title: Acute Changes in Ambient Temperature Are Associated With Adverse Changes in Cardiac Rhythm.
abstract: BACKGROUND
  Both increases and decreases in ambient temperature have been associated with increased cardiovascular mortality and morbidity. However, the mechanism(s) remain unclear.
  
  
  OBJECTIVE
  We examined associations between biomarkers of pathways thought to, in part, explain these associations and changes in ambient temperature in a panel of predominantly post-myocardial infarction or post-stent patients.
  
  
  METHODS
  We studied 76 subjects who had a recent coronary event and were participating in a cardiac rehabilitation program. In these patients, we measured heart rate variability, repolarization, and baroreflex sensitivity parameters using Holter ECG recordings before and during supervised, graded, twice weekly, exercise sessions. Hourly temperature measurements were made at a monitoring site near the rehabilitation center.
  
  
  RESULTS
  Using linear mixed models, we observed decreases in rMSSD (square root of the mean of the sum of the squared differences between adjacent NN intervals) and deceleration capacity, associated with increases in ambient temperature in the previous four days. Additionally, decreased rMSSD was associated with both increasing temperature (mean in previous 6 hours) in the summer and decreasing temperature (mean in the previous 3 weeks) in the winter.
  
  
  CONCLUSIONS
  In a panel of cardiac rehabilitation patients, changes in ambient temperature were associated with decreases in markers of heart rate variability and baroreflex sensitivity, which may lead to increased risk of arrhythmic events and sudden death in post-infarction patients.
authors.affiliation: Department of Public Health Sciences, University of Rochester School of Medicine and Dentistry, 265 Crittenden Boulevard, CU420644, Rochester, NY 14642.
authors.forename: Erin B
authors.initials: EB
authors.lastname: Wasserman
authors.affiliation: Division of Cardiology, Department of Medicine, University of Rochester School of Medicine and Dentistry, 265 Crittenden Boulevard, Rochester, NY 14642.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Zareba
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Box 692, Rochester, NY 14642.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Utell
authors.affiliation: Department of Biostatistics and Computational Biology, University of Rochester School of Medicine and Dentistry, 601 Elmwood Ave, Box 630, Rochester, NY 14642.
authors.forename: David
authors.initials: D
authors.lastname: Oakes
authors.affiliation: Department of Chemical and Biomolecular Engineering, Clarkson University, PO Box 5708, Potsdam, NY 13699-5708.
authors.forename: Philip K
authors.initials: PK
authors.lastname: Hopke
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Box 692, Rochester, NY 14642.
authors.forename: Mark
authors.initials: M
authors.lastname: Frampton
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Box 692, Rochester, NY 14642.
authors.forename: David
authors.initials: D
authors.lastname: Chalupa
authors.affiliation: Department of Medicine, Mount Auburn Hospital, 330 Mount Auburn Street, Cambridge, MA 02138.
authors.forename: William
authors.initials: W
authors.lastname: Beckett
authors.affiliation: Department of Public Health Sciences, University of Rochester School of Medicine and Dentistry, 265 Crittenden Boulevard, CU420644, Rochester, NY 14642.
authors.forename: David Q
authors.initials: DQ
authors.lastname: Rich
keywords: ambient temperature; cardiac rehabilitation; heart rate variability; repolarization