Abstract
ObjectivesThe 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.MethodsWe 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.ResultsShort-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.ConclusionsShort-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 RegistrationClinicalTrials.gov NCT02007031
Highlights
Wintertime is associated with increased morbidity and mortality and a majority of this is related to cardiovascular causes [1,2], such as myocardial infarctions [3], ruptures/dissection of aortic aneurysms [4], heart failures [5], as well as strokes [6]
Men aged 55–65 years were randomly chosen from the population register in Oulu, Finland (65uN, 25uE), interviewed for eligibility and performed home blood pressure (BP) measurements according to the recommendations of the European Society of Hypertension [24]
The results are expressed as means and their standard deviations (SD) or 95% confidence intervals (CI)
Summary
Wintertime is associated with increased morbidity and mortality and a majority of this is related to cardiovascular causes [1,2], such as myocardial infarctions [3], ruptures/dissection of aortic aneurysms [4], heart failures [5], as well as strokes [6]. On the other hand, is known to increase the vagal tone through the trigeminal nerve stimulation with a decrease in HR [11] This may serve as a protective cardiovascular effect. For instance during whole body cold water immersion [12] or facial cooling [13] a co-activation of sympathetic and parasympathetic nervous system is observed. This causes conflicting inotropic and chronotropic drives to the heart (autonomic conflict) which may have an additional arrhythmogenic effect over the sympathetic activation alone [12,13]
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