title: Influence of prolonged exercise on myocardial distribution of 123I-MIBG in long-distance runners.
abstract: BACKGROUND
  A study was conducted to determine if prolonged exercise could provoke sympathetic neuronal alteration in an athlete's heart through assessment of myocardial distribution of 123I-metaiodobenzylguanidine (MIBG) in nine ultramarathon runners at baseline and after a 4-hour race.
  
  
  RESULTS
  After injection of 370 MBq of 123I-MIBG, the athletes ran for 4 hours, covering 45 +/- 8 km. Planar and single-photon emission computed tomography (SPECT) images of the thorax were acquired at the end of the race. Two weeks later, studies at baseline were performed. A heart:mediastinum ratio (HMR) was calculated to quantify MIBG uptake. Basal MIBG studies showed normal myocardial tracer uptake, on both planar and SPECT images, and the HMR was 1.84 +/- 0.16. After the 4-hour race, MIBG studies showed decreased myocardial uptake in all athletes, and the HMR was 1.70 +/- 0.18 (p < 0.005). A positive correlation between the percentage of decrease of HMR after the race and the distance covered was observed (r = .910, p < 0.001).
  
  
  CONCLUSIONS
  Myocardial MIBG activity is decreased by prolonged exercise in long-distance runners. The degree of reduction of myocardial MIBG activity is related to the distance covered. Prolonged exercise, as sustained sympathetic stimulus, may alter myocardial distribution of MIBG.
authors.affiliation: Department of Nuclear Medicine, Hospital de Sant Paul, Barcelona, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Estorch
authors.forename: R
authors.initials: R
authors.lastname: Serra-Grima
authors.forename: I
authors.initials: I
authors.lastname: Carrió
authors.forename: A
authors.initials: A
authors.lastname: Flotats
authors.forename: A
authors.initials: A
authors.lastname: Lizárraga
authors.forename: L L
authors.initials: LL
authors.lastname: Bernà
authors.forename: T
authors.initials: T
authors.lastname: Prats
authors.forename: R
authors.initials: R
authors.lastname: Segura
mesh_terms: D019797:3-Iodobenzylguanidine; D000328:Adult; D015444:Exercise; D006321:Heart / Q000000981:diagnostic imaging* / Q000294:innervation; D006801:Humans; D008297:Male; D008875:Middle Aged; D019275:Radiopharmaceuticals; D012420:Running; D013564:Sympathetic Nervous System / Q000502:physiology; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D019275:Radiopharmaceuticals; D019797:3-Iodobenzylguanidine