Collateral back pressure-Is it a valid predictor of infrainguinal bypass graft patency?

While it is generally thought that collateral back pressure (CBP) is a reliable predictor of graft patency, this correlation has not yet been validated. We have used a new, simple technique to measure CBP without direct puncture of the recipient artery. After the distal anastomosis is completed, the graft is filled with saline and clamped proximally. A transducer connected needle is then inserted into the distal portion of the graft for CBP measurements (mm Hg). These were obtained in 84 grafts (43 femoropopliteals [FP] and 41 femorodistals [FD]). Outflow resistance (OR) measurements (mm Hg/ml/min) were also obtained in 70 (36 FP; 34 FD) of these grafts by a previously described technique. The mean CBP for FP and FD bypasses was 41 ± 17 and 26 ± 19 mm Hg, respectively (P < 0.001). Although early graft patency (3 months) (13 occluded, 71 patent) did not correlate with angiographic findings of popliteal runoff or integrity of pedal arch, it did significantly relate to CBP. Mean CBP for occluded grafts was 22 ± 17 mm Hg and for patent grafts it was 36 ± 19 mm Hg (P < 0.01). Similarly, mean OR was significantly related to patency, 1.29 ± 0.23 mm Hg/ml/min for occluded grafts and 0.36 ± 0.23 mm Hg/ml/min for patent grafts (P < 0.0001). Moreover, only OR was a significant predictor of infrapopliteal graft patency (P < 0.01). OR was found to be a better predictor of graft patency than CBP by stepwise logistic regression analysis (P < 0.0001). We conclude that CBP is a more reliable predictor of graft outcome than angiographic criteria. However, OR measurement remains the superior predictor for infrainguinal arterial bypass patency and the only reliable predictor of infrapopliteal bypass patency.