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Noticias
The parallel nature of PGs relates to the course and position of the conduit in relation to the intra-aortic stent-graft, but it is not a reflection of their mutual relationship when multiple. Given the current proliferation of technical modifications and new iterations emerging over the past few years, it is the authors’ view that proposal of a simple but clear classification should prove helpful for description, documentation, and reporting purposes.
The new classification recognizes 2 basic PG types depending on where the proximal (inflow-taking) end of the conduit resides, whether in the lumen of the native aorta or in a stent-graft device (Table 2):
2. Type II PG, on the other hand, designates a PG conduit that travels(usually for several centimeters or more) from the lumen of an aortic stent-graft to the target branch vessel, including a segment of 5 cm or more where the conduit is sandwiched between two aortic endografts. The sandwich graft (and variations thereof) and the multiple thoraco-abdominalvisceral/renal conduits can be cited as prototypical examples (Figure 3).
Two recently published review papers provide a useful summary of currently available evidence.Overall, the authors noted the high technical success rate of the chimney technique and relatively few complications and low risk but also pointed to the many unknowns, including choice of an optimal stent device for a given case. Clearly we need more information on a larger pool of patients and with longer term follow-up.
Data on sandwich grafts and other long thoraco-abdominal PGs are also limited. Recent publications offer a glimpse into the actual potential of these techniques, but it is only the beginning.
Clinical use of PGs is clearly growing. But amid the heightened attention we must remember their currently imperfect nature and important limitations. Worthy of mention among these are the relatively small clinical dataset and insufficient information on long-term follow-up, the gutters that result from their interaction with the aortic stent-graft (Figure 4) and resultant potential for endoleak, and the absence of clear guidelines on best choices for device type in a given situation. Some, if not all, of these issues may be resolved or improved upon in theforeseeable future through better techniques and – perhaps – the development of better suited PG conduit technologies. This may become an imperative of sorts as long PGs and sandwich grafts become ever more popular in the hands of operators managing complex aortic pathologies (Figure 5).