AHA Scientific Statement on Critical Limb Ischemia

Megan Brooks

August 15, 2019

A new scientific statement from the American Heart Association (AHA) highlights the importance of early diagnosis and treatment of critical limb ischemia (CLI) and addresses the strengths and limitations of noninvasive techniques and devices for assessing blood flow and other diagnostic considerations.

The statement was published online August 12 in Circulation.

CLI is a severe manifestation of peripheral artery disease (PAD) and the major cause of nontraumatic leg amputation.

"Timely diagnosis and treatment is likely to preserve limb viability and improve quality of life," Mark A. Creager, MD, past AHA president and director, Heart and Vascular Center, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire, commented in email to theheart.org | Medscape Cardiology.

This scientific statement, said Creager, "provides a comprehensive discussion of the available and investigational tools that clinicians may use to make an accurate diagnosis of critical limb ischemia. This knowledge is important in determining which patients are at risk for limb loss and whom may benefit from revascularization."

"In the broader perspective, greater awareness of PAD and appropriate use of diagnostic tests and evidenced-based treatments will save lives and limbs," Creager said.

12 Million Americans Affected

Despite the high prevalence of CLI, affecting an estimated 12 million adults in the United States, diagnosis and management of CLI can be "challenging" and strategies for perfusion assessment "remain limited," the statement writing group, led by Sanjay Misra, MD, Mayo Clinic, Rochester, Minnesota, point out.

"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," the writing group says.

The AHA/American College of Cardiology guidelines for lower-extremity PAD define CLI as the presence of ischemic rest pain, nonhealing wound/ulcer, or gangrene for at least 2 weeks with associated evidence of hypoperfusion as measured by ankle-brachial index (ABI), ankle pressure, toe-brachial index (TBI), toe systolic pressure, transcutaneous oximetry (TcPo2), or skin perfusion pressure (SPP).

The ABI is the most widely used perfusion method, although its utility might be limited in patients with CLI, the writing group notes.

The ABI has been shown to be an accurate predictor of wound healing or major adverse limb events. It provides important prognostic information, but in roughly 30% of patients with angiographically documented CLI, the ABI is normal or noncompressible, they point out.

Recent data suggest that toe pressure might be a better predictor of major adverse limb events and tibial disease in patients with CLI, especially in those with isolated below-knee disease. "However, to date, there is no solid evidence with core laboratory–adjudicated wound healing data for ABI or TBI to assess the sensitivity and specificity of these tests as perfusion tools to assess wound healing or limb salvage," the writing group says.

"Other more advanced perfusion tools such as TcPo2 and SPP have single-center data with limited sample size as predictors of perfusion for wound healing. Furthermore, these techniques are not widely available and have many limitations," they point out.

The writing group also reviews experimental technologies for lower-extremity perfusion assessment, including indigo carmine angiography, CT perfusion, MRI, contrast-enhanced ultrasound, and hyperspectral imaging.

They also touch on other potential diagnostic approaches in the pipeline, such as implantable biosensors. One such device is the Lumee oxygen platform (Profusa Inc), which provides continuous, real-time monitoring of tissue oxygen levels. The device received CE mark in Europe but remains investigational in the United States.

"New technologies offer potential opportunities to improve the precision and quality of CLI management," the writing group concludes, with the goal of earlier detection and treatment to reduce amputations and disability, as well as improving the quality of life for patients.

Misra and Creager have no relevant financial disclosures. Disclosures for the writing committee are listed in the paper.

Circulation. Published online August 12, 2019. Abstract

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