Hemodynamics of vein graft stenosis

Abstract

The hemodynamics of 56 femorodistal saphenous vein bypasses (in situ [n = 53] or reversed [n = 3]) identified to have residual or recurrent graft stenoses were characterized with Doppler-derived blood flow velocity and resting limb systolic pressure measurements. The magnitude and configuration of the graft blood flow velocity waveform were the best predictors of graft stenosis. Transformation of the graft blood flow velocity waveform from a triphasic to a monophasic or biphasic configuration coupled with a low (less than 45 cm/sec) or decrease (greater than 30 cm/sec) in peak systolic blood flow velocity relative to initial postoperative levels reliably predicted the presence of a remote occlusive lesion. In 20 (36%) of the 56 limbs, the ankle-brachial systolic pressure index (ABI) did not identify graft stenosis. The low sensitivity of ABI in the identification of graft stenosis was due to insignificant decrease (less than 0.15) of ABI (n = 11), incompressibility of the tibial arteries (n = 6), or residual occlusive lesions after surgery (n = 3). Duplex scanning of grafts with low blood flow velocity localized the site of stenosis in 31 (86%) of 36 patients examined. Graft revision increased systolic blood flow velocity from 33 ± 9 to 77 ± 18 cm/sec (mean ± one standard deviation) a velocity similar to immediate postoperative levels (74 ± 17 cm/sec). Resting ABI increased from 0.61 ± 0.2 to 0.92 ± 0.1 after graft revision. Four grafts with low systolic blood flow velocity (range 18 to 40 cm/sec) not revised occluded 5 to 45 days later. A graft surveillance protocol that includes duplex sonography can identify vein bypasses with occlusive lesions that decrease flow and threaten patency.