you know the same thing happend to me the first time it tried holosync delta waves.

I was spooked and had to pull off the headophones. being paranoid i thought it was going to slow my heart beat down until it stopped. But i have since experienced the delta waves quite a few times and it just takes quite a bit of time to get used to being concious at this low level of brain activity.
Basically if scientists measure your brain activity during deep dreamless sleep, your basically in a coma or unconcious, scientists dont know what goes on during this.
The binaural beats can let you be concious whilst your brain operates at delta brainwaves. Now im no expert so i don't know what this could lead to.

If you felt heart pain then i would suggest you dont try it again. But i suspect that it wouldent to you any harm if you did. Ive not heard any reports of negtive effects like that in what ive read so far. But they do warn epileptics not to use it....

My guess is that its safer than drugs.