Vascular Outflow Resistance and Angiographic Assessment of Lower Limb Arterial Reconstructive Procedures

Abstract

In an attempt to predict early graft occlusion secondary to poor distal run‐off, the outflow resistance was measured intra‐operatively and compared with the intra‐operative angiogram in 50 patients undergoing lower limb bypass procedures. With arterial inflow occluded, 60mL of plasmalyte was infused via a catheter and the resultant pressure generated in the graft was measured through a second catheter connected to a pressure transducer and recorder. Using the infusion rate and integrated pressure value, outflow resistance was calculated. High resistance measurements were defined as grafts with outflow resistance > 1.1 mmHg/mL per min, low measurements were defined as values < 0.5 mmHg/mL per min and intermediate measurements were those in the range 0.5–1.1 mmHg/mL per min. Angiograms were classified independently of resistance measurements by scoring the numbers of run‐off vessels crossing the ankle and stenoses, with subsequent assignment of the patient to one of three groups with either low, intermediate, or high probability of graft failure. Early graft failure was defined as cessation of graft function within 3 months of surgery. Early graft failure occurred in both cases with high outflow resistance and in seven of 44 with low outflow resistance. Of these nine occluded bypasses, six had been placed in the high probability of occlusion category on angiographic appearance and three in the intermediate category. Assessment of angiographic appearance and prediction of patency on a prospective basis had a sensitivity rate of 67% and a specificity rate of 78%. The corresponding sensitivity and specificity rates with resistance measurements were 22% and 100%, respectively. Thus, intraoperative angiographic assessment of the run‐off was more useful than outflow resistance measurement in predicting early graft patency. The presence of diabetes did not assist in the prediction of patients who subsequently developed early graft occlusion.

Patency and Limb Salvage After Infrainguinal Bypass With Severely Compromised ("Blind") Outflow

“…Although this hemodynamic measurement was not performed in the current series, our results are consistent with most studies examining the effects of outflow resistance on graft patency. Studies performed by Peterkin et al, 12 Cooper et al, 18 and others 19 have failed to demonstrate hemodynamic outflow resistance as a predictor of infrainguinal graft patency. Although Ascer et al 20 maintain that outflow resistance does predict graft patency, anatomically blind outflow may not translate directly into high outflow resistance.…”

Resistance Within Hemodialysis Shunts Predicts Patency

“…In one earlier study intraoperative measurements of input impedance (based on P2 and Q waveforms only) at the venous end of arteriovenous fistulae found that low input impedance correlated with increased patency, 23 consistent with studies showing that outflow vein diameter is predictive of subsequent patency. 24 Previous studies have also shown that for lower extremity arterial bypasses with autologous saphenous vein, intraoperative measurements of longitudinal impedance strongly correlate with subsequent patency, as longitudinal impedance is a marker of the effective diameter in the bypass vein conduit. 21 In previous studies of resistance in PTFE grafts, narrowing at the venous outlet has been the most commonly observed locus of significant resistance -more common than either arterial inlet or midgraft resistance.…”