title: Chronic clenbuterol administration negatively alters cardiac function.
abstract: OBJECTIVE
  Chronic administration of pharmacological levels of beta2-agonists have been shown to have toxic effects on the heart; however, no data exist on cardiac function after chronic clenbuterol administration. The purpose of this study was to examine the effect of therapeutic levels of clenbuterol on cardiac performance.
  
  
  METHODS
  Twenty unfit Standardbred mares were divided into four experimental groups: clenbuterol (2.4 microg.kg(-1) twice daily 5 d.wk(-1)) plus exercise (20 min at 50% .VO(2max)) (CLENEX; N = 6), clenbuterol (CLEN; N = 6), exercise (EX; N = 4), and control (CON; N = 4). M-mode and two-dimensional echocardiography (2.5-MHz sector scanner transducer) were used to measure cardiac size and function before and immediately after an incremental exercise test, before and after 8 wk of drug and/or exercise treatments.
  
  
  RESULTS
  After treatment, CLENEX and CLEN demonstrated significantly higher left ventricular internal dimension (LVD) at end diastole (+23.7 +/- 4.8%; +25.6 +/- 4.1%), LVD at end systole (+29.2 +/- 8.7%; +40.1 +/- 7.9%), interventricular septal wall thickness (IVS) at end diastole (+28.9 +/- 11.0%; +30.7 +/- 7.0%), IVS at end systole (+29.2 +/- 8.7%; +40.1 +/- 7.9%), and left ventricular posterior wall systolic thickness (+43.1 +/- 14.%; +45.8 +/- 14.1%). CLENEX and CLEN had significantly increased aortic root dimensions (+29.9 +/- 6.1%; +24.0 +/- 1.7%), suggesting increased risk of aortic rupture.
  
  
  CONCLUSIONS
  Taken together, these data indicate that chronic clenbuterol administration may negatively alter cardiac function.
authors.affiliation: University of Pennsylvania, School of Veterinary Medicine, Philadelphia, PA, USA.
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Sleeper
authors.forename: Charles F
authors.initials: CF
authors.lastname: Kearns
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: McKeever
mesh_terms: D000318:Adrenergic beta-Agonists / Q000008:administration & dosage / Q000009:adverse effects*; D000818:Animals; D001013:Aorta, Thoracic / Q000000981:diagnostic imaging / Q000473:pathology; D002976:Clenbuterol / Q000008:administration & dosage / Q000009:adverse effects*; D025401:Echocardiography, Stress; D005260:Female; D006321:Heart / Q000187:drug effects* / Q000503:physiopathology*; D006352:Heart Ventricles / Q000187:drug effects / Q000473:pathology; D006736:Horses; D009206:Myocardium / Q000473:pathology; D010805:Physical Conditioning, Animal / Q000502:physiology; D012146:Rest / Q000502:physiology; D020257:Ventricular Remodeling
chemical_list: D000318:Adrenergic beta-Agonists; D002976:Clenbuterol