Wijesinghe L D, Scott D J
Department of Vascular and Endovascular Surgery, St. James's University Hospital, Beckett Street, Leeds, LS9 7TF, UK.
Eur J Vasc Endovasc Surg. 2001 Dec;22(6):509-15. doi: 10.1053/ejvs.2001.1527.
Impedance is the equivalent in pulsatile flow of resistance in steady flow. The impedance index has been used successfully in the surveillance of vein grafts, but its use has not been reported in the context of PTFE femorodistal grafts.
Twenty-eight patients (median age 68 years (IQR 59-73 years) and 20 men) undergoing 28 PTFE femorodistal grafts with a vein cuff were evaluated prospectively comparing the impedance index with standard duplex graft surveillance. All grafts were performed for critical ischaemia. At risk grafts were identified and treated appropriately after angiography.
The primary patencies at 1 and 2 years were 82% and 50% respectively. Duplex identified 11 at risk grafts of which 9 had an identifiable correctable lesion. Impedance analysis overpredicted at risk status when compared with duplex in the immediate postoperative phase and was unsuccessful in detecting inflow disease or low flow relating to cardiac failure. Using a threshold index of 0.5, impedance analysis has a sensitivity of 87%, specificity of 88%, with positive and negative predictive values of 76% and 94% respectively.
Impedance index is a non-invasive method of graft surveillance which is applicable to PTFE femorodistal bypasses and may be a useful alternative to duplex although formal validation studies will be required.
在脉动血流中，阻抗相当于稳流中的阻力。阻抗指数已成功用于监测静脉移植物，但在聚四氟乙烯股腘动脉移植物方面尚未见相关报道。
对28例行带静脉套袖的聚四氟乙烯股腘动脉移植物手术的患者（年龄中位数68岁（四分位间距59 - 73岁），男性20例）进行前瞻性评估，将阻抗指数与标准双功超声移植物监测进行比较。所有移植物均用于治疗严重缺血。对有风险的移植物进行血管造影后识别并适当处理。
1年和2年时的初始通畅率分别为82%和50%。双功超声识别出11例有风险的移植物，其中9例有可识别的可纠正病变。与双功超声相比，术后即刻阻抗分析对有风险状态的预测过度，且在检测流入道疾病或与心力衰竭相关的低流量方面未成功。使用0.5的阈值指数，阻抗分析的敏感性为87%，特异性为88%，阳性预测值和阴性预测值分别为76%和94%。
阻抗指数是一种用于移植物监测的非侵入性方法，适用于聚四氟乙烯股腘动脉旁路移植术，尽管需要进行正式的验证研究，但可能是双功超声的一种有用替代方法。
