From the Journals

AHA highlights limitations of perfusion testing for critical limb ischemia



A new assessment statement from the American Heart Association reviewed the strengths and limitations of current imaging techniques for critical limb ischemia (CLI), the severest form of peripheral arterial disease (PAD).

The main techniques discussed were the ankle-brachial index (ABI), toe-brachial index (TBI), toe systolic pressure, transcutaneous oximetry (TcPO2) and skin perfusion pressure (SPP). The literature review also identified what the authors saw as opportunities for technology improvement.

“No single vascular test has been identified as the most important predictor of wound healing or major amputation for the threatened limb,” wrote Sanjay Misra, MD, of the Mayo Clinic in Rochester, Minn., and colleagues, on behalf of the American Heart Association Council on Peripheral Vascular Disease, the Council on Clinical Cardiology, and the Council on Cardiovascular and Stroke Nursing.

Of particular concern were limitations seen in the use of ABI, the most widely used assessment method. “Although ABI was first described to diagnose PAD, it has not been shown to be an accurate predictor of wound healing or major adverse limb events. Clearly, the ABI provides important prognostic information, including the risk of death, myocardial infarction, and stroke ... and should be performed in all patients suspected of having PAD,” but in about 30% of patients with angiographically documented CLI, the ABI is normal or noncompressible, the authors wrote.

And, although recent data indicate that toe pressure may be a better predictor of major adverse limb events and tibial disease in patients with CLI, especially among those with isolated below-knee disease, there was no solid evidence that ABI or TBI have the sensitivity or specificity to be used as perfusion tools to assess wound healing or limb salvage, the authors stated.

However, there may be some technological improvements on the horizon for assessing limb perfusion that might provide eventual benefits, according to the reviewers. These include the use of indigo carmine angiography to evaluate microcirculation and angiosomal revascularization, the use of CT perfusion or MRI to quantify perfusion and monitor treatment response, the use of contrast-enhanced ultrasound to assess calf muscle perfusion, and hyperspectral imaging.

Among the other issues of concern raised in the AHA statement were the significant demographic disparities that occur in detection and treatment of CLI. The authors noted differences in how CLI is diagnosed, the coexisting conditions that were present, and the disparities in treatment given based on sex and racial differences. For example, women were more likely to experience emergency hospitalization, have differences in blood flow, and have higher disability and death rates.

As for racial disparities, the reviewers found that black and Hispanic patients with CLI were more likely to have diabetes and chronic kidney disease, and were more likely to develop gangrene, compared with white patients, who were more likely to have ulcers and pain in their legs while at rest.

In terms of treatment, black patients were 78% more likely to receive lower extremity amputation for CLI, compared with their white peers, even after adjustment for socioeconomic status, access to facilities with revascularization services, and other factors, according to the report, which was published online in Circulation.

“CLI is a complex disease process with great morbidity. This statement highlights the importance of incorporating perfusion assessment into the care of CLI patients. Despite the high prevalence of CLI, strategies for perfusion assessment remain limited. New technologies offer potential opportunities to improve the precision and quality of CLI management,” the researchers concluded.

Dr. Misra and the majority of the authors reported having no relevant disclosures. Several authors reported receiving funding from the pharmaceutical and medical device industries.

SOURCE: Chandra S. et al. Circulation. 2019;140:00-00. doi: 10.1161/CIR.0000000000000708.

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