ControversiesChallengesConsensus

Call for an advance in the treatment of aortic dissections at CX


Experts in the Thoracic Aortic Plenary sessions yesterday discussed cutting-edge topics that lack support from strong data, making consensus difficult to achieve. Many unanswered questions were raised such as which patients with thoracic disease should get early vs. late treatment; whether centralisation of aortic services would tackle the existing “postcode lottery” that determines the type of treatment patients receive; and whether the current classification of thoracic dissection is satisfactory. Experts agreed that treatments should be decided on an individual basis, according to anatomy and pathology, comorbidities, anticipated durability and by using a multidisciplinary approach.

The day began with Stéphan Haulon, Lille, France, making the case that there are different thoracic pathologies that needed different approaches. This idea gained broad consensus with experts agreeing that the different pathologies need to be distinguished when reporting study results.

“The clinical applications of endografts go beyond aortic aneurysmal disease. Although most of our studies and devices have focused on aneurysms, pretty much all that we will talk about today is applicable to the entire spectrum of aortic diseases—aneurysms, dissections, intramural haematoma, penetrating ulcers and trauma,” he said. Acute aortic syndrome could result from aortic dissection, intramural haematoma or a penetrating ulcer.
Aortic dissection is the most common aortic emergency seen in 10–15 cases per 100,000 adults/year. Of these, two thirds are type A and one third type B. In the acute type B, 30% are complicated and 70% uncomplicated. Also one in eight patients with aortic dissection have intramural haematoma or penetrating ulcer.

“With regard to treatment of intramural haematoma, asymptomatic patients may show resolution in 50–80% of cases. Thicker intramural haematomas are much likelier to progress and need frequent reimaging. Symptomatic patients are associated with a 33% rupture risk and the most likely treatment is stent graft repair. For penetrating ulcer, the treatment could be a simple TEVAR,” he said.

“For acute type B dissection, intervention is generally reserved for symptoms such as malperfusion of end organs; rupture; impending rupture (rapid expansion); and persistent pain and hypertension. The goals of TEVAR are coverage of primary tear, decreased pressure in the false lumen, repressurisation of true lumen, reperfusion of branch vessels and thrombosis of false lumen,” elaborated Haulon while explaining the treatment for acute dissection.

Which patients with “uncomplicated” dissections should we treat? “We need to try to predict progression. The timing of repair of uncomplicated dissections suggests that severe complications are more common in the acute and delayed acute (p=0.04) phase and that delayed intervention lowers the risk,” he clarified.

Once the dissection progresses to chronic phase, noted Haulon, 50% of patients rupture or require repair within four years. False lumen growth averages 3mm/year. TEVAR for chronic dissections results in 20% reintervention for persistent sac growth. In such cases, direct false lumen occlusion using the candy plug technique, or knickerbocker technique have been suggested.

For chronic dissections, treatment is tailored to age, genetic disorder, clinical risk and anatomy. “It is logical to assume that the benefits of endovascular therapy will be even greater when this is applied to more challenging anatomy given that more extensive dissection, higher clamp site, visceral ischaemia and reconstruction are all factors associated with increased morbidity,” he said.

With regard to aneurysmal disease, TEVAR is a first line strategy that has excellent immediate outcomes. High-risk patients may have poor long-term outcomes that are not related to the aortic disease.

Haulon also touched on aortic injury including that from trauma, other conditions such as aorto-bronchial fistulas and mycotic aneurysms, outlining individual treatment strategies for each. TEVAR is the first-line therapy in specific cases, with specific devices. As the majority of these patients are acute cases, the most promising results are achieved with a 24/7 aortic team, he said.

Ascending aorta

Rodney A White, Torrance, USA, then presented on ascending aortic remodelling for various pathologies. He spoke on a feasibility study set out to evaluate the Valiant (Medtronic) thoracic endograft for the treatment of ascending thoracic lesions with preserved “tubular” aortic anatomy (non-aneurysmal). Preliminary evaluation of the endograft demonstrates accurate deployment, secure fixation and no migration, he reported.

“There is a specially designed device inventory for ascending TEVAR device deployment. A single-centre investigational device exemption has been submitted to the FDA for approval. All procedures are performed in a hybrid operating room suite,” said White, who added that the hybrid operating rooms have been critical in the development of ascending aortic technologies. In the USA, the FDA is asking for data supporting the stability of endografts in the ascending aorta alone before evaluating more complex platforms, emphasised White.

In response to the concept that disease in the ascending aorta and the arch can be treated by endovascular means, the audience was asked to vote on the statement “total aortic endovascular repair beats open surgery hands down” debated by Timothy Resch, Malmö, Sweden, and Heinz Jakob, Essen, Germany. Seventy two per cent of the audience backed Jakob, voting against the motion. Jakob first outlined the goals of aortic intervention, which are to avoid the risk of rupture (for dissections and aneurysms); restore the true lumen perfusion and resolve malperfusion (in cases of dissection); warrant the durability of aortic restoration (for both dissection and aneurysms); and prepare easily accessible segments to facilitate secondary intervention. He called endovascular repair beyond the descending aorta “a brave new world”. He argued that the motion was incorrect as endovascular repair is currently in the early phase of application in selected centres that have a high level of experience in a highly selected patient population,” he said. Today, open repair beats endovascular repair, but in the future, both will work together closely.

Descending thoracic aorta

In another debate, a majority of CX delegates, 72%, voted their support for the Stanford system of classification’s current-day relevance in distinguishing between types of thoracic aortic dissection. The classification was proposed in 1970.

On the motion “For dissecting thoracic aneurysm terms type A and B are no longer satisfactory” Tilo Kölbel, Hamburg, Germany, who spoke against it, said: “The Stanford classification simplified the thoracic aortic dissection patients into two types: A and B. This new classification met the clinical need for the urgent triage in patients presenting with aortic dissection. Type A patients need surgery and patients with type B dissection are generally in need of less urgent intervention and can be managed medically, unless presenting with complications.”

He further added: “The important value of this initial classification according to the Stanford system is unchanged as it allows every physician to make the initial most important life-saving decision about where the patient should be directed: to the operating room (type A patients) or to the intensive care unit (type B patients).”

“Patients with aortic dissection require individualised treatment strategies according to their specific needs during the course of treatment. While many factors have to be taken into account, the Stanford classification is the unchanged first important step in stratifying patients with aortic dissection,” he said.

“It is time to adapt the Stanford classification—it is no longer satisfactory,” said Dittmar Böckler, Heidelberg, Germany, who was speaking for the motion.

Böckler noted that contemporary treatment of aortic dissections was influenced by two fundamental major developments: the International Registry of Acute Aortic Dissection (IRAD) and endovascular therapy for aortic dissection with the introduction of stent grafting by Michael Dake, Christoph Nienaber and others. “I believe that 50 years after the introduction of classification by Crawford, 37 years after the implementation of the Stanford classification and 18 years after the first successful endovascular treatment of aortic type B dissection, it is time to question if the current definitions of type A and B dissections are still useful,” said Böckler.

Building on his argument, Böckler made the point that the therapy for aortic dissection has become varied and multimodal for both type A and B. “There are also variants of aortic dissection that are unable to be assigned within the Stanford classification and anatomical differentiation should not decide where the patient goes.

“Treatment of dissection should be organised within interdisciplinary teams. The terms type A and B have been helpful for decades, but are not up to date anymore if we want to apply new knowledge and tools in an innovative changing medical environment,” he concluded.

Joseph Lombardi, Camden, USA, then told the audience that complicated means complicated and implies that there is a need to consider urgent intervention for these patients. He presented on the STABLE trial (using the Zenith endograft, Cook Medical) and noted that the data from both STABLE I and II show a low 30-day mortality and paraplegia rates with TEVAR. There is still a risk of disease progression, which requires close surveillance and reintervention as needed. “Bare stent management can be advantageous in early- and long-term presentations and management of complicated type B aortic dissection is a long-term commitment,” he said.

Uncomplicated chronic type B dissections

Speaking on the natural history and predictors of chronic type B dissection, Böckler commented that there were few long-term data on the natural history of these dissections. There appears to be an 80% to 90% mid- and long-term survival with best medical therapy. The annual aortic expansion rate is around one to two millimetres per year. “Data from randomised controlled trials shows that remodelling is better after TEVAR, but there is no proven survival benefit in the long term as yet. There are also image-based predictors for progression that are defined,” said Böckler.

He concluded that with regard to aortic-related mortality, the natural history in the chronic phase is relatively benign. “Recent guidelines still recommend best medical therapy for uncomplicated acute type B dissection. Nevertheless, there is a trend towards early intervention in patients at higher risk for aortic expansion based on the predictors of expansion,” he concluded.

Kölbel then presented a disease-specific approach for acute, subacute and chronic uncomplicated type B dissection. “Aortic dissection requires custom-made treatment strategies. Tubular stent grafts are sufficient in the majority of cases of type B aortic dissection. There is a need for advanced techniques in the acute and chronic settings. Access, choice of landing site and false lumen occlusion require planning, sound endovascular skills and a large variety of devices,“ Kölbel explained.

In a clear voting result, 92% of the CX audience backed the idea that a disease-specific approach should be adopted for acute, subacute and chronic uncomplicated type B dissection.

Jean-Marc Alsac, Paris, France, then spoke about a technique to stabilise and obliterate the false lumen, making the point that closure of the proximal tear is efficient but not always sufficient. The STABILISE (Stent-assisted balloon-induced intimal disruption and relamination in aortic dissection repair) approach, he said, is a feasible endovascular technique that shows promise to achieve repair of the dissected aorta by inducing complete false lumen obliteration. His experience with 52 patients showed no late adverse events and no aortic ruptures, stent migration, intimal flap erosion or redissection.

Alsac added that the technique is efficient to treat acute complications and seems to prevent aneurysmal progression, with a low reintervention rate. “The restoration of uniluminal flow in the thoracoabdominal aorta has the potential to improve long-term outcomes. Prospective, multicentre investigations are required to implement this strategy more broadly and to define the best indications and timing for such an aggressive therapeutic option,” he said.

Delegates were then asked to vote on the treatment they would favour for uncomplicated chronic type B dissections—14% chose fenestrated or branched EVAR; 8% elected to plug the false lumen; and 78% said they would avoid any intervention if the patient was stable.
Cerebral embolisation

Another point of discussion during the thoracic plenary programme was the risk of embolisation after aortic arch procedures. After a presentation by Richard Gibbs, London, UK, on the use of embolic filters to reduce the stroke risk in TEVAR (see more on page 15), delegates were asked to vote on whether “filters have an uncertain value.” The majority (75%) voted “yes”. Fiona Rohlffs, Hamburg, Germany, then presented on gaseous cerebral embolisation from endovascular aortic arch procedures.

2017-04-28T08:31:08+00:00