title: Reduced heart rate variability correlates with insulin resistance but not with measures of obesity in population undergoing laparoscopic Roux-en-Y gastric bypass.
abstract: BACKGROUND
  Obesity is associated with a pathologic predominance of sympathetic over parasympathetic tone. With respect to the heart, this autonomic dysfunction presents as a decreased heart rate variability (HRV), which has been associated with increased cardiovascular morbidity. Gastric bypass (GB) reduces cardiovascular mortality, and, thus, could beneficially affect the HRV. We sought to identify the factors predictive of HRV in a severely obese population of undergoing GB at a university hospital in the United States.
  
  
  METHODS
  The data of all patients presenting for GB were included in a prospective database. The homeostatic model of assessment (HOMA) was used to calculate the insulin resistance and glucose disposition index. A 24-hour Holter monitor was used to assess the HRV. Measurements were repeated at 2 weeks and 6 months postoperatively. The correlations between variables were determined using linear mixed models.
  
  
  RESULTS
  We studied 30 patients undergoing GB. All exhibited some degree of reduced HRV that improved postoperatively. The HOMA-insulin resistance inversely correlated with the HRV, and the HOMA-glucose disposition index directly correlated with the parameters of HRV in our longitudinal models. Weight, body mass index, excess body weight, gender, and age did not correlate with HRV. Improvements in HRV correlated with reductions in the average heart rate, underscoring a postoperative increase in relative vagal tone.
  
  
  CONCLUSIONS
  HRV in the severely obese is better predicted by the degree of insulin resistance, than by the degree of obesity, age, or gender. GB led to an improvement in HRV, the magnitude of which correlated with the change in insulin resistance and glucose disposition index, but not with weight loss.
authors.affiliation: University of Massachusetts Memorial Health Care, Worcester, Massachusetts, USA. peruginr@ummhc.org
authors.forename: Richard A
authors.initials: RA
authors.lastname: Perugini
authors.forename: YouFu
authors.initials: Y
authors.lastname: Li
authors.forename: Lawrence
authors.initials: L
authors.lastname: Rosenthal
authors.forename: Karen
authors.initials: K
authors.lastname: Gallagher-Dorval
authors.forename: John J
authors.initials: JJ
authors.lastname: Kelly
authors.forename: Donald R
authors.initials: DR
authors.lastname: Czerniach
mesh_terms: D000328:Adult; D000367:Age Factors; D001786:Blood Glucose / Q000032:analysis; D015716:Electrocardiography, Ambulatory; D005260:Female; D015390:Gastric Bypass; D006329:Heart Conduction System / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009767:Obesity, Morbid / Q000503:physiopathology* / Q000601:surgery*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012737:Sex Factors; D016896:Treatment Outcome
chemical_list: D001786:Blood Glucose; D007328:Insulin