Rationale
Peripheral vascular disease (PVD) is a condition cause by arterial blockages causing inadequate blood flow, resulting in pain and gangrene of the legs. The prevalence of PVD in the North American general population over 50 years of age is estimated at 17.4%, and is rising in association with the increasing prevalence of diabetes [
1]. Bypass surgery is typically reserved for patients with severe forms of PVD, and minimally invasive options of angioplasty (“endovascular surgery”) are emerging as the treatment of choice for most patients with PVD. Angioplasty is the foundational treatment of endovascular therapy, which may be augmented by treatments such as stenting and atherectomy. Unfortunately, the 2-year patency of balloon angioplasty for PVD is poor, reported between 50–80%, depending on lesion location and characteristics [
2]. The 1-year amputation rate despite endovascular revascularization has been reported as high as 32% in patients with lower limb critical limb ischemia [
3]. This has prompted investigation into the predictors of failure, and potential solutions to optimize the success rate of revascularization. One proposed method is to evaluate the physiologic improvement in limb perfusion intraoperatively, to provide the operator with an opportunity to evaluate the procedural success and potentially guide intraoperative decision-making.
One of the most important predictors of clinical success following endovascular surgery for PVD is the post-procedure ankle-brachial index (ABI) [
4]. This measurement is performed by applying a blood pressure cuff at the level of the lower leg (“Ankle Pressure”) and the arm. The ABI is a ratio of the blood pressure at the ankle when compared with the arm. Similarly, a smaller cuff around the great toe can determine the absolute toe pressure, which can also be used to calculate the toe-brachial index (TBI). The change in ABI following endovascular surgery can be detected a day after the procedure, and remains stable throughout the month following the procedure [
5]. Several other postoperative markers of limb perfusion have also been investigated. Magnetic resonance arterial spin labeling correlates with postoperative ABI and clinical outcomes [
6]. Furthermore, some authors have investigated markers of limb perfusion during surgery, finding correlation between postoperative ABI and intraoperative 2-dimensional perfusion angiography [
7] and indocyanine green intra-arterial injection [
8]. Other methods such as laser doppler [
9], near-infrared spectroscopy [
10,
11], transcutaneous oxygen saturation [
12], and micro-oxygen sensors [
13] have also been evaluated. While these methods have been established as markers of perfusion in the outpatient setting, their role in guiding intraoperative decision-making is unclear.
The potential of physiologic measures to predict clinical outcomes after endovascular revascularization presents several opportunities. The current practice of waiting until the postoperative period to measure the limb pressure after surgery may miss opportunities to guide intraoperative decision-making. While angiogram is currently the primary form of intraoperative feedback, conventional angiogram provides only anatomic feedback, which may not correlate with physiologic perfusion of blood due to microvascular disease and diffuse disease.
Objectives
The aim of this systematic review is to evaluate if in patients undergoing endovascular surgery for lower extremity atherosclerotic peripheral arterial disease, do changes in physiologic measures of limb perfusion during surgery correlate with clinical outcomes. Physiologic measures include non-invasive and invasive arterial pressure measurements, transcutaneous oxygen measurement, infrared spectroscopy, laser doppler flowmetry, and angiogram perfusion calculations.
Secondary questions that will be addressed by this review will investigate the correlation of intraoperative physiologic measures with non-clinical postoperative outcomes such as radiographic patency and hemodynamic outcomes.