Background:
Several studies have shown that pulsed electromagnetic field (PEMF) can stimulate growth and proliferation of various biological tissues, healing of skin lesions, angiogenesis, and reduction of infarct size. One of the proposed mechanism of action include blocking of the ATP-sensitive K+ ion channels which may affect myocardial action potential and peripheral electrocardiogram (ECG).
Aim: To investigate the effect of extremely low PEMF on ECG morphology of normal rats and swine.
Methods:
Extremely low PEMF (10X10-6 - 10X10-12 Tesla, sinusoidal waves, 16Hz) was applied for 15 minutes to anesthetized rats (n=16) and swine (n=6). ECG was recorded during PEMF and at different time points after termination of the magnetic field. In another set of experiment, cytosolic Ca2+ flux was measured on neonatal cardiomyocyets (n=3) which have been exposed for 40 min to PEMF.
Results:
P wave, T amplitude, QRS amplitude and QT duration were shortened following PEMF application in rats: (-13.2%±4%, -23.7%±6%, -7.7%±3%, and -8.8%±3 respectively; P<0.05) using magnetic field of 80nT and frequency of 16Hz. QRS amplitude and T wave amplitude were shortened in swine (-18.6%±4% and -21.1%±3.6% respectively; P<0.05). These changes were maintained for several hours even after the PEMF was stopped. In the isolated cardiac myocytes PEMF reduced cytosolic Ca+ content by approximately 60%.
| parameter | Rates (n=16), % Change | Swine (n=6), % Change |
| P wave duration | -13.2±4* | |
| QRS complex duration | -7.7±3* | -9.9±3.3 |
| QRS Amplitude | -15±4* | -18.6±4.4* |
| T wave duration | -13.4±6* | -3.3±1.5 |
| T wave amplitude | -23.7±7* | -21.1±3.6* |
| QT period | -8.8±3* | +17.6±4.2* |
Conclusions:
These data demonstrate that extremely low PEMF induce ECG changes in vivo characterized by hyperpolarization probably due to the activation of KATP channels during repolarization, however, further studies are warranted to elucidate this hypothesis.
