Letter to the Editor Exercise-test-related heart rate variability and mortality The Finnish cardiovascular study Johanna Leino a , Matti Virtanen b , Mika Kähönen a , Kjell Nikus c , Terho Lehtimäki d,e , Tiit Kööbi a , Rami Lehtinen a,f , Väinö Turjanmaa a , Jari Viik b, ⁎ , Tuomo Nieminen g,h a Department of Clinical Physiology, Tampere University Hospital and Medical School, University of Tampere, Finland b Ragnar Granit Institute, Tampere University of Technology P.O. Box 692FI-33101, Tampere, Finland c Heart Center, Department of Cardiology, Pirkanmaa Hospital District, Finland d Laboratory of Atherosclerosis Genetics, Department of Clinical Chemistry, Tampere University Hospital, Finland e Centre for Laboratory Medicine, Medical School, University of Tampere, Finland f Tampere Polytechnic, Room B1-37, Teiskontie 33, P.O. Box 21, FI-33521 Tampere, Finland g Department of Pharmacological Sciences, Medical School, University of Tampere, Finland h Department of Internal Medicine, Tampere University Hospital, Finland Received 18 October 2008; accepted 14 December 2008 Abstract Decreased heart rate variability (HRV) at rest associates with worse prognosis, while a recent study found that greater HRV during an exercise treadmill test was linked to increased risk of death. As a part of the Finnish Cardiovascular Study (FINCAVAS), weevaluated the prognostic power of HRV during bicycle ergometer test in 1876 patients. During the follow-up (mean ± SD 47.5 ± 12.8 months) period, there were 101 (5.4%) deaths. Cox regression analysis was performed during four periods (pre-exercise, first and last minute of exercise, and first 2 min of recovery). During the pre-exercise period, greater HRV was clearly linked to better prognosis. During the first minute of exercise, a single HRV parameter was associated with decreased risk. None of the HRV parameters were connected to mortality at peak exercise or during the recovery phase. In conclusion, HRV does not have prognostic value during the physical exertion in an exercise test. However, our results support previous studies, where decreased HRV at rest has been associated with worse prognosis. © 2008 Elsevier Ireland Ltd. All rights reserved. Keywords: Heart rate variability; Exercise; Prognosis Heart rate variability (HRV) or differences in beat-to-beat interval (R–R interval) is believed to reflect the status and the balance between the sympathetic and parasympathetic nervous systems [1]. Previously, it has been shown that lower resting HRV is associated with worse prognosis in many different patient populations, including survivors of acute myocardial infarction and patients without coronary heart disease (CHD) [2]. In contrast to the results at rest, a recent study found that greater HRV during an exercise treadmill test was linked to increased risk of death [2]. Specifically, a greater root mean square difference in R–R intervals (RMSSD) and several frequency domain variables were associated with increased risk of all-cause and cardiovascular death during peak exer- cise and the recovery phase [2]. We analyzed whether HRV parameters predict mortality in the patients of the Finnish Cardiovascular Study (FINCAVAS). All consecutive patients coming in for a clinically indicated exercise test using a bicycle ergometer at Tampere University Hospital and willing to participate in the study were recruited between October 2001 and December 2004. The main indi- cations for the exercise test were diagnosis of CHD (frequency 45%), testing vulnerability to arrhythmia during exercise (20%), and evaluation of work capacity (18%) and adequacy of the CHD treatment (16%). After excluding patients with insuffi- cient recordings, marked arrhythmias or ectopic heartbeats, the International Journal of Cardiology xx (2009) xxx – xxx IJCA-11673; No of Pages 2 www.elsevier.com/locate/ijcard ⁎ Corresponding author. Tel.: +358 3 3115 2158; fax: +358 3 3115 3162. E-mail address: jari.viik@tut.fi (J. Viik). 0167-5273/$ - see front matter © 2008 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijcard.2008.12.123 ARTICLE IN PRESS Please cite this article as: Leino J, et al, Exercise-test-related heart rate variability and mortality. The Finnish cardiovascular study, Int J Cardiol (2009), doi:10.1016/j.ijcard.2008.12.123