Program Book - Keck School of Medicine of USC - University of ...

Treatment of Ischemic Steal Syndrome:Unreliable techniques that are often ineffective –BandingPlicationReason for lack of reliability and efficacy:Based on premise that increasing resistance in the circuit can improve distal perfusion.Generally unreliable, insufficient, and often result in fistula thrombosisEffective procedures:Distal Revascularization Interval Ligation (DRIL):First suggested by Schanzer and colleagues in 1988, this procedure works on theperipheral circulation aspect of the fistula equation rather than on the resistance side.Although these authors also recognized that the ischemic steal syndrome resulted from adiscordant relationship between the resistance in the fistula and periphery, they suggestedworking the equation from the side of the peripheral circulation. They suggested that apotential mechanism of inadequate peripheral circulation resulted from a poorly formedcollateral network. In an attempt to reduce the resistance in the peripheral circuit, abypass graft (in essence, a low-resistance collateral) was created between the arteryproximal to the fistula and the artery distal to the fistula. This reduced the resistance ratiobetween the peripheral circulation and the fistula, reduced the brachial shunt fraction, anddirected a greater proportion of blood flow toward the periphery. To prevent retrogradeflow back up the native artery distal to the fistula, the artery distal to the fistula wasligated (Fig. 4A).Since this initial report, patients in whom this technique has been utilized haveexperienced excellent access patency and relief of ischemic symptoms. DRIL has the besttrack record in achieving these dual goals of ISS therapy.DRIL: mechanism of actionOne must remember that surgically created fistulas are of the large variety and that theprimary determinant of magnitude of blood flow through the fistula remains a function ofthe diameter of the donor artery. By definition the process of banding, or plication, mustnarrow the fistula sufficiently to convert a large, flow-independent fistula to a small, flowdependent fistula, the natural history of which is to eventually thrombose. Because theplication technique increases the resistance of the fistula it necessarily increases theresistance of the total circuit. In the face of a fixed inflow pressure the result is a globalreduction in circuit blood flow, of which a smaller fraction is shunted through the fistula.Although sometimes sufficient to improve peripheral perfusion, it creates a low-flowstate in the fistula and induces thrombosis. The resultant graft thrombosis, which usuallyoccurs subsequent to banding, remains predictable.In contradistinction the DRIL procedure (Fig. 4A) reduces resistance not only1167