title: Effect of heart rate correction on pre- and post-exercise heart rate variability to predict risk of mortality-an experimental study on the FINCAVAS cohort.
abstract: The non-linear inverse relationship between RR-intervals and heart rate (HR) contributes significantly to the heart rate variability (HRV) parameters and their performance in mortality prediction. To determine the level of influence HR exerts over HRV parameters' prognostic power, we studied the predictive performance for different HR levels by applying eight correction procedures, multiplying or dividing HRV parameters by the mean RR-interval (RRavg) to the power 0.5-16. Data collected from 1288 patients in The Finnish Cardiovascular Study (FINCAVAS), who satisfied the inclusion criteria, was used for the analyses. HRV parameters (RMSSD, VLF Power and LF Power) were calculated from 2-min segment in the rest phase before exercise and 2-min recovery period immediately after peak exercise. Area under the receiver operating characteristic curve (AUC) was used to determine the predictive performance for each parameter with and without HR corrections in rest and recovery phases. The division of HRV parameters by segment's RRavg to the power 2 (HRVDIV-2) showed the highest predictive performance under the rest phase (RMSSD: 0.67/0.66; VLF Power: 0.70/0.62; LF Power: 0.79/0.65; cardiac mortality/non-cardiac mortality) with minimum correlation to HR (r = -0.15 to 0.15). In the recovery phase, Kaplan-Meier (KM) survival analysis revealed good risk stratification capacity at HRVDIV-2 in both groups (cardiac and non-cardiac mortality). Although higher powers of correction (HRVDIV-4and HRVDIV-8) improved predictive performance during recovery, they induced an increased positive correlation to HR. Thus, we inferred that predictive capacity of HRV during rest and recovery is augmented when its dependence on HR is weakened by applying appropriate correction procedures.
authors.affiliation: Department of Electronics and Communication Engineering, Tampere University of Technology Tampere, Finland ; BioMediTech Tampere, Finland.
authors.forename: Paruthi
authors.initials: P
authors.lastname: Pradhapan
authors.affiliation: Department of Applied Physics, University of Eastern Finland Kuopio, Finland ; Department of Clinical Physiology and Nuclear Medicine, Kuopio University Hospital Kuopio, Finland.
authors.forename: Mika P
authors.initials: MP
authors.lastname: Tarvainen
authors.affiliation: Heart and Lung Centre, Helsinki University Central Hospital Helsinki, Finland.
authors.forename: Tuomo
authors.initials: T
authors.lastname: Nieminen
authors.affiliation: Tampere Polytechnic, University of Applied Sciences Tampere, Finland.
authors.forename: Rami
authors.initials: R
authors.lastname: Lehtinen
authors.affiliation: School of Medicine, University of Tampere Tampere, Finland ; Heart Centre, Department of Cardio-Thoracic Surgery, Tampere University Hospital Tampere, Finland.
authors.forename: Kjell
authors.initials: K
authors.lastname: Nikus
authors.affiliation: School of Medicine, University of Tampere Tampere, Finland ; Fimlab Laboratories, Department of Clinical Chemistry Tampere, Finland.
authors.forename: Terho
authors.initials: T
authors.lastname: Lehtimäki
authors.affiliation: School of Medicine, University of Tampere Tampere, Finland ; Department of Clinical Physiology, Tampere University Hospital Tampere, Finland.
authors.forename: Mika
authors.initials: M
authors.lastname: Kähönen
authors.affiliation: Department of Electronics and Communication Engineering, Tampere University of Technology Tampere, Finland ; BioMediTech Tampere, Finland.
authors.forename: Jari
authors.initials: J
authors.lastname: Viik
keywords: FINCAVAS; Kaplan-Meier; heart rate correction; heart rate variability; receiver operating characteristics