title: Association of heart rate variability with clinical outcome in parkinsonian patients after subthalamic deep brain stimulation: a retrospective cohort study.
abstract: OBJECTIVE
  Lower sympathetic and parasympathetic function increases the morbidity in Parkinsonian patients. We conducted this retrospective study to elucidate the effect of subthalamic deep brain stimulation (STN-DBS) on autonomic cardiovascular regulation of patients with Parkinson's disease.
  
  
  METHODS
  Twelve men and four women with advanced Parkinson's disease (mean age: 63 years) who underwent bilateral STN-DBS were followed up for 9-32 months. Daytime electrocardiography for 5 minutes and rating scores were recorded before and after surgery. Good response was defined as improvement >50% in the Unified Parkinson's Disease Rating Scale (UPDRS), and a fair response as improvement between 10% and 50% after surgery. Digitalized electrocardiography signals such as high-frequency power [HF; 0.15-0.45 Hz, to reflect vagal (parasympathetic) regulation], low-frequency power (LF; 0.04-0.15 Hz, contributed from mixed sympathetic and parasympathetic divisions), and the fraction of LF/(HF + LF) in normalized units (LF%, to reflect sympathetic regulation) were transformed with fast Fourier transformation to power spectrum and heart rate variables.
  
  
  RESULTS
  Six male and two female patients were good responders and the others were fair responders. There were no significant differences in height, weight, duration of disease, levadopa equivalent daily dose, preoperative and postoperative UPDRS, and DBS-off and levodopa-off UPDRS between the good and fair response groups. There were no significant differences between the good and fair response groups for preoperative heart rate interval, LF values, LF% values, and HF values. Compared with preoperative values, the good response group showed a significant increase in LF but not in heart rate, LF%, and HF after surgery. In contrast, the fair response group showed no significant change in all heart rate variables postoperatively.
  
  
  CONCLUSIONS
  Our study showed an improvement in autonomic cardiovascular regulation in Parkinsonian patients with >50% improvement in rating scale after STN-DBS, which implied morbidity reduction in nonmotor symptoms among such patients.
authors.affiliation: School of Medicine, Tzu Chi University, Hualien, Taiwan.
authors.forename: Shin-Yuan
authors.initials: SY
authors.lastname: Chen
authors.forename: Cheryl C H
authors.initials: CC
authors.lastname: Yang
authors.forename: Terry B J
authors.initials: TB
authors.lastname: Kuo
authors.forename: Tomor
authors.initials: T
authors.lastname: Harnod
mesh_terms: D000368:Aged; D015331:Cohort Studies; D046690:Deep Brain Stimulation; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology / Q000628:therapy*; D012189:Retrospective Studies; D020531:Subthalamic Nucleus / Q000502:physiology*