Good question! I've been trying to retrace my steps of a few days ago when I was searching for an explanation of a cause of death given in some Pensions Appeal paperwork dating from April 1925. The cause of death was 'Endocarditis and failure of compensation. Cardiac Syncope'.
Although I can't seem to re-discover the actual site that I found before posting, I've found something along similar lines where the definition is - "Syncope, a sudden, transient loss of consciousness and postural tone" and "cardiac syncope is often indicative of a potentially fatal, underlying disease process, carrying a one-year mortality rate of 30%. Cardiac syncope occurs when the source of one's loss of consciousness stems from a problem in the heart that prevents it from supplying enough nutrients and oxygen to the brain".
https://www.ncbi.nlm.nih.gov/books/NBK526027/ So, yes 'fainting' 'sudden' and (with 'cardiac') 'heart (failure)' are all there, I suppose, but maybe not quite as I originally explained! Sorry.....
Blimey, woke me up from a deep slumber to attend this near 15yo thread.

Where did you find your definition of 'syncope'?
Synope, more commonly known as fainting - ref:
wikipedia.