ABSTRACT
Although deficit of the peripheral pulses can be acutely reversed with surgical repair of the dissected thoracic aorta in approximately 90%, patients with mesenteric or renal ischemia do not fare well. Mortality of patients with associated renal ischemia is 50 to 70% and increases to as high as 87% when mesenteric ischemia is present.5-7 Surgical mortality rates in patients with acute peripheral vascular ischemic complications are similar to those with mesenteric ischemia, approaching in-hospital mortality rates of 89%.8-11 Operative mortality of surgical fenestration of the dissection varies from 21 to 61%. This has encouraged percutaneous interventional management by endovascular balloon fenestration of a dissecting aortic membrane to treat mesenteric ischemia, a concept discussed as a niche indication in such complicated cases of malperfusion.10-12
The interventional management of Stanford type B (De Bakey type III; Figure 58.1) dissection and the use of stentgrafts evolved slowly in anticipation of the risk of paraplegia resulting from spinal artery occlusion, which may occur in up to 18% of cases after open surgery.11,12 With further technical improvements, a large series of cases has now been successfully treated in various specialized centers by placement of endovascular stent-grafts covering the entry tears in the descending aorta as well as in the aortic arch. Recent studies have demonstrated that closure of proximal entry tears is essential to reconstruct the aortic wall and to reduce the total aortic diameter. Closure of entry tears promotes decompression of the false lumen, formation of thrombus in the false lumen (Figure 58.5), and remodeling of the entire aorta.2,3,12 In the near future, combined surgical and interventional procedures, even for proximal dissection, are likely to evolve.13-15
Current indications for fenestration and endovascular aortic repair The exact role of percutaneous fenestration and stent-grafting in the treatment of aortic dissection is not fully established yet. There appears to be a role for interventional management in several aspects of the treatment. These include treatment of static or dynamic obstruction of aortic branch arteries, overcoming static obstruction of a branch by placing endovascular stents in the ostium of the compromized side branch, and treating dynamic obstruction with stents in the aortic true lumen with or without additional fenestration with a balloon or stenting of a side branch. In classic aortic dissection, successful fenestration leaves the pressure in the true lumen unchanged.16 Sometimes bare stents deployed from the true lumen into side branches are
useful to buttress the flap in a stable position.17 In chronic dissection, in which fenestration of a fibrosed dissecting membrane may result in the collapse of the connection between the true and false lumen, a stent may be necessary to keep the fenestration open. A rare use of fenestration is to create a re-entry tear for the dead-end false lumen back into the true lumen with the aim of preventing thrombosis of the false lumen and compromise of branches fed exclusively from the false lumen or jointly from the false and true lumen. This concept, however, lacks clinical proof of its efficacy. Conversely, fenestration may increase the longterm risk of aortic rupture, because a large re-entry 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 lumen.17,18
The most effective method to exclude an enlarging and aneurysmally dilated false lumen is to seal the proximal entry tears with a customized stent-graft; the absence of a distal re-entry tear is desirable for optimal results but not a
prerequisite. Adjunctive treatment by fenestration and/or ostial bare stents may help to establish blood flow to the compromised aortic branches. Compression of the true aortic lumen cranial to the main abdominal branches with distal malperfusion (so called pseudo-coarctation) may also be corrected by stent-grafts that enlarge the compressed true lumen and improve distal aortic blood flow.2,3,10,12
Decompression and shrinking of the false lumen is the most beneficial result to be gained, ideally followed by complete thrombosis of the false lumen and remodeling of the entire dissected aorta (Figure 58.6), and on rare occasions, even in retrograde type A dissection.14 As in previously accepted indications for surgical intervention in type B dissection, scenarios such as intractable pain with descending aortic dissection, rapidly expanding diameter of the false lumen, extra-aortic blood collection as a sign of imminent rupture, or distal malperfusion syndrome are accepted indications for emergency placement of stent-grafts.15,17-19 Moreover, late onset of complications such as malperfusion of vital side branches of the aorta may justify endovascular
stent-grafting of an occlusive lamella (or fenestration) to improve flow in the distal true lumen as a first option. Only after an unsuccessful attempt may surgery be employed, considering that surgical repair has failed to prove its superiority over interventional treatment even in uncomplicated cases; in complicated cases the concept of endoluminal treatment is currently replacing open surgery in advanced aortic centers.1-3,17-20 A summary of treatment options is listed in Table 58.1.
