Preliminary report: modification of cardiac contraction rate by pulsed magnetic fields

Isolated rat hearts and excised canine cardiac tissues were subjected to pulsed magnetic fields. The fields excited in coils by tandem pairings of sinusoidal pulses were presented at various inter-pair delays and repetition rates. The waveform of the magnetic field was a single or multiple sinusoid followed after a variable delay by another single or multiple sinusoid. Small but reliable increases in the beating rate of rat heart were observed. Similar increases occurred in contraction rates of canine tissues. Both preparations exhibited a contraction-rate dependency on the repetition rate of the paired magnetic pulses: 4.5-6 rep/s for canine tissue, and 20-25 and 40-55 reps/s for rat heart. Flux-density thresholds for both preparations approximated 10 mT (100 gauss) rms.