Most vascular interventionalists would generally agree that the technical success of an intervention is the presence of antegrade flow through a treated lesion at the conclusion of a procedure. This can be measured semi-objectively through palpation of distal pulses and Doppler flow, duplex scanning, angioscopy, and most frequently completion angiography. Angiography is typically the simplest, most effective, and widely used measure of technical success. Unlike Doppler flow, intraoperative duplex scanning, and angioscopy, angiography can rapidly evaluate the conduit, tunnel, proximal and distal anastomoses, and outflow for graft-threatening lesions with relatively minimal contrast, time, and increased user-friendliness. Mills et al. prospectively evaluated 214 consecutive infrainguinal bypass grafts (209 reversed vein and five PTFE) with the use of visual inspection, pulse palpation, Doppler flow patterns, and completion angiography. Their group identified 8 % significant lesions requiring revision with angiography, with a higher incidence in tibial than popliteal reconstructions [2].

Graft patency, although with a wide range of definitions, is an objectively measured outcome. It is described as primary, assisted primary, or secondary patency rates. Primary patency describes a continuously patent graft without any intervention to itself directly. This definition varies in the endovascular literature since the native artery was patent before treatment; thus, most include recurrent stenosis in this patency rate, which is usually 50 % restenosis [3]. Other reported measures of primary patency have included duplex ultrasound-obtained velocity ratios >2.4 or ABI decreases >0.15 [4]. Assisted primary patency describes patency after an intervention, whether endovascular or open, to maintain patency without an occlusive event. Stenotic lesions found after primary intervention and treated by endovascular means have the same low morbidity as those “de novo” lesions treated with primary endovascular therapy [5]. Lastly, secondary patency describes an occluded graft or vessel in which patency was restored after successful reintervention. Thus, overall, primary patency reflects the durability and technical success of the initial bypass graft or endovascular procedure, assisted primary patency reflects the impact of surveillance and appropriate reintervention before occlusion, and secondary patency reflects the timing of intervention and efforts of the surgeon in restoring patency after occlusion. The use of patency rates in terms of successful outcomes should be used with caution, however, as it does not correlate well with limb preservation. For example, Smith et al. [6] found that 10 % of patients who underwent lower extremity bypass did not improve clinically despite having a patent graft at 1 year postoperatively.

Target lesion revascularization (TLR) is typically used to define a reintervention performed on a recurrent lesion within 5 mm of the lesion treated during the index procedure. Similarly, target vessel revascularization characterizes any repeat intervention on the same vessel as the index procedure. Although the concept of TLR was first used to assess the safety, efficacy, and durability of percutaneous interventions, it has been shown to be a surrogate endpoint of patency with no direct correlation with healing, function, and limb preservation. It can also overestimate the efficacy of the index reintervention since patients may elect not to undergo surgery for mild symptoms, such as claudication. Thus, the usage of TLR as an endpoint is typically less accurate than patency rates.

Measurement of the ABI is the simplest and preferred noninvasive method of detecting lower extremity arterial occlusive disease and its progression. The standard deviation for the ABI is approximately 0.07, so differences of twice this deviation (0.15) represent a significant and clinical difference [7]. The ABI has been validated against angiography in the detection of stenoses greater than 50 % [8]. It has also been correlated with an increase in mortality, regardless of whether leg symptoms are present [9].

Measurement in transcutaneous oxygen (tcPO2) is a noninvasive method of determining the partial pressure of oxygen transcutaneously. A small sensor is placed on the skin, and by heating the sensor and skin to 44 °C, local hyperemia results in decreased flow resistance and vasodilation of capillary blood. Several studies have shown that tcPO2 levels have an accuracy of 87–100 % in wound healing [10]. Increases in tcPO2 levels greater than 30 mmHg following lower extremity revascularization are predictive of successful clinical outcomes [11]. In terms of selecting the optimal level of amputation, direct comparisons between segmental pressures, and skin blood flow, tcPO2 levels have been the most accurate predictor of wound healing [12] (Table 56.2).

Wound healing , which is the time required to achieve complete epithelialization of all lesions, is a major challenge after endovascular or open revascularization [16]. Chung et al. [16] determined that the baseline lesion severity predicted wound healing rather than graft patency and other clinical characteristics (serum albumin level and duration of symptoms). Although most patients with CLI treated with the optimal revascularization procedure healed all wounds and retained their functional status, a significant minority did not heal their wounds and lost ambulatory capacity and independent living status. One-fourth of patients did not achieve wound healing at 1 year of follow-up, 19 % had lost ambulatory function, and 5 % had lost independent living status.

Goshima et al. [17] attempted to define the expenditure of effort, complications, and difficulties encountered by the patient and the surgical team to achieve limb salvage in the early and intermediate postoperative period. They analyzed three specific, nontraditional outcomes measures: (1) reoperation within 3 months, (2) readmission in the first 6 months after the index revascularization, and (3) time to complete wound healing. Hospital readmissions within 6 months were required in 49.3 % of patients. Less than half of those patients presenting with ischemic tissue loss achieved complete wound healing within a 3-month period. In this study, diabetes proved to be the dominant risk factor for the prolonged wound healing. The pathophysiologic relationship between diabetes and impaired wound healing is complex, but vascular, neuropathic, immunogenic, and biochemical abnormalities all contribute to a diminished capacity for tissue repair [18]. Diabetic patients, particularly those with renal failure, often suffer nonhealing wounds despite patent, functional bypass grafts. Numerous studies have suggested that the presence of renal failure interferes with wound healing. In the present report, although renal failure was a major risk factor for repeat operation and readmissions, it was not a major risk factor for prolonged wound healing. In a study published by Johnson et al. [19], failure of foot salvage in renal failure patients was related to poor wound healing, such as ongoing ischemia or uncontrollable infection, despite a functional graft. These patients may ultimately require major limb amputation despite ongoing graft patency [20]. Elderly patients with preoperative ambulatory impairment, dementia, and end-stage renal disease often achieved very little improvement in their functional performance after successful revascularization, regardless of whether the treatment was percutaneous or open bypass [21].

Conte and authors [14] state that patients with CLI and nonhealing wounds incur pain, disability, and extensive treatments that may be dramatically relieved by effective revascularization. Wound healing is an important measure of clinical success, but is fraught with difficulties as a clinical trial endpoint. They suggested that wound care guidelines should be established by protocol to provide uniform care for all subjects in a trial where healing is an endpoint. Ulcers should be photographed at baseline; 3, 6, and 12 months posttreatment; and prior to revascularization or major amputation. An independent core laboratory should review the size of ischemic ulcers at baseline and an independent observer (physician) should confirm the complete healing of the target ulcers posttreatment. The duration of complete healing as confirmed by the outside observer should be at least 2 weeks.