title: Group III/IV muscle afferents impair limb blood in patients with chronic heart failure.
abstract: OBJECTIVE
  To better understand the hemodynamic and autonomic reflex abnormalities in heart-failure patients (HF), we investigated the influence of group III/IV muscle afferents on their cardiovascular response to rhythmic exercise.
  
  
  METHODS
  Nine HF-patients (NYHA class-II, mean left ventricular ejection-fraction: 27 ± 3%) performed single leg knee-extensor exercise (25/50/80% peak-workload) under control conditions and with lumbar intrathecal fentanyl impairing μ-opioid receptor-sensitive muscle afferents.
  
  
  RESULTS
  Cardiac-output (Q) and femoral blood-flow (QL) were determined, and arterial/venous blood samples collected at each workload. Exercise-induced fatigue was estimated via pre/post-exercise changes in quadriceps strength. There were no hemodynamic differences between conditions at rest. During exercise, Q was 8-13% lower with Fentanyl-blockade, secondary to significant reductions in stroke volume and heart rate. Lower norepinephrine spillover during exercise with Fentanyl revealed an attenuated sympathetic outflow that likely contributed to the 25% increase in leg vascular conductance (p<0.05). Despite a concomitant 4% reduction in blood pressure, QL was 10-14% higher and end-exercise fatigue attenuated by 30% with Fentanyl-blockade (p<0.05).
  Although group III/IV muscle afferents play a critical role for central hemodynamics in HF-patients, it also appears that these sensory neurons cause excessive sympatho-excitation impairing QL which likely contributes to the exercise intolerance in this population.
authors.affiliation: Department of Medicine, University of Utah, Salt Lake City, UT, USA; Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA; Geriatric Research, Education, and Clinical Center, VAMC Salt Lake City, UT, USA. Electronic address: markus.amann@hsc.utah.edu.
authors.forename: Markus
authors.initials: M
authors.lastname: Amann
authors.affiliation: Department of Medicine, University of Utah, Salt Lake City, UT, USA.
authors.forename: Massimo
authors.initials: M
authors.lastname: Venturelli
authors.affiliation: Geriatric Research, Education, and Clinical Center, VAMC Salt Lake City, UT, USA.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Ives
authors.affiliation: Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA.
authors.forename: David E
authors.initials: DE
authors.lastname: Morgan
authors.affiliation: Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Gmelch
authors.affiliation: Geriatric Research, Education, and Clinical Center, VAMC Salt Lake City, UT, USA.
authors.forename: Melissa A H
authors.initials: MA
authors.lastname: Witman
authors.affiliation: Geriatric Research, Education, and Clinical Center, VAMC Salt Lake City, UT, USA.
authors.forename: H
authors.initials: H
authors.lastname: Jonathan Groot
authors.affiliation: Department of Medicine, University of Utah, Salt Lake City, UT, USA; Geriatric Research, Education, and Clinical Center, VAMC Salt Lake City, UT, USA.
authors.forename: D
authors.initials: D
authors.lastname: Walter Wray
authors.affiliation: Department of Medicine, University of Utah, Salt Lake City, UT, USA.
authors.forename: Josef
authors.initials: J
authors.lastname: Stehlik
authors.affiliation: Department of Medicine, University of Utah, Salt Lake City, UT, USA; Geriatric Research, Education, and Clinical Center, VAMC Salt Lake City, UT, USA.
authors.forename: Russell S
authors.initials: RS
authors.lastname: Richardson
mesh_terms: D000368:Aged; D002908:Chronic Disease; D015444:Exercise; D006333:Heart Failure / Q000503:physiopathology*; D006801:Humans; D007866:Leg; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000294:innervation* / Q000503:physiopathology; D009475:Neurons, Afferent / Q000502:physiology*; D012039:Regional Blood Flow
keywords: Autonomic control; Circulation; Exercise pressor reflex; Sensory neurons