title: Early Parasympathetic Reinnervation Is Not Related to Reconnection of Major Branches of the Vagus Nerve after Heart Transplantation.
abstract: OBJECTIVE
  Bicaval heart transplantation (HTx) may promote parasympathetic reinnervation. However, the prevalence and timing of reinnervation have not been fully investigated. Heart rate variability (HRV) and direct vagal stimulation were used to evaluate the presence of parasympathetic reinnervation after bicaval HTx.
  
  
  METHODS
  A total of 21 patients (time after HTx 0.52-4.41 years, mean 1.8±1.2 years) who received a bicaval HTx was enrolled. Reinnervation was evaluated using HRV values from 24-hour Holter recordings. A cross-sectional analysis of the HRV at 0.5-1, 1-2, and >2 years after HTx was performed. We also applied high-frequency electrical stimulation (16.7 Hz, 1 msec pulse width, ≤10 V) to the cardiac branches of the vagus nerve at the level of the superior vena cava in eight patients at 6 and 12 months after HTx.
  
  
  RESULTS
  The degree of parasympathetic reinnervation corresponded to the time after HTx. The HRV analysis revealed that the root mean square of the successive differences between consecutive RR-intervals (RMSSD) and high-frequency power were significantly higher during the late period (>2 years) compared with the early period (0.5-1 year) after HTx. None of the eight patients who underwent direct vagal stimulation responded during the stimulation at 6 and 12 months, whereas incremental trends in HRV parameters were observed, which indicated that parasympathetic reinnervation began within 1 year after HTx.
  
  
  CONCLUSIONS
  Parasympathetic reinnervation seemed to begin in the early period (<1 year) after bicaval HTx. Reconnection of major branches of the vagus nerve may not be related to early reinnervation.
authors.affiliation: Department of Internal Medicine, Division of Cardiology, Seoul National University Hospital, Seoul, Korea.
authors.forename: So-Ryoung
authors.initials: SR
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine, Division of Cardiology, Seoul National University Hospital, Seoul, Korea.
authors.forename: Do-Yoon
authors.initials: DY
authors.lastname: Kang
authors.affiliation: Department of Internal Medicine, Division of Cardiology, Seoul National University Hospital, Seoul, Korea.
authors.forename: Youngjin
authors.initials: Y
authors.lastname: Cho
authors.affiliation: Department of Internal Medicine, Division of Cardiology, Seoul National University Hospital, Seoul, Korea.
authors.forename: Hyun-Jai
authors.initials: HJ
authors.lastname: Cho
authors.affiliation: Department of Internal Medicine, Division of Cardiology, Seoul National University Hospital, Seoul, Korea.
authors.forename: Hae-Young
authors.initials: HY
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine, Division of Cardiology, Seoul National University Hospital, Seoul, Korea.
authors.forename: Eue-Keun
authors.initials: EK
authors.lastname: Choi
authors.affiliation: Department of Internal Medicine, Division of Cardiology, Seoul National University Hospital, Seoul, Korea.
authors.forename: Seil
authors.initials: S
authors.lastname: Oh
keywords: Heart transplantation; Parasympathetic; Reinnervation; Vagus nerve