched grafts have some advantage: the sealing zone is in the thoracic aorta, targeted arteries can be inside the aneurysm sac, and only one iliac access is needed.

The chimney technique (chEVAR) should be indicated as a bailout procedure for accidentally overstented aortic branches, adjunct to enable EVAR for a juxtarenal aneurysm in an urgent or emergency setting, and as an alternative option for patients not suitable for open repair or branched or fenestrated EVAR. It is contraindicated in aortic dissection and aortic stenosis. chEVAR has some advantages over branched or fenestrated EVAR as it is less complex, more available in smaller centers, cheaper, can be performed without previous device planning and customization, sizing is less crucial and can be an immediate solution in an acute setting. The chEVAR technique implies previous catheterization of targeted arteries before graft delivery, but allows different configurations (chEVAR juxtarenal, snorkel, and sandwich).

Subsequently, the author presented a series published in 2012 of 90 consecutive patients with juxtarenal aneurysms who were treated by fEVAR, chEVAR, or open repair, depending on the morphology and the clinical characteristics. This study demonstrated that: (i) either chEVAR or fEVAR are safe for the short-term management of juxtarenal aneurysms; (ii) chEVAR is quicker than fEVAR; and (iii) open repair is associated with longer hospital stays and higher blood transfusion requirements (Donas KP et al. J Vasc Surg. 2012,56:285-290).

The author concluded that fEVAR, branched grafts, and chEVAR are efficient and safe and should be adapted to each patient based on the anatomy and the setting of the presentation (elective/emergency setting).

Paraplegia following fenestrated and branched EVAR: incidence, severity, and ways to prevent it.
R. McWilliams

Spinal cord ischemia (SCI) is one of the major complications after fenestrated and branched endovascular aortic repair (EVAR). The GLOBALSTAR database (GLOBAL collaborators on advanced Stent-graft Techniques for Aneurysm Repair registry) of fEVAR in the UK records 5 cases of SCI in 318 registered patients (British Society for Endovascular Therapy; GLOBALSTAR Registry. Circulation. 2012;125:2707-2715). All were in grafts with four fenestrations, which is consistent with the known increased risk of SCI with greater aortic coverage. For this reason, the risk of paraplegia is much higher with thoracoabdominal branched grafts.

Strategies to reduce the risk of SCI include limitation of the reduction in the blood supply through the preservation of the left subclavian and hypogastric arteries and minimizing the length of aortic coverage, staging complex endovascular procedures, adjusting CSF and mean arterial pressures to maintain the spinal cord perfusion pressure, and using dedicated paraplegia prevention branches in endografts.

Neuromonitoring using evoked potentials has an established role in open repair of thoracoabdominal aortic aneurysms. Changes in the recorded traces are used to guide modifications to surgery and spinal cord perfusion pressure.

The author’s group has started using motor evoked potential (MEP) monitoring during thoracic endovascular aortic repair (TEVAR), fEVAR, and branched EVAR. One sensor is placed in each arm (internal control) and two to three are placed in each leg. A 50% or greater loss of amplitude in the leg MEPs is considered indicative of cord malperfusion. Meanwhile, monitoring is only valuable if there is a potential response strategy if the motor evoked potentials deteriorate. Unfortunately, there are no resheathable endografts, so if the MEPs deteriorate during a procedure, then the response strategy is aimed at increasing spinal cord perfusion through changes in cerebrospinal fluid and mean arterial pressure and, if this fails, by trying to increase spinal cord perfusion directly by inducing an endoleak. MEP monitoring may also be used during a procedure to test occlusion of the last branch and decide if this should be left open as per a paraplegia prevention branch. Ischemia from large groin sheaths and arm access can complicate the interpretation of changes to MEPs.

The author concluded that prevention of SCI should be based on graft planning, optimization of spinal cord blood supply, maintenance of spinal cord perfusion pressure, and, possibly, neuromonitoring the patient to guide the procedure.

1.1.4 Controversy: Off-the-shelf grafts. Are they needed and up to the job?

For the motion.
S. Haulon

Fenestrated and branched endografts have evolved as an effective treatment option for patients with juxtarenal, pararenal, and thoracoabdominal aneurysms. However, these technologies have required that they be specifically manufactured to fit an individual patient’s anatomy. More recently, off-the-shelf technologies have emerged as an additional option. These devices simplify case planning and preparation as visceral anatomy can be simply compared with device anatomical requirements. In addition, they are available for treatment of acute or symptomatic patients. When used within their indicated anatomical requirements, short-term results for some off-theshelf fenestrated and branch grafts are comparable with their custom-manufactured counterparts (Guillou M et al. J Vasc Surg. 2012;56:65-73).

The author concluded that if off-the-shelf grafts can apparently be suitable for more than 70% of the juxtarenal aneurysms (Sobocinski J et al. J Endovasc Ther. 2012;19:165- 172), then its use may be more limited for pararenal and thoracoabdominal aneurysms.

Against the motion.
C. Bicknell

It is very hard to argue against the need for off-the-shelf grafts, but it should be kept in mind that with advances in technology, this may not be the only mechanism with which to treat urgent/emergency complex aneurysms. The technique of in-situ fenestration or rapid in-house customized manufacturing would certainly challenge the need for offthe- shelf grafts with advances in imaging and robotics.

Even if the author admitted that an off-the-shelf solution is the only viable prospect of treating this group of patients, there are many unanswered questions. The main question is regarding tolerance of different anatomical configurations. With custommade manufacturing fenestrations/branches can be matched exactly to the required height and clock face orientation. However, if the fenestration/branch is misaligned there may be significant difficulties. Double diameter reducing ties and certainly intelligent catheter technologies will smooth the cannulation of vessels and introduction of branch stents, but the long-term durability of misaligned branches is yet to be understood due to aortic remodeling and the potential for fracture, kinking, and dislocation.

With dome shaped fenestrations, wide celiac artery scallops, and branch technology, the number of patients that may be treated with a few graft configurations is thought to be acceptable in morphological studies. However, there should be some caution because urgent and emergency cases are significantly larger with more complex anatomical configurations.

The author concluded that the range of aneurysms who can be treated with off-theshelf grafts is limited, that data relating to the number of patients that can be treated is fundamentally flawed, that there is no data on durability and late complications, and there is no proof that these grafts are what is needed or that they are up to the job at the present time.