title: Patterns of physical activity and survival following cardiac resynchronization therapy implantation: the ALTITUDE activity study.
abstract: OBJECTIVE
  Cardiac resynchronization therapy with implantable defibrillator backup (CRT-D) improves outcomes, but predictors and markers of response remain limited. Physical activity information collected by CRT devices may provide insights to CRT response and the relationship between activity changes and survival.
  
  
  RESULTS
  Patients entered into the LATITUDE remote monitoring system from 2008 to 2012 after receipt of a new CRT-D were eligible. Mean daily activity was calculated from LATITUDE uploads at baseline (first 3-10 days following implant) and 6 months (180-210 days). Pairwise differences for baseline-6-month activity were calculated, and survival according to quintiles of 6-month activity change was assessed. Cox regression was used to examine the adjusted association between survival and baseline-6-month activity change. A total of 26 509 patients were followed for a median of 2.3 years (mean age 70.2 ± 11.0 years, 70.7% male). Mean baseline activity was 66.2 ± 47.7 min/day, with mean paired increase at 6 months of 37.1 ± 48.2 min/day [95% CI (confidence interval), 36.5-37.6, P < 0.0001], though 15.5% of patients did not improve or worsened at 6 months. Survival at 3 years was significantly higher in the largest baseline-6-month activity change quintile vs. the lowest quintile (88.9% vs. 62.1%, log-rank P-value < 0.001). Adjusted for age and gender, higher 6-month activity change was associated with a lower risk of death (adjusted hazard ratios 0.65 per 30 min increase in activity, 95% CI, 0.63-0.67).
  
  
  CONCLUSIONS
  Change in physical activity between baseline and 6 months following CRT implantation is strongly associated with survival.
authors.affiliation: Richard and Susan Smith Center for Outcomes Research in Cardiology, Division of Cardiology, Department of Medicine, Beth Israel Deaconess Medical Center, 185 Pilgrim Road, Boston, MA 02215, USA.|Harvard Medical School, Boston, MA, USA.|Hebrew SeniorLife Institute for Aging Research, Boston, MA, USA.
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Kramer
authors.affiliation: Boston Scientific, St. Paul, MN, USA.
authors.forename: Paul W
authors.initials: PW
authors.lastname: Jones
authors.affiliation: North American Science Inc., Minneapolis, MN, USA.
authors.forename: Tyson
authors.initials: T
authors.lastname: Rogers
authors.affiliation: Harvard Medical School, Boston, MA, USA.|Hebrew SeniorLife Institute for Aging Research, Boston, MA, USA.
authors.forename: Susan L
authors.initials: SL
authors.lastname: Mitchell
authors.affiliation: Richard and Susan Smith Center for Outcomes Research in Cardiology, Division of Cardiology, Department of Medicine, Beth Israel Deaconess Medical Center, 185 Pilgrim Road, Boston, MA 02215, USA.|Lahey Hospital & Medical Center, Burlington, MA, USA.|Harvard Clinical Research Institute, Boston, MA, USA.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Reynolds
mesh_terms: D056044:Actigraphy / Q000379:methods; D000368:Aged; D000369:Aged, 80 and over; D058406:Cardiac Resynchronization Therapy / Q000009:adverse effects / Q000401:mortality; D058409:Cardiac Resynchronization Therapy Devices; D016009:Chi-Square Distribution; D015444:Exercise; D017079:Exercise Tolerance; D005260:Female; D006333:Heart Failure / Q000175:diagnosis / Q000401:mortality / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D020127:Recovery of Function; D012042:Registries; D058998:Remote Sensing Technology; D012815:Signal Processing, Computer-Assisted; D013686:Telemetry / Q000379:methods; D013997:Time Factors; D016896:Treatment Outcome
keywords: Cardiac resynchronization therapy; Exercise; Heart failure; Outcomes research; Remote monitoring