Perfusion Assessment in Critical Limb Ischemia: Principles for Understanding and the Development of Evidence and Evaluation of Devices: A Scientific Statement From the American Heart Association

Abstract

There are >12 million patients with peripheral artery disease in the United States. The most severe form of peripheral artery disease is critical limb ischemia (CLI). The diagnosis and management of CLI is often challenging. Ethnic differences in comorbidities and presentation of CLI exist. Compared with white patients, black and Hispanic patients have higher prevalence rates of diabetes mellitus and chronic renal disease and are more likely to present with gangrene, whereas white patients are more likely to present with ulcers and rest pain. A thorough evaluation of limb perfusion is important in the diagnosis of CLI because it can not only enable timely diagnosis but also reduce unnecessary invasive procedures in patients with adequate blood flow or among those with other causes for ulcers, including venous, neuropathic, or pressure changes. This scientific statement discusses the current tests and technologies for noninvasive assessment of limb perfusion, including the ankle-brachial index, toe-brachial index, and other perfusion technologies. In addition, limitations of the current technologies along with opportunities for improvement, research, and reducing disparities in health care for patients with CLI are discussed.

Keywords: AHA Scientific Statements; ischemia, lower extremity; perfusion imaging; peripheral arterial disease.

Figure 1.. Examples of noninvasive techniques that have been used to assess the effect of revascularization on microvascular perfusion or oxygen content.

(A) Foot and ankle angiosomal distribution. Adapted from Sumpio et al with permission from the Society for Vascular Surgery. Copyright © 2013, Society for Vascular Surgery. (B) Noninvasive hyperspectral imaging of the plantar aspect of the foot illustrating progressive improvement in oxyhemoglobin (red spectrum) in 2 separate angiosomes after lower extremity revascularization. Reproduced from Sumpio with permission. Copyright © 2018, BIBA Medical Ltd.

Figure 2.. Noninvasive indocyanin green fluorescence imaging of the dorsal foot at rest (quantitative curves at top) illustrating shorter time-to-peak and mean transit time after multilevel percutaneous revascularization.

The corresponding transcutaneous oximetry (TcPo₂) measurements are shown below. PDE10 indicates fluorescence intensity measured 10 seconds after onset of fluorescence; and T1/2, time elapsed from onset of fluorescence to half-maximum intensity. Adapted from Sumpio et al with permission from the Society for Vascular Surgery. Copyright © 2013, Society for Vascular Surgery.

Figure 3.. Quantitative perfusion imaging before and after percutaneous revascularization.

(A) Quantitative contrast-enhanced ultrasound perfusion imaging from the calf during plantar-flexion exercise illustrating background-subtracted images, and (B) corresponding time-intensity data, where improvement in muscle exercise perfusion was achieved after percutaneous revascularization. (C) Pre- and post-revascularization angiograms are also shown. Post-revasc indicates post-revascularization; Pre-op, preoperatively; and VIU, volumetric iodine uptake. Courtesy of J.R. Lindner.