ECG Changes in Humans Exposed to 50 Hz Magnetic Fields

Abstract

ECG Changes in Humans Exposed to 50Hz Magnetic Fields: Srdjan S. BORJANOVIC, et al. Institute of Occupational Health "Dr. Dragomir Karajovic", Serbia and Montenegro-Possible health issues of ELF EMFs include cardiovascular effects since both electrocardiogram and heart-rate changes have been reported in the literature. A non-linear relationship between field strength and biological response has been reported in some studies. In this study, a total of 59 subjects, divided into three independent magnetic field strength groups, were compared. A calculated 12-hour time weighted average (TWA) value of the fields was used as an exposure metric for each of the three locations ("low": 0.067 µT, "medium": 1.18 µT and "high": 5.2 µT) and subsequently used to estimate workers' exposure at these sites. Electrocardiograms were recorded in the resting position. Five parameters were derived from the ECG: heart rate (HR), duration of P wave and QRS wave, and duration of PR and QT intervals. The QT intervals were normalized to a heart rate of 60 (QTc). The obtained data were analyzed first by means of multivariate analysis of covariance and then oneway univariate analyses of covariances (ANCOVA) using exposure duration as a covariate. Only the ANCOVA on the QTc interval was significant. Our results suggest that the relationship between field strength and response is non-linear: the adjusted mean QTc values are similar between the "low" and the "high" group, but significantly lower in the "medium" group. One possible interpretation of our results is that a specific exposure pattern might be responsible for the non-linear effects observed, so that generally, characterizing exposure to electric and magnetic fields using simple metrics such as TWA may be insufficient. Among the possible health effects of exposure to extremely low frequency electromagnetic fields (ELF EMFs), cardiovascular effects have been reported in the database of EMF bioeffects. Studies of ELF EMFs and the cardiovascular system have generally focused on acute rather then long-term effects. Both electrocardiogram (ECG) changes and heart-rate changes have been reported in the literature. An increase in the amplitude of the Twave signal in the rat electrocardiogram was observed during exposure to magnetic fields. This change, however, was the result of a superimposed electrical potential generated by aortic blood flow in the presence of the magnetic field 1) . The T-wave was affected rather than other components of ECG, since blood flows through the aorta during the period when ventricular repolarization is taking place. The increased T-wave voltage was unrelated to the electrical activity of the pacemaker area of the heart and the ECG change was simply a reflection of the coincident "magnetohydrodynamic" voltage generated by the blood flow in the presence of the applied magnetic field.Investigators at one laboratory (Midwest Research Institute, Kansas City, Missouri., USA) have studied the effects of EMFs on the heart rate in humans for several years 1,2...

Heart rate variability monitoring due to 50 Hz electromagnetic field exposure and statistical processing

“…The most relevant effect, resulting from exposure to combined 50 Hz electric and magnetic fields, is slowing the mean HR (lengthening of the cardiac inter beat interval). This biological effect (Fig 7) was also observed in many studies performed with healthy young men [13], [14], [15] and this response appears attributable to the magnetic aspect of exposure. In our study statistical processing of results (Fig 7), regarding the 50 Hz electromagnetic filed exposure, has an decreasing effect to HR Mean (Student's t-test: Pt=0.001; Mann-Whitney U-test PU=0.003; average difference D=13.2).…”

An Investigation on the Effect of Extremely Low Frequency Pulsed Electromagnetic Fields on Human Electrocardiograms (ECGs)

“…Examples from these studies include the ELF-PEMF effect on heart rate variability (HRV) alterations (the low frequency (LF) and high frequency (HF) ratio) [15,16,17], the effect on the 16 Hz/28.3 μT MF exposure to HRV [18], the effect on an intermittent 16.7 Hz MF exposure to heart rate (HR) [19], and the effect on time interval parameters derived from the ECG wave, such as the duration of P and QRS waves, the duration of PR and QT intervals, and corrected QT (QTc) [20]. Graham et al studied specific exposure circumstances under which changes in heart rate variability (HRV) will occur [21].…”

A literature review: the cardiovascular effects of exposure to extremely low frequency electromagnetic fields

“…In a small population cohort of utility workers of 59 substation workers divided into three diVerent exposure categories ("low": 0.067 T; "medium": 1.18 T; "high": 5.2 T), Borjanovic et al found a non-linear response for the cardiac QTc interval: the normalized time between the start of the Q wave and the end of the T wave in the cardiac cycle was shorter in the medium group (Borjanovic et al 2005). Despite these changes, no eVect was found on mean HR or HRV.…”

“…No association between risk of myocardial infarction and elevated workplace EMF exposure Santangelo et al (2005) 28 railway drivers exposed to ELF EMF Exposure not increase the risk of arrhythmias Borjanovic et al (2005) 59 substation workers divided into three diVerent exposure level cohorts…”