Indications For Stent Placement And Fenestration

The exact role of percutaneous fenestration and stent placement in the treatment of aortic dissection continues to evolve. In dissection, there appears to be a role for stent-graft placement in the treatment of static or dynamic obstruction of aortic branch arteries because static obstruction of a branch can be overcome by placing endovascular stents across the vessel origin, and dynamic obstruction may benefit from stents in the aortic true lumen with or without additional balloon fenestration. In classic aortic dissection, successful fenestration leaves true and false lumen pressure unchanged. Sometimes bare stents must be deployed in the true lumen to buttress the flap in a stable position remote from branch artery origins7. In chronic dissection where fenestration of a fibrosed dissecting membrane may result in collapse of the connection between true and false lumen, a stent may be necessary to keep the fenestration open. A rare use of fenestration is to create a reentry tear for the dead-end false lumen back into the true lumen with the aim to supply blood to branches fed exclusively from the false lumen or jointly from the false and true lumen— a concept, however, that lacks any clinical proof. Conversely, fenestration may in fact increase long-term risk of aortic rupture because a large reentry tear promotes flow in the false lumen and provides the basis for aneurysmal expansion of the false lumen. There is also a risk of peripheral embolism from a patent but partly thrombosed false lumen7,8.

The most effective method to exclude an enlarging and aneurysmal dilated false lumen is the sealing of the proximal entry tear with a customized stent graft; the absence of a distal reentry tear is desirable but not a prerequisite. Adjunctive treatment by fenestration and/or ostial bare stents may help establish flow to compromised aortic branches. Compression of the true aortic lumen cranial to the main abdominal branches with distal malperfusion may also be corrected by stent grafts that enlarge the compressed true lumen and improve blood flow2,3,10,12. Depressurization and shrinking of the false lumen is the most beneficial result to be gained, ideally followed by thrombosis and remodeling of the entire aorta and in rare occasions even in retrograde type A dissection14. Similar to previously accepted indications for surgery in type B dissection, scenarios such as intractable pain with a descending dissection, a rapidly expanding false lumen diameter, or extraaortic blood collection as a sign of imminent rupture or distal malperfusion syndrome are accepted indications for emergent stent graft placement16-19. Dissection of a chronically aneurysmal aorta may still be considered a surgical emergency. However, late onset of complications such as malperfusion of vital aortic side branches warrants endovascular stent grafting of an occlusive lamella (or fenestration) to improve distal true lumen flow. After an unsuccessful attempt, surgery may still be required. At present, surgical repair failed to prove superiority over interventional treatment even in uncomplicated cases; in complicated cases the concept of endovascular treatment is currently replacing surgical interventions in advanced aortic centers1-3,17-20 (Figure 8.2).

Besides dissection, however, focal true (or false) aneurysm of the descending thoracic aorta represents another potential indication for endovascular repair instead of open surgical repair. A number of studies have documented

Percutaneous Fenestration
Figure 8.2.

not only feasibility and safety but also favorable short- and midterm outcomes especially in patients with multiple comorbid conditions subjected to elective stent-graft treatment for circumscribed thoracic aneurysms that otherwise would been considered for surgical therapy based on pathoanatomi-

Tevar Endovascular Radiology

before stent-graft after stent-graft

Figure 8.3.

before stent-graft after stent-graft

Figure 8.3.

cal features21-23. With the most recent technical refinements of endovascu-lar devices, previous shortcomings of homemade stent-grafts are likely to be overcome24. Treatment of descending thoracic aneurysms—if anatomically suitable—by endovascular stent grafting is the primary management consideration today25.

Penetrating aortic ulcers, often originating from a localized intramural hematoma of the aorta, may become an attractive indication for stent-graft patching, both in emergency and elective scenarios. However, few reports to date have documented successful sealing of ulcers by use of commercial stent grafts in an endovascular approach. While aortic ulcers may only occasionally progress so rapidly to generate a medical emergency, traumatic aortic rupture or partial or even complete transsection of the descending thoracic aorta is always a truly emergent life-threatening condition.

Partial or complete rupture almost always occurs as a result of deceleration trauma as in a car accident or fall from a significant height. The aorta most frequently ruptures at the fixation points and may be contained by nothing more than the adventitia. Emergent or better delayed (but timely) endovascular management by stabilization of the disrupted aorta with a suitable stent graft has proven feasible, with resultant reconstruction of the thoracic aorta by virtue of the inner lining by the endoprothesis that prevented enlargement, aneurysm formation and eventual rupture, but also promoted self healing of the transsected aortic tissues26 (Figure 8.3).

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