I have an old book from the early twentieth century, "Medical and Nursing Dictionary and Encyclopaedia" by Evelyn Pearce.
She says, "Syncope is a word used to describe fainting, which may be slight or severe. It also implies sudden heart failure which may be immediately fatal. Fainting is due to brain anaemia, resulting from weak heart action. The patient feels sick and dizzy, his skin becomes cold and clammy, beads of sweat appear on his face. His pulse is feeble and he passes into unconsciousness. After a varying time he begins to come round, sighs, his pulse improves, and he recovers consciousness".