Figure 510

Outflow vein stenosis. Stenotic lesions are most often found at a polytetrafluoroethylene (PTFE) graft's venous anastomotic site or within its outflow vein. A, Radiograph depicting an angioplasty balloon inflated across an outflow vein with a stenotic lesion. The "waist" in the balloon (arrow) indicates the location of the stenosis. With increasing inflation pressure the waist disappears, an indication of successful angioplasty. Failure to eliminate the waist in the balloon indicates incomplete dilatation of the lesion. Occasionally, outflow vein stenoses are very resistant to dilatation and require high inflation pressures. This is not surprising given the amount of scarring and intimal hyper-plasia that can develop in a dialysis access site. B, Resected graft-venous anastomosis from a one-year-old PTFE graft. The vein wall seen here is enormously thickened. Angioplasty of lesions such as these is often unsuccessful, as this rigid material is likely to rebound to its stenotic state with any manipulation.

be necessary to permit removal of this material under direct visualization. Failure to remove this meniscus invariably leads to rethrom-bosis. B, This type of clot is demonstrated in an arteriogram performed through the brachial artery following thrombolytic therapy. The arterial end of this polytetrafluoroethylene (PTFE) graft demonstrates a residual intraluminal thrombus (arrow), which is typical of the platelet-rich plug or arterial type thrombus. A third type of clot (not shown) consists of a white laminar material that lines the graft over time, especially in sites of repeated puncture. This material can create a stenosis along the body of the graft and may be removed by curettage at the time of thrombectomy using an atherectomy catheter. Failure to remove this material decreases blood flow through the graft and may lead to rethrombosis. According to Poiseuille's law, if blood pressure remains constant, a 6-mm graft with 1 mm of circumferential laminar clot accommodates only 20% of the flow originally present, since flow is inversely related to the fourth power of the radius.

Eighty percent of thrombosed accesses have an associated stenotic lesion. C, An eccentric focal stenosis is demonstrated at the anastomosis of a PTFE forearm graft and its outflow vein (arrow), which did not respond to percutaneous transluminal angioplasty. The lesion was subsequently resected using a Simpson atherectomy catheter, which consists of a concealed cutting chamber that is deflected into contact with the stenotic lesion of the vessel wall by inflating the associated balloon. With the lesion projecting into the cutting chamber, a high-speed cylindrical cutting blade resects tissue into a collecting chamber. This chamber is rotated sequentially until the circumference of the lesion has been treated. D, The Simpson atherectomy catheter is placed across the stenotic lesion. E, The postprocedure venogram shows that the lesion was successfully resected.

How To Reduce Acne Scarring

How To Reduce Acne Scarring

Acne is a name that is famous in its own right, but for all of the wrong reasons. Most teenagers know, and dread, the very word, as it so prevalently wrecks havoc on their faces throughout their adolescent years.

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