UVA Health cardiovascular experts have found a new way to track peripheral arterial disease (PAD), a serious condition involving atherosclerosis of the arteries of the legs that affects more than 200 million people worldwide. The researchers say the approach will greatly benefit efforts to better understand the disease, which decreases blood flow to the limbs, and improve treatment options for patients.
UVA researchers were able to use a new magnetic resonance imaging (MRI) technique at the end of exercise to understand the effects of PAD on the calves of patients with the disease and to distinguish them from normal volunteers. The approach they used, called chemical exchange saturation transfer, or CEST, produced results comparable to the current gold standard, which does not produce an image. CEST, they found, offered additional benefits without requiring highly specialized equipment not available to many hospitals and researchers.
“The beauty of CEST is that it creates a picture of energy stores in muscle that we can match to blood flow pictures,” said researcher and imaging expert Christopher M. Kramer, MD, chief of the UVA Health Division of Cardiovascular Medicine and Professor of Cardiology and Radiology at the University of Virginia School of Medicine. “It gives us a new understanding of how atherosclerosis in the arteries of the legs causes problems in the muscles downstream.”
Understanding Peripheral Arterial Disease
PAD affects over 7% of Americans over 40 and over 29% of those over 70. The disease can cause pain when walking, feeling cold or numbness in the lower leg, painful cramps in the legs or arms, trouble sleeping, and erectile dysfunction, some of which include other symptoms, although it may also cause no symptoms.
Lack of adequate blood flow to the limbs can make it difficult for wounds to heal and can, in severe cases, lead to amputation. Existing treatments include drugs to improve blood circulation and manage pain; for appropriate cases, doctors may also consider options such as surgery or placing a stent to open clogged arteries.
The novel diagnostic approach identified at AVU will advance efforts to better understand and treat PAD. To see if CEST would work for this purpose, the research team conducted a clinical trial comparing CEST to the current gold standard approach, phosphorus magnetic resonance spectroscopy. The researchers used CEST to image 35 volunteers with PAD and compared the results with imaging obtained from 29 control subjects after performing a calf exercise in the MRI scanner. They found that CEST was effective in identifying PAD in the lower legs, differentiating patients from normal subjects, and the results compared favorably with phosphorus magnetic resonance spectroscopy.
CEST, they concluded, could offer many benefits to researchers. CEST has better special resolution, creates an image and does not require expensive equipment needed for phosphor magnetic resonance spectroscopy. This means that more centers could take advantage of the approach.
CEST can also be combined with other magnetic resonance imaging methods that measure blood flow in the calf to better understand the effects of PAD, the researchers note.
“Combining CEST with muscle blood flow measurement techniques with MRI allows for an exciting new approach to investigating the potential benefits of established and novel therapies in this disease,” Kramer said.
Kramer and his collaborators have published their findings in the medical journal Circulation: Cardiovascular Imaging. The team consisted of Helen L. Sporkin, Toral R. Patel, Yaqub Betz, Roshin Mathew, Christopher L. Schumann, Craig H. Meyer, and Kramer.
The work was supported by the National Institutes of Health, grants R01 HL075792, T32 HL007284, and T32 EB003841.
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