Hemodynamics of distal revascularization-interval ligation

Distal revascularization-interval ligation (DRIL) empirically corrects steal after arteriovenous fistula (AVF) creation in most cases, but because there is no topologic alteration in anatomy, it is unclear as to why it is effective. To explore this issue, nine symptomatic patients underwent intravascular pressure and flow measurements before and after DRIL following upper arm autologous AVFs. Mean pre-DRIL systolic pressure (mmHg; mean ± SD) in the proximal brachial artery (PROX) was 102 ± 17, while that at the AV anastomosis (AV ANAST) was 47 ± 38 (p < 0.0006). Flow (mL/min) distal to AV ANAST was retrograde with the fistula open (-21 ± 64) but became antegrade (58 ± 29; p < 0.03) with occlusion of the fistula. Following DRIL, pressures at both PROX and AV ANAST sites did not change (104 ± 24 and 51 ± 43, respectively). However, pressure at the point at which the blood flow split to supply the hand or the fistula, now PROX, increased from 47 ± 38 (pre-DRIL AV ANAST) to 104 ± 24 (p < 0.0001). Pressure in the brachial artery distal to the ligature increased to 104 ± 27 (p < 0.0001), flow at this point (to the hand) became antegrade (51 ± 39; p < 0.03), and occlusion of the fistula did not significantly change pressure at this site. We hypothesize that improvement in hand perfusion following DRIL is due to a higher pressure at the point at which the blood flow splits to supply both hand and fistula (pre-DRIL: AV ANAST; post-DRIL: PROX), allowing antegrade flow down the new bypass to the lower pressure forearm. This increased pressure must be due to the increased resistance of the fistula created by interposing the arterial segment between the original AV ANAST and new PROX ANAST. As such, DRIL is schematically equivalent to banding, but resistance is increased in a fashion that is physiologically and empirically acceptable.