Procedural Techniques May Boost Aortic Remodeling After TEVAR, but Only for Acute Dissections

Certain procedural techniques may be more important than others when it comes to aortic remodeling and clinical outcomes after thoracic endovascular aortic repair (TEVAR) of type B aortic dissection, according to a small study. Moreover, these factors only seem to influence the results of acute—but not chronic—cases. 

Fabrizio Fanelli, MD, of University of Rome “Sapienza” in Italy, and colleagues note that aortic remodeling after TEVAR—typically achieved by excluding the false lumen created by the dissection, leading to subsequent enlargement of the true lumen but not the total aortic diameter—is associated with better outcomes. But just which procedural characteristics are associated with remodeling remains unclear.

For their study, published this week in the Journal of the American College of Cardiology, Fanelli et al looked at 60 consecutive patients who underwent TEVAR for complicated type B acute aortic dissection (n = 29) or chronic aortic dissection (n = 31). All procedures took place between November 2009 and January 2011. They involved 5 different commercially available stent grafts, with patients being followed for at least 3 years.

The researchers report that the clinical success rate was 93.1% in the acute dissection group and 100% in the chronic dissection group. Technical success was achieved in all patients, with correct deployment of the stent grafts and complete exclusion of the primary entry tear.

By 3 years, TEVAR for acute aortic dissection resulted in an overall increase in true lumen diameter and a decrease in the false lumen diameter, as measured at a range of prespecified levels within the aorta above, below, and within the stent. Less prominent  changes were seen in the chronic dissection patients.

Type I and II endoleaks were noted in 28% of all patients (17.6% type I and 82.3% type II).

As seen in other studies, false lumen thrombosis was directly associated with freedom from major adverse events and endoleaks in the acute aortic dissection group but not in the chronic aortic dissection patients.

Insights into Technical Differences

In terms of which procedural factors were important to aortic remodeling, Fanelli and colleagues looked specifically at:

• Stent graft oversizing 
• Balloon dilation after stent deployment 
• Number of stent grafts implanted 
• Length of aorta covered 
• Covering of the left subclavian artery 
• Embolization of the left subclavian artery during TEVAR 

Of these, balloon dilation after stent deployment and embolization of the left subclavian artery were associated with increased aortic remodeling in acute aortic dissections, but not in chronic aortic dissections, where none of the procedural factors appeared to play a significant role.

Fanelli and colleagues say the results confirm that in acute dissection, false lumen thrombosis and shrinkage “is directly proportional to the absence of [major adverse events] and endoleaks. By comparison, [false lumen] thrombosis in CAD is less prominent initially and at the same time has a weak correlation with [major adverse events] and endoleak occurrence.”

They also note that in all patients with chronic dissection, successful treatment involved covering a significantly longer segment of the aorta compared with the amount covered in an acute dissection. “This may indicate the need to extend the stent grafts more distally to obtain complete exclusion of the [false lumen] and to increase the [true lumen] diameter,” Fanelli and colleagues write. “By comparison, in [acute dissection], shorter distances can be covered given the high clinical success rate and remodeling and the higher risk of paraplegia.”

Patient-Focused Endpoints

Philip P. Goodney, MD, MS, of Dartmouth-Hitchcock Medical Center (Lebanon, NH), told TCTMD in a telephone interview that the observational study provides a novel endpoint—aortic remodeling —that is important for operators performing TEVAR, but less so the patients themselves.

“From the patient’s point of view you’re not worried about whether your lumen is thrombosed or patent. You want to make sure that your pain goes away and your aorta doesn’t rupture and that you don’t go into kidney failure or have the blood supply to your intestines disturbed,” he said. “But aortic remodeling is important to patients in the long-term, because patients whose false lumens don’t thrombose are at higher risk of needing secondary procedures at a later date or developing aneurysmal degeneration of the aorta.”

Goodney added that the study also shows that there is a much better understanding now than in the early days of TEVAR regarding the differences between acute and chronic aortic dissections. “In terms of [whether we have] learned exactly how to navigate all the treatment challenges, I think that answer is still in play and we’re still learning,” he said. “We know that they are different and they are challenging, each in different ways, but the methods used in this paper will help us find the ultimate best decisions in the future.”

In an editorial accompanying the study, Santi Trimarchi, MD, PHD, of IRCCS Policlinico San Donato (Milan, Italy), and Kim A. Eagle, MD, of University of Michigan Health System (Ann Arbor, MI), add that some of the procedural factors have not been well studied previously, including oversizing, left subclavian artery embolization, and length and number of implanted devices.

It is noteworthy that oversizing did not influence the occurrence of endoleaks, remodeling, or major adverse events, and that the length of coverage did not have any influence on remodeling, the editorialists observe. However, they suggest caution in interpreting the findings from such a small cohort.

“The focus of the current paper is on diameter only; however, a volumetric analysis of the true and false lumen and the size and precise location of the entry tear would have added even more value to the paper, because this gives a more clear indication of the changes in both lumens after TEVAR,” Trimarchi and Eagle note.

Sources: 
1. Fanelli F, Cannavale A, O’Sullivan GJ, et al. Endovascular repair of acute and chronic aortic type B dissections: main factors affecting aortic remodeling and clinical outcome. J Am Coll Cardiol Intv. 2016;9:183-191.
2. Trimarchi S, Eagle KA. Thoracic endovascular aortic repair in acute and chronic type B aortic dissection [editorial]. J Am Coll Cardiol Intv. 2016;9:192-194. 

Disclosures:

• Fanelli and Goodney report no relevant conflicts of interest. 
• Trimarchi reports having served as a consultant and speaker for Medtronic and WL Gore.  
• Eagle reports having received research grants from Medtronic, Terumo and WL Gore. 

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