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Neoaortoiliac (NAIS) System Bypass
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Neoaortoiliac (NAIS) System Bypass | ||
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Related narrative: Neoaortoiliac System (NAIS) Bypass of Infected Aortofemoral Graft Optimal treatment of an infected vascular prosthetic device includes removal of the infected graft and revascularization of the affected circulation through clean tissue planes. Disappointment with the results of extra-anatomic bypass led to the use of autologous tissue to replace the aortic prosthesis. Early results demonstrated that the saphenous vein is inadequate as an aortic conduit due to size mismatch and the propensity for early graft failure due to neointimal fibroplasia (1). On the other hand, the superficial femoral-popliteal vein (SFPV) has proved to be an ideal alternative. It has an excellent size match with the aorta and assisted patency rates approaching 100% (1,2). The SFPV has proven to be durable even in patients with multiorganism infections and intraperitoneal abscesses. Direct anastomosis with the aorta prevents the problem of aortic stump blow-out. Following implantation, the grafts undergo adaptation with wall thickening; there have been no reports of aneurysmal degeneration to date. Most encouraging, the mortality and amputation rates following creation of the neoaortoiliac system (NAIS) have been lower than those reported for patients undergoing extra-anatomic bypass (2). The major hesitancy to harvest the SFPV has been the concern for venous congestion and subsequent chronic venous stasis. Shulman et al. (3) published seminal work that demonstrated the minimal venous morbidity associated with SFPV harvest, and this has been corroborated by others. In a report of 61 patients who underwent 86 SFPV harvests, our group found that 32% of limbs had mild residual edema at three years (4). There were no instances of skin changes, ulcerations, or claudication. Follow-up venous Duplex scans showed abundant venous collaterals between the popliteal stump and the profunda femoris vein. Thus, there appear to be minimal mid- to late-term venous morbidity after SFPV harvest. The main limitation of the NAIS procedure that precludes its universal application is the operative time involved. The mean operative time has approached 8 hours in our experience (3) and may be even longer in cases involving complex revascularization procedures. We have found that a two-team approach can reduce the operative time by a significant margin. Each team harvests a SFPV, then one team exposes the femoral arteries while the other exposes the aortic graft in the abdomen. Even with these time-saving maneuvers, however, there are some patients who are too ill to undergo these extensive operations. We have found that severely debilitated patients are too ill to undergo the NAIS procedure, especially those with advanced malnutrition. While patients with other medical illnesses such as severe cardiac dysfunction, pulmonary insufficiency , and renal failure have been successfully treated with the NAIS, it is important to determine operative candidacy on an individual basis. Several major technical steps during SFPV harvest deserve re-emphasis (5). During SFPV exposure, it is important to mobilize the sartorius muscle on the lateral border to avoid compromising the muscle's blood supply. The SFPV has multiple branches, and many are large. We have found it necessary to double-ligate branches in order to prevent the catastrophic sequella of suture slippage. Since many patients have extensive lower extremity atherosclerosis, it is important to preserve arterial branches during dissection of the vein. Finally, the proximal end of the SFV should be divided flush with the profunda femoris vein in order to prevent creation of a "stump", with the potential for pulmonary embolism. References 1. Clagett GP, Bowers BL, Lopez-Viego MA, et al. Creation of a neo-aortic system from lower extremity deep and superficial veins. Ann Surg 1993; 218: 239-249. 2. Clagett GP, Valentine RJ, Hagino RT. Autogenous aortoiliac/femoral reconstruction from superficial femoral-popliteal veins: Feasibility and durability. J vasc Surg 1997; 25: 255-270. 3. Shulman ML, Badhey MR, Yatco R, et al. A saphenous alternative: Preferential use of superficial femoral and popliteal veins as femoropopliteal bypass grafts. Am J Surg 1986; 152: 231-237. 4. Wells JK, Hagino RT, Bargmann KM, et al.: Venous morbidity after superficial femoral-popliteal vein harvest. J Vasc Surg 1999; 29: 282-291. 5. Valentine RJ. Harvesting the superficial femoral vein as an autograft. Semin Vasc Surg 2000; 13: 27-31.
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