What are runoff vessels in Peripheral Vascular Disease (PVD)?

Runoff Vessels in Peripheral Vascular Disease

Runoff vessels are the patent distal arteries below the knee (tibial and pedal arteries) that provide outflow from a bypass graft or revascularization site to the foot, and their quality is the single most critical determinant of bypass graft success and limb salvage in PVD. 1

Anatomic Definition

Runoff vessels specifically refer to the outflow arterial pathway distal to a revascularization target, comprising:

• Below-knee popliteal artery 1
• Infrapopliteal (tibial) arteries: anterior tibial, posterior tibial, and peroneal arteries 1, 2
• Pedal arteries in the foot 1

The term "runoff" describes the venous drainage pathway in vascular access contexts 3, but in PVD it exclusively refers to arterial outflow vessels that receive blood flow from proximal revascularization procedures.

Clinical Significance for Revascularization

Impact on Graft Patency

The number and quality of patent runoff vessels directly determines surgical outcomes:

• Poor runoff (hemodynamically significant tibial arterial occlusive disease) accelerates prosthetic graft failure 1
• Single-vessel runoff distal to ankle is considered a finding that favors surgical over endovascular revascularization due to the technical challenges and poor durability of endovascular approaches in this anatomy 1
• The least-diseased tibial or pedal artery with continuous flow to the foot should be selected as the outflow vessel for distal bypass construction 1

Graft Material Selection Based on Runoff

Runoff quality dictates conduit choice:

• Bypasses to below-knee popliteal or tibial/pedal vessels (poor runoff scenarios) strongly favor autogenous vein over prosthetic material 1
• Prosthetic grafts to tibial arteries should be avoided entirely when runoff is compromised 1
• Five-year patency for femorotibial grafts: 70% with vein vs. 27% with prosthetic material 1

Assessment of Runoff Vessels

Preoperative Evaluation

In acute ischemia from thromboembolism, catheter-directed thrombolytic therapy is valuable for:

• Re-establishing patency of popliteal and tibial trunks 1
• Determining whether adequate target vessels exist for revascularization 1
• Clearing as much thrombus as possible from tibioperoneal and plantar arteries, since limb salvage correlates directly with the number of available runoff vessels 1

Imaging Considerations

Pulse-generated runoff (PGR) provides more accurate functional assessment than angiography alone:

• Angiography may show the peroneal artery as best preserved (79% patent vs. 47% posterior tibial, 38% anterior tibial) 2
• However, PGR studies demonstrate no significant difference in actual patency between the three calf vessels (peroneal 91%, posterior tibial 88%, anterior tibial 79%) 2
• PGR better predicts graft success or failure than angiography because it assesses functional rather than just anatomic patency 2

Critical Pitfalls

• Never assume angiographic appearance alone reflects functional runoff capacity—the peroneal artery may appear better preserved on imaging but functional studies show equivalent patency across all three tibial vessels 2
• Failure to restore adequate runoff through thrombolysis or thromboembolectomy before bypass grafting significantly compromises limb salvage rates 1
• Using prosthetic conduits for distal bypasses when runoff is poor leads to dramatically inferior patency (33% at 5 years for below-knee prosthetic grafts vs. 70% for vein grafts to tibial vessels) 1