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Journal of Nuclear Cardiology

, Volume 7, Issue 4, pp 354–358 | Cite as

Myocardial sympathetic innervation in the athlete's sinus bradycardia: Is there selective inferior myocardial wall denervation?

  • Montserrat EstorchEmail author
  • Ricard Serra-Grima
  • Albert Flotats
  • Carina Marí
  • Lluís Bernà
  • Ana Catafau
  • Joan Carles Martín
  • Ana Tembl
  • Jagat Narula
  • Ignasi Carrió
Original Articles

Abstract

Background

Sinus bradycardia in trained athletes is predominantly a manifestation of increased vagal tone, but it is not known whether an alteration in the cardiac sympathetic system can contribute to blunted chronotropic response. This study assessed the integrity of the sympathetic system in trained athletes with sinus bradycardia by means of the iodine-123-metaiodobenzylguanidine (123I-MIBG) procedure.

Methods and Results

Fourteen athletes with sinus bradycardia and 8 athletes with a normal heart rate were explored by means of planar and single photon emission computed tomography MIBG studies. The heart/mediastinum ratio, regional myocardial distribution, and percent of regional myocardial MIBG uptake were evaluated. The heart/mediastinum ratio in athletes with sinus bradycardia was 1.87±0.10, and in athletes with a normal heart rate, the heart/mediastinum ratio was 1.86±0.16 (P= not significant). In athletes with sinus bradycardia, the regional distribution of MIBG showed an inferior and apical uptake defect in 8 athletes, an inferior, apical, and septal defect in 3 athletes, an inferior defect in 1 athlete, and normal distribution in 2 athletes (14%). In athletes with a normal heart rate, the regional distribution of MIBG showed an apical uptake defect in 3 athletes and normal distribution in 5 athletes (63%). The percent of regional MIBG uptake in the inferior region was significantly reduced in athletes with sinus bradycardia (44%±13% vs 72%±11%, P<.01).

Conclusion

These results show severely reduced myocardial MIBG distribution in the inferior region in athletes with sinus bradycardia, suggesting selective inferior myocardial wall sympathetic denervation, which may be related to increased vagal tone.

Key Words

Sinus bradycardia iodine-123-metaiodobenzylguanidine iodine-123-metaiodobenzylguanidine scintigraphy athlete vagal tone 

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Copyright information

© American Society of Nuclear Cardiology 2000

Authors and Affiliations

  • Montserrat Estorch
    • 1
    Email author
  • Ricard Serra-Grima
    • 2
  • Albert Flotats
    • 1
  • Carina Marí
    • 1
  • Lluís Bernà
    • 1
  • Ana Catafau
    • 1
  • Joan Carles Martín
    • 1
  • Ana Tembl
    • 1
  • Jagat Narula
    • 3
  • Ignasi Carrió
    • 1
  1. 1.Department of Nuclear MedicineHospital de la Santa Creu i Sant PauBarcelonaSpain
  2. 2.Department of CardiologyHospital de la Santa Creu i Sant PauBarcelonaSpain
  3. 3.Cardiac UnitHahnemann University HospitalPhiladelphia

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