title: Exercise performance and skeletal muscles in patients with advanced Chagas disease.
abstract: OBJECTIVE
  This study was designed to evaluate the peripheral muscle metabolic and structural characteristics in patients with advanced Chagas disease (ChD), and whether they were related with exercise performance.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  Outpatient cardiomyopathy clinic of a university hospital.
  
  
  METHODS
  We studied 11 stage II patients, 8 stage III patients, and 11 healthy volunteers. All patients underwent exercise testing and peripheral muscle biopsies. The muscles were also studied in control subjects. Muscle biopsy specimens were analyzed for histochemical characteristics. In six patients, the muscle was studied ultrastructurally.
  
  
  RESULTS
  The data demonstrate more glycolytic and less oxidative capacity of the peripheral muscle in patients with advanced ChD (increased proportion of type IIb fibers, increased proportion of fibers with low nicotinamide adenine dinucleotide diaphorase activity, high proportion of darkly stained fibers for alpha-glycerophosphate dehydrogenase activity, and lower levels of citrate synthase). Many capillaries in patients with ChD had an abnormal aspect: they were either closed or showed a thicker wall. The ultrastructural study also showed fiber atrophy and abnormal capillaries even in patients with normal functional capacity. Some muscle characteristics (enzyme activity, mean cross-sectional area of the fiber, and capillarity) related with exercise parameters (anaerobic threshold, and peak oxygen pulse).
  
  
  CONCLUSIONS
  These findings indicate that patients with advanced ChD have decreased oxidative capacity and a shift to anaerobic metabolism in the skeletal muscle. They also suggest that muscular abnormalities are related to oxygen delivery, which is probably reduced in part by the abnormal muscle microvasculature. Those changes could affect oxygen extraction, and therefore exercise tolerance in these patients.
authors.affiliation: Pulmonary Division, University Hospital of Caracas, Central University of Venezuela. mmdeoca@cantv.net
authors.forename: María
authors.initials: M
authors.lastname: Montes de Oca
authors.forename: Sonia H
authors.initials: SH
authors.lastname: Torres
authors.forename: José G
authors.initials: JG
authors.lastname: Loyo
authors.forename: Francia
authors.initials: F
authors.lastname: Vazquez
authors.forename: Noelina
authors.initials: N
authors.lastname: Hernández
authors.forename: Begoña
authors.initials: B
authors.lastname: Anchustegui
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Puigbó
mesh_terms: D001706:Biopsy; D002196:Capillaries / Q000473:pathology; D002598:Chagas Cardiomyopathy / Q000473:pathology / Q000503:physiopathology; D014355:Chagas Disease / Q000473:pathology* / Q000503:physiopathology*; D003430:Cross-Sectional Studies; D004452:Echocardiography; D018618:Echocardiography, Doppler, Color; D025401:Echocardiography, Stress; D015444:Exercise; D017079:Exercise Tolerance; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D010101:Oxygen Consumption; D011659:Pulmonary Gas Exchange