Physiologic test identifies peripheral artery disease

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Assessment of calf muscle phosphocreatine (PCr) recovery after exercise, using magnetic resonance spectroscopy, is useful in identifying and gauging the severity of peripheral artery disease, new research suggests.

PCr recovery is dependent on the arterial oxygen supply to the muscle as well as on the tissue's capacity to use substrate, according to the report in the Journal of the American College of Cardiology for June 6. The current findings indicate that after exercise, PCr recovery is delayed in PAD patients compared with healthy controls, and that longer delay times correlate with worse outcomes.

"The current tests we have for assessing peripheral artery disease are limited, particularly, in terms of measuring the response to new therapeutic interventions," senior author Dr. Christopher M. Kramer, from the University of Virginia Health System in Charlottesville, told Reuters Health. "Spectroscopy is an older test, but it has not been studied rigorously in the evaluation of PAD."

The present study involved 20 patients with symptomatic PAD and 14 normal subjects. While supine in the MR unit, the subjects exercised one leg to exhaustion using a special plantar flexion device. Spectroscopic analysis was then performed to gauge PCr recovery at the mid-calf.

PAD patients exercised for a median period of 162.5 seconds, shorter, but not significantly different from the 195.0 seconds noted in the control group. Although the exercise period was shorter in the PAD group, the PCr recovery time was much longer: 91.0 vs. 34.7 seconds.

"The PCr recovery time was also prognostically important," Dr. Kramer noted. "The patients with the longest times ended up having troubles as we followed them for over a year."

Dr. Kramer said that he believes current imaging methods will "continue to be the mainstay for making the diagnosis of PAD, whereas PCr recovery with spectroscopy will be primarily used to assess disease severity and measure the therapeutic response."