title: Improved Ventilatory Efficiency with Locomotor Muscle Afferent Inhibition is Strongly Associated with Leg Composition in Heart Failure.
abstract: BACKGROUND
  Skeletal muscle atrophy contributes to increased afferent feedback (group III and IV) and may influence ventilatory control (high VE/VCO2 slope) in heart failure (HF).
  
  
  OBJECTIVE
  This study examined the influence of muscle mass on the change in VE/VCO2 with afferent neural block during exercise in HF.
  
  
  METHODS
  17 participants [9 HF (60±6 yrs) and 8 controls (CTL) (63±7 yrs, mean±SD)] completed 3 sessions. Session 1: dual energy x-ray absorptiometry and graded cycle exercise to volitional fatigue. Sessions 2 and 3: 5 min of constant-work cycle exercise (65% of peak power) randomized to lumbar intrathecal injection of fentanyl (afferent blockade) or placebo. Ventilation (VE) and gas exchange (oxygen consumption, VO2; carbon dioxide production, VCO2) were measured.
  
  
  RESULTS
  Peak work and VO2 were lower in HF (p<0.05). Leg fat was greater in HF (34.4±3.0 and 26.3±1.8%) and leg muscle mass was lower in HF (63.0±2.8 and 70.4±1.8%, respectively, p<0.05). VE/VCO2 slope was reduced in HF during afferent blockade compared with CTL (-18.8±2.7 and -1.4±2.0%, respectively, p=0.02) and was positively associated with leg muscle mass (r2=0.58, p<0.01) and negatively associated with leg fat mass (r2=0.73, p<0.01) in HF only.
  
  
  CONCLUSIONS
  HF patients with the highest fat mass and the least leg muscle mass had the greatest improvement in VE/VCO2 with afferent blockade with leg fat mass being the only predictor for the improvement in VE/VCO2 slope. Both leg muscle mass and fat mass are important contributors to ventilatory abnormalities and strongly associated to improvements in VE/VCO2 slope with locomotor afferent inhibition in HF.
authors.affiliation: Department of Cardiovascular Diseases, Mayo College of Medicine, Rochester, MN 55905. Electronic address: kell0529@umn.edu.
authors.forename: Manda L
authors.initials: ML
authors.lastname: Keller-Ross
authors.affiliation: Department of Cardiovascular Diseases, Mayo College of Medicine, Rochester, MN 55905.
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Johnson
authors.affiliation: Department of Health Sciences Research, Mayo College of Medicine, Rochester, MN 55905.
authors.forename: Rickey E
authors.initials: RE
authors.lastname: Carter
authors.affiliation: Department of Anesthesiology, Mayo College of Medicine, Rochester, MN 55905.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Joyner
authors.affiliation: Department of Anesthesiology, Mayo College of Medicine, Rochester, MN 55905.
authors.forename: John H
authors.initials: JH
authors.lastname: Eisenach
authors.affiliation: Department of Anesthesiology, Mayo College of Medicine, Rochester, MN 55905.
authors.forename: Timothy B
authors.initials: TB
authors.lastname: Curry
authors.affiliation: Department of Cardiovascular Diseases, Mayo College of Medicine, Rochester, MN 55905.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Olson
mesh_terms: D000344:Afferent Pathways / Q000187:drug effects / Q000502:physiology; D000368:Aged; D015444:Exercise / Q000502:physiology; D017079:Exercise Tolerance / Q000502:physiology; D005260:Female; D006333:Heart Failure / Q000175:diagnosis* / Q000503:physiopathology*; D006801:Humans; D007866:Leg / Q000294:innervation* / Q000473:pathology / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation / Q000473:pathology / Q000502:physiology*; D009407:Nerve Block / Q000379:methods; D010101:Oxygen Consumption / Q000502:physiology; D012123:Pulmonary Ventilation / Q000502:physiology*
keywords: Group III/IV; exercise; fentanyl; ventilation