Abstract
We defined chronobiologic norms for supraventricular and ventricular single extrasystoles (SV and VE, respectively) in healthy older males in lowland areas. The study was extended to higher altitudes, where hypobaric hypoxia was expected to increase extrasystole frequency, while perhaps not changing rhythmicity. In healthy men (lowland n = 37, altitude n = 22), aged 49–72 years, mean numbers of SVs and VEs were counted over a 24-h period. Cosinor regression was used to test the 24-h rhythm and its 2nd–10th harmonics. The resulting approximating function for either extrasystole type includes its point, 95% confidence interval of the mean, and 95% tolerance for single measurement estimates. Separate hourly differences (delta) between altitude and lowland (n = 59) were also analysed. Hourly means were significantly higher in the mountains versus lowland, by +0.8 beats/h on average for SVs, and by +0.9 beats/h for VEs. A relatively rich chronogram for VEs in mountains versus lowland exists. Delta VEs clearly display a 24-h component and its 2nd, 3rd, 4th and 7th harmonics. This results in significantly higher accumulation of VEs around 8.00 a.m., 11.00 a.m. and 3.00 p.m. in the mountains. The increase in extrasystole occurrence in the mountains is probably caused by higher hypobaric hypoxia and resulting sympathetic drive. Healthy men at elevated altitudes show circadian and several ultradian rhythms of single VEs dependent on the hypoxia level. This new methodological approach—evaluating the differences between two locations using delta values—promises to provide deeper insight into the occurrence of premature beats.
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statistics@nel.edu or stefan.kujanik@upjs.sk
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Acknowledgements
This paper is supported by grant № 1/0239/08 from the Slovak grant agency VEGA. We are grateful to Mr. Jan Vokal MD, PhD and Juraj Podracky MD, PhD for help in obtaining the primary ECG data, and to Dipl. Ing. Irina Fialkova from the Center for Health Information of Slovak Republic for the MEDLINE search. There are no actual or potential conflicts of interest.
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Kujanik, S., Mikulecky, M. Circadian and ultradian extrasystole rhythms in healthy individuals at elevated versus lowland altitudes. Int J Biometeorol 54, 531–538 (2010). https://doi.org/10.1007/s00484-010-0302-8
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DOI: https://doi.org/10.1007/s00484-010-0302-8