By examining the physiology of patients who exercised under a magnetic resonance imaging scanner (MRI), doctors at the University of Virginia Health System have devised a new test to diagnose and follow peripheral arterial disease. The test shows promise in helping drug companies test new PAD medications and, perhaps in the near future, may give doctors the ability to tell which patients are at risk for developing PAD-related complications and require stenting, bypass surgery or even amputation of a leg.

UVa cardiologist Dr. Christopher Kramer and colleagues measured how fast the leg muscles of patients with PAD, and people without PAD, recovered a phosphorus substance called phosphocreatine (PCr), the major energy “store” in muscle cells. Tests at UVa on 20 patients with mild to moderate PAD and 14 people without PAD, showed that the median time to recover phosphocreatine at the end of exercise in PAD patients was three times slower, 91 seconds in the PAD group versus 35 seconds in the normal group.

What was unusual is that the UVa doctors stepped back in time and used a measurement technique developed in the 1970’s called MR spectroscopy, the forerunner to modern MR imaging. “We were somewhat surprised that of all new tests for PAD that we have been developing, the one that seemed to work the best is spectroscopy. It’s relatively simple and not particularly sexy, but very accurate physiologically,” Kramer said.

All of the patients tested exercised to exhaustion on a special push-pedal machine in an MRI scanner. A spectroscopy coil in the MRI then took readings of the phosphocreatine level in the legs every 15 seconds for several minutes afterward. “If the blood flow is poor,” Kramer explained, ”PCr recovery is slow, because the muscle is not getting the energy sources it needs to restore PCr. It is an energy-dependant process.”; Source: University of Virginia Health System