title: Auto-entrainment risk assessment in heart failure.
abstract: BACKGROUND
  Risk assessment studies use a suite of nominally independent noninvasive heart rate metrics, often brought together in a statistical model to compute a risk score. The ongoing need to noninvasively identify the higher risk patients requiring more invasive investigations/interventions drives the search for better noninvasive predictive metrics, with increased sensitivity. Many varieties of autoregulatory malfunction occur within the cardiovascular system; thus, it seems a daunting challenge to build predictive models that account for all potential modes of failure. Auto-entrainment (AE) methodology was developed to help address this challenge.
  
  
  RESULTS
  AE methodology tests intrinsic capacity to maintain a stable and coherent oscillatory dynamic of autoregulatory control via respiratory entrainment of the blood pressure and heart period. Using cardiovascular death (n=18) at follow-up (1.5 years) as the end point, analysis of AE measurements from 148 patients with heart failure revealed 2 parameters significantly predictive of death. Using logistic regression, the magnitude of systolic pulsus alternans measured during AE had predictive sensitivity of 90% (confidence interval, 62%-100% and specificity of 62% (confidence interval, 49%-74%). The capacity to maintain a stable oscillatory dynamic was measured by the fraction of the total RR-interval spectral power contained within the AE-band. This capacity had predictive sensitivity of 73% (confidence interval, 47%-99%) and specificity of 55% (confidence interval, 43%-66%).
  
  
  CONCLUSIONS
  AE methodology provides a noninvasive platform to assess the integrity of cardiovascular autoregulatory control systems for risk assessment in heart failure patients.
authors.affiliation: Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Roach
authors.forename: Margaret L
authors.initials: ML
authors.lastname: Morck
authors.forename: Robert S
authors.initials: RS
authors.lastname: Sheldon
authors.forename: Henry J
authors.initials: HJ
authors.lastname: Duff
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017704:Baroreflex; D001794:Blood Pressure; D002940:Circadian Rhythm; D004562:Electrocardiography; D005260:Female; D006333:Heart Failure / Q000175:diagnosis* / Q000401:mortality / Q000503:physiopathology / Q000628:therapy; D006339:Heart Rate; D006706:Homeostasis; D006801:Humans; D053208:Kaplan-Meier Estimate; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009991:Oscillometry; D010865:Pilot Projects; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D056152:Respiratory Rate; D018570:Risk Assessment; D012307:Risk Factors; D012680:Sensitivity and Specificity; D013997:Time Factors