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PLoS One. 2014 Jul 1;9(7):e99973. doi: 10.1371/journal.pone.0099973. eCollection 2014.

Cardiac repolarization and autonomic regulation during short-term cold exposure in hypertensive men: an experimental study.

Author information

1
Center for Environmental and Respiratory Health Research, University of Oulu, Oulu, Finland; Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland.
2
Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland; Institute of Clinical Medicine, Department of Internal Medicine, University of Oulu, Oulu, Finland.
3
Department of Exercise and Medical Physiology, Verve Research, Oulu, Finland; Department of Applied Science, London South Bank University, London, England.
4
Department of Exercise and Medical Physiology, Verve Research, Oulu, Finland.
5
Institute of Health Sciences, University of Oulu, Oulu, Finland.
6
Institute of Health Sciences, University of Oulu, Oulu, Finland; Unit of General Practice, Oulu University Hospital, Oulu, Finland.
7
Medical Informatics and Statistics Research Group, University of Oulu, Oulu, Finland.
8
Institute of Biomedicine, Department of Physiology and Biocenter of Oulu, University of Oulu, Oulu, Finland; Department of Psychiatry, Kuopio University Hospital, Kuopio, Finland.
9
Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland; Institute of Health Sciences, University of Oulu, Oulu, Finland; Oulu City Hospital, Oulu, Finland.
10
Institute of Biomedicine, Department of Physiology and Biocenter of Oulu, University of Oulu, Oulu, Finland; Finnish Institute of Occupational Health, Oulu, Finland.
11
Center for Environmental and Respiratory Health Research, University of Oulu, Oulu, Finland; Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland; Institute of Health Sciences, University of Oulu, Oulu, Finland; Department of Medicine, Oulu University Hospital, Oulu, Finland.
12
Center for Environmental and Respiratory Health Research, University of Oulu, Oulu, Finland; Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland; Institute of Health Sciences, University of Oulu, Oulu, Finland.

Abstract

OBJECTIVES:

The aim of our study was to assess the effect of short-term cold exposure, typical in subarctic climate, on cardiac electrical function among untreated middle-aged hypertensive men.

METHODS:

We conducted a population-based recruitment of 51 hypertensive men and a control group of 32 men without hypertension (age 55-65 years) who underwent whole-body cold exposure (15 min exposure to temperature -10°C, wind 3 m/s, winter clothes). Conduction times and amplitudes, vectorcardiography, arrhythmias, and heart rate variability (autonomic nervous function) were assessed.

RESULTS:

Short-term cold exposure increased T-peak to T-end interval from 67 to 72 ms (p<0.001) and 71 to 75 ms (p<0.001) and T-wave amplitude from 0.12 to 0.14 mV (p<0.001) and from 0.17 to 0.21 mV (p<0.001), while QTc interval was shortened from 408 to 398 ms (p<0.001) and from 410 to 401 ms (p<0.001) among hypertensive men and controls, respectively. Cold exposure increased both low (from 390 to 630 ms2 (p<0.001) and 380 to 700 ms2 (p<0.001), respectively) and high frequency heart rate variability (from 90 to 190 ms2 (p<0.001) and 150 to 300 ms2 (p<0.001), respectively), while low-to-high frequency-ratio was reduced. In addition, the frequency of ventricular ectopic beats increased slightly during cold exposure. The cold induced changes were similar between untreated hypertensive men and controls.

CONCLUSIONS:

Short-term cold exposure with moderate facial and mild whole body cooling resulted in prolongation of T-peak to T-end interval and higher T-wave amplitude while QTc interval was shortened. These changes of ventricular repolarization may have resulted from altered cardiac autonomic regulation and were unaffected by untreated hypertension.

TRIAL REGISTRATION:

ClinicalTrials.gov NCT02007031.

PMID:
24983379
PMCID:
PMC4077657
DOI:
10.1371/journal.pone.0099973
[Indexed for MEDLINE]
Free PMC Article

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