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The Hemodynamic Relationships that Exist between Various Parts of the Lower Extremity Arterial Circuit Containing a Bypass Graft: Case Study

Introduction Circuits containing bypass grafts are made up of four elements: (1) the inflow tract, (2) the graft, (3) the collateral beds, and (4) the outflow tract. The fundamental principles developed by Poiseuille, Ohm, and Bernoulli can facilitate our understanding of the hemodynamics that occur within the arterial circuit containing bypass grafts. Case Report A 59-year-old man was seen at our diagnostic vascular unit with severe claudication. Invasive and noninvasive vascular studies revealed occlusion of his aorta and bilateral common iliac arteries with reconstitution at bilateral groins by way of visceral vessels. Elective aortobifemoral bypass graft surgery was performed. Postoperatively, duplex ultrasonography (Phillips/ATL 5000, Bothell, WA, 7-MHz linear array transducer) performed on bilateral groins revealed prograde flow distal to the anastomoses and retrograde flow involving the distal external iliac arteries proximal to the anastomoses. Discussion Depending on the outflow resistance, flow might be prograde to the leg or retrograde to the pelvis and/or muscle proximal to the anastomosis or a combination of both as demonstrated in this case study. Such retrograde flow is desirable when one needs to perfuse the pelvis or thigh and not desirable if it steals blood from distal circulation. Conclusions The preceding fundamental principles refer to flow and pressure as inseparable manifestations of the total energetics of circulation. These principles are applied to the following case study and demonstrate competitive flow and pressure resistance relationships that exist within the arterial circuit containing a bypass graft.