Factors associated with limb loss despite a patent infrainguinal bypass graft.

Lower-extremity limb salvage should parallel infrainguinal bypass graft patency. To determine factors associated with limb loss despite a patent bypass, we reviewed 191 consecutive infrainguinal bypasses in 158 patients followed prospectively over 42 months. In this series of 176 (92%) vein grafts, 15 (8%) expanded polytetrafluoroethylene grafts, 122 (64%) tibial artery bypasses, and 170 (89%) bypasses placed for limb salvage, 29 major lower-extremity (above-knee or below-knee) amputations were performed in 29 patients, 12 because of ischemia after graft thrombosis and 17 (9% of series) due to progression of soft tissue infection/necrosis despite a functioning bypass. Primary and secondary 36-month vein graft patencies by life-table analysis were 61 per cent and 81 per cent, respectively. When the 17 cases of limb loss were compared to the rest of the series, nonstatistically significant variables included male sex [11 (65%) vs 79 (56%); P = 0.608] and diabetes [12 (71%) vs 80 (57%); P = 0.310]. Statistically significant variables included black race [9 (53%) vs 39 (28%); P = 0.048]; chronic renal failure [6 (35%) vs 12 (9%); P = 0.005], placement to a tibial/pedal artery [15 (88%) vs 107 (62%); P = 0.034], distal anastomosis to the anterior tibial/dorsalis pedis (AT/DP) artery [8 (47%) vs 27 (16%); P = 0.004], and grafts requiring late revision [7 (41%) vs 22 (13%); P = 0.006]. Thirteen (76%) extremities had an intact pedal arch. Nine amputations were performed within 30 days (early group), and eight were performed from 45 days to 20 months (median, 8 months) after bypass placement (late group). The most common primary causes of limb loss in the early group were overwhelming progression of soft-tissue infection despite patent bypass (n = 4; 44%) and insufficient runoff in the foot (n = 3; 33%). In the late group, amputation most often followed long treatment of a chronic proximal diabetic neuropathic foot ulcer with osteomyelitis. Five (63%) grafts in this group were anastomosed to the AT/DP arteries. These data suggest that patients with chronic renal failure, chronic neuropathic heel ulcers, and an AT/DP bypass are at greater risk for amputation despite a working bypass, especially if the graft develops a hemodynamically significant stenosis. Careful judgment and patient selection under these circumstances are thus justified.