The Tuesday morning session “Extreme EVAR and TEVAR: Exploring the limits of endovascular technology” was full of “great cutting-edge stuff,” said course director Shaun Samuels. “It is where we would all like to be in a few years.”
Claudio J Schonholz, began the session with a discussion of chimneys, snorkels and periscopes. These techniques are an alternative to stent grafts with fenestrations or branches, and preserve blood flow to side branches in the sealing zones of aortic stent grafts.“They were developed by the same people that pioneered fenestration and branch grafting technology,” Schonholz said.
Chimneys are bare metal or covered stents that provide a path through which blood from the aorta is carried away to maintain perfusion of a branch vessel. Snorkels are bare metal or covered stents that are extended above the proximal edge of an aortic stent graft to maintain perfusion of a branch vessel, while periscopes are extended below the distal edge of an aortic stent graft. Each of these devices is relatively new, so there are only a few published reports on a small number of cases, Schonholz said.
“Results show low incidence of type I endoleak and high patency rate of branches, but what is going to happen long term?” he asked. “We really do not know.” Chimneys, snorkels and periscopes look technically simpler than fenestration, he said, but it also appears that they entail complex measurements. At this point, there are a variety of mathematical formulas to determine when these devices should be used. In conclusion, there is very little science on these devices, and “we need to do more work,” Schonholz said.
Frank J Criado said there is growing interest in chimneys and increased adoption by many operators around the world. However, although there are numerous “chimney papers,” there is low-level scientific evidence. Arch chimneys are great for bailout and rescue, they are readily available and they seem to work in most cases—in fact, they work better than they should, Criado said. The disadvantages are a potential for type I endoleak, chimney-endograft interaction and uncertain durability.
“The bottom-line question is can they be justified outside bailout/rescue indication?” Criado asked. “The answer is yes, but a qualified yes, because one has to have favorable anatomy: a neck beyond the chimney.”
Roy Greenberg followed with an update on branched and fenestrated grafts for aortic repair. Fenestrated and branch grafting began in 2001. Now there are reinforced fenestrations, used for type IV thoracoabdominal aortic aneurysms, dissections and small aortic lumens; external or external/internal side-arm branches, used for type II and III thoracoabdominal aortic aneurysms; and internal side-arm branches, which are used for arch aneurysms.
Greenberg said the latest data shows:
• Fenestrated and branched grafting for thoracoabdominal aneurysms is a reasonable alternative to open surgical repair, and appears effective at preventing rupture.
• Complications relating to renal dysfunction and paraplegia remain at a level of significance that should prompt further investigations and development.
• Branch durability is good, but there are no comparison groups (open surgery or hybrid techniques) with radiologic data at late follow-up time points.
• Mortality is similar to other aneurysm studies and similarly serious diseases, justifying the use of these treatment options in patients considered high surgical risk.
Noting that there are no comparative trials on parallel endografts, David Minion presented observations he has made on a CT analysis of 63 parallel endografts in 33 patients. “I do not believe that appropriate sizing alone will ensure success with parallel endografts; however, inappropriate sizing will likely lead to failure,” he said.
His conclusions were:
• The imperfect seal is a weakness of parallel endografts.
• When two equal-sized parallel endografts are used, each should be 82% of the diameter of the main graft.
• When a smaller parallel graft is used, self-expanding endografts conform much better than balloon-expanding endografts.
• The larger parallel graft (aortic endograft) should be oversized by a third to half the diameter of the smaller parallel graft (snorkel).
Source: ISET Daily News