title: Is abnormal adrenergic activation associated with abnormal Heart Rate Recovery?
abstract: BACKGROUND
  Heart Rate Recovery (HRR) reflects the capacity of the cardiovascular system to reverse the vagal withdrawal caused by exercise. Scintigraphy with metaiodobenzylguanidine (I(123) MIBG) evaluates innervation and cardiac adrenergic activation. The association of these two methods is not well established.
  
  
  OBJECTIVE
  To evaluate the association between HRR and washout rate (WO) of I(123) MIBG in patients with heart failure (HF).
  
  
  METHODS
  Twenty-five patients with ejection fraction < 45% underwent exercise testing, and analysis of the variation of HRR from the 1st to the 8th minute after exertion. Submitted to I(123) MIBG, they were separated into groups by WO: G1) <27% and G2) ≥ 27%. For the statistical analysis Mann-Whitney's U test and Spearman's correlation coefficient were used.
  
  
  RESULTS
  G2 showed a slower variation of HRR: 1st minute: G1: 21.5 (16.12 to 26.87) vs. G2: 11.00 (8.5 to 13.5) bpm, p = 0.001; 2nd minute: G1: 34 (29-39) vs. G2: 20 (14 - 26) bpm, p = 0.001; 3rd minute: G1: 46 (37.8 - 54.1) vs. G2: 30 (22 - 38) bpm, p = 0.005; 5th minute: G1: 51.5 (42 - 61) vs. G2: 39 (31.5 to 46.5) bpm, p = 0.013, and in the 8th minute: G1: 54.5 (46.5 - 62.5) vs. G2: 43 (34 - 52) bpm, p = 0.037. HRR in the 1st (r = -0.555, p = 0.004), and in the 2nd minute (r = -0.550, p = 0.004) were negatively correlated with WO.
  
  
  CONCLUSIONS
  Patients with high HF and WO showed an abnormal HRR compared with patients with normal WO. These findings suggest that adrenergic activation may influence the HRR.
authors.affiliation: Universidade Federal Fluminense, Niterói, RJ, Brazil. lmessias@cardiol.br
authors.forename: Leandro Rocha
authors.initials: LR
authors.lastname: Messias
authors.forename: Maria Angela M de
authors.initials: MA
authors.lastname: Queiroz Carreira
authors.forename: Sandra Marina
authors.initials: SM
authors.lastname: Miranda
authors.forename: Jader Cunha de
authors.initials: JC
authors.lastname: Azevedo
authors.forename: Isabela Ambrósio
authors.initials: IA
authors.lastname: Gava
authors.forename: Ronaldo Campos
authors.initials: RC
authors.lastname: Rodrigues
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Maróstica
authors.forename: Claudio Tinoco
authors.initials: CT
authors.lastname: Mesquita
mesh_terms: D019797:3-Iodobenzylguanidine; D000368:Aged; D003430:Cross-Sectional Studies; D005080:Exercise Test; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging; D006333:Heart Failure / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D018709:Statistics, Nonparametric; D013997:Time Factors
chemical_list: D019275:Radiopharmaceuticals; D019797:3-Iodobenzylguanidine