You feel flustered in your dream, and your nightmare of being attacked is palpitation caused by palpitation or rapid heartbeat. It's like the dream of finding a toilet is stimulated by objective things such as urgency. The reason why you feel urgent in your dream is the same, and the specific dream has no special significance. If the heartbeat is too slow, it will cause the nightmare of flying people falling, which is an illusion caused by the hanging heart pounding and the heart sinking. In a word, the psychological activities during sleep, like all psychological activities, are the reflection of objective things in the human brain. For example, being stimulated by cold objective things on a cold night will make people have cold dreams repeatedly all night, and so on.
Palpitation is a symptom of cardiovascular disease, which often occurs in healthy people. It is easy to happen after people are tired, frightened, stressed and suddenly engaged in strenuous exercise, and generally do not need treatment.