title: Delayed calf muscle phosphocreatine recovery after exercise identifies peripheral arterial disease.
abstract: OBJECTIVE
  In this study we intend to characterize phosphocreatine (PCr) recovery kinetics with phosphorus-31 ((31)P) magnetic resonance spectroscopy in symptomatic peripheral arterial disease (PAD) patients compared with control subjects and determine the diagnostic value and reproducibility of this parameter.
  
  
  BACKGROUND
  Due to the inconsistent relationship between flow and function in PAD, novel techniques focused on the end-organ are needed to assess disease severity and measure therapeutic response.
  
  
  METHODS
  Fourteen normal subjects (5 men, age 45 +/- 14 years) and 20 patients with mild-to-moderate symptomatic PAD (12 men, age 67 +/- 10 years, mean ankle brachial index 0.62 +/- 0.13) were studied. Subjects exercised one leg to exhaustion while supine in a 1.5-T magnetic resonance scanner using a custom-built plantar flexion device. Surface coil-localized, free induction decay acquisition localized to the mid-calf was used. Each 31P spectrum consisted of 25 signal averages at a repetition time of 550 ms. The PCr recovery time constant was calculated by monoexponential fit of PCr versus time, beginning at exercise completion.
  
  
  RESULTS
  Median exercise time was 195.0 s in normal subjects and 162.5 s in PAD patients (p = 0.06). Despite shorter exercise times in patients, the median recovery time constant of PCr was 34.7 s in normal subjects and 91.0 s in PAD patients. Area under the receiver-operating characteristic curve was 0.925 +/- 0.045. Test-retest reliability was excellent.
  
  
  CONCLUSIONS
  The PCr recovery time constant is prolonged in patients with symptomatic PAD compared with normal subjects. The method is reproducible and may be useful in the identification of disease. Further study of this parameter's ability to track response to therapy as well as its prognostic capability is warranted.
authors.affiliation: Department of Medicine, University of Virginia Health System, University of Virginia, Charlottesville, Virginia 22908, USA.
authors.forename: David C
authors.initials: DC
authors.lastname: Isbell
authors.forename: Stuart S
authors.initials: SS
authors.lastname: Berr
authors.forename: Alicia Y
authors.initials: AY
authors.lastname: Toledano
authors.forename: Frederick H
authors.initials: FH
authors.lastname: Epstein
authors.forename: Craig H
authors.initials: CH
authors.lastname: Meyer
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Rogers
authors.forename: Nancy L
authors.initials: NL
authors.lastname: Harthun
authors.forename: Klaus D
authors.initials: KD
authors.lastname: Hagspiel
authors.forename: Arthur
authors.initials: A
authors.lastname: Weltman
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Kramer
mesh_terms: D000328:Adult; D001158:Arteries; D016022:Case-Control Studies; D015444:Exercise; D005260:Female; D006801:Humans; D007700:Kinetics; D007866:Leg; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism*; D016491:Peripheral Vascular Diseases / Q000175:diagnosis* / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism*; D015203:Reproducibility of Results
chemical_list: D010725:Phosphocreatine