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AHA: ‘Thorough evaluation of limb perfusion’ critical in CLI
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The American Heart Association released a scientific statement outlining the options for perfusion assessment in patients with critical limb ischemia.
“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,” Sanjay Misra, MD, FAHA, radiologist at Mayo Clinic and chair of the writing committee, and colleagues wrote.
The authors also outlined disparities in patients with CLI, noting women are more likely than men to experience emergency hospitalization and to die or become disabled, whereas black and Hispanic patients are more likely than white patients to have diabetes or chronic kidney disease and to develop gangrene and less likely than white patients to have leg ulcers or pain at rest. They also noted black patients are more likely than others to receive lower-extremity amputation.
“Although implicit provider bias has been implicated as a potential cause of these disparities, the study of perfusion differences in the limbs of white and nonwhite patients with CLI would provide further insight into potential differences in the anatomic distribution and severity of presentation among races,” Misra and colleagues wrote. “Perfusion imaging would also serve as another unbiased covariate by which amputation rates among black patients could be adjusted to understand the contributors to these apparent disparities.”
Unfortunately, the authors wrote, “No single vascular test has been identified as the most important predictor of wound healing or major amputation for the threatened limb. Furthermore, the management of [peripheral artery disease] based on these results is inconsistent, largely because of a lack of consensus-driven high-quality clinical data.”
According to the authors, ankle-brachial index for evaluation of PAD has a sensitivity of 69% to 79% and a specificity of 89% to 99%, transcutaneous oximetry for predicting resolution of nonhealing wounds or gangrene has a sensitivity of 98% and a specificity of 44%, skin-perfusion pressure for predicting wound healing has a sensitivity of 72% and a specificity of 88%, the indocyanine green biomarker for predicting resolution of nonhealing wounds or gangrene has a sensitivity of 85% and a specificity of 100%, and there are no good data on sensitivity and specificity for phosphorescence biosensors for monitoring PAD progression and treatment response.
Ankle-brachial index and toe-brachial index are the most common evaluation techniques, but neither can quantify oxygenation and cannot help clinicians determine whether a wound has enough perfusion to heal, Misra and colleagues wrote.
Other technologies that can be used for lower-extremity perfusion assessment include indigo carmine angiography, CT perfusion, MRI, contrast-enhanced ultrasound and hyperspectral imaging, the authors wrote. – by Erik Swain
Disclosures: Misra reports no relevant financial disclosures. Please see the statement for the other authors’ relevant financial disclosures.
Perspective
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Lawrence Garcia, MD
Importantly, the issue of skin perfusion remains an important parameter in CLI that has been suggested as a method to determine outcomes or durability. The problem is that for all the perfusion parameters we have and the devices on the landscape, not one device has the validation for outcomes that we desperately need. In fact, all the devices listed in the scientific statement have internal data sets that show they can show a difference in a pre-CLI and post-CLI patient. However, none have the studies/data to show they have been validated on the outcomes we need: limb perfusion, limb salvage or durability. Most importantly, not one device has a validation as to a tracking ability, ie, at this level your need for revascularization is critical or it is just watch and wait.
I think the knowledge gaps are perennial to this problem. We need to validate even one device to have something that works for a perfusion metric prior to getting a perfusion metric as a parameter. This would be critical, as the idea of amputation-free survival or primary patency have not borne out their usefulness as to being a good discriminator.
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