title: Structure of skeletal muscle in heart transplant recipients.
abstract: OBJECTIVE
  This study sought to define the ultrastructural characteristics of skeletal muscle in heart transplant recipients (HTRs) in relation to exercise capacity compared with that in age-matched control subjects.
  
  
  BACKGROUND
  Muscle structural features seem to play an important role in the limitation of exercise capacity of HTRs long after transplantation.
  
  
  METHODS
  The structure of the vastus lateralis muscle was analyzed by ultrastructural morphometry in 16 HTRs and 20 healthy control subjects. Maximal oxygen consumption (peak Vo2) was determined by an incremental exercise test.
  
  
  RESULTS
  Peak Vo2 was significantly lower (by 35%) in HTRs. Fiber size, volume density of mitochondria and intramyocellular lipid deposits were not significantly different between HTRs and control subjects. In contrast, the capillary density and the capillary/fiber ratio were both significantly reduced in HTRs (by 24% and 27%, respectively).
  
  
  CONCLUSIONS
  A normal volume density of mitochondria and a reduced capillary network are the main characteristics of muscle ultrastructure in HTRs by 10 months after transplantation. The muscle structural abnormalities and reduced exercise capacity might be related to immunosuppressive therapy with cyclosporine and corticosteroids as well as deconditioning.
authors.affiliation: Service des Explorations Fonctionnelles Respiratoires et de l'Exercice, University Hospital of Strasbourg, France.
authors.forename: E
authors.initials: E
authors.lastname: Lampert
authors.forename: B
authors.initials: B
authors.lastname: Mettauer
authors.forename: H
authors.initials: H
authors.lastname: Hoppeler
authors.forename: A
authors.initials: A
authors.lastname: Charloux
authors.forename: A
authors.initials: A
authors.lastname: Charpentier
authors.forename: J
authors.initials: J
authors.lastname: Lonsdorfer
mesh_terms: D000328:Adult; D001706:Biopsy; D005080:Exercise Test; D005260:Female; D016027:Heart Transplantation / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008931:Mitochondria, Muscle / Q000648:ultrastructure; D018482:Muscle, Skeletal / Q000098:blood supply / Q000648:ultrastructure*; D010101:Oxygen Consumption