I frequently have experiences like this on acid, ayahuasca, and even just weed on its own. In my case, they centre around thoughts of being eviscerated, decapitated, impaled or, most commonly, having my beating heart sliced out of my chest. At higher doses, fear of these things does become quite real. I too once spent an entire trip trying to escape from the viciously vivid sensation and image of having a katana slice through my neck, parting the flesh, muscle and veins from one side to the other, leaving me for an instant in a state of total pain and disorientation as the weight of my body vanished and my head fell to the ground. Over and over again for hours this vision came. Sometimes LSD is not gentle.
I do not interpret these as past or future events. These are extraordinary claims and they require extraordinary evidence. I first look to simpler, more workable explanations. Where does it come from?
I've gone into the experience repeatedly to find out. It was at its most vicious on ayahuasca, where I could basically feel the utter sharpness of the knife and how my mortal body, the nexus of my radiant consciousness, was just another object that could be punctured, tortured, killed in the coldest, most deliberate manner. I recalled that the Aztecs had sacrificed 80,000 people in this way during a single ritual. I remembered that the Incans had even done it to their own children, the younger the better, so as to feed the sun with the agony of innocent blood. At this, I got the image of a young boy crying and struggling and begging for mercy as he was held down by larger men, one of them drawing a blade and looking down at the child's bared chest. This has happened in real life more times than I can imagine. I sat upright in the ceremony, clawing at my face and hair and pleading with the astral world for these visions to stop. It was the senseless horror of existence, the unbounded suffering where there could have been light and peace instead, the way mankind adapts to the terror of the world by becoming even more monstrous. The solemn faces of the men and women around me were of the same genetic line that had gotten the crazy idea into their heads that they ought to sacrifice their own kids to the fucking sun. It hit me in full force at that moment: we are in hell. This is it, right now, and we are creating it for ourselves.
If Mother Ayahuasca was telling me one thing, it was, "You create what you see."
Now that particularly baptism of hellfire, an all-weekend drinking session punctuated by a double shot at one point, had many other nasty things in store for me. But as this one is a recurring theme in my trips, I kept coming back to it. What does it say about my mind, that these thoughts compel me? Clearly I have a deep need to understand the nature of evil in this world. Clearly I am coming to terms with the implications of being in a body. I am scared, because these things could happen to me, but will they? Is it rational to dwell on them, or is my mind just projecting? One thing the ayahuasca showed me for sure was that I am in a very high, high state of anxiety and stress all the time simply due to the way I see the world. There is a form of OCD in which the person is obsessed with being as clean as possible, and finds the very idea of the body partly consisting of bacteria and other microscopic horrors nauseating. Perhaps this is something similar? Your mind grappling with something that scares you, in creative ways that become especially vivid when you trip?
Yes, what you are experiencing is anxiety and paranoia. If you are serious about your pursuits, the thing to do is to face it, carefully. Know that what you are dealing with could wreck your brain, and show it the appropriate respect. No, your fast heart rate is not an issue. I had the same thought as recently as last night, while stoned. I breathed, cleared my head, and observed that I was totally fine, and had been the entire time. That is the trick to it. Look at the people around you. The substance they are on is physically safe. Your state of agitation is all in your head. As you learn to control these things, you will develop emotionally. That's what the experiences are really for.