Extra-anatomic bypass: a new look (opposing view).

The criteria by which revascularizations are measured ultimately is patency, since cessation of blood flow equates with a failed graft and usually signals a return to the preoperative limb perfusion or less. An uncommonly analyzed criterion for graft function is blood flow capacity through the reconstruction which is critically important when increased blood flow demands are required with exercise. This is particularly true in the aortoiliac segment when the bypass must meet large blood flow requirements. When the extra-anatomic bypass is evaluated in this manner, it is often inadequate to meet the blood flow demands required with activity. The source of blood flow is the subclavian artery and not the aorta. The graft diameter is almost one half that used to bypass or substitute for the aorta and four times as long. It is not surprising, therefore, that increases in blood flow are limited in this remote subcutaneous bypass circuit. The axillofemoral and, to some extent, the femorfemoral bypass grafts produce hemodynamic gradients to blood flow increases above basal rates. Thus, graft patency alone does not realistically measure the functional capacity of an aortoiliac reconstruction. The conceptual design of an extra-anatomic bypass results in hemodynamic liabilities that produce an inferior performance to that observed with in-line direct aortofemoral bypass. This observation further supports our contention that extra-anatomic bypass of the aortoiliac segment should be restricted to circumvent a prosthetic graft infection in the aortoiliac segment to maintain limb perfusion following graft removal. Whether it has a role in selected patients with a short life span and critical ischemia who appear to be a prohibited risk for in-line aortofemoral reconstruction will always be debatable. Current experience does not justify expanded indications for extra-anatomic bypass in symptomatic patients with aortoiliac disease. The proven effective and durable intervention is aortofemoral revascularization.