title: Cardiac sympathetic reserve and response to cardiac resynchronization therapy.
abstract: BACKGROUND
  The objective of the present study was to investigate the effect of cardiac resynchronization therapy (CRT) on cardiac autonomic function.
  
  
  RESULTS
  This prospective study included 45 consecutive patients with heart failure who received CRT devices with defibrillator and 20 age-matched, healthy control subjects. At baseline and 3 months and 6 months after CRT, we assessed New York Heart Association (NYHA) class, 6-minute walk distance, plasma sympathetic biomarker nerve growth factor, echocardiography, heart rate variability and cardiac presynaptic sympathetic function determined by iodine 123 metaiodobenzylguanidine scintigraphy. After CRT, NYHA class improved by 1 class (P<0.001), and left ventricular ejection fraction increased by 8% (P<0.001). Along with improvement in the standard deviation of all normal-to-normal R-R intervals (85.63±31.66 ms versus 114.79±38.99 ms; P=0.004) and the standard deviation of the averaged normal-to-normal R-R intervals (82.62±23.03 ms versus 100.50±34.87 ms; P=0.004), the delayed heart/mediastinum (H/M) ratio increased (1.82 [0.58] versus 1.97 [0.59]; P=0.03), whereas the mean (SD) H/M washout rate was reduced (48% [19%] versus 37% [22%]; P=0.01). Twenty-two of 45 study patients responded to CRT, with a reduction of left ventricular end-systolic volume index >15%. Compared with nonresponders, responders had a higher delayed H/M ratio (2.11 versus 1.48; P=0.003) and lower H/M washout rate (37% versus 62%; P=0.003) at baseline.
  
  
  CONCLUSIONS
  CRT improved sympathetic function. Cardiac sympathetic reserve may be a marker for the reversibility of failing myocardial function.
authors.affiliation: Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN 55905, USA. ycha@mayo.edu
authors.forename: Yong-Mei
authors.initials: YM
authors.lastname: Cha
authors.forename: Panithaya
authors.initials: P
authors.lastname: Chareonthaitawee
authors.forename: Ying-Xue
authors.initials: YX
authors.lastname: Dong
authors.forename: Bradley J
authors.initials: BJ
authors.lastname: Kemp
authors.forename: Jae K
authors.initials: JK
authors.lastname: Oh
authors.forename: Chinami
authors.initials: C
authors.lastname: Miyazaki
authors.forename: David L
authors.initials: DL
authors.lastname: Hayes
authors.forename: Robert F
authors.initials: RF
authors.lastname: Rea
authors.forename: Samuel J
authors.initials: SJ
authors.lastname: Asirvatham
authors.forename: Tracy L
authors.initials: TL
authors.lastname: Webster
authors.forename: Connie M
authors.initials: CM
authors.lastname: Dalzell
authors.forename: David O
authors.initials: DO
authors.lastname: Hodge
authors.forename: Regina M
authors.initials: RM
authors.lastname: Herges
authors.forename: Yan-Zhong
authors.initials: YZ
authors.lastname: Yong
authors.forename: Yanhua
authors.initials: Y
authors.lastname: Zhang
authors.forename: Peng-Sheng
authors.initials: PS
authors.lastname: Chen
mesh_terms: D000368:Aged; D058406:Cardiac Resynchronization Therapy; D005260:Female; D006321:Heart / Q000294:innervation*; D006333:Heart Failure / Q000097:blood / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D020932:Nerve Growth Factor / Q000097:blood; D011877:Radionuclide Imaging; D013564:Sympathetic Nervous System / Q000503:physiopathology*
chemical_list: D020932:Nerve Growth Factor