That's got to be so scary! Syncope is "fainting"/losing consciousness. It appears to be a heart/blood pressure thing most often, can happen with several kinds of "exertion" including sex and/or different positions (kneeling). The things one learns here at PC :-)

http://filer.case.edu/dck3/heart/history.html

http://www.pubmedcentral.nih.gov/art...i?artid=481100

His doctor should check all that out; there's a couple of new drugs that can have that side effect too. I hope he's okay now and they have a clue?